USSR State Committee for Supervision

for the safe conduct of work in the nuclear power industry

RULES AND REGULATIONS IN NUCLEAR POWER

UNIFIED METHOD FOR CONTROL OF BASIC MATERIALS (SEMI-FINISHED PRODUCTS), WELDED JOINTS AND SURFACE OF NPP EQUIPMENT AND PIPELINES

Tightness control.
gas methods.
PNAE G-7-019-89

1. GENERAL PROVISIONS

1.1. The tightness control of structures and their components is carried out in order to detect leaks caused by the presence of through cracks, lack of fusion, burns, etc. in welded joints and metallic materials.
1.2. Tightness control is based on the use of test substances and registration of their penetration through leaks in structures using various devices - leak detectors and other means of recording a test substance.
1.3. Depending on the properties of the test substance and the principle of its registration, control is carried out by gas or liquid methods, each of which includes a number of methods that differ in the technology for implementing this principle of registration of the test substance. At the same time, depending on the method used, the location of the leak or the total leakage (leakage degree) is determined during the tightness control. The list of applied methods and methods of control is given in Table 1
1.4. The magnitude of a leak or total leakage is estimated by the air flow through the leak or all leaks present in the product, under normal conditions, from the atmosphere to vacuum. The flow unit ratios are given in the reference Appendix 1.
1.5. The control system is understood as a combination of certain methods and modes of control and the method of preparing the product for control.
1.6. The threshold sensitivity of the control system is characterized by the value of the minimum detected leaks or total leakage.

2. CLASSIFICATION AND SELECTION OF LEAK CONTROL SYSTEMS

2.1. All sensitivity control systems are divided into five tightness classes given in Table. 2.
2.2. The tightness class is established by the design (design) organization in accordance with the requirements of the current Control Rules, depending on the purpose, operating conditions of the product and the feasibility of the control and preparation methods assigned to this class, and is indicated in the design documentation.
2.3. The choice of a specific control system is determined by the assigned tightness class, structural and technological features of the product, as well as technical and economic indicators of control.
2.4. In accordance with the assigned class of tightness, control is carried out according to the technology of control flow charts, which indicate specific methods of control and preparation of the product for control. In case of deviations from the requirements of this methodology, the documents must be agreed with the leading industry materials science organization.

3. EQUIPMENT AND MATERIALS

3.1. When testing the tightness, equipment, instruments and materials must be selected in accordance with reference appendices 2 and 3. It is allowed to use domestic and imported equipment, instruments and materials that do not meet the requirements of this document and are not specified in the annexes.
3.2. The parameters and technical characteristics of the equipment, instruments and materials used for leak testing must comply with the passport values, state standards and technical conditions.
3.3. Instruments are subjected to metrological verification, in the passports of which the scope and nature of verifications are indicated. Verifications are carried out by Gosstandart bodies at the respective enterprises. The frequency of verifications is carried out in accordance with the requirements of the passport for the device.
3.4. Leak detectors, regardless of the selected control method, must be set to optimal sensitivity in accordance with the instructions in the technical description and instructions for their operation.

4. GAS METHODS OF TIGHTNESS CONTROL

4.1. Requirements for the preparation of the surface of structures subject to control of tightness by gas methods

4.1.1. If a protective coating is applied to the surface of the product, assembly unit, it should be carried out before the specified operation.
Note . In case of technical impossibility, it is allowed to carry out after the application of protective coatings, which should be specified in the production technical documentation(PTD).
4.1.2. The surface of products, assembly units, welded joints of products to be tested for tightness should not have traces of rust, oil, emulsion and other contaminants.
4.1.3. organic pollution from accessible areas of the surface of the product should be removed by washing with organic solvents, followed by tilting the product or bubbling the poured solvent. The volume of solvent to be poured must be at least 100% of the free volume of the product.
4.1.4. Alcohol, acetone, white spirit, gasoline, freon-113 or other organic solvents should be used as cleaning liquids, providing high-quality removal of organic contaminants.
4.1.5. After cleaning, the solvent should be drained and the cavity of the product should be blown with dry clean air until the smell of the solvent is completely removed.
4.1.6. The quality of cleaning should be controlled by wiping the controlled surface with a clean white lint-free cloth, followed by its inspection. The absence of dirt on the fabric indicates a quality cleaning of the surface.
4.1.7. If appropriately indicated in the technical process, the quality of cleaning should be controlled by examining the surface area of ​​the product or welded joint in the rays of ultraviolet light, and if the surface is unacceptable for inspection in the rays of ultraviolet light, a piece of calico after wiping the surface with it. The absence of luminous spots on the controlled surface or a piece of coarse calico when illuminated with ultraviolet light indicates a high-quality surface cleaning.
4.1.8. The final preparation operation - drying the surface of products and cavities of possible through defects from moisture and other liquid media - should be carried out immediately before the tightness test. After drying, in order to maintain the purity of the products, work should be carried out in clean overalls (robe or overalls) and gloves made of linen fabric.
4.1.9. Electric furnaces, inductors, heaters, installations, steaming stands, etc. should be used as heating means. For heating, you can use the method of electrical resistance using alternating or direct current.
4.1.10. When drying without evacuation, the holding time at the required temperature must be at least 5 minutes. The temperature is determined by the given tightness class.
4.1.11. If it is impossible to check the tightness of products immediately after drying, it is allowed to store the dried product for no more than 5 days. under the following conditions:

• controlled areas must be protected from contamination and liquid media by protective materials;
• atmospheric air moisture must not condense on the surface of the controlled product. To prevent the phenomenon of moisture condensation (for example, when products are brought into a room where the air temperature is higher than the surface temperature of the product, the air temperature in the room decreases, when the product is cooled when test gas is supplied from a cylinder), it is necessary to take measures, guided by reference tables of temperature ratios ambient air, relative and absolute humidity. For example, at a relative air humidity of 80% and a temperature of 20°C, the surface temperature of the product should not be less than 17°C;
• humidity in the room for storing dried products should not exceed 80%.

4.1.12. If it is necessary to transport products, the possibility of contamination and condensation of moisture on the surface of the product should be excluded.

4.2. Leak testing with helium leak detectors

4.2.1. Threshold sensitivity of helium leak detectors and control methods. Working scale.

4.2.1.1. The threshold sensitivity of leak detectors is characterized by the minimum flow of the test substance that the leak detector can register. The threshold sensitivity of helium leak detectors must be at least 1.3.10-10 m3* Pa/s (1.10-6 l×µm Hg/s). The threshold sensitivity of the control method is characterized by the minimum flow or amount of the test substance, which is fixed in the control scheme.
4.2.1.2. The threshold sensitivity of helium leak detectors is determined at the beginning of each shift according to the method given in Appendix 4.
4.2.1.3. The threshold sensitivity of the control method is determined after testing the product, a batch of similar products or a simulator, the design of which is consistent with the HOMO according to the method given in Appendix 5.
4.2.1.4. The threshold sensitivity of the vacuum (helium) chamber and thermal vacuum methods should be at least 6.7.10-10 m3 × Pa / s (5.10-6 l × μm Hg / s), helium blowing methods and helium probe - at least 6, 7.10-9 m3×Pa/s (5.10-5 L×µmHg).
4.2.1.5. If the threshold sensitivity of the control method is below the values ​​specified in clause 4.2.1.4, then the product or batch of products must be re-inspected.
4.2.1.6. A sign of the presence of a through defect is an increase in the instrument readings above the average background readings by a value equal to the difference between the maximum and minimum background values ​​in the test circuit. This value must not exceed 50 mV for all control methods (except for the probe method) and 100 mV for the probe method.

Notes :
1. Average background readings before starting the test by any method should not be more than 2/3 of the working scale.
2. If background readings exceed the specified value, a background compensation circuit should be used.

4.2.2. Helium (vacuum chamber) method.

4.2.2.1. The essence of the helium or vacuum chamber method lies in the fact that the controlled product is placed in a sealed metal chamber. A leak detector is connected to the chamber or product through an auxiliary pumping system, after which helium is supplied under pressure to the chamber (helium chamber method) or to the product (vacuum chamber method). In the presence of a leak, helium, as a result of a pressure drop, enters the evacuated volume connected to the leak detector. The control scheme by the vacuum chamber method is shown in Fig.1.

Rice. 1. Scheme of installation for control by the vacuum chamber method
1 - helium leak detector,
2 - leak,
3 - cylinder with argon,
4 - camera,
5 - product,
6 - manovacuummeter,
7 - gearbox,
8 - helium balloon,
9 - Vacuum pump,
10 - vacuum valve,
11 - calibrated leak
4.2.2.2. When designing and manufacturing a helium (vacuum) chamber, the following requirements must be taken into account:

• to speed up pumping, the shape of the chamber is recommended to be cylindrical (it is allowed to manufacture the chamber according to the design configuration);
• the tightness of flange connections should be provided, as well as the tightness of the outlet from the structure itself or the technological adapter from the structure to the helium cylinder;
• the controlled structure must not come into contact with the inner surface of the chamber.

4.2.2.3. Control procedure:

• the controlled product is prepared in accordance with the requirements of subsection. 4.1;
• the product is placed in a metal chamber, the inner surface of which is pre-cleaned and dried;
• after sealing the chamber cover and installing a pressure gauge, the cavity of the chamber (product) is pumped out to a residual pressure of 7 - 8 Pa [(5-6) .10 -2 mm Hg. Art.;
• before filling the controlled product (chamber) with helium, its cavity is preliminarily pumped out to a pressure not higher than 700-1400 Pa (5-10 mm Hg);
• after reaching the required residual pressure in the chamber (product), the inlet valve of the leak detector opens and the auxiliary pumping system is turned off;
• in the case of a gradual decrease in pressure in the mass spectrometer chamber, it is necessary to supply dry nitrogen to the mass spectrometer chamber using control valves;
• in the event of an increase in pressure in the chamber of the mass spectrometer, it is necessary to partially open the valve of the auxiliary pumping system or close the inlet valve of the leak detector;
• helium or an air-helium mixture is supplied into the cavity of the product (chamber) in the proportions established by the technological map for control;
• holding the product (chamber) under pressure.

4.2.2.4. The duration of exposure of the product (chamber) under pressure should be at least 5 minutes at a vacuumized volume of up to 0.1 m3, from 0.1 to 0.5 m3 - at least 10 minutes, more than 0.5 to 1.5 m3 - not less than 15 minutes, over 1.5 to 3.5 m3 at least 20 minutes, over 3.5 - 40 minutes.
4.2.2.6. Helium should be removed by blowing the cavity of the product (chamber) with dry compressed air or pumping it out.
It is allowed to collect the removed helium for use in the subsequent control.
4.2.2.5. If it is necessary to control a section of a product or a separate welded joint, it is allowed to install a local camera on the controlled section or a welded joint.
The control procedure is similar to that specified in clause 4.2.2.3.
The duration of exposure under pressure is set depending on the pumped volume in accordance with clause 4.2.2.4.
4.2.2.7. When checking the closing weld of the product, the product is evacuated and helium is supplied into the cavity of the product, followed by welding of the closing seam in a helium flow. After welding, it is necessary to test the closing seam using the local vacuum chamber method. The duration of the control is determined by the volume of the chamber in accordance with clause 4.2.2.4.
4.2.2.8. Quantification of the total flow of the test substance through leaks in the product should be carried out according to the method described in Appendix 6 (reference).

4.2.3. A method for pressurizing closed shells with helium.

4.2.3.1. The control method of pressing closed shells consists in the fact that the product or the closing seam is placed in a special chamber in which helium pressure is created. If there is a leak in the seam, helium penetrates into the closed volume of the product. Next, the product is controlled by the accumulation of helium in a vacuum chamber in which the product is placed.
4.2.3.2. It is recommended to check the tightness of the closing weld by pressure testing for products with small volumes (up to 10 l).
4.2.3.3. Control should be carried out in the following sequence:

• the product is placed in a pressure test chamber and kept under helium pressure for a certain time;
• after pressure testing, the product is removed from the chamber, the outer surface of the product is blown with compressed air or nitrogen to remove helium and kept in air for 1–2 hours;
• before installing the product, the internal cavity of the chamber attached to the leak detector is pumped out with an auxiliary pump. The background readings of the outlet device of the leak detector are recorded at a pressure in the chamber of 1 - 7 Pa [(1 - 5) .10 -2 mm Hg. Art.] with the auxiliary pump turned off;
• the product pressed with helium is placed in a vacuum chamber and the chamber with the product is pumped out to a pressure of not more than 1-7 Pa, the auxiliary pump is turned off and helium is accumulated in the chamber for at least 1 hour, after which the inlet valve of the leak detector is opened and the leak detector readings are recorded.
• Exceeding the signal of the output device of the leak detector by 1 V or more above the background readings is a sign of a leak in the closing seam of the product.

Note . In order to exclude an increased helium background during the testing process, it is forbidden to use the chamber in which the product was pressed with helium.
4.2.3.4. The duration of pressure testing of the product with helium should be at least 120 hours at a pressure of 1.106 Pa (10 kgf/cm2), at least 50 hours at 2.106 Pa (20 kgf/cm2), at least 13 hours at 5.105 Pa (50 kgf/cm2).

4.2.4. The method of thermal vacuum testing.

4.2.4.1. The essence of the tests lies in the fact that the product to be controlled is heated in a vacuum chamber to a temperature of 380 - 400 ° C at a pressure inside and outside the product not higher than 0.1 Pa (10 -3 mm Hg), and then it is controlled when helium is supplied into the heated article or into the chamber in which it is placed.
4.2.4.2. Control procedure:

• the product is prepared for control in accordance with paragraphs 4.1.1 - 4.1.7;
• the product is placed in a metal chamber;
• the chamber and the internal cavity of the product are evacuated to a pressure not higher than 0.1 Pa (10 -3 mm Hg);
• the product is heated in furnaces or heating devices to a temperature of 380 - 400 ° C and maintained at this temperature for 3 - 5 minutes. The heating rate is determined by maintaining a constant pressure in the chamber and the product not higher than 0.1 Pa (10 -3 mm Hg) and the design of the product;
• the inlet valve of the leak detector opens when the pumping group of the chamber (or product) is turned off at the same time.
• Steady background readings of the leak detector are recorded;
• helium is supplied to the controlled product (or chamber) up to the required pressure;
• the product (chamber) is maintained under pressure, while the readings of the leak detector are recorded. The duration of exposure is selected in accordance with clause 4.2.3.4;
• after cooling to a temperature not exceeding 50°C, the chamber opens.

