How to choose the right technical pressure gauge.
Each vessel or pipeline must be equipped with pressure gauges. The pressure gauge is installed on the vessel fitting or pipeline between the vessel and the stop valves. Pressure gauges must have an accuracy class of at least: 2.5 - at a vessel operating pressure of up to 2.5 MPa (25 kgf / cm2), 1.5 - at a vessel operating pressure above 2.5 MPA (25 kgf / cm2). The pressure gauge must be selected with such a scale that the working pressure measurement limit is in the second third of the scale. On the pressure gauge scale, the owner of the vessel must put a red line indicating the working pressure in the vessel. Instead of a red line, it is allowed to attach a metal plate to the pressure gauge case, painted red and tightly adjacent to the pressure gauge glass. The pressure gauge must be installed so that its readings are clearly visible to the operating personnel. The diameter of the case of pressure gauges installed at a height of up to 2 meters from the level of the observation site for them must be at least 100 mm, at a height of 2 to 3 meters - at least 160 mm. Installation of pressure gauges at a height of more than 3 meters from the level of the site is not allowed.
The pressure gauge is not allowed for use in cases where:
there is no seal or brand with a mark on the verification;
verification period is overdue;
the arrow, when it is turned off, does not return to the zero reading of the scale by an amount exceeding half the permissible error for this device;
the glass is broken or there is damage to the case, which may affect the correctness of its readings.
Verification of pressure gauges with their sealing or branding should be carried out at least once every 12 months. In addition, at least once every 6 months, an additional check of working pressure gauges with a control pressure gauge should be carried out at the facility with the results recorded in the log of control checks.
9. Technological scheme of the hydrogen sulfide stripping column UPVSN (DNS) - description.
The hydrogen sulfide stripping column is designed to remove hydrogen sulfide from oil. The meaning of the process lies in the fact that the gas, purified from hydrogen sulfide upon repeated contact, hydrogen sulfide containing oil, releases hydrogen sulfide from oil. The better the contact of gas with oil, the better the purification of oil.
Description of the technological scheme:
Hydrogen sulfide containing oil, after PTB-10 No. 1,2,3 furnaces, is fed into the upper part of the K-1 column. To ensure good contact between oil and gas, the cavity of the column is filled with special nozzles of the ABP type (see figure), through which oil flows to the lower part of the column.
To prevent gas leakage through the bottom of the column, it is necessary to maintain a certain level of liquid in the lower part of the column, it is maintained automatically by an electric valve.
1) maintain an appropriate ratio of gas to oil. If the electric valve is fully open, but there is not enough gas, then the MUSO does not provide the necessary amount of gas, it is necessary to allow the MUSO and warn the responsible engineers of the shop.
2) if the level in the column is higher than the maximum and there was a sharp increase in pressure in the column, it means that the column was filled with oil and oil entered the heat exchanger. It is necessary to immediately reduce the oil consumption on N-1, N-2, check the electric valve (whether it is closed), slightly open the bypass on the electric valve.
10. Level gauge U-1500 - purpose, device, principle of operation.
The U1500 level gauge is designed for automatic remote determination of the liquid level (or phase separation level) in a tank via two independent channels (sensors) and displaying the measurement results on a digital display with alternate indication for each channel, as well as outputting the measurement result in the form of an analog current signal (only on the first channel) and as a digital signal on a serial channel in the B5-485 standard for use in control, signaling and registration systems.
In addition, it is possible to set and continuously monitor two level values: the upper signaled level (VSU) and the lower signaled level (LSL), upon reaching which sound and light alarms are triggered, as well as the corresponding relays and optocoupler are activated.
In the process of operation, continuous monitoring of the operability of sensors and communication lines is carried out with the corresponding light and sound signaling of failures for each channel.
Measurement range, m 0.2..15
Measurement resolution, cm 1
Communication line length, m, no more than 1000
Type of cable coaxial (RK-50, RK-75)
- The procedure for preparing the device for repair.
For independent work on maintenance of vessels operating under pressure, operators of the OOU are allowed:
Not younger than 18 years old, persons not younger than 21 years old are allowed in deposits with a high content of hydrogen sulfide;
Having a medical certificate on suitability for work in insulating type breathing apparatus;
Trained, knowledge tested and certified for the right to service pressure vessels;
Passed an introductory briefing, a briefing at the workplace and a knowledge test on the specifics of the work performed, including electrical safety, with the assignment of the II qualification group; - have passed classes in fire-technical minimum and have a certificate in fire safety.
