REGULATORY DOCUMENTS FOR THERMAL POWER PLANTS AND BOILER HOUSES

METHODOLOGICAL INSTRUCTIONS ON
PRESERVATION OF HEAT-MECHANICAL
EQUIPMENT USING
FILM-FORMING AMINES

RD 34.20.596-97

INDUSTRY GUIDANCE DOCUMENT

This Industry Guidance Document:

Designed in accordance with the requirements of the Rules for Technical Operation power stations and networks of the Russian Federation (RD 34.20.501-95);

It applies to the main thermal mechanical equipment of thermal power plants and establishes the method of conservation and the sequence of operations for its implementation during various types of shutdowns (scheduled and emergency shutdowns, shutdowns for current, medium and major repairs, shutdowns in reserve for a certain and indefinite period);

Designed for operating personnel of thermal power plants, hot water boilers, personnel of commissioning enterprises, manufacturing plants power equipment, design and research organizations.

1. GENERAL PROVISIONS

1.1. Preservation of thermal power equipment (boilers, turbines, heaters) using amine-containing compounds is carried out to protect against atmospheric corrosion of steam and water tracts in the following cases:

Short-term planned or emergency shutdowns;

Shutdowns for current, medium or major repairs:

Transfer of equipment to the reserve;

When decommissioning equipment for a long period of time.

1.2. The protective effect is provided by creating a molecular adsorption preservative film on the internal surfaces of the equipment, which protects the metal from the effects of oxygen, carbon dioxide, and other corrosive impurities and significantly reduces the rate of corrosion processes.

1.3. The choice of conservation process parameters (time characteristics, preservative concentrations, etc.) is carried out on the basis of a preliminary analysis of the state of the power unit equipment (specific contamination of surfaces, composition of deposits, water chemistry, etc.).

1.4. Concomitant partial washing of steam-water paths of equipment from iron- and copper-containing deposits and corrosive impurities is carried out during conservation.

1.5. The quality of conservation is assessed by the value of the specific sorption of the preservative on the surface of the equipment, which should not be lower than 0.3 µg/cm 2 . If possible, gravimetric studies of witness samples are carried out and electrochemical tests of cut samples are performed.

1.6. The advantages of this conservation technology are as follows:

Reliable protection of equipment and pipelines is provided, including in hard-to-reach places and stagnant zones, from leakage parking corrosion for a long period of time (for a period of at least 1 year);

Significantly reduces equipment start-up time. operation;

It is possible to provide corrosion protection not only for specific equipment individually, but also for the entire set of this equipment, i.e. the energy block as a whole;

The corrosion-protective effect is preserved after drainage and opening of the equipment, as well as under a layer of water;

No special measures are required for depreservation, a quick re-commissioning of both individual elements and all mothballed equipment as a whole is ensured;

Allows you to carry out repair and maintenance work with the opening of equipment;

Conservation is carried out without significant time labor, heat and water consumption;

Ensuring environmental safety;

Avoid the use of toxic preservatives.

1.7. On the basis of these guidelines, each power plant should draw up and approve a working instruction for the conservation of equipment with a detailed indication of measures to ensure strict implementation of the conservation technology and the safety of the work being carried out.

2. DETAILS ABOUT THE PRESERVATIVE

2.1. For conservation, the preservative flotamin (technical stearic octadecylamine), produced by the domestic industry, is used, which is one of the highest film-forming aliphatic amines. This is a white waxy substance, the main properties of which are given in TU-6-36-1044808-361-89 dated 04/20/90 (instead of GOST 23717-79). Along with the domestic preservative, a foreign analogue of ODACON (ODA condensing) of a high degree of purification, corresponding to the European standard DIN EN ISO 9001:1994 with the following main parameters, can be used:

2.2. Preservative sampling and acceptance rules must be carried out in accordance with GOST 6732 (organic dyes, intermediate products for dyes, textile auxiliaries). The indicators of technical requirements provided for by the technical specifications correspond to the world level and the requirements of consumers.