4.2.5. Helium probe method.

4.2.5.1. The essence of the method lies in the fact that the product is filled with helium or a helium-air mixture to a pressure above atmospheric, after which the outer surface of the product is controlled by a special probe connected by a metal or vacuum rubber hose to a leak detector. As a result of the pressure difference, helium penetrates through the existing through defect and enters the chamber of the leak detector mass spectrometer through the probe and hose. A certain design of the tip of the probe, made in accordance with the profile of the controlled surface, allows you to determine the location of the through defect in the product. The tip of the probe must cover the area to be checked in width by at least 5 mm on each side. If the width of the nozzle is smaller, then the control should be carried out in several passes.
The control scheme by the helium probe method is shown in fig. 2


Rice. 2. Scheme of installation for control by means of a probe
1 - helium leak detector,
2 - thermocouple lamp,
3 - vacuum hose,
4 - vacuum pump,
5 - (Note from Webmaster: nothing for 5)
6 - product,
7 - probe,
8 - manovacuummeter,
9 - helium balloon
4.2.5.2. When checking by the probe method, adjustable probes-catchers with a conical nozzle with a volume of not more than 1 mm3 and a distance of an adjustable locking needle from the controlled surface of not more than 5 mm are used. One of options design execution is a probe-catcher according to hell. 358-00-00 and 358-01-00.
4.2.5.3. The following requirements apply to a helium probe test facility:

• all connections of the installation must be checked with the probe in the closed position by blowing;
• the part of the installation intended for supplying helium to the controlled product must be tested by the helium probe method at a helium pressure of at least 1.5 P, where P is the helium pressure during control;
• in the case of using a hose made of vacuum rubber to connect the probe to the leak detector, the hose must be flushed to reduce gas separation with an alkali solution (15%), clean running water, distilled water and dried with rectified alcohol. The outer surface of the hose is wiped with castor oil;
• the length of the line connecting the probe to the leak detector should be minimal. possible. Maximum length the highway is determined by clause 4.2.1.4 when assessing the sensitivity of the method according to Appendix 5.

4.2.5.4. Control should be carried out in the following sequence:

• with probe 7 closed (see Fig. 2), hose 3 is evacuated by vacuum pump 5 for 15–20 minutes;
• the probe is adjusted so that when the auxiliary vacuum pump and leak detector pumps work together, the residual pressure measured by thermocouple lamp 2 installed at the leak detector flange is 25 - 30 Pa [(1.8-2.2) .10-1 mm Hg. st.]. Setting the working pressure in the hose connecting the probe to the leak detector must be carried out simultaneously by adjusting the probe and the leak detector inlet valve;
• a pump with a pumping speed of 1 - 3 l / s should be used as an auxiliary pump. If a pump with a higher pumping speed is used, valve 4 should be closed, ensuring the appropriate pumping speed;
• the product prepared for testing, after plugging the holes and flange outlets, is pumped out to a pressure not higher than 700 - 1400 Pa (5-10 mm Hg);
• helium and a helium-air mixture (not less than 50% helium) are supplied to the product to the excess pressure required during testing.

You can see an illustration of the method in the video:

Notes:
1. If it is impossible to preliminarily pump out pipelines or chamber-type products, it is allowed to purge the cavity with helium until it appears at the outlet of the pipeline or product. The appearance of helium is fixed with a probe by increasing the readings of the device above the background by 100 mV and above.
2. To obtain a helium concentration of at least 60% under a pressure of 0.1 MPa (1 kgf/cm2), after purging the cavity with helium, helium is supplied to the product or pipeline to a pressure of 0.1 MPa (1 kgf/cm2). To obtain a helium concentration of at least 75%, the pressure is reduced to atmospheric pressure and helium is again supplied to a pressure of 0.1 MPa.
3. For products with dead-end cavities, which exclude the possibility of purging and vacuuming, the holding time to achieve the required helium concentration is determined experimentally in each specific case on a simulator.
4.2.5.5. The control is carried out by moving the probe along the surface of the product at a constant speed equal to 0.10 - 0.15 m/min:

• when moving, the probe must be in direct contact with the controlled surface. Removing the probe from the controlled surface by 5 mm reduces the detection of defects by 10 - 15 times;
• control should begin with the lower parts of the product with a gradual transition to the upper.

4.2.6. Helium blowing method.

4.2.6.1. The essence of the method lies in the fact that the product being tested is connected to a leak detector, evacuated to a pressure that allows the inlet valve of the leak detector to be fully opened, after which the outer surface of the product is blown with a helium jet.
If there is a leak in the product, helium enters its cavity and is fixed by a leak detector.
The control scheme by the blowing method is shown in fig. 3.


Rice. 3. Diagram of installation for controlling the blowing method
1 - helium leak detector,
2 - leak,
3 - helium leak,
4 - vacuum pump,
5 - cylinder with argon,
6 - vacuum valve,
7 - product,
8 - blower,
9 - chamber with helium
4.2.6.2. Control should be carried out in the following sequence:

• prepared in accordance with the requirements of subsection. 4.1 the product is evacuated to a pressure of 7 - 8 MPa [(5 - 6) .10 -2 mm Hg. Art.];
• when the inlet valve of the leak detector is open to the product, the auxiliary pumping system is turned off and the outer surface of the product is blown with helium. If it is impossible to maintain the required pressure in the mass spectrometer chamber with the auxiliary pumping system turned off, it is allowed to carry out control with the valve of the auxiliary pumping system not completely closed or open, while determining the sensitivity according to Appendix 5 should be at the same position of the valve;
• airflow should be started from the points of connection of the auxiliary pumping system to the leak detector; then the product itself is blown, starting from its upper sections with a gradual transition to the lower ones;
• at the first stage of testing, it is recommended to install a strong helium jet, which immediately covers a large area when blowing. If a leak is detected, reduce the helium jet so that it is slightly felt when bringing the blower gun to the lips, and accurately determine the location of the through defect. The speed of movement of the blower on the controlled surface is 0.10-0.15 m/min; when checking products of large volume and length, it is necessary, taking into account the signal delay time, to reduce the blowing speed;
• in the presence of large through defects and the impossibility of achieving the required vacuum in the product to fully open the inlet valve of the leak detector with the auxiliary pumping system turned off, through defects should be found with the auxiliary pumping system turned on. After the detection of large through defects and their elimination, a repeated control is carried out in order to find defects with a small amount of leakage.

4.2.6.3. In order to control the entire surface of the product or part of it in individual cases the controlled surface is covered with a soft cover. Helium is supplied under the cover in an amount approximately equal to the volume of space under the cover.
The duration of exposure of the product under the cover is 5-6 minutes.
4.2.6.4. The blowing method can be used to control open structural elements. For its implementation, vacuum suction cups should be used, superimposed or fixed on the controlled surface from the side opposite to the blown one. One of the chamber designs is shown in Fig. 4. Test modes are specified in 4.2.6.2.

Rice. 4. Construction of the suction chamber
1- cover,
2- building,
3- rubber seals,
4- design,
5- pipeline,
6- welded joint

4.3. Leak testing with halogen leak detectors. Halide atmospheric probe method

4.3.1. Adjustment of leak detectors, determination and testing of the threshold sensitivity of halide leak detectors should be carried out using calibrated halide leaks in accordance with technical description and the manufacturer's instruction manual.
4.3.2. The essence of the halide probe method lies in the fact that the test product, previously evacuated, is filled with freon or a mixture of freon with air to a pressure above atmospheric. As a result of the pressure drop, freon penetrates through the existing leak and is captured by the leak detector probe connected by an electric cable to the leak detector measuring unit.
4.3.3. The scheme of installation for control by the halogen probe method is shown in fig. 5.


Rice. 5. Scheme of installation for control by the method of halogen probe:
1 - cylinder with freon;
2 - reducer;
3 - vacuum pump;
4 - manovacuummeter;
5 - valve;
6 - product;
7 - measuring block of the leak detector;
8 - remote probe of the leak detector
The installation for injecting freon into the controlled product must be checked for tightness with a halogen leak detector at a pressure of saturated halon vapor at the test temperature.
4.3.4. Control procedure:

• after plugging the holes and flange outlets with through and blind plugs, the product is pumped out to a residual pressure of not more than 700 - 1400 Pa (5 - 10 mm Hg);
• by closing the valve, the vacuum pump is turned off and freon is supplied to the product to the excess pressure required during testing;
• in case of impossibility of preliminary evacuation of pipelines, it is allowed to displace air with freon with fixation of the presence of freon at the remote end of the pipeline. Next, freon is injected into the pipeline to ensure the freon concentration in the pipeline is at least 50%;
• for chamber-type products, freon injection is allowed without pumping out the product, provided that the freon concentration in the product is at least 50%;
• control is carried out by moving the remote probe along the surface of the product at a constant speed;
• when moving, the probe should be at the minimum possible distance from the surface. Removing the probe from the controlled surface by 5 mm reduces the detection of defects by 10 - 15 times;
• control should begin with the upper sections of the product with a gradual transition to the lower ones.

4.3.5. Control modes by halogen leak detectors:
the speed of movement of the probe on the surface of the product should not exceed 0.10 - 0.15 m/min;
the pressure of freon-12 or freon-22 must comply with the instructions of the working drawings or flow sheet for control. Freon pressure in the product must be lower than its saturated vapor pressure.
Note . The pressure of saturated vapors of freon-12 and freon-22, depending on the temperature, is given in help application 7.
4.3.6. After the control, freon must be removed from the structure outside the working room by pumping to a residual pressure of 130 - 650 Pa (1 - 5 mm Hg). After that, air must be admitted into the controlled product and re-pumped to the same pressure.
Note . Double evacuation of the controlled product to a residual pressure of 130 - 650 Pa guarantees a residual content of freon-12 no more than 0.01 mg/l, and freon-22 - no more than 0.006 mg/l.

4.4. Bubble leak test

4.4.1. Pneumatic method by air inflating.

4.4.1.1. The essence of the method lies in the fact that the controlled product is filled with test gas under excess pressure. A foaming composition is applied to the outer surface of the product. Test gas at leaks causes bubbles to form in the foam formulation (bubbles or breaks in the soap film when using soap emulsion; foam cocoons or breaks in the film when using a polymer formulation).
4.4.1.2. Control procedure:

• in the controlled product, the required overpressure of the test gas is created;
• With a soft hair brush or paint sprayer, a foaming composition is applied to the controlled surface of the product and visual observation is carried out.

Note . The components of foam formulations are given in Annex 8 (informative).
4.4.1.3. The time of monitoring the state of the surface when applying the soap emulsion is no more than 2 - 3 minutes after its application to the surface.
4.4.1.4. When applying a polymer composition to detect large defects (more than 1.10 -4 m 3 Pa / s), the inspection should be carried out immediately after applying the polymer composition. To detect small defects, the inspection time should be at least 20 minutes from the moment the composition was applied. Foamy cocoons are stored during the day.

4.4.2. Pneumohydraulic aquarium method.

4.4.2.1. The essence of the method lies in the fact that the product, which is filled with gas under pressure, is immersed in a liquid. Gas escaping at leaks from the product causes bubbles to form in the liquid.
4.4.2.2. Control is carried out in the following sequence:

• the controlled product is placed in a container;
• a test pressure of test gas is created in the product;
• liquid is poured into the container to a level of at least 100 - 150 mm above the controlled surface of the product.

4.4.2.3. A sign of a leak in the product is the formation of air bubbles floating to the surface of the liquid, periodically forming on a certain area of ​​the product surface, or a line of bubbles.

4.4.3. bubble vacuum method.

4.4.3.1. The essence of the method lies in the fact that before installing the vacuum chamber, the controlled area of ​​the structure is wetted with a foaming composition, a vacuum is created in the chamber. In places of leaks bubbles, cocoons or film breaks are formed, visible through the transparent top of the chamber.
4.4.3.2. To ensure complete control of the entire welded joint, the vacuum chamber is installed so that it overlaps the previous controlled section of the weld by at least 100 mm.
The vacuum chamber may have different shape depending on the design of the controlled product and the type of welded joint. For butt welded joints of sheet structures, flat chambers are made, for fillet welds - fillet welds, to control the circumferential welds of pipelines, annular chambers can be made. One of the possible options structural design vacuum chamber is shown in fig. 6.


Rice. 6. Scheme of a vacuum chamber for tightness control:
1 - rubber seals;
2 - camera body;
3 - window;
4 - vacuum valve;
5 - leak in the welded joint
6 - rubber seals
4.4.3.3. Control is carried out in the following sequence:

• a foaming composition is applied to the controlled area of ​​the open structure;
• a vacuum chamber is installed on the controlled area;
• a pressure of 2.5 - 3.10 4 Pa ​​(180 - 200 mm Hg) is created in the vacuum chamber;
• the time from the moment of applying the composition to the moment of inspection should not exceed 10 minutes;
• visual inspection of the controlled area is carried out through the transparent top of the chamber.

Note . In the case of application in the control of the polymer composition, the pattern of defects is preserved for a day.

4.5. Tightness control by manometric method (by pressure drop)

4.5.1. To carry out control by the manometric method, the product is filled with test gas at a pressure above atmospheric and kept for a certain time.
4.5.2. The pressure and pressure testing time are set by the technical specifications for the product or design (project) documentation.
4.5.3. The product is considered sealed if the pressure drop of the test gas during holding under pressure does not exceed the norms established by the technical specifications or design (project) documentation.
4.5.4. Gas pressure is measured by pressure gauges of accuracy class 1.5 - 2.5 with a measurement limit of 1/3 more than the pressure of pressure testing. A shut-off valve must be installed on the supply pipe to regulate the gas supply.
4.5.5. A quantitative assessment of the overall leakage is carried out according to the formula

where
V- internal volume of the product and elements of the test system, m3;
DR- change in test gas pressure during pressure testing, Pa;
t- pressing time, s.

The leak detection machine is designed to detect leaks in shut-off solenoid valves and prevent the gas burner from starting if leaks are detected. To test the valves for tightness, two shut-off valves must be mounted in series on the burner.

Safety regulations PB 12-529-03 prescribe that burners operating on natural gas and having a power of more than 1.2 MW be equipped with a tightness control circuit. If the burner power is unknown, then it can be calculated using the natural gas flow rate through the burner. With a natural gas calorific value of 35.84 MJ/Nm3, every 10 Nm3 volume of consumed natural gas corresponds to 0.1 MW of burner power.

We will consider a typical algorithm for the operation of a tightness control machine using the example of a TC 410 machine from KromSchroder. The leak tester checks valves V1 and V2 for leaks in several steps. Both valves are checked for tightness, but only one of the valves can be open at a time. Pressure control, according to the measurement results of which the tightness of the valves is determined, is carried out by an external adjustable pressure sensor with a normally open contact. The TC 410 leak tester can perform a valve test before the burner is ignited or after the burner has been switched off.