Before starting work, it is necessary to check and put in order overalls, safety shoes and other personal protective equipment (gas mask filtering insulating type, hose gas mask PSh-1 or PSh-2, safety belt, gloves, ladders, rescue ropes, helmets, dielectric gloves). All protective equipment must be checked and have appropriate documentation of the control carried out. Before carrying out work on maintenance of the vessel (audit of the control panel, internal inspection of the vessel), a work permit for carrying out gas hazardous work must be issued. Before carrying out an internal inspection, the apparatus must be stopped, the pressure must be released to atmospheric pressure, freed from the medium filling it, and plugs must be installed in the flange connections of the inlet and outlet pipelines. Then steam the apparatus for at least 24 hours, drain the condensate into the sewer, then cool it to a temperature not exceeding 30 degrees Celsius, install a plug on the drain valve. Take an analysis of the air environment for gas contamination in several places inside the apparatus. If the gas content exceeds the MPC, the apparatus is steamed again, then the air environment is analyzed. Before starting gas hazardous work, the person responsible for their implementation must interview each performer about his well-being. It is only possible to enter a gas hazardous area with the permission of the person responsible for carrying out the work and in the appropriate protective equipment worn outside the danger zone.
0.6; 1.0; 1.6; 2.5; 4.0
6 10 16 25 40
60 100 160 250 400
600 1000 1600 kgf/cm 2
Ticket number 7
Pressure gauges with a single-coil tubular spring OBM
OBM-100; OBM-160 - general purpose pressure gauges;
100, 160 - body diameter in mm.
These devices are the most common. Their advantages: simplicity of the device; reliability in work; compactness; large measuring range; low cost.
The principle of operation is based on balancing the measured pressure with the force of elastic deformation of the spring.
Under the action of pressure, the cross section of the tube tends to take a round shape, as a result of which the tube unfolds by an amount proportional to the pressure. When the pressure is reduced to atmospheric, the tube returns to its original shape.
The sensitive element (SE) of the pressure gauge is a single-turn tubular spring, which is a tube bent around the circumference with an oval-shaped cross section. The tubular spring is made of bronze, brass or steel, depending on the purpose of the device and the measurement limits.
One end of the tube is soldered into a holder with a fitting, which is designed to connect the pressure gauge to a pressure source.
The other end of the tube is free, hermetically closed.
A rod is attached to the free end of the tubular spring. The other end of the rod is connected to the shank of the gear sector. The shank of the toothed sector has a slot (scene) along which the end of the rod can be moved when adjusting the device.
The toothed sector is held on the axis and engages with a small gear called a pinion. It is rigidly mounted on the axis of the arrow.
To eliminate the "dead motion" of the arrow, caused by the presence of backlash in the connections, the pressure gauge is equipped with an elastic hair of a spiral shape, made of phosphor bronze. The inner end of the hair is attached to the axis of the arrow, and the outer end to the fixed part of the device.
Under the action of pressure inside the tube, its free end moves and pulls the rod along with it. At the same time, the toothed sector and the tribka rotate, on the axis of which the arrow is mounted. The end of the arrow shows the value of the measured pressure on the scale of the device.
Rice. 2.4 Spring gauge:
1 - nipple;
2 - holder;
3 - (body) board;
5 - gear (tribe);
6 - spring;
7- Bourdon tube;
8- sealed end;
9 - gear sector;
10 - arrow;
Depending on the purpose, pressure gauges have the following markings:
MTP, MVTP - vibration-resistant;
SV - ultrahigh pressure;
MTI, VTI - accurate measurements (accuracy class 0.6; 1.0);
MO, VO - exemplary (class 0.4);
MT, MOSH, OBM - technical.
Ticket number 9
Selection of pressure gauges according to the permitted
operating pressure
The scale of the manometer must be marked with a red line corresponding to the permitted working pressure.
The red line is placed on 2/3
manometer scales.
Rice. 2.5. red line gauge
Ticket number 10
If you need to select a pressure gauge according to the permitted pressure P razr, then 
and select the nearest higher value from the gauge series.
Example:
Select the scale of the pressure gauge, if R razr = 10 kgf / cm 2
There is no such scale, so the scale is selected from 0 to 16 kgf / cm 2 .
Ticket number 11
Electrocontact pressure gauges
They have an electrical contact device that is triggered when a predetermined pressure is reached and sends a pulse to signaling devices.