2.3. Maximum allowable concentration of flotamin in the air working area should not exceed 1 mg/m 3 (GOST 12.1.005-88).

5.1. Preservation with calcium hydroxide solution

5.1.1. The method is based on highly effective inhibitory abilities of Ca(OH) calcium hydroxide solution.
The protective concentration of calcium hydroxide is 0.7 g/kg and above.
Upon contact with the metal of calcium hydroxide solution, a stable protective film is formed within 3-4 weeks.
When emptying the boiler from the solution after contact for 3-4 weeks or more, the protective effect of the films remains for 2-3 months.
This method is regulated by the "Guidelines for the use of calcium hydroxide for the conservation of thermal power and other industrial equipment at the facilities of the Ministry of Energy RD 34.20.593-89" (M.: SPO Soyuztekhenergo, 1989).

5.1.2. When implementing this method, the boiler is completely filled with a solution. If it is required to carry out repair work, solution after soaking in the boiler for 3-4 weeks. can be drained.
5.1.3. Calcium hydroxide is used for the conservation of all types of hot water boilers at power plants with lime water treatment plants.
5.1.4. Conservation with calcium hydroxide is carried out when the boiler is taken into reserve for up to 6 months or taken out for repairs for up to 3 months.
5.1.5. The calcium hydroxide solution is prepared in wet lime storage cells with a floating suction device (Fig. 4). After sending lime (fluff, building lime, calcium carbide slaking waste) into the cells and mixing, the milk of lime is allowed to settle for 10-12 hours until the solution is completely clarified. Due to the low solubility of calcium hydroxide at a temperature of 10-25 ° C, its concentration in solution will not exceed 1.4 g / kg.

Fig.4. Scheme of preservation of hot water boilers:

1 - tank for the preparation of chemical reagents; 2 - boiler filling pump

a solution of chemical reagents; 3 - make-up water; 4 - chemical reagents;

5 - milk of lime in pre-treatment mixers, 6 - cells of lime milk;

7 - hot water boilers; 8 - to other hot water boilers;

9 - from other hot water boilers;

conservation pipelines

When pumping the solution out of the cell, it is necessary to monitor the position of the floating suction device, avoiding the capture of sediments at the bottom of the cell.
5.1.6. To fill the boilers with a solution, it is advisable to use the scheme of acid washing of hot water boilers, shown in Fig. 4. A tank with a pump for conservation of energy boilers can also be used (see Fig. 2).
5.1.7. Before filling the boiler with a preservative solution, the water from it is drained.
Calcium hydroxide solution from lime cells is pumped into the reagent preparation tank. Before pumping, the pipeline is flushed with water to prevent lime milk supplied through this pipeline for pre-treatment of the water treatment plant from entering the tank.
It is advisable to fill the boiler when the solution is recirculated along the circuit "tank-pump-pipeline for supplying the solution-boiler-pipeline for discharging the solution-tank". In this case, the amount of lime mortar prepared must be sufficient to fill the mothballed boiler and the recirculation circuit, including the tank.
If the boiler is filled with a pump from the tank without organizing recirculation through the boiler, then the volume of prepared milk of lime depends on the water volume of the boiler.
The water volume of the PTVM-50, PTVM-100, PTVM-180 boilers is 16, 35 and 60 m3, respectively.

5.1.8. When put into reserve, the boiler is left filled with solution for the entire downtime.
5.1.9. If it is necessary to carry out repair work, the drainage of the solution is carried out after exposure in the boiler for at least 3-4 weeks in such a way that after the repair is completed, the boiler is put into operation. It is desirable that the duration of the repair does not exceed 3 months.
5.1.10. If the boiler is left with a preservative solution during the downtime, then it is necessary to check the pH value of the solution at least once every two weeks. To do this, organize the recirculation of the solution through the boiler, take samples from the air vents. If the pH value is 8.3, the solution from the entire circuit is drained and filled with fresh calcium hydroxide solution.