At the first stage of testing, the valves V1 and V2 are closed, there is no gas in the intervalve space, the pressure sensor contacts are open. The inlet gas pressure is equal to the value Pe, the pressure sensor is set to operate when the pressure rises to the value Pz > Pe/2.

The valve solenoid coil V1 is supplied with a supply voltage (usually 220V AC) from the leak tester. The valve is opened for a short time, the space between the valves is filled with gas with pressure Pe. The pressure sensor is triggered, since Pz = Pe > Pe/2.

After that, the coil of valve V1 is de-energized, valve V1 closes and, together with the closed valve V2, creates a closed volume. The leak control starts a timer with a delay time Tw. During this time, the gas pressure inside the closed volume should not fall below the Pe/2 value. In the event of a leak through valve V2 and a drop in gas pressure below the Pe/2 level, the automatic leak control generates a fault signal and blocks the burner from starting. If the gas pressure in the closed volume does not fall below the threshold value, then the shut-off valve V2 is tight and the circuit proceeds to testing the valve V1.

Valve V2 opens for a short time (TL=2 sec) relieving gas from the space between the valves. During this time, the gas pressure should ideally drop to almost zero and the pressure sensor contacts should open.

Valve V2 closes, timer Tm starts. If the valve V1 is leaking, then the gas pressure in the intervalve space will begin to increase, which will lead to the pressure sensor triggering and the formation of a failure signal by the automatic leak control. Burner ignition will be blocked. If during the time Tm the pressure sensor does not work, then the valve V1 is tight. In this case, the ready signal "OK" is generated and the burner is allowed to start.

If, due to safety or technology requirements, the discharge of natural gas through the burner during leak testing is prohibited, then the discharge is carried out to the candle through an auxiliary valve.

The test time Ttest can be set by the service personnel. For the TC 410-1 breaker it can vary within 10…60 seconds, for the TC 410-10 100…600 sec. The test time is the sum of the waiting times Tw and Tm and the purge time TL. The setting is carried out using jumpers. Or, as in the AKG-1 automatic machine of the Proma company, with disk digital switches. The test time depends on the inlet gas pressure, the volume to be tested and the size of the allowable leaks. A leakage Vut (in l/h) not exceeding 0.1% of the maximum gas flow (in Nm3/h) through the burner is considered acceptable.

The test volume Vtest is the sum of the gas volumes of the valves, which are given in the passports for the valves, and the volume of the pipeline connecting them. Leak testers are available both for in-panel mounting and for mounting directly on shut-off valves. In this case, it has a built-in pressure sensor to measure intervalve pressure.

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ANNOTATION

The master's thesis was developed and researched automated systems tightness tests by the manometric method of shut-off and distribution gas equipment.

A review and analysis of methods for monitoring the tightness of shut-off and distribution gas equipment was carried out.

The main stages of designing devices for monitoring the tightness of shut-off and distribution gas fittings are considered. Produced simulation manometric method tightness control of gas shut-off and distribution equipment.

The design of the stand for testing the tightness of shut-off and distribution valves has been developed.

The explanatory note contains 100 pages, 35 figures, 3 tables, 3 appendices, 43 bibliography titles.

The graphic part is made in the program power point and presented on 14 slides.

Introduction

CHAPTER 2

2.1 Algorithm for designing automated equipment

for tightness control

2.2 Schemes and principle of operation of devices for monitoring tightness by the manometric method

2.3 Simulation of the manometric method for monitoring the tightness of gas shut-off and distribution valves

CHAPTER 3

3.1 Layout and technical characteristics of the stand

3.2 The principle of operation of the stand for testing the tightness of gas shut-off and distribution valves

3.2.1 Pre-purge

3.2.2 Clamp - fixing the product

3.2.2.1 Calculation of the scheme of clamping, fixing and sealing of the valve

3.2.2.2 Development of the valve clamping, fixing and sealing unit

3.3.3 Rotation

3.2.4. Positioning

3.2.5 Leak test

3.2.6 Regulation

3.2.7 Opening - releasing

3.2.8 Operation and display

3.3 Development of an automated technological process for tightness control

Conclusion

List of used literature

INTRODUCTION

In the manufacture of equipment (shut-off valves, pneumatic valves, taps, etc.), in which the working medium is compressed air or another gas, the existing standards and technical conditions regulate one hundred percent control of the “tightness” parameter. This is explained by the fact that the main unit - the working element of such equipment is a movable pair that is difficult to seal: spool - body; nozzle - damper; ball, seat and cone valves, as well as stationary sealing elements, which often work under high pressure conditions. Leakage of this equipment, i.e. the presence of a leak that exceeds the allowable one can lead to serious accidents, breakdowns and other negative results in the operation of complex expensive equipment in which it is used.

The tightness control of structures is used in various branches of science and technology. The widespread use of this type of control has led to the development of a variety of methods and means of control, with different sensitivities and areas of rational use.

It can be considered that one of the most urgent problems of the present time - increasing the sensitivity of control - in a number of cases has been fundamentally solved. Leak-detecting equipment has been created, which makes it possible to detect leaks comparable to the intermolecular distance, and to register leaks bordering on the permeability of materials.

The problem of increasing the productivity and reliability of leak detection equipment, its simplification and expansion of operational capabilities remains topical. At the same time, it should be taken into account that the reliability of the equipment does not yet unambiguously determine the reliability of tests. The quality of preparation of the tested objects, the correct choice of equipment, test modes and conditions are essential. environment. This, in turn, puts forward the need to solve problems of a methodological and technological nature. In particular, there are problems of developing rational methods for monitoring objects using several methods of leak detection, creating industrial auxiliary equipment that makes it possible to economically use well-known methods for monitoring tightness in production conditions.

Of great importance are the issues of mechanization and automation in leak detection. In the best samples of leak detection equipment, the control process is almost completely automated. However, few special devices, production lines and conveyor installations have yet been created in which the processes of preparation, filling or application of indicator substances, control and objective recording of the state of tightness of the controlled product are mechanized and automated.

The aim of the master's thesis is the development and research of automated devices and control systems for leak testing of shut-off and distribution gas equipment.

Research objectives:

Analysis known methods tightness tests of shut-off and distribution gas equipment.

Investigation of systems used for testing the tightness of shut-off and distribution gas equipment.

Simulation of the parameters of the pressure sensor used in the tightness test of shut-off and distribution gas equipment.

Development of a stand for testing the tightness of shut-off and distribution gas equipment.

shut-off valve tightness

CHAPTER 1. Review and analysis of methods for monitoring the tightness of shut-off and distribution gas equipment

1.1 Basic terms and definitions

In accordance with the requirements and recommendations given in the scientific and technical literature and regulatory documentation for products and structures operating or controlled under excessive gas pressure, the following terms and definitions are adopted in this study.

Leakage - a through defect in the wall of the product or at the junctions of its elements through which gas can pass.

The flow through the leak - the amount of gas in volume units passing through the leak per unit time at the current pressure drop. The flow through the leak in most cases is determined by the formula

where V is the internal volume of the tested product with one leak;

Change in gas pressure value (pressure drop);

t is the test time.

Leak - a flow through a leak at a normalized pressure drop, for which a value equal to the physical atmosphere (10.1 MPa) is taken.

Leakage - the total flow through the leakage of a product or structure: . Units - , . It is allowed to express leakage in units of volume flow - , .

Tightness - the ability or property of a product to prevent gas from passing through the walls and joints of its elements. Tightness Г of structures operating under excessive pressure is a value proportional to volume and inversely proportional to leakage, which corresponds to the dependence

where is the total internal volume of the product;

total leakage.

The physical meaning of tightness is the time required to change the pressure in the internal volume of the product per unit - s / Pa.

Leak testing - for pressure products - is a type of non-destructive testing, consisting in measuring or evaluating the total leakage of a test substance penetrating through leaks, for comparison with the allowable leakage value. Leak tests are carried out to determine the degree of leakage of products, as well as to identify individual leaks.

The degree of leakage is a quantitative characteristic of tightness. It is characterized by gas flow, flow rate, pressure drop per unit of time and other similar values, reduced to operating conditions.

Working substance (working medium) - the gas with which the product is filled during operation.

Test substance (indicator medium, indicator substance) - a gas or other substance intended to penetrate through the leaks of the product during testing with its subsequent registration by visual, chemical or instrumental methods. The test medium can be a single gas or a mixture of gases, such as compressed air.

The sensitivity of the tightness control is the smallest leakage of the working medium that can be registered during the testing of the product using a test substance.

A control (calibrated) leak is a device with which a constant-in-time and known-by-value flow of a test substance is obtained.

Terms and definitions related directly to the study are considered and explained in the process of presenting the relevant material.

1.2 Features of control of tightness of distribution and shut-off gas fittings

Under the gas fittings considered in present work, are understood as devices intended for use in various systems in which the working medium is a gas or a mixture of gases under pressure (for example, natural gas, air, etc.), to perform the functions of cut-off, distribution, etc.

Gas fittings include: valves, distributors, valves and other means of industrial pneumatic automation of high (up to 1.0 MPa) and medium pressure (up to 0.2 ... 0.25 MPa), shut-off valves for household gas stoves operating at low pressure (up to 3000 Pa).

Both finished products and their constituent elements, individual components, etc. are subjected to a leak test. Depending on the purpose of the products, the conditions in which they are operated and the design features, they are subject to different requirements regarding their tightness.

The tightness of gas fittings is understood as its ability not to let the working medium supplied under excess pressure through the walls, joints and seals. In this case, a certain amount of leakage is allowed, the excess of which corresponds to the leakage of the product. The presence of leakage is explained by the fact that the main unit - the working element of such devices is a movable, difficult to seal pair: spool-body, nozzle-flap, ball, cone or saddle valves, etc. In addition, the design of the device, as a rule, contains fixed sealing elements: rings, cuffs, oil seals, lubricants, defects of which can also cause leakage. Leakage of gas fittings, i.e. the presence of leakage of the working medium exceeding the allowable one, can lead to serious accidents, breakdowns and other negative results in the operation of the equipment in which it is used.

The stopcock (Fig. 1.1) is an important part of household gas stoves. It is designed to regulate the supply of natural gas to the burners of the stove and cut it off at the end of work. Structurally, the valve is a device with a rotary valve element 1, mounted in a split housing 2, which has channels for the passage of gas. The points of interface of the crane parts need to be sealed to ensure its maximum possible tightness. Sealing is carried out with a special graphite grease - sealant, manufactured in accordance with TU 301-04-003-9. Poor sealing leads to the leakage of natural gas during the operation of the stove, which, in the conditions of a limited space of domestic premises, is explosive and fire hazardous, in addition, the ecology (human habitat) is violated.

In accordance with GOST, the following requirements are established when testing the tightness of a shut-off valve. The tests are carried out with compressed air at a pressure of (15000±20) Pa, since higher pressures may damage the sealing lubricant. Air leakage must not exceed 70 cm3/h.

1.3 Design principles for pneumatic and hydraulic testing operations

Hydraulic (pneumatic) testing, as the main form of control of valve products, is an experimental determination of quantitative and qualitative indicators of product properties as a result of exposure to it during its operation, as well as during object modeling.

Basis for design technological operations is their classification, which creates conditions for the organization of specialized jobs, sites and divisions, provides the possibility of mechanization of accounting, search and storage of information. Figure 1.2 shows the classification of pneumatic and hydraulic tests according to the controlled characteristic (first stage) and according to the test method (second stage). The boundaries between the classification groupings shown in Figure 1.2 are not fixed once and for all. Depending on the tasks set by the engineer designing the test operation, they can be combined. Thus, it is advisable to carry out tightness control by the luminescent method and strength tests on the same equipment. In cases where safety engineering allows it, hydraulic leak tests can be replaced by pneumatic ones.

The choice of test method is determined by the cost of their implementation, the required measurement accuracy, the amount of economic damage from a missed marriage, and other factors.

Figure 1.2 - Classification of pneumatic and hydraulic

controlled characteristic tests

The objectives of the tests are different at various stages of design and manufacture of valves. The main objectives of the tests include:

a) selection of optimal design and technological solutions when creating new products;

b) fine-tuning products to the required level of quality;

c) an objective assessment of the quality of products when they are put into production and during the production process;

d) guaranteeing the quality of products in international trade.

Testing is an effective means of improving quality by identifying:

Deficiencies in the design and manufacturing technology of shut-off valves, leading to a failure to perform the specified functions under operating conditions;

Deviations from the chosen design or accepted technology;

Hidden defects in materials or structural elements that cannot be detected by existing methods of technical control;

Reserves for improving the quality and reliability of the developed structural and technological version of the product.

Based on the results of testing products in production, the developer determines the reasons for the decline in quality.

All valves are subject to hydraulic testing after their manufacture.

Products, the manufacture of which is completed at the installation site, transported to the installation site in parts, are subjected to a hydraulic test at the installation site.

Shut-off valves with a protective coating or insulation are subjected to a hydraulic test before coating or insulation is applied.

Shut-off valves with an outer casing are subjected to a hydraulic test before the installation of the casing.

Hydraulic testing of shut-off valves, with the exception of cast ones, should be carried out with a test pressure Ppr, MPa, determined by the formula:

where P - design pressure of valves, MPa (kgf/cm2);

[d20], [dt] - allowable stresses for the material of stop valves or its elements, respectively, at 200 C and design temperature, MPa (kgf / cm2).

Hydraulic testing of cast parts should be carried out with a test pressure Ppr, MPa, determined by the formula:

It is allowed to test castings after assembly and welding in an assembled unit or finished product with a test pressure adopted for stop valve products, subject to 100% control of castings by non-destructive methods.

When filling the test article with water, the air must be completely removed from it.

For hydraulic testing of valves, water with a temperature of at least five degrees Celsius and not higher than 400 C should be used, if in specifications no specific value of the temperature allowed under the condition of preventing brittle fracture is indicated.

Upon agreement with the test developer, another liquid may be used instead of water.

The pressure in the product under test should be gradually increased. The pressure rise rate must be indicated: for testing the product in the manufacturer - in the technical documentation, for testing the vessel in the process of operation - in the installation and operation instructions.

The pressure during the test must be controlled by two pressure gauges of the same type, measurement limit, the same accuracy classes, scale divisions.

The exposure time of the tested product under test pressure is set by the project developer.

After holding under the test pressure, the pressure is reduced to the design pressure, at which the outer surface of the tested product, all its detachable and welded joints are inspected.

Tapping of the body walls, welded and detachable joints of the tested product during the tests is not allowed.

The product is considered to have passed the hydraulic test if it is not found:

Leaks, cracks, tears, sweating in welded joints and on the base metal;

Leaks in detachable connections;

Visible residual deformations, pressure drop on the manometer.