The manometer is supplied with two control arrows with contacts. The control arrows are set to "max" and "min" pressure, and the arrow of the device, which carries the contacts, moving, gives a signal if the pressure has reached the values set by the control arrows.
EKM - electrocontact pressure gauge (used to signal parameters in explosion-proof rooms);
EKV - electrocontact vacuum gauge;
VE-16rb - electrocontact pressure gauge, explosion-proof design.
Ticket number 12
Pressure control circuit
Some conditions for the designation of instrumentation and automation:
- a device installed locally (on a pipeline, apparatus);
- a device installed on a shield, remote control;
Р – pressure;
I - indication;
R - registration (record);
T - remote transmission;
Each vessel and separate cavities with different pressures must be equipped with direct-acting pressure gauges. The pressure gauge is installed on the vessel fitting or pipeline between the vessel and the stop valves.
Pressure gauges must have an accuracy class of at least: 2.5 - at a working pressure of the vessel up to 2.5 MPa (25 kgf / cm2), 1.5 - at a working pressure of the vessel above 2.5 MPa (25 kgf / cm2).
The pressure gauge must be selected with such a scale that the working pressure measurement limit is in the second third of the scale.
On the pressure gauge scale, the owner of the vessel must put a red line indicating the working pressure in the vessel. Instead of a red line, it is allowed to attach a metal plate to the pressure gauge case, painted red and tightly adjacent to the pressure gauge glass.
The pressure gauge must be installed so that its readings are clearly visible to the operating personnel.
The nominal diameter of the case of pressure gauges installed at a height of up to 2 m from the level of the observation site for them must be at least 100 mm, at a height of 2 to 3 m - at least 160 mm.
Installation of pressure gauges at a height of more than 3 m from the level of the site is not allowed.
Between the pressure gauge and the vessel, a three-way valve or a device replacing it should be installed, which allows periodic checking of the pressure gauge using a control one.
If necessary, the pressure gauge, depending on the operating conditions and the properties of the medium in the vessel, must be equipped with either a siphon tube, or an oil buffer, or other devices that protect it from direct exposure to the medium and temperature and ensure its reliable operation.
On vessels operating under pressure above 2.5 MPa (25 kgf / cm2) or at an ambient temperature above 250 ° C, as well as with an explosive environment or harmful substances of the 1st and 2nd hazard classes according to GOST 12.1.007-76 instead of a three-way valve, it is allowed to install a separate fitting with a shut-off device for connecting a second pressure gauge.
On stationary vessels, if it is possible to check the pressure gauge within the time limits established by the Rules by removing it from the vessel, the installation of a three-way valve or a device replacing it is optional.
Pressure gauges and pipelines connecting them to the vessel must be protected from freezing.
The pressure gauge is not allowed for use in cases where:
· there is no seal or brand with a mark on the verification;
verification period has expired;
· the pointer, when it is turned off, does not return to the zero reading of the scale by an amount exceeding half of the permissible error for this device;
The glass is broken or damaged, which may affect the correctness of its readings.
Verification of pressure gauges with their sealing or branding should be carried out at least once every 12 months. In addition, at least once every 6 months, the owner of the vessel must carry out an additional check of the working pressure gauges with a control pressure gauge, recording the results in the log of control checks. In the absence of a control pressure gauge, it is allowed to carry out an additional check with a tested working pressure gauge that has the same scale and accuracy class with the tested pressure gauge.
On the scale of instruments intended for measuring pressure, a red line must be applied without fail. What does she mean? For what purposes is it established?
On the territory of our country, there are many regulatory documents that regulate the rules for the operation of pipelines, tanks, etc. And, in almost every document, it is indicated that a red strip must be applied on the pressure gauge scale. Its purpose is to indicate the limit values of the measured parameter. Instead of drawing a line on the scale, it is permissible to use other marking methods, for example, a red metal flag. This is necessary in order to be able to observe the controlled parameter from afar.
In accordance with the safety rules in the oil and gas industry, it is expressly stated that pressure gauges located at a height of more than two meters must be affixed with such a mark.
The technical pressure gauge in its design is classified as a tubular-spring mechanism. Structurally, it consists of:
- corps;
- riser;
- hollow curved tube;
- arrow(s);
- sector with applied teeth;
- gears;
- springs.
The key part is the tube. Its lower end is connected to the hollow part of the riser. The upper end of the tube is sealed and can move, while it transmits movement to the sector installed on the riser, and at the end of this mechanism, a gear is installed with an arrow attached to it. After turning on the pressure gauge to the tank or pipeline on which the pressure will be measured. The pressure, which is concentrated inside the pressure gauge, through the mechanism described, tries to straighten the tube. The movement of the tube, as a result, leads to the movement of the arrow. After all this, the arrow shows the measured pressure.