5.1.11. Drainage of the preservative solution from the boiler is carried out at a low flow rate, diluting it with water to a pH value of 5.1.12. Before start-up, the boiler is washed with network water to the hardness of the washing water, having previously drained it if it was filled with a solution.

5.2. Preservation with sodium silicate solution

5.2.1. Sodium silicate (liquid sodium glass) forms a strong, dense protective film on the metal surface in the form of FeO FeSiO compounds. This film shields the metal from the effects of corrosive agents (CO and O).

5.2.2. When implementing this method, the boiler is completely filled with a solution of sodium silicate with a concentration of SiO in the preservative solution of at least 1.5 g/kg.
The formation of a protective film occurs when the preservative solution is kept in the boiler for several days or when the solution circulates through the boiler for several hours.

5.2.3. Sodium silicate is used for conservation of all types of hot water boilers.
5.2.4. Preservation with sodium silicate is carried out when the boiler is taken into reserve for a period of up to 6 months or the boiler is taken out for repair for a period of up to 2 months.
5.2.5. To prepare and fill the boiler with a sodium silicate solution, it is advisable to use the scheme of acid washing of hot water boilers (see Fig. 4). A tank with a pump for conservation of energy boilers can also be used (see Fig. 2).
5.2.6. The sodium silicate solution is prepared with softened water, since the use of water with a hardness above 3 meq/kg can lead to the precipitation of sodium silicate flakes from the solution.
A preservative solution of sodium silicate is prepared in a tank with water circulating according to the "tank-pump-tank" scheme. Liquid glass is poured into the tank through the hatch.
5.2.7. Approximate consumption of liquid commercial sodium silicate corresponds to no more than 6 liters per 1 m3 of preservative solution.

5.2.8. Before filling the boiler with a preservative solution, the water from it is drained.
The working concentration of SiO in the preservative solution should be 1.5-2 g/kg.
It is advisable to fill the boiler when the solution is recirculated along the circuit "tank-pump-pipeline for supplying the solution-boiler-pipeline for discharging the solution-tank". In this case, the required amount of sodium silicate is calculated taking into account the volume of the entire circuit, including the tank and pipelines, and not just the volume of the boiler.
If the boiler is filled without organization of recirculation, then the volume of the prepared solution depends on the volume of the boiler (see clause 5.1.7).

5.2.9. When put into reserve, the boiler is left filled with preservative solution for the entire downtime.
5.2.10. If it is necessary to carry out repair work, the drainage of the solution is carried out after exposure in the boiler for at least 4-6 days in such a way that after the completion of the repair, the boiler is put into operation.
The solution can be drained from the boiler for repair after circulation of the solution through the boiler for 8-10 hours at a speed of 0.5-1 m/s.
The duration of the repair should not exceed 2 months.
5.2.11. If the boiler is left with a preservative solution for the downtime, an overpressure of 0.01-0.02 MPa is maintained in it with network water by opening the valve on the bypass at the boiler inlet. During the conservation period, samples are taken from the air vents once a week to control the concentration of SiO in the solution. When the concentration of SiO is less than 1.5 g/kg, the required amount of liquid sodium silicate is added to the tank and the solution is recirculated through the boiler until the required concentration is reached.

5.2.12. The depreservation of the hot water boiler is carried out before it is kindled by displacing the preservative solution into the network water pipelines in small portions (by partially opening the valve at the outlet of the boiler) at 5 m/h for 5-6 hours for the PTVM-100 boiler and 10-12 hours for the PTVM boiler -180.
At open systems of heat supply, the displacement of the preservative solution from the boiler must take place without exceeding the MPC norms - 40 mg / kg SiO in the network water.