The tested products, in which defects were revealed during the test, after their elimination, are subjected to repeated hydraulic tests with a test pressure established by these rules.

A hydraulic test carried out at the manufacturer's organization must be carried out on a special test stand that has an appropriate fence and meets the safety requirements and instructions for conducting hydraulic tests in accordance with the regulatory documentation approved in the prescribed manner.

It is allowed to replace the hydraulic test in the manufacture of shutoff valve products with a pneumatic one, provided that this product is controlled by a method agreed with the Gosgortekhnadzor of Russia.

Pneumatic tests must be carried out according to instructions that provide for the necessary safety measures and approved in the prescribed manner.

Pneumatic testing of products of shutoff valves is carried out with compressed air or inert gas.

The value of the test pressure is assumed to be equal to the value of the test hydraulic pressure. The holding time of the vessel under test pressure is set by the project developer. Then the pressure in the tested product should be reduced to the design one and the product should be inspected to check the tightness of its seams and detachable joints with a soapy solution or in another way.

The test pressure value and test results are recorded in the product passport by the person who conducted these tests.

1.4 Methods and methods of tightness control

The tightness control method is selected based on the design and technological characteristics of the product, technical and economic parameters and production capabilities.

The sensitivity of the method is chosen such that it is possible to detect leaks, the magnitude of which is approximately one order of magnitude less than the allowable ones. The numerical value of the tightness requirements serves as the initial parameter for choosing a rational scheme and technical modes of tightness control.

The classification of methods and means of tightness control is presented in the form of table 1.1.

The first group includes all methods and means that determine leakage through a discontinuity by creating in a controlled volume an overpressure of the working pressure test medium with and without test gas.

The second group combines numerous methods and devices that determine the tightness directly in a controlled object or in a vacuum chamber in which the test product is placed, by registering a change in a pre-created, well-defined vacuum that occurs due to the penetration of a sample gas into the discharged volume (second group).

These groups include two subgroups. The first includes all methods and means in which clean air, air mixed with a test gas, or air mixed with various radioactive isotopes is used as a working compression medium.

In the second - methods and devices in which a liquid component, including liquefied gas, is used to determine the location of the discontinuity. Further division is carried out depending on the technology for determining the discontinuity.

Table 1.1 Classification of methods and means of tightness control

Table 1.3 - Classification of means of tightness control using redundant

pressure of various liquids.

To control the tightness of household gas appliances, the group of compression methods is the most promising. Compression methods of tightness control are based on registration of the parameters of the indicator liquid and gases penetrating under pressure into through defects of the controlled object.

In the hydrostatic method, liquid is poured into the test object and excess pressure is created. After a certain exposure, an inspection or application of filter paper on the surface of the tested joint is carried out. The tightness of the object is evaluated depending on the presence or absence of liquid drops on the surface being monitored or spots on the filter paper used as an indicator. The amount of leakage Y, MPa/s is determined by the amount of leaked liquid and the time of its collection according to the formula:

where VL is the volume of leaked liquid, m3;

Observation time, s.

For the convenience of indicating leaks, in some cases, a chalk coating 40–60 µm thick is preliminarily applied to the outer surface of the controlled object. For coating, a creamy aqueous solution of chalk is prepared and applied with a stiff hair brush or in any other way in a thin uniform layer on the surface and dried. Approximately 0.3 l of chalk coating is required for one m2 of the surface to be checked.

On filter paper and chalk, liquid stains, especially oil and kerosene, are more visible. In addition, it is convenient to determine the volume of the leaked liquid by weighing the filter paper before and after collecting the leaked liquid according to the formula:

where m2 and m1 are the mass of paper, respectively, before and after collecting the liquid, kg;

Liquid density, s.

The sensitivity of the hydrostatic method at the same pressure depends on the holding time of the tested object under pressure.

The dependence of the sensitivity of the hydrostatic test method on the exposure time and the diameter of the oil spot is shown in Figure 1.2.

The sensitivity of the control increases with increasing exposure time to 10-15 minutes. A further increase in the exposure time is inappropriate, since it does not lead to a noticeable increase in sensitivity. The sensitivity of the hydrostatic method largely depends on the purity of the indicator liquid. Mechanical impurities clog channels of leaks and are the centers of formation of obliteration layers that reduce the lumen of the channel. Soluble contaminants increase the viscosity of the test fluid, which reduces flow. Surfactants have a special effect - components of lubricants used in the assembly of hydro-gas systems, washed out with kerosene during control. If they are present in kerosene, the flow through a relatively small leak can stop. The use of contaminated indicator liquids can lead to the presence of hidden leaks that are not detected during the control process, which can appear as significant leaks under the action of operational factors.

A characteristic error of the hydrostatic control method is to take as a defect the spots on the chalk coating or filter paper arising from the lubricant protruding from the joints used during the assembly of the system. Therefore, before checking, all connections must be cleaned from the outside of traces of grease.

Figure 1.3 - Dependence of the sensitivity D of the hydrostatic test method on the holding time c and the diameter of the oil spot d, mm

In the pneumatic test method, the controlled object is filled with air or nitrogen at an overpressure specified in the technical specifications. An indicator substance is applied to the outer surface of the object. In the presence of leaks, the indicator gas penetrates through them, forming bubbles in the indicator substance. According to them, a qualitative assessment of the tightness of the object is made. A qualitative assessment of the overall tightness is carried out by measuring the pressure drop over a certain period of time, followed by conversion to the amount of leakage Y, MPa/s, determined by the formula:

where V is a controlled volume with several leaks, m3;

Change in pressure value, MPa;

Pressure drop measurement time, s

Foam emulsions or glycerin-based masses are used as indicator substances. The components of the mass must be well mixed and whipped on a mixer-type device immediately before application and every hour during application. Glycerin mass can be used for control at ambient temperature from 233 to 303 K.

It should be borne in mind that the observation time should not exceed 5 minutes, since after this time the soap film begins to dry out, lose its elastic properties and separate sections form cavities.

Inspection of the glycerin mass in order to identify gas bubbles, swellings, craters during the control is carried out twice: the first time after 3 - 5 minutes after application, the second - after 20 - 30 minutes.

The dependence of the sensitivity of the pneumatic method on the time of observation of the state of the foam emulsion and the diameter of the bubbles is shown in Figure 1.4.

1 - diameter 2 mm; second diameter - 1 mm

Figure 1.4 - Dependence of the sensitivity - D of the pneumatic method on the time of observation of the state of the foam emulsion and the diameter of the bubbles

In the pneumohydraulic method, the test structure is pressurized with air or nitrogen and immersed in a liquid bath. The depth of immersion in water is 3-5 mm.

Leaks are indicated by the frequency and diameter of gas bubbles that appear at the leaks.

To obtain pure transparent water, aluminum alum is added to it at the rate of 500 g of alum per 3 m3 of water. After thorough mixing and holding for one or one and a half days, the water is ready for use.

The leakage value Y, MPa mm/s is approximately determined by the formula:

where do is the bubble diameter at the moment of separation, mm;

Time to bubble break, s;

Change in pressure, MPa.

The observation time for an individual bubble should not exceed 30 minutes.

With the frequent appearance of bubbles, it is advisable to calculate their number for a certain period of time, expressed by the formula:

where n is the number of bubbles.

Then the amount of leakage is approximately determined by the formula:

With increasing exposure time, the sensitivity of the method sharply increases. So, with an increase in the test time from three to 30 minutes, the sensitivity increases by a factor of 10. Therefore, depending on the required tightness when using the pneumohydraulic method, it is necessary to indicate the time during which the tightness control should be carried out. The dependence of the sensitivity of the pneumohydraulic method on the test time and bubble diameter is shown in Figure 1.5.

1-- diameter 1 mm; 2 - diameter 1.5 mm; 8 - diameter 2 mm; 4 - diameter 3 mm.

Figure 1.5 - Dependence of the sensitivity - D of the pneumohydraulic method on the time t of the check and the bubble diameter

When testing, it should be taken into account that air bubbles may appear on the surface of the controlled structure due to the temperature difference between the surface of the structure and the liquid, or may be brought along with the test object. These bubbles should be removed.

Halogen leak detectors (GTI-2, GTI-3) can be used to check tightness of critical joints. The method involves filling controlled objects or lines with test gas under test pressure. Leakage points are determined using a leak detector equipped with a dial gauge or other secondary alarm. The leak detector has a sensor consisting of a diode with platinum electrodes heated to a temperature of 800 - 900°C. The number of positive ions emitted by an incandescent platinum filament is recorded by a pointer device. In the presence of gases containing halides in the air, there is a sharp increase in the emission of ions. Freon-12 or freon-22 with saturated vapor pressure depending on temperature from 2 to 15 105 N/m2 are used as test gases containing halogens. The overpressure of the test gases must be 5 104 N/m2 lower than the saturated vapor pressure at the corresponding temperature. Freon content in the gas mixture must be at least 10%. Installation for pneumatic testing according to the method of halogen leak detectors, it includes halogen leak detectors GTI-2 or GTI-3, a safety valve, pressure gauges for measuring the pressure of freon and a mixture of gases, a leak detector probe, a system of shut-off valves and secondary indicator devices. The search for leaks is carried out by slowly moving the flow detector over the test area while observing the device and listening to the level of sound signals. The deviation of the pointer of the indicating device and the increase in the frequency of sound indicates the presence of a leak.

Detection of leaks by accumulation method and mass spectrometric method is carried out by helium leak detectors PTI-6 and PTI-7. The operation of these instruments is based on their ability to detect the presence of helium in the test object. The installation for testing the tightness by this method includes a PTI-6 type leak detector, a VPU-1 remote device, vacuum hoses, pressure gauges for measuring the pressure of helium and a mixture of gases, a probe, a mechanical vacuum pump, a safety valve and a system of valves. The control gas is sucked in by the probe through leaky connections into the leak detector, the deviation of the arrow of which and the change in the frequency of sound signals indicate the leakage of the tested area. The accumulation method is based on the penetration of gas from the test volume into a sealed chamber created around this volume, followed by the detection (registration) of the test gas by leak detectors. The sealed chamber can be a metal, plastic or fabric casing with devices for connecting leak detectors. The accumulation method can be used to find leaks during the operation of connections that are not available for direct verification not only by helium leak detectors, but also by other gas analyzers with remote signal transmission devices.

The method of testing the tightness with an indicator mass consists in applying a mass containing a substance sensitive to ammonia from the outside to the test area and feeding it into the test area. test volume of air-ammonia mixture. During depressurization, the indicator mass changes its color. The equipment for checking the tightness of the indicator mass includes a spray gun for applying the mass, an ammonia cylinder, pressure gauges, a valve system and a leak standard, with the corresponding color of the indicator mass.

Signal tightness control methods are based on receiving an electrical signal or a signal from gas analyzers to the monitoring console from sensors that are triggered by direct contact with a liquid penetrating through the seal or from signals that are sensitive to analyzer liquid vapors.

1.5 Automation of tightness control

One of the ways to solve the problem of automating the tightness control of hollow products, for example, shut-off valves, is the development of a multi-position reconfigurable stand for automatic control of the tightness of products with compressed air, according to the manometric method. There are many designs of such devices. Known automatic control of the tightness of products, containing a table with a drive, an elastic sealing element, a rejecting device, a source of compressed gas, a copier and a device for clamping the product.

However, automation of the process is achieved due to the significant complexity of the design of the machine, which reduces the reliability of its operation.

Known machine for monitoring the tightness of hollow products, containing sealing units with leakage sensors, a test gas supply system, mechanisms for moving products and a rejection mechanism.

The disadvantage of this machine is the complexity of the process of monitoring the tightness of products and low productivity.

Closest to the invention is a stand for testing products for tightness, containing a rotor, a drive for its stepping movements, control blocks placed on the rotor, each of which contains a comparison element connected to a rejecting element, an element for sealing a product containing an outlet tube and a drive for its movement, which is made in the form of a copier with the possibility of interaction with the output tube.

However, this device does not allow to increase productivity, as this reduces the reliability of product testing.

Figure 1.6 shows an automated chamber-based leak tester. It consists of a chamber 1, in the cavity of which a controlled product 2 is placed, connected to the air preparation unit 3 through a shut-off valve 4, a membrane separator 5 with a membrane 6 and cavities A and B, a jet element OR-NOT OR 7. Cavity A of the membrane separator 5 is connected to the cavity of the chamber 1, and cavity B through the nozzle 8 - with the output 9 OR of the jet element 7. To its other output 10 NE OR is connected a pneumatic booster 11 with a pneumatic lamp 12. The cavity B is additionally connected by a channel 13 to the control input 14 of the jet element 7, atmospheric channels 15 of which are provided with plugs 16.

The device works as follows. The controlled product 2 is supplied with pressure from the air preparation unit 3, which is cut off by the valve 4 when the test level is reached. to the control input 14 of the jet element 7. Thus, in the absence of leakage from the controlled product 2, the jet element 7 is in a stable state under the action of its own output jet. In the presence of a leak from the product 2 in the internal cavity of the chamber 1 there is an increase in pressure. Under the influence of this pressure, the membrane 6 bends and closes the nozzle 8. The pressure of the air jet at the outlet 9 of the jet element 7 increases. At the same time, the jet disappears at the control input 14, and since the jet element OR - NOT OR is a monostable element, it switches to its stable state when the jet exits through the output 10 NOT OR. In this case, the amplifier 11 is triggered and the pneumatic lamp 12 signals the leakage of the product 2. The same signal can be fed into the jet sorting control system.

This device is built on the elements of jet pneumoautomatics, which increases its sensitivity. Another advantage of the device is the simplicity of design and ease of configuration. The device can be used to control the tightness of gas fittings by compression methods at low test pressure, if the diaphragm seal is used as a sensor connected directly to the controlled product. In this case, the presence of abnormal leakage can be controlled by opening the membrane and nozzle.

Figure 1.6 ? Leak test device

Figure 1.8 shows a device that automates the control of the tightness of pneumatic equipment, for example, electro-pneumatic valves, that is, products similar to the gas fittings considered in the dissertation.

The tested product 1 is connected to the pressure source 2, the electromagnetic bypass valve 3 is installed between the output 4 of the product 1 and the exhaust line 5. The electromagnetic shut-off valve 6 with its input 7 is connected during the test with the output 4 of the product 1, and the output 8 - with the pneumatic input 9 of the converter 10 of the leakage measurement system 11, which is made in the form of a heat flow meter. The system 11 also includes a secondary unit 12 connected to the control input 13 of the converter 10, the pneumatic output 14 of which is connected to the exhaust line 5. The valve control unit 15 includes a multivibrator 16 and a block 17 for delay and pulse formation. One output of the multivibrator 16 is connected to the control input 18 of the shut-off valve 6, the other - to the control input 19 of the valve 3 and the block 17 connected in the control process to the drive 20 of the tested product 1. The calibration line 21 consists of an adjustable throttle 22 and a shut-off valve 23. It connected in parallel to product 1 and serves to configure the device.