How to use a technical manometer
Service of the technical pressure gauge consists of several simple operations. In particular, this is a check of its performance, removal of information from the measuring scale, pressure supply, zeroing. If the liquid in the device is contaminated, then it must be changed, otherwise, this will lead to distortion of the measurements. When carrying out maintenance, it is necessary to check the presence of a sufficient amount of working fluid. If its level is insufficient, it must be topped up, guided by the requirements of the operating instructions for the measuring device.
All pressure measuring devices must be leveled to measure. Otherwise, the readings will vary.
Most inclined instruments have a built-in device for leveling the pressure gauge. The device can be rotated until the bubble in the level takes the correct position at the zero mark.
Measuring pressure range
In practice, the following types of pressure are divided: absolute, barometric, excess, vacuum.
Absolute is a measure of pressure measured relative to full vacuum. This indicator cannot be lower than zero.
Barometric is atmospheric pressure. Its level is influenced by the height above zero (sea level). At this altitude, it is generally accepted that the pressure is 760 mm R.S. for pressure gauges, this value is zero.
Gauge pressure is a measurement between absolute and bromometric pressure. This is especially true when the absolute pressure is in relation to the barometric.
Vacuum is a value that shows the difference between absolute and barometric pressure when the barometric pressure is exceeded.
That is, the vacuum pressure cannot exceed the barometric pressure. In other words, instruments for measuring vacuum measure its discharge.
Pressure gauges. Pressure units
Manometers are designed to measure pressure, vacuum. Pressure gauges installed on the HP, TP (pipelines), devices show excess pressure. To obtain absolute pressure, it is necessary to add 1 (atmospheric pressure) in kgf / cm2 to the number of excess pressure taken from the pressure gauge.
Pressure gauges installed in gas supply systems are divided into:
· Liquid;
· Spring;
· Electrocontact;
· Pressure vacuum meters.
Pressure vacuum meters, designed to measure not only Rizb, but also to measure rarefaction, i.e. pressure is less than atmospheric.
Liquid manometers. They are designed to measure small pressures.
The zero mark of the scale is in the middle. One end of the tube freely communicates with the atmosphere. The second - through a rubber hose is connected to the measured medium HP. The tube up to the "0" mark is filled with water (tinted); alcohol, antifreeze, etc. can be used, but it is necessary to correct for density, i.e. bring its density to the density of water.
To take readings fromU-shaped liquid manometer, it is necessary to add the decrease in level in one knee with its increase in the other.
Spring gauges. They are designed to measure all pressures. The spring pressure gauge consists of a round box - a body in which there is a bent brass tube of oval section. One end of the tube is sealed, and the other is connected to the measured medium through a three-way valve. The sealed end of the tube (Bourdon), through the lever, is connected to the gear sector, coupled with the gear, on the axis of which there is an arrow.
The pressure gauge has a scale (dial), on which the following data is printed:
1. GOST manometer;
2. Case size (100, 160mm);
3. Release date;
4. Pressure gauge accuracy class;
5. Accuracy expressed in %;
6. Pressure gauge scale units (MPa, kgf/cm, bar, kPa, Pa);
7. Limit of pressure measurement by this manometer;
8. Type (MTP, OBM, MO, etc.).
Electrocontact pressure gauges. This is a variation of the conventional spring pressure gauge. (EKM).
In addition to the black indicating arrow, EKM has one or more light contact arrows. Voltage is applied to the ECM through a special device.
EKM work in the system of automation, safety and regulation.
EKM are installed on the drums of boilers, in front of the burners of the boilers for pressure control, on the burner strictly according to the project.
Gauge faults:
· There is no stigma or seal of the sovereign.
· The state verification of the pressure gauge has expired.
· The glass is broken, the body is dented, the glass is dirty.
· There may be gas leaks through a leaky Bourdon tube on the pressure gauge.
· When landing on "0" the arrow does not sit on the zero mark.
· When checking the working pressure gauge, the control readings do not match.
The serviceability and correctness of the pressure gauge readings is checked at the following times:
1. Once a year - state verification in the laboratory of the state verification.
2. At least once per shift - landing on "0".
3. At least 1 time in 2 months - check with a control pressure gauge.
The working position of the pressure gauge needle should be in the second third of the scale.