6. METHODS FOR PRESERVATION OF TURBO PLANTS

6.1. Preservation with heated air

6.1.1. Purging the turbine plant with hot air prevents moist air from entering the internal cavities and the occurrence of corrosion processes. Especially dangerous is the ingress of moisture on the surface of the flow part of the turbine in the presence of deposits of sodium compounds on them.
6.1.2. Preservation of a turbine plant with heated air is carried out when it is put into reserve for a period of 7 days or more.
Preservation is carried out in accordance with the guidelines "Guidelines for the conservation of steam turbine equipment of thermal power plants and nuclear power plants with heated air: MU 34-70-078-84" (M.: SPO Soyutekhenergo, 1984).
6.1.3. If the power plant does not currently have a conservation unit, it is necessary to use mobile fans with a heater to supply heated air to the turbine plant. Air can be supplied both to the entire turbine plant, and at least to its individual parts (LPC, LPC, boilers, to the upper or lower part of the condenser or to the middle part of the turbine).
To connect a mobile fan, it is necessary to provide for the installation of an inlet valve.
Recommendations MU 34-70-078-34 can be used to calculate the fan and intake valve.
When using mobile fans, drainage and vacuum drying measures specified in MU 34-70-078-84 should be carried out.

6.2. Preservation with nitrogen

6.2.1. When filling the internal cavities of the turbine plant with nitrogen and subsequently maintaining a small excess pressure, the ingress of moist air is prevented.
6.2.2. Filling is carried out when the turbine plant is put into reserve for 7 days or more at those power plants where there are oxygen plants that produce nitrogen with a concentration of at least 99%.
6.2.3. For conservation, it is necessary to have a gas supply to the same points as air.
It should be taken into account the difficulties of sealing the flow part of the turbine and the need to ensure the nitrogen pressure at the level of 5-10 kPa.
6.2.4. The supply of nitrogen to the turbine is started after the turbine is stopped and the vacuum drying of the intermediate superheater is completed.
6.2.5. Preservation with nitrogen can also be applied to the steam spaces of boilers and heaters.

6.3. Preservation with volatile corrosion inhibitors

6.3.1. Volatile corrosion inhibitors of the IFKhAN type protect steel, copper, brass by being adsorbed on the metal surface. This adsorbed layer significantly reduces the rate of electrochemical reactions that cause the corrosion process.
6.3.2. To preserve the turbine plant, air saturated with the inhibitor is sucked through the turbine. Air is sucked through the turbine plant by means of a seal ejector or a starting ejector. Air is saturated with an inhibitor when it comes into contact with silica gel impregnated with an inhibitor, the so-called linasil. Linasil is impregnated at the factory. To absorb excess inhibitor at the outlet of the turbine, the air passes through pure silica gel.
Conservation with a volatile inhibitor is carried out when placed in reserve for a period of more than 7 days.
6.3.3. To fill the turbine with inhibited air at its inlet, for example, a cartridge with linasil is connected to the steam supply pipeline to the front seal of the HPC (Fig. 5). To absorb the inhibitor excess, cartridges with pure silica gel are installed at the outlet of the equipment, the volume of which is 2 times greater than the volume of linasil at the inlet. In the future, this silica gel can be additionally impregnated with an inhibitor and, during the next conservation, installed at the inlet to the equipment.

Fig.5. Preservation of turbines with a volatile inhibitor:

1 - main steam valve; 2 - check valve high pressure;

3 - high pressure control valve; 4 - protective valve of the middle

pressure; 5 - medium pressure control valve; 6 - suction chambers

steam-air mixture from end seals of cylinders;

7 - sealing steam chamber; 8 - sealing steam pipeline;

9 - existing valves; 10 - collector of steam-air mixture for seals;

11 - steam-air mixture suction manifold; 12 - supply pipeline

an inhibitor; 13 - cartridge with linasil; 14 - newly mounted gate valves;

15 - seal ejector; 16 - exhaust into the atmosphere; 17 - cartridges with clean

silica gel to absorb the inhibitor; 18 - suction pipeline

steam-air mixture from the chambers; 19 - intermediate superheater;

20 - air sampling; 21 - flange; 22 - valve

To fill the turbine with inhibited air, standard equipment is used - a seal ejector or a starting