Leak control is carried out as follows. When the valve control unit 15 is turned on, a pulse appears at the output of the multivibrator 16, which opens the valve 3 and the block 17 of the delay and pulse formation. The same pulse opens the tested product 1 after a set delay time by applying an electrical signal from block 17 to actuator 20. In this case, the test gas is vented through valve 3 into exhaust line 5. After a time set by multivibrator 16, the pulse is removed from valve 3, closing it, and is fed to the inlet 18 of the shut-off valve 6, opening it. In this case, the gas, the presence of which is due to leakage from the product 1, enters the leakage measurement system 11 and, passing through it, generates in the converter 10 an electrical signal proportional to the gas flow rate. This signal enters the secondary unit 12 of the leak measurement system, in which it is corrected, and the amount of gas flow through the closed test item 1 is recorded.

The disadvantages of this device include the following. The device is designed to control the tightness of gas fittings of only one type, equipped with an electromagnetic drive. At the same time, only one product is controlled, that is, the process is inefficient.

Figure 1.8 shows a diagram of an automated device for monitoring gas leaks using a compression method with a pneumatic-acoustic measuring transducer. The device consists of intermediate blocks and providing control of large leaks (more than 1 /min) and a pneumo-acoustic block for monitoring small leaks (0.005 ... 1) /min. The pneumo-acoustic converter unit has two amplifying manometric stages, consisting of micromanometers 1, 2 and acoustic-pneumatic elements 3, 4, interconnected through a distribution element 5. The measurement results are recorded by a secondary device 6 of the EPP-09 type, connected to the unit through distributor 7. Controlled product 8 is connected to the test pressure source through the shut-off valve K4. The operation of the device is carried out in continuous-discrete automatic mode, which is provided by the logical control unit 9 and valves -. Controlled product 8 with the help of block 9 is connected in series to the blocks and, by the corresponding inclusion of valves and, where the preliminary value of leakage of the test gas is determined. In the case of a small leakage value (less than 1 /min), the product is connected by means of a valve to the pneumo-acoustic unit, where the leakage value is finally determined, which is recorded by the secondary device 6. The device provides gas leakage control with an error of no more than ± 1.5%. Supply pressure and element tube - tube in block 1800 Pa.

This device can be used for automatic control of gas fittings with a wide range of allowable gas leaks. The disadvantages of the device are the complexity of the design due to a large number measuring blocks, as well as the simultaneous control of only one product, which significantly reduces the productivity of the process.

Figure 1.8 Automated device for monitoring gas leaks by compression.

Devices that provide simultaneous testing of several products are promising for monitoring the tightness of gas fittings. An example of such devices is an automatic device for checking the tightness of hollow products, shown in Figure 1.14. It contains a frame 1 fixed on the uprights 2 and covered by a casing 3, as well as a turntable 4 with a drive 5. The turntable is equipped with a faceplate 6, on which eight sockets 7 for products 8 are evenly located. The sockets 7 are made removable and have cutouts 9. Sealing nodes 10 are fixed on the frame 1 with a step twice as large as the pitch of the nests 7 on the faceplate 6. Each sealing unit 10 contains a pneumatic cylinder 11 for moving the product 8 from the slot 7 to the sealing unit and back, on the rod 12 of which a bracket 13 with a sealing gasket 14 is installed In addition, the sealing unit 10 contains a head 15 with a sealing element 16, which is communicated through pneumatic channels with the air preparation unit 17 and with the leakage sensor 18, which is a membrane pressure sensor with electrical contacts. The rejection mechanism 19 is mounted on the frame 1 and consists of a rotary lever 20 and a pneumatic cylinder 21, the rod of which is pivotally connected to the lever 20. Good and rejected products are collected in the appropriate bins. The machine has a control system, the current information about its operation is displayed on the board 22.

The machine works as follows. The controlled product 8 is installed at the loading position in the slot 7 on the faceplate 6 of the turntable 4. The drive 5 performs a step rotation of the table by 1/8 of a full turn at certain time intervals. To control the tightness by actuating the pneumatic cylinder 11 of one of the sealing units 10, the product 8 rises in the bracket 13 and is pressed against the sealing element 16 of the head 15. After that, a test pressure is supplied from the pneumatic system, which is then cut off. The pressure drop in the product 8 is recorded by the leakage sensor 18 after a certain control time, which is set by the table 4 step. Thus, when the table is rotated by one step, one of the following operations is performed at each of its positions: product loading; lifting the product to the sealing unit; tightness control; lowering the product into the socket on the faceplate; unloading of good products; removal of defective products. The latter enter position VIII, while the lever 20 under the action of the pneumatic cylinder rod 21 rotates in the hinge, and with its lower end passes through the cutout 9 of the socket 7, removing the product 8, which falls into the hopper under its own weight. Similarly, suitable products are unloaded at position VII (the unloading device is not shown).

The disadvantages of the device are: the need to lift the product from the faceplate in the sealing unit to control the tightness; the use of a membrane pressure transducer with electrical contacts as a leakage sensor, which has low accuracy characteristics compared to other types of pressure sensors.

The conducted studies have shown that one of the promising ways to improve the manometric method of tightness control is the joint use of bridge measuring circuits and various differential type transducers.

The pneumatic bridge measuring circuit for tightness control devices is based on two pressure dividers (Fig. 1.9).

Fig.1.9 Pneumatic bridge measuring circuit built on two pressure dividers

The first pressure divider consists of a fixed throttle fli and an adjustable throttle D2. The second one consists of a constant choke Dz and an object of control, which can also be conditionally considered a choke D4. One diagonal of the bridge is connected to the test pressure source pk and the atmosphere, the second diagonal is measuring, a PD converter is connected to it. To select the parameters of the elements and adjust the bridge circuit, consisting of laminar, turbulent and mixed chokes, the dependence is used:

where R1 R2, R3, R4 are the hydraulic resistances of the elements D1, D2, D3, D4, respectively.

Given this dependence, the possibility of using both balanced and unbalanced bridge circuits, as well as the fact that hydraulic resistance Since there are few supply channels compared to the resistance of the chokes and therefore it can be neglected, then on the basis of the above pneumatic bridge circuit it is possible to build devices for monitoring the tightness of various objects. At the same time, the control process can be easily automated. It is possible to increase the sensitivity of the device through the use of unloaded bridge circuits, i.e. install transducers having R = in the measuring diagonal. Using the formulas for gas flow in subcritical mode, we obtain dependencies for determining the pressure in the interthrottle chambers of an unloaded bridge.

For the first (upper) branch of the bridge:

for the second (lower) branch of the bridge:

where S1, S2, S3, S4 are the flow area of ​​the channel of the corresponding throttle; Рв, Рн - pressure in the interthrottle chamber of the upper and lower branches of the bridge, рк - test pressure.

Dividing (2) by (3) we get

Dependence (4) implies a number of advantages of using a bridge circuit in devices for tightness control using the manometric method: the pressure ratio in the interthrottle chambers does not depend on the test pressure, which makes it possible to unambiguously determine the amount of leakage; it is not required to cut off the object in the process of control from the source of test pressure. Given that the value of S4 is determined by the total area of ​​defects (leaks) in the controlled object, and therefore is related to the total leakage, then using an adjustable throttle as D2 and selecting the required S2, you can create a constant pressure drop across the throttle D1 and thereby configure the circuit to measure or control various levels of leakage, i.e. significantly expand the range of application of the manometric method of tightness control.

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Checking the tightness of the valves of the shut-off valves installed in series in front of the burner, carried out before ignition of the burner after purging gas outlet. The procedure for checking depends on the degree of automation of the burner and its thermal output and is determined by the project. The check is made by creating a pressure difference on both sides of the valve and monitoring the change in pressure.

Leak testin manual mode(Fig. 109). When checking the tightness of two shut-off valves 1,2 installed in series before the burner, it is necessary to control the pressure between them. To do this, in front of the tap on the safety pipeline 5 a fitting is installed to which a pressure gauge is connected 4.

Work procedure:

Install a pressure gauge on the fitting (the shut-off valve in front of the burner is closed, and the valve on the safety pipeline is open);

Close the valve on the safety pipeline and if installed pressure gauge does not show a change in pressure, then the first shut-off valve along the gas flow is tight;

With shut-off valves in front of the burner closed, open and close the first of them along the gas flow. The pressure gauge will show the gas pressure equal to the pressure in the supply gas pipeline, and if this pressure does not change, then the second shut-off valve along the gas flow and the valve on the safety pipeline are tight. If the valves are not tight, ignition of the burners is prohibited.

The check can also be performed using shut-off valves on the branch, while it becomes possible to check both the valve itself on the branch and the protection slam-shut.

Leak testin automatic mode .

An electric shut-off valve is installed in front of the burner and on the safety pipeline, and instead of a pressure gauge, a tightness control relay (pressure sensor) is installed.

Checking is carried out in the same way as in manual mode. mode(Fig. 109), but with automatic control.

Leak test,when installing a double solenoid valve and a tightness control unit upstream of the burner(Fig. 110). The tightness test is carried out before each burner start-up. If the double solenoid valve is not tight 1 the gas supply is stopped. When not in use, both solenoid valves are closed.

Leak control unit 2 consists of: solenoid valve 3 , internal pump 4 and built-in pressure switch (pressure sensor) 5 , which are sequentially placed on the bypass of the first valve along the gas flow.

Before the tightness test, the gas pressure in front of the double solenoid valve corresponds to the operating pressure ( R slave). At the beginning of the test, the solenoid valve 3 opens and internal pump 4 creates more gas pressure ( R con) in the control area between the solenoid valves, compared to the gas pressure in the outlet gas pipeline. When the required control pressure is reached, the pump switches off. A built-in pressure switch monitors the test area and if the pressure does not change, then both valves of the double solenoid valve are tight.

The furnaces and flues of gasified installations must be ventilated before being put into operation. The ventilation time is determined by calculation and set by the instruction, but not less than 10 minutes, and for automated burners - by the start-up (ignition) program.

Before starting gas into the burner, the tightness of the shut-off valves in front of the burner is checked. The shut-off valve on the gas pipeline in front of the burner opens after ignition of the ignition device.

Starting gas after conservation, repair, seasonal shutdown boiler room or production

The start-up of gas after conservation, repair, seasonal shutdown, as well as the initial start-up of gas after the completion of installation work is carried out by the owner company or specialized organization(according to the contract). The inclusion of gas-using equipment is formalized by an act prepared with the participation of a representative of the operating organization.

Before starting gas and gas networks, it is necessary:

Inspect equipment;

Ventilate the room;

Carry out control pressure testing of gas pipelines;

Remove the plug on the gas pipeline;

Blow gas pipelines with gas;

Take a gas sample and verify that the purge is complete. Purging is gas-hazardous work and is carried out according to a work permit.

Stop boiler room (manufacturing) for conservation (for repairs, seasonal stop)

Before stopping the gas-using installation for repair, its external inspection is carried out in accessible places in order to check the technical condition and clarify the scope of work. The shutdown of gas-using equipment is documented by an act prepared with the participation of a representative of the operating organization.

Operating procedure:

According to the instructions, the equipment is stopped (if necessary, hydraulic fracturing);

Gas pipelines must be disconnected and purged with air. Disconnection of the internal gas pipeline is carried out with the installation of a plug on the gas pipeline behind the shutoff valves. This is a gas-hazardous job and is performed under a work permit.

The shut-off valves on the purge pipelines must remain in the open position after the gas pipeline is turned off.

When the gas supply system or separate gas-using equipment is turned off at a long period or for repair the consumer is advised to notify the supplier at least three days in advance.

The shutoff valve drives are de-energized (fusible links are removed) and locked with locks, the keys to which are handed over by shift, and warning signs are hung on the shutoff valves.

Work performed at withdrawal from the reserve gas-using installation

Conclusion from reserve gas-using installation is a gas-hazardous job and is performed under a work permit or in accordance with the production instructions. The work is carried out by a team of workers consisting of at least two people under the guidance of a specialist:

· take off plug on the way to gas-using installation

The order of turning on the burners of gas-using installations depends on the design of the burners, their location on the gas-using equipment, the type of ignition device, the presence and type of safety and regulation automation.

the sequence of actions for ignition of the burners is determined in accordance with the requirements production instructions developed on the basis of existing norms and instructions.

Start-up of a gas-using plant (see fig. 96) produced according to written order of the person responsible for the safe operation of gas consumption facilities, in accordance with the production instructions . Personnel must be warned in advance by the responsible person about the start time of work.

Before firing up a gas-fired boiler, the tightness of the shut-off valve in front of the burners must be checked in accordance with the regulations in force.

If there are signs of gas pollution in the boiler room, switching on electrical equipment, kindling the boiler, as well as using open fire is not allowed.

Before starting the gas, it is necessary:

Using a gas analyzer or by smell, check the room and make sure that there is no gas contamination;

According to the operational documentation, make sure that there is no prohibition on commissioning;

Inspect the position of the shut-off valves on the gas pipeline to the installation: all valves, except for valves on the purge pipelines, safety pipelines, in front of instrumentation and automation sensors, must be closed;

Make sure that the equipment for burning gas fuel in the furnace, gas ducts, air ducts, shut-off and control devices, control and measuring instruments, headsets, smoke exhausters and fans, as well as check for natural draft;

Make sure that the gates on non-working units are closed;

Blow out the general boiler (general workshop) gas pipeline if the first installation is put into operation;

Turn on the smoke exhauster and the fan, before turning on the smoke exhauster to ventilate the furnace and gas ducts, you must make sure that the rotor does not touch the casing of the smoke exhauster, for which the rotor is turned manually;

gas start:

Open the shut-off valves at the gas pipeline outlet to the unit; fix, in the open position of the slam-shut protection; slightly open the control valve of automatic control by 10%; blow off the outlet to the unit, take a gas sample from the fitting on the purge pipeline;

Make sure that there are no gas leaks from gas pipelines, gas equipment and fittings by washing or using a device (leak detector);

Check the compliance of the gas pressure on the pressure gauge, and when using burners with forced air supply, additionally, the compliance of the air pressure with the set pressure;

Ventilate the furnace, gas ducts and air ducts for 10-15 minutes. and adjust the draft of the melted boiler by setting the vacuum in the upper part of the furnace 20-30 Pa (2-3 mm w.c. st.), and at the level gas burners at least 40-50 Pa(4-5 mm w.c. Art.);

Close the air damper;

Check the tightness of the valves of the shut-off valves installed in front of the burner;

Using a portable gas analyzer, take a sample of air from the top of the furnace, make sure that there is no gas in it.

Ignition of gas burners.

The ignition of gas burners must be carried out by at least two operators.

Manual ignition forced air burners:

Open the tap to the portable igniter and ignite the gas coming out of the igniter;

With stable operation of the igniter, bring it into the furnace to the mouth of the main burner being turned on;

Close the tap on the safety pipeline;

Open the first shut-off valve along the gas flow in front of the burner, and then slowly open the second shut-off valve along the gas flow, letting gas into the burner;

After igniting the gas, slightly increase its supply, making the flame stable;

Open the air damper;

By increasing the gas supply, then air, while controlling the rarefaction in the furnace, bring the burner to the minimum mode according to the regime map;

Remove the igniter from the furnace and close the tap in front of it;

Put the rest of the burners into operation in the same way.

The kindling of the gas-using installation is carried out within the time specified by the instruction.

Protection and automatic control are put into operation according to the instructions.

Information about the work performed is recorded in the journal.

Ignition of injection burners produced in a similar way, and since If there is no fan, the furnace is ventilated without a fan. After igniting the gas, open the air washer,

adjust the vacuum in the furnace and, by increasing the gas supply, while monitoring the vacuum in the furnace, bring the burner to the minimum mode according to the regime map.

Ignition of the burners with the help of the RZZU:

Turn the control key of the gas-using installation to the “Ignition” position. In this case, the RCPD is activated: the time relay is turned on, the gas solenoid valve (PZK) of the igniter opens, the ignition device is turned on (when the igniter flame goes out, the flame control electrode of the RCPD gives an impulse to deflect the high-voltage transformer);

If the igniter flame is stable, close the safety gas valve and fully open the shut-off valve in front of the main burner.

Personnel actions in case of accidents (incidents) on burners

In case of separation, flashover or extinction of the flame during ignition or in the process of regulation, it is necessary:

immediately stop the gas supply to this burner (burners) and the ignition device;

ventilate the furnace and gas ducts for at least 10 minutes;

find out the cause of the problem;

report to the responsible person;

After eliminating the causes of the malfunctions and checking the tightness of the shut-off valve in front of the burner, at the direction of the responsible person, according to the instructions, re-ignite.

Startinto the work of the PIU (GRU) and ignition first burner

a. The hydraulic fracturing is put into operation in accordance with the production instructions.

b. The start-up of the gas-using installation is carried out in accordance with the production instructions.

in. Before ignition of the first burner, the valve on the purge gas line must be open.

Worksperformed at decommissioning of the gas-using installation in reserve

Stopping (see Fig. 96) of gas-using equipment in all cases, except for emergency, is carried out at the written direction of the technical manager, in accordance with the production instructions. If necessary, training of personnel is carried out.

Work order:

Set the operating mode of the burners of the installation to the minimum, according to the regime map;

Lock in the open position of the protection slam-shut;

- for forced burners by giving air, close the air damper in front of the burner, and then the second shut-off valve along the gas flow on the gas pipeline to the burner, and for injection burner close the second shut-off valve along the gas flow to the burner, and then the air washer;

Check visually the cessation of combustion;

Close the control valves and open the valve on the safety pipeline;

Remove other burners of the plant in the same way;

Close the shut-off valves at the outlet to the installation;

Open the purge pipeline and the safety pipeline;

Close slam-shut protection;

Open the air damper (washer) and ventilate the furnace for 10 minutes;

Turn off the fan (if any) and the smoke exhauster, close the air damper (washer) and the gate;

Make a journal entry.

The shutdown of gasified boilers with control and safety automatics and with complex automatics is carried out in accordance with the production instructions.

10.Maintenance and repair

TR 870. Mandatory requirements. installed to gas distribution networks during the operation phase (including Maintenance and current repairs)

To establish the possibility of operation of gas pipelines, buildings and structures and technological devices networks of gas distribution and gas consumption after the terms specified in the design documentation, their technical diagnostics should be carried out.

Deadlines for the further operation of objects of technical regulation of this technical regulation should be established based on the results technical diagnostics .

Dissertation abstract on the topic "Automation of gas valve tightness control based on the manometric test method"

As a manuscript

Barabanov Viktor Gennadievich

AUTOMATION OF TIGHTNESS CONTROL OF GAS FITTINGS ON THE BASIS OF MANOMETRIC TEST METHOD

Specialty 05 13 06 - Automation and control of technological

processes and industries (industry)

dissertations for competition degree candidate of technical sciences

Volgograd - 2005

The work was carried out at the Volgograd State Technical University.

Scientific adviser - doctor of technical sciences, professor

Serdobindev Yuri Pavlovich.

Official opponents: doctor of technical sciences, professor

Chaplygin Eduard Ivanovich.

Candidate of Technical Sciences, Associate Professor Yarmak Vladimir Alekseevich.

Leading organization - Federal State Unitary Enterprise Central Design Bureau "TITAN", Volgograd

Special thanks are expressed to Doctor of Technical Sciences, Professor 1Dipershtein Mikhail Borisovich! for help with the dissertation.

The defense will take place "2.?" June_2005 at hours at a meeting of the dissertation council K 212.028 02 at the Volgograd State Technical University at the address: 400131, Volgograd, Lenina Avenue, 28.

The dissertation can be found in the library of the Volgograd State Technical University.

Scientific secretary of the dissertation council ^^ "Bykov Yu. M.

1 and GENERAL DESCRIPTION OF OPERATION

Relevance of the topic. AT industrial production shut-off, distribution, switching gas valves, the existing regulatory and technical documentation for its acceptance regulates one hundred percent control of the "tightness" parameter reliability, safety and environmental friendliness of all equipment in which it is used.

The development of modern theory and practice of tightness control is the subject of research by Zazhigin A. S., Zapunny A. I., Lanis V. A., Levina L. E., Lembersky V. B., Rogal V. F., Sazhina S. G., Trushchenko A. A., Fadeeva M. A., Feldmana L. S. Analysis of scientific, technical and patent literature showed that nine methods and more than a hundred automated control devices have been developed for testing products for tightness using only a gaseous test environment. However, information about the automation of gas valve tightness control is reflected mainly in patent materials. At the same time, there are no data on their study in the scientific and technical literature. This is due to the fact that there are significant problems and limitations in the development and implementation of means for monitoring the tightness of gas fittings. Most of the high-precision methods and means of control can be applied economically only in a single or small-scale production of large-sized products, in which complete tightness must be ensured. Gas fittings, for example, pneumatic automation equipment, shut-off valves for household stoves, as a rule, are small-sized and leakage of the working medium is allowed in it, and its production volumes are not lower than serial ones. At the same time, the control of the tightness of gas fittings is a laborious, lengthy and complex process, therefore, the choice of a method for testing it for tightness is determined by the possibility of creating high-performance, automated control and sorting equipment on its basis.

Based on the analysis of the main characteristics of gas tightness testing methods, it was concluded that it is promising to use the comparison method and the compression method for automating the tightness control of gas fittings, which implement the manometric test method. In the scientific and technical literature, little attention has been paid to these methods due to the relatively low sensitivity of the manometric test method, however, it is noted that it is most easily automated. At the same time, there are no calculation methods and recommendations for choosing the parameters of tightness control devices made according to the method of comparison with continuous supply of test pressure, which is most consistent with the operation of gas fittings under constant pressure. In this regard, the processing and study of means for monitoring the tightness of gas fittings ^ 4g "^ IP" ZHNTSH!

sorting equipment is an urgent scientific and practical task. The relevance of the work is confirmed by its implementation within the framework of the state budget research project No. 35-53 / 302-99 "Research of the processes of automatic control and management of complex nonlinear systems."

Objective. Development and study of means for monitoring the tightness of gas fittings, for which a certain leakage of the working medium is allowed, and the creation on this basis of high-performance, automated control and sorting devices, as well as the development of recommendations for their calculation and design.

To achieve this goal, the following tasks were solved:

1. Determine the mathematical models for the selected methods for implementing the manometric method of testing for tightness, which will allow establishing and investigating the dependencies for the main parameters of the circuits corresponding to these testing methods and identifying the most promising method for creating gas valve tightness control devices based on it.

2. Conduct a theoretical study of the temporal characteristics of the tightness control circuits for the compression method with test pressure cut-off and the method of comparison with continuous test pressure supply, which will make it possible to determine ways to reduce the duration of control.

3. To carry out the development of an experimental setup and experimental models that will allow us to study accuracy, static and dynamic characteristics tightness control devices.

5. To carry out the development of standard schemes and structures that provide automation of gas valve tightness control using the manometric method, as well as algorithms for the automated calculation of their operating parameters and structural elements.

Research methods. Theoretical studies were carried out on the basis of the laws of gas dynamics, methods of computational mathematics using modern computing facilities. Experimental studies were carried out using statistical processing of measurement results and probabilistic calculations.

Scientific novelty:

Mathematical expressions are proposed that establish the dependence of the tightness control time by the method of comparison with the continuous supply of test pressure on the value of this pressure, the value of the controlled leakage, the design parameters of the reference and measuring lines of the control device under various gas-dynamic modes "p: its" work.

Analytical dependences of the measuring pressure on the value of the controlled leakage, the sensitivity of the tightness control by means of comparison on the value of the test pressure and leakage under various modes of gas flow at the inlet chokes of the lines of the control device are obtained.

Practical value:

The design of the tightness sensor with improved performance for automating the manometric test method, protected by RF patent No. 2156967, and a method for its calculation have been developed.

Designs of an automated multi-position stand for leak control by the method of comparison with continuous supply of test pressure and its main devices are developed, protected by RF patents No. 2141634, No. 2194259; methods of calculation and recommendations for choosing the operating parameters of these structures are proposed.

Algorithms for the automated selection and calculation of parameters of devices designed to automate the control of tightness by the manometric test method are proposed.

The following are submitted for defense:

Temporal characteristics of the tightness control circuit according to the method of comparison with continuous supply of test pressure and the results of their theoretical and experimental research.

The results of a theoretical study of the influence of the test pressure value, the leakage value on the sensitivity of the tightness control according to the method of comparison and comparative evaluation sensitivity of this method with the sensitivity of the compression method of tightness control.

The results of studies of the static, dynamic and accuracy characteristics of the tightness control device by the method of comparison with continuous supply of test pressure.

Mathematical model of physical processes occurring in the tightness sensor with the manometric test method and the method of its calculation

New designs of an automated multi-position stand for tightness control, a tightness sensor with improved performance, providing automation of tightness control using a manometric test method.

Approbation of work. The main results of the dissertation work were reported and discussed at the IV International Scientific and Technical Conference "Technique and Technology of Machine Assembly" (Rzeszow, Poland).

2001), at the All-Russian conference with international participation "Progressive technological processes in mechanical engineering" (Tolyatti, 2002), at the VI traditional scientific and technical conference of the CIS countries "Processes and equipment ecological productions"(Volgograd, 2002), at the International Conference "Actual problems of design and technological support of machine-building production" (Volgograd, 2003), at the Interregional scientific and technical conference "Progressive technologies and automation in industry" ( Volgograd, 1999), at the conferences of young scientists of the Volgograd region (Volgograd, 1997-2004), at the annual scientific conferences of Volgograd State Technical University (1997-2005).

Publication. The main materials of the dissertation were published in 21 publications, including 3 patents of the Russian Federation.

Workload. The dissertation work is presented on 158 pages of typewritten text, illustrated with 44 figures, 7 tables and consists of an introduction, 4 chapters, general conclusions, a list of references from 101 titles and 2 applications on 18 pages

In the introduction, the relevance of the work is substantiated, its content is briefly stated.

The first chapter contains the main terms and definitions used in the study. It is noted that the tightness control of gas fittings operating under pressure is a type of non-destructive test, which consists in measuring or evaluating the total leakage of a test substance penetrating through leaks for comparison with the allowable leakage value. In this study, the objects of testing include industrial pneumoautomatic equipment operating under pressure up to 1.0 MPa, and shut-off valves for household gas stoves operating at pressure up to 3000 Pa. The features of monitoring the tightness of gas fittings are considered. Based on a review of scientific, technical and patent literature, a classification of gas tightness testing methods and means of their implementation is proposed. Reviews and analysis are provided famous designs sensors, automated systems and tightness control devices, which led to the conclusion about the advantages and prospects of using the manometric test method to create automatic control of gas fittings.

On the basis of the foregoing, the goal and objectives of theoretical and experimental research are formulated.

The second chapter deals with issues related to the theoretical study of time dependences and the assessment of sensitivity in the control of tightness by the method of comparison with the continuous supply of test pressure.

The possible modes of flow through tightness in the presence of leakage in the test objects under consideration (gas fittings), which can be laminar and turbulent, are determined.

Figure 1, a shows a diagram explaining the control of tightness by the method of comparison with the continuous supply of test pressure. The reference pressure line contains an input pneumatic resistance (choke) with a conductance of a capacitance with an adjustable volume and an output pneumatic resistance with an adjustable conductivity /2, which are designed to adjust the circuit. The measuring line contains an input pneumatic resistance with a conductivity of /3 and a test object RO, which can be represented as a container with a volume of Va, which has a leak equivalent to the gas flow through the pneumatic resistance with a conductivity of /4. Comparison of pressures in the lines of the circuit is carried out by means of a differential pressure gauge measuring device IU. Each line of the circuit represents a flow capacity.

Graphic dependences of pressure change in the measuring and reference lines of this tightness control scheme are shown in fig. 1b. Behind-

Rice. 1 Tightness control according to the comparison method a - control scheme, b - graphical dependencies.

the dark area, limited by the values ​​of pressure p0 and pr, is the area corresponding to the allowable leakage At the lower boundary of the area (graph 1), a line of reference pressure pe is set. If there is no leakage in the controlled product, then the steady pressure in the measuring line will be equal to the test pressure pp-p0, and it coincides with the upper boundary of the shaded area (graph 2). If the leakage is within the allowable range, then the steady pressure p "u in the measuring line will be within the shaded area (graph 3) the ratio of pb and pu after the control time ¡k can be judged on the amount of gas leakage, and, consequently, on the tightness of the tested product.

Equations for the flow capacity with input and output chokes are obtained, corresponding to:

1 boundary condition for the transition from turbulent to laminar flow at a laminar inlet choke depending on leakage

where Ru is the steady pressure in the flow tank, is the diameter of the inlet throttle;

the boundary condition for the transition from laminar to turbulent flow at the outlet laminar choke depending on the leakage

RLRg-RshG- 3.314-10"(2)

where ¡2 is the length of the output choke;

the boundary condition for the transition from turbulent to laminar flow at the turbulent inlet choke depending on the leakage

2 8.536-10" P0----

The dependencies for calculating the time intervals are determined for various modes of gas flow at the inlet and outlet chokes in the flow tank, on the basis of which, as well as equations (1.3), the dependencies for calculating the control time are obtained, presented in Table 1. The following designations are adopted in these dependencies : pl - boundary pressure for the input throttle; pt2 - boundary pressure for the output throttle

As a result of studying the dependence of r = f(/?)-test time on pressure in the flow tank, it was found that in order to reduce the time of tightness control in circuits made according to the comparison method, it is necessary to: reduce the test pressure; set the volumes of the reference and measuring lines equal and as small as possible; set the duration of control equal to the time to reach a steady pressure in the reference line.

The formulas for determining the sensitivity of Y, the control of tightness by the comparison method are calculated:

in turbulent subcritical mode at the input throttle

\Pm, + P* Po-Pyy, where Ue, p^ - leakage and steady-state pressure in the reference line, pi - pressure corresponding to the sensitivity threshold of the differential manometric device;

in laminar flow regime at the inlet choke

Table 1 Time dependencies for calculating the control time

Pressure ratio options

The sequence of changing flow regimes at the inlet and outlet drosses in the transient process

Time dependencies

Rp > Ru Ru > 2 p, Ra * 4p „ Ra<2рл

1.turbulent supercritical-laminar -> 2.turbulent supercritical-turbulent sub-critical-» Turbulent supercritical-turbulent supercritical-^ 4.turbulent subcritical-turbulent supercritical

■ ar^!^- - - 2ct -

- (0.5yaAt - 1p | D? -2A, y [W) - A 1p | * t - 0.5 | +

to,. .1-^- +<7-9,2 2ЙТ 12

UK, \ 2 , „ , | ?!

inlet throttle bridge in turbulent flow,

*, „ = - H),

/V) >/>y Ru >2/"., L,

1. turbulent supercritical-laminar ->

2 turbulent supercritical - turbulent supercritical -» 3turbulent subcritical - turbulent supercritical

-(0.5 * 4, - 1p | D5- 2kt + A 1p | Lt - 0.5 | -

A 1n|*7 - 2^ + m 1n

Graphical dependences 4 of sensitivity on pressure corresponding to allowable leakage, Y, =f(pd) for the compression- ^ ^ method of tightness control I Uch =F (Rzu) for tightness control according to the method of comparison at various values rp

У„,х10 m/s

A "Ay"

are presented in fig. 3 and at times 3 34 36 38 4

personal p0 - in fig. 4. When compare- Fig 3 Graphs "^ „¿^^ y, ^); ! _

nitential assessment of sensitive- ^ = 3000 Pa, 2- /, n = 2000 Pa. Graphs of the dependence of the tightness control com- uch = Ф^): 3^p = 3000 Pa; 4-Pp = 2000Sh.

Х10"*m" /s/

R>"RF>

using the pressure method and the studied method of comparison, it was established that with similar working 3 5 parameters, the same test pressure and the sensitivity threshold of a manometric 2"5 measuring device, the sensitivity of the control circuits performed 1.5 according to the method of comparison,) higher on average by 40%.

Based on the results of the theoretical 3 3.2 3.4 3.6 3.8

research on the method 4 Graphs of dependence Y„ =<р (рд):1-

bu comparison with continuous supply - ^ - 5 -u "Pa; 2-pn \u003d 4.5-10511a; 3-d, \u003d 4-105Pa.

whose test pressure _ . ., / \ . ,

Graphs 1aniimoS1 and U = F (p ",): 4 p" = 5 -10 Pa, recommendations are proposed for you; ^"

the choice of parameters as the basis for 5 - p0 = 4.5 10 Pa; 6~ro =410 Pa. development of methods for calculating and designing devices for monitoring the tightness of gas fittings according to this method.

The third chapter presents the results of an experimental study of the static and dynamic characteristics of the tightness control circuit according to the comparison method.

The study was carried out on a special laboratory stand, which is equipped with the necessary measuring instruments and provides preparation of compressed air for purity and pressure stabilization in the required range, as well as on an experimental setup that allows simulating tightness control devices and investigating their characteristics. An experimental study was carried out according to the developed methodology using serial samples of shut-off valves for household gas stoves (at low test pressure), pneumatic automation equipment (at medium and high test pressure), as well as leak models.

To test the operability of the tightness control circuit, made by the method of comparison with the continuous supply of test pressure, an experiment was carried out to determine the characteristic p = /(r) - pressure changes in its lines during the control at high (Fig. pressure (Fig. 5.6), which are used in the control of tightness in various gas fittings. The analysis of the obtained graphic dependences showed that the difference between the calculated and experimental pressure values ​​in the line capacitance throughout the entire length of the graphs is no more than 6%.

For practical confirmation of the possibility of using lines with a flow capacity to build tightness control schemes by the method of comparison with a continuous supply of test pressure, their experimental characteristics p = /(?) were determined at various values ​​of air leakage:< Уя < У2. В эксперименте были приняты параметры, соответствующие техническим характеристикам 21 наименования пневмоаппаратуры, приведенным в нормативно-технических материалах. На рис. 6 приведены гра-

theoretical p, kPa -1

theoretical

0 10 20 30 40 50 60 70 /, 0 20 40 60 80 100 120 140 t,s

Fig. 5 Graphs of the characteristic p = f(t) of the flow capacity of the line at test pressure: a - high (0.4 MPa); b - low (15 kPa)

characteristics of the characteristic p = /(r), obtained experimentally in the range of small pressure changes, which corresponds to the working section. Characteristic 1 corresponds to the leakage value U) = 1.12-10-5 m3 / s for suitable products; characteristic 2 - leakage Ud \u003d 1.16-10 "5 m3 / s; characteristic 3 - leakage U2 \u003d 1.23-10 ~ 5 m3 / s for defective products. The value corresponds to the time to reach a steady pressure with leakage U!; value 12 - the time to reach a steady pressure in case of a leak Y d, the value of r3 is the time to reach a steady pressure in case of a leak Y2 Thus, the obtained experimental characteristics p = /(/) (Fig. 6) confirm the conclusions from a theoretical study on the possibility of constructing devices for tightness control scheme of the method of comparison with continuous supply of test pressure.Moreover, in the reference line, the pressure pe corresponding to the allowable leakage for the controlled product (graph 2) must be set; defective product (graph 3) The difference between p and pk is a measure of gas leakage in the controlled product. la should be set equal to the time 12 to reach a steady pressure in the reference line, which will correspond to the required (at the same time, the minimum allowable) control time, since during this time the steady pressure of the measuring line is guaranteed to be reached with a suitable controlled product, in which< Уд. В случае бракованного изделия, у которого У >Ud, the time to reach a steady value will be longer and may not be maintained during operation of the circuit.

On fig. 7 shows the graphs of the characteristic / = / (U) of a line with a flow

capacity. The analysis of the presented graphical characteristics / = /(Y) showed that the difference between the experimental and calculated values ​​of time is no more than 5%.

Rice. 6 Graphs of characteristic p = /(I) 7 Characteristic curves /s

Experimental study of characteristics? = /(K) confirmed the theoretical recommendation that when using the leak control schemes by the comparison method, it is necessary to provide equal volumes of the reference and measuring lines, which reduces the control error. At the same time, the volumes of the lines should be as small as possible (preferably less than 4-10"4m1), which makes it possible to reduce the control time, and, consequently, increase the performance of the control and sorting devices.

On fig. Figure 8 shows graphs of the static characteristic pm - /(Y), obtained at high (/? 0 ~ 0.4 MPa), low (p0 = 15 kPa) test pressure and various diameters of inlet chokes. From the analysis of the obtained ha-

Rice. 8 Experimental characteristics pm = ((U) of the measuring line of the tightness control circuit: a - p0 = 0.4 MPa; b - p0 = 15 kPa

characteristic pku = /(U) follows: with an increase in test pressure p„, the sensitivity of the control circuit decreases, which coincides with the analytical dependencies; with a decrease in the diameter d of the input choke of the measuring line, the sensitivity of the control circuit increases, but the range of controlled leakage decreases, which requires an increase in the test pressure pa. Moreover, the value of pressure p>y in the reference

line, corresponding to the allowable leakage U d, can be set depending on the required sensitivity and operating parameters of the control circuit according to the corresponding experimental graphs pu = /(U). In this case, p>y will coincide with the value of py for a given Y4. Possible options for choosing p.)y for a certain Yp are shown by a dotted line in the graphs of fig. eight.

Experimental verification of performance and evaluation of the accuracy characteristics of the device for monitoring tightness by the method of comparison

la was made on a prototype model of this device. To check the operability of the device for leak control, a study was made of its operating characteristic Δp = fit) - the dependence of the pressure difference in the measuring and about the reference lines on the duration of control at various values ​​of leakage, which is shown in Fig. 9. From the analysis of the obtained graphs of the characteristic Δp = /(0 it follows that for each value

a certain value of the differential pressure Ap is established, corresponding to this particular leakage value, by which it is possible to judge the suitability or defectiveness of the controlled product by the "tightness" parameter.

The error 5K of devices based on the comparison scheme is defined as the total root-mean-square error using the formula

= ^ + 5d2+5y2+5p2+5n2 , (6)

where SM is the error of the differential gauge sensor; Sd - error due to non-identity of the parameters of the input chokes; Sy - error of setting the leakage in the reference line; Sp - error from the instability of the test pressure; Sa is the error from the difference in pneumatic capacities in the measuring and reference lines. The total error of the device calculated by formula (6) does not exceed 3.5%, which is a good indicator of accuracy for the manometric test method.

To assess the reliability of sorting products by parameter

"tightness" on the automatic control and sorting equipment, a device was used to measure the amount of leakage in the shut-off gas valves. As a result of measuring leakage in a batch of 1000 products, experimental data were obtained, presented in the form of a table and a histogram of the distribution of pressure, equivalent to the leakage in stopcocks. Based on the probabilistic calculation of the reliability of sorting products according to the "tightness" parameter, recommendations are proposed that allow, when setting up automated control and sorting devices, to exclude defective products from falling into suitable ones.

The fourth chapter is devoted to the practical implementation of the research results.

A description of typical schemes of automation of the manometric test method and recommendations for the design of automated equipment for tightness control are given.

A design of a tightness sensor with improved performance characteristics has been developed (RF patent No. 2156967), designed to automate the manometric method of leak testing, which makes it possible to take into account the change in the pressure of the test gas in a wide range, as well as to set and monitor the monitoring time. A mathematical model of the physical processes occurring in the sensor during its operation and a method for calculating this sensor are proposed.

To control the tightness of gas fittings, a reconfigurable multi-position automated stand of the original design was developed (RF patents No. The following operations are carried out in automatic mode on the stand: clamping and sealing of the product for the duration of the pressure test; supply of test gas to the product and maintenance of the test pressure at a given level with the required accuracy; exposure of the product under test pressure for a specified time; choice of control device depending on the level of test pressure; docking of the test block with the control module; registration of control results, undocking of the test block and the control module, unfixing of the product; implementation of stepping movement of the rotary table with the required time delay and accuracy.

The method of calculating the parameters of the control modules of the stand, made by the method of comparison with continuous supply of test pressure, is given.

Methods for calculating two variants of sealing seals are proposed, which ensure reliable installation of products on test blocks of an automated stand.

A nomogram is given to determine the performance of an automated leak test bench, which allows, according to the accepted duration of the working cycle, to determine the maximum possible hourly productivity of the bench, to choose a rational number of test blocks and the appropriate table rotation speed.

Algorithms for selecting and calculating the parameters of devices for automating the control of the tightness of products have been developed.

MAIN RESULTS AND CONCLUSIONS

1. It has been established that the creation of automated devices for tightness control, made according to the comparison scheme with continuous supply of test pressure, is a promising direction in solving the problem of automation of acceptance tests in the production of gas fittings. The feasibility and efficiency of using such automated devices is based on their relative simplicity and ease of use, the necessary accuracy characteristics, as well as on the compliance of the control process with these devices with the actual technical conditions for the operation of gas fittings.

2. The time dependencies are determined, the theoretical study of which made it possible to establish that in order to reduce the time of tightness control by the method of comparison with the continuous supply of test pressure, it is necessary: ​​to choose the reference and measuring lines of the control circuit as equal and with the minimum allowable capacitance; reduce the test pressure; set the control duration equal to the time to reach a steady pressure in the reference line.

3. It has been established that at the same test pressures and sensitivity thresholds of the manometric measuring devices used, the sensitivity of the control circuit based on the method of comparison with the continuous supply of test pressure is higher than the sensitivity of the control circuit that implements the compression method.

4. The results of the study of tightness control schemes based on the method of comparison with continuous supply of test pressure revealed a discrepancy between theoretical and experimental characteristics in their working areas of no more than 5%, which made it possible to determine the dependencies for choosing the operating parameters of the corresponding control and sorting devices.

5. An experimental study of a pilot model of a device for checking tightness with a leakage value and a test pressure corresponding to the technical characteristics of serial pneumatic equipment confirmed the possibility of creating automated control and sorting devices based on the comparison method, the error of which does not exceed 3.5%, and the sensitivity corresponds to specified sensitivity range for the manometric leak test method.

10. All methods for calculating devices used to automate leak testing are presented in the form of algorithms, which, together with their "typical diagrams and designs, makes it possible to create CAD equipment for automating the manometric method of leak testing.

1. Barabanov V.G. Development of means of automation of the compression method of tightness control // Progressive technologies and means of automation in the industry: Mater. Interregional. Scientific-technical Conf., 11-14 Sept. 1999 / VolgP U. - Volgograd, 1999. - S. 14-15.

2. Barabanov V.G. Automation of control of tightness of gas valves I IV Regional conference of young researchers of the Volgograd region, Volgograd, December 8-11, 1998: Abstracts / VolgGTU and others - Volgograd, 1999. - P. 95-96.

3. Barabanov V.G. To the question of the study of the manometric method of testing for tightness // Automation of technological production in mechanical engineering: Interuniversity. Sat. scientific tr. / VolgGTU, - Volgograd, 1999. - S. 67-\u003e 73.

4. Barabanov V.G. Ways to automate the control of tightness of gas shut-off equipment // V Regional Conference of Young Researchers "Volgograd Region, Volgograd, November 21-24, 2000: Abstracts / VolgGTU and others - Volgograd, 2001. - P. 67-68.

5. Barabanov V.G. Algorithm for choosing the time characteristic of a differential tightness control circuit // Automation of technological production in mechanical engineering: Interuniversity. Sat. scientific tr. / VolgGTU - Volgograd, 2001.-S. 92-96.

6. Barabanov V.G. Automation of quality control of assembly of gas equipment // Technique and technology of assembly of machines (TTMM-01): Mater. IV Intern. Scientific-technical conf. - Rzeszow, 2001. - S. 57-60.

7. Barabanov V.G. Development and research of tightness sensors with improved performance // VI Regional Conference

young researchers of the Volgograd region, Volgograd, November 13-16, 2001: Abstracts / VolgGTU and others - Volgograd, 2002. - P. 35-36.

8. Barabanov V.G. Performance of automated stands for discrete-continuous leak control // Automation of technological production in mechanical engineering: Interuniversity. Sat. scientific tr. / VolgGTU, - Volgograd, 2002. - S. 47-51.

9. Barabanov V.G. Automation of quality control of assembly of gas fittings according to the parameter "tightness" // Bulletin of the Automechanical Institute: Trudy Vseros. conf. with international, participation. "Progressive processes in mechanical engineering" / Togliatti state. un-t - Tolyatti, 2002. - No. 1.- S. 27-30.

10. Barabanov V.G. Control of gas leakage at industrial and domestic installations // Processes and equipment of environmental production - Materials of the VI traditional scientific. Tech. Conf. CIS countries / VolgGTU and others - Volgograd, 2002. - S. 116-119.

11. Barabanov V.G. Device for automatic clamping and sealing of gas valves during leak testing // Automation of technological production in mechanical engineering: Mezhvuz. Sat. scientific tr. / VolgGTU - Volgograd, 2003. - S. 75-79.

12. Barabanov V.G. Automation of gas leakage control in stop valves // Actual problems of design and technology! Technical support of machine-building production: Mater, Intern. conf., 16-19 Sept. 2003 / VolgGTU and others - Volgograd. 2003. - S. 228-230.

13. Barabanov V.G. Development of automated equipment for monitoring the tightness of gas shut-off equipment // VIII Regional Conference of Young Researchers of the Volgograd Region, Volgograd, November 11-14, 2003: Abstracts of reports / VolgGTU and others - Volgograd, 2004. -S. 90-91.

14. Barabanov V.G. Investigation of the time dependences of the tightness control scheme according to the comparison method. Izv. VolgGTU. Ser. Automation of technological processes in mechanical engineering: Interuniversity. Sat. scientific articles. - Volgograd, 2004. - Issue. 1. - S. 17-19.

15. Diperstein M.B., Barabanov V.G. Peculiarities of constructing automation schemes for control of tightness of shut-off valves // Automation of technological production in mechanical engineering: Mezhvuz. Sat. scientific tr. / Volg GTU. Volgograd, 1997. - S. 31 -37.

16. Diperstein M.B., Barabanov V.G. Application of bridge measuring circuits for automating the manometric method for monitoring tightness. // Automation of technological production in mechanical engineering: Interuniversity. Sat. scientific tr. / VolgGTU - Volgograd, 1998. - S. 13-24.

17. Diperstein M.B., Barabanov V.G. Development of a typical mathematical model of pressure alarms // Automation of technological production in mechanical engineering: Interuniversity. Sat. scientific tr. / VolgGTU - Volgograd, 1999. -S. 63-67.

18. Diperstein M.B. Barabanov V.G. Automation of quality control of gas valves in terms of tightness // Automation of techno-

logical industries in mechanical engineering: Interuniversity. Sat. scientific tr. / VolgGTU-Volgograd, 2000. - S. 14-18.

19. Patent 2141634 RF, MKI v 01 M 3/02. Automated stand for testing products for tightness / V.G. Barabanov, M.B. Diperstein, G.P. Drums. - 1999, BI No. 32.

20. Patent 2156967 of the Russian Federation, MKI in 01 L 19/08. Pressure signaling device / V.G. Barabanov, M.B. Diperstein, G.P. Drums. - 2000, BI K "27.

21. Patent 2194259 RF, MKI v 01 M 3/02. Automated stand for testing products for tightness / V.G. Barabanov, G.P. Drums. - 2002, BI No. 34.

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Introduction.:.

Chapter 1 Analysis of the state of the problem of automation of tightness control and formulation of the research problem.

1.1 Basic terms and definitions used in this study.

1.2 Features of control of tightness of gas fittings. II

1.3 Classification of gas test methods and analysis of the possibility of their application to control the tightness of gas fittings.

1.4 Review and analysis of automatic tightness control by manometric method.

1.4.1 Primary transducers and sensors for automatic tightness control systems.

1.4.2 Automated systems and devices for leak control.

Purpose and objectives of the study.

Chapter 2 Theoretical Study of the Manometric Leak Test Method.

2.1 Determination of gas flow regimes in test objects.

2.2 Study of the compression method of leak testing.

2.2.1 Study of time dependences in the control of tightness by compression method.

2.2.2 Investigation of the sensitivity of tightness control using a compression method with a cut-off.

2.3 Study of the method of comparison with continuous supply of test pressure.

2.3.1 Scheme of tightness control according to the method of comparison with continuous supply of test pressure.

2.3.2 The study of time dependences in the control of tightness by the method of comparison.

2.3.3 Investigation of the sensitivity of the tightness control by the method of comparison with the continuous supply of test pressure.

2.3.4 Comparative assessment of the sensitivity of tightness control by compression method with cut-off and the comparison method.

Conclusions to chapter 2.

Chapter 3 Experimental study of the parameters of tightness control circuits based on the comparison method.

3.1 Experimental setup and research methodology.

3.1.1 Description of the experimental setup.

3.1.2 Methodology for the study of tightness control schemes.

3.2 Experimental study of the tightness control scheme based on the comparison method.

3.2.1 Determination of the characteristic p = /(/) of the lines of the tightness control circuit.

3.2.2 Studies of the temporal characteristics of the lines of the tightness control circuit according to the comparison method.

3.2.3 Study of the static characteristic of the measuring line of the tightness control circuit.

3.3. Experimental study of a device for tightness control, made on the basis of the comparison method.

3.3.1 Investigation of a model of a device for monitoring tightness with a differential pressure gauge.

3.3.2 Evaluation of the accuracy characteristics of devices for tightness control, made according to the comparison scheme.

3.4 Probabilistic assessment of the reliability of sorting products in the control of tightness by the method of comparison.

3.4.1 Experimental study of the distribution of the pressure value equivalent to the leakage of test gas in a batch of products.

3.4.2 Statistical processing of the results of the experiment to assess the reliability of sorting.

4.3 Development of leakage sensors with improved performance.

4.3.1 Leakage sensor design.

4.3.2 Mathematical model and algorithm for calculating the tightness sensor.

4.4 Development of an automated test bench for tightness control

4.4.1 Design of the automated multi-position stand.

4.4.2 Selection of parameters for tightness control schemes.

4.4.2.1 Method for calculating the parameters of the tightness control circuit according to the compression method with a cut-off.

4.4.2.2 Method for calculating the parameters of the tightness control circuit according to the comparison method.

4.4.3 Determination of the performance of an automated test bench for tightness control.

4.4.4 Determining the parameters of seals for an automated stand.

4.4.4.1 Calculation procedure for a sealing device with a cylindrical cuff.

4.4.4.2 Method for calculating the mechanical ring seal.

Introduction 2005, dissertation on computer science, computer technology and management, Barabanov, Viktor Gennadievich

An important problem in a number of industries is the increased requirements for the quality and reliability of manufactured products. This causes an urgent need to improve existing, create and implement new methods and means of control, including tightness control, which refers to flaw detection - one of the types of quality control systems and products.

In the industrial production of shut-off and distribution valves, in which the working medium is compressed air or another gas, the existing standards and technical conditions for its acceptance regulate, as a rule, one hundred percent control of the "tightness" parameter. The main unit (working element) of such fittings is a movable pair "plunger-body" or a rotary valve element, which operate in a wide pressure range. Various sealing elements and lubricants (sealants) are used to seal gas fittings. During the operation of a number of gas valve structures, a certain leakage of the working medium is allowed. Exceeding the permissible leakage due to low-quality gas fittings can lead to incorrect (false) operation of the production equipment on which it is installed, which can cause a serious accident. In domestic gas stoves, an increased leakage of natural gas can cause a fire or poison people. Therefore, exceeding the allowable leakage of the indicator medium with appropriate acceptance control of gas fittings is considered a leak, i.e., a product defect, and the exclusion of marriage increases the reliability, safety and environmental friendliness of the entire unit, device or device in which gas fittings are used.

Checking the tightness of gas fittings is a laborious, lengthy and complex process. For example, in the production of pneumatic mini-equipment, it takes 25-30% of the total labor input and up to 100-120% of the assembly time. This problem can be solved in large-scale and mass production of gas fittings by using automated methods and control tools, which should provide the required accuracy and performance. In real production conditions, the solution of this problem is often complicated by the use of control methods that provide the necessary accuracy, but are difficult to automate due to the complexity of the method or the specifics of the test equipment.

About ten methods have been developed for testing the tightness of products using only a gaseous test medium, for the implementation of which over a hundred different methods and means of control have been created. Zazhigin A.S., Zapunny A.I., Lanis V.A., Levina L.E., Lembersky V.B., Rogal V.F., Sazhin S.G. are devoted to the development of modern theory and practice of tightness control. , Trushchenko A. A., Fadeeva M. A., Feldmana L. S.

However, there are a number of problems and limitations in the development and implementation of tightness control tools. Thus, most high-precision methods can and should be applied only to large-sized products, in which complete tightness is ensured. In addition, restrictions of an economic, constructive nature, environmental factors, and safety requirements for maintenance personnel are imposed. In serial and large-scale production, for example, of pneumatic automation equipment, gas fittings for household appliances, in which a certain leakage of the indicator medium is allowed during acceptance tests and, consequently, the requirements for control accuracy are reduced, the possibility of its automation and provision on this basis of high performance of the appropriate control and sorting equipment, which is necessary for 100% product quality control.

An analysis of the features of the equipment and the main characteristics of the gas tightness testing methods most used in the industry made it possible to conclude that it is promising to use the comparison method and the compression method that implement the manometric method for automating the control of gas valve tightness. In the scientific and technical literature, little attention has been paid to these test methods due to their relatively low sensitivity, however, it is noted that they are most easily automated. At the same time, there are no recommendations on the selection and calculation of the parameters of tightness control devices, made according to the comparison scheme with a continuous supply of test pressure. Therefore, research in the field of gas dynamics of blind and flow tanks, as elements of control circuits, as well as gas pressure measurement technology as the basis for creating new types of transducers, sensors, devices and systems for automatic control of the tightness of products, promising for use in the production of gas fittings.

In the development and implementation of automated devices for monitoring tightness, an important question arises about the reliability of the control and sorting operation. In this regard, a corresponding study was carried out in the dissertation, on the basis of which recommendations were developed that allow, with automatic sorting by the "tightness" parameter, to exclude the ingress of defective products into suitable ones. Another important issue is to ensure the desired performance of automated equipment. The dissertation gives recommendations on the calculation of the operating parameters of an automated test stand for tightness control, depending on the required performance.

The work consists of an introduction, four chapters, general conclusions, a list of references and an appendix.

The first chapter discusses the features of monitoring the tightness of gas fittings, which allow a certain leak during operation. The review of methods of gas tightness testing, classification and analysis of the possibility of their application for automating the control of gas fittings is given, which made it possible to choose the most promising - the manometric method. Devices and systems that provide automation of tightness control are considered. The goals and objectives of the study are formulated.

In the second chapter, two methods of tightness control that implement the manometric method are theoretically investigated: compression with pressure cut-off and the method of comparison with continuous supply of test pressure. The mathematical models of the studied methods were determined, on the basis of which their time characteristics and sensitivity were studied under various gas flow regimes, different line capacitances and pressure ratios, which made it possible to identify the advantages of the comparison method. Recommendations on the choice of parameters for tightness control schemes are given.

In the third chapter, the static and temporal characteristics of the lines of the tightness control circuit are experimentally investigated by the method of comparison at various values ​​of leakage, line capacitance and test pressure, and their convergence with similar theoretical dependencies is shown. The operability was experimentally checked and the accuracy characteristics of the device for tightness control, made according to the comparison scheme, were evaluated. The results of evaluating the reliability of product sorting by the "tightness" parameter and recommendations for setting up the corresponding automated control and sorting devices are given.

In the fourth chapter, a description of typical schemes of automation of the manometric test method and recommendations for the design of automated equipment for tightness control are given. The original designs of the tightness sensor and the automated multi-position stand for tightness control are presented. Methods for calculating the tightness control devices and their elements, presented in the form of algorithms, as well as recommendations for calculating the operating parameters of the control and sorting stand, depending on the required performance, are proposed.

The Appendix presents the characteristics of gas tightness testing methods and time dependences for possible sequences of changing gas flow regimes in a flow tank.

Conclusion thesis on "Automation of gas valve tightness control based on the manometric test method"

4. The results of the study of tightness control schemes based on the method of comparison with continuous supply of test pressure revealed a discrepancy between theoretical and experimental characteristics in their working areas of no more than 5%, which made it possible to determine the dependencies for choosing the operating parameters of the corresponding control and sorting devices.

5. An experimental study of a pilot model of a device for monitoring tightness at a leak rate and test pressure corresponding to the technical characteristics of serial pneumatic equipment confirmed the possibility of creating automated control and sorting devices based on the comparison method, the error of which does not exceed 3.5%, and the sensitivity corresponds to specified sensitivity range for the manometric leak test method.

6. A method for probabilistic assessment of the reliability of sorting products by the "tightness" parameter is determined, and on its basis, recommendations are proposed for setting up automated control and sorting devices based on the comparison method.

7. Typical schemes of automation of the manometric method of testing for tightness and recommendations for the design of automated equipment for tightness control are proposed.

8. The design of the tightness sensor with improved performance, protected by RF patent No. 2156967, has been developed, a mathematical model and a method for its calculation have been proposed, which makes it possible to evaluate the characteristics of sensors of this type at the design stage.

9. The design of an automated multi-position stand for tightness control, protected by RF patents No. 2141634, No. 2194259, and recommendations for determining the operating parameters of the stand, depending on the required performance, have been developed; a method for calculating the leak control device by the method of comparison with a continuous supply of test pressure, which is used in the design of the stand, and methods for calculating two types of sealing devices that ensure reliable installation of the tested products in the working positions of the stand, which expands the possibilities of designers of automated equipment for leak control, are proposed.

10. All methods for calculating devices used to automate leak testing are presented in the form of algorithms, which, together with their typical schemes and designs, makes it possible to create CAD equipment for automating the manometric method of leak testing.

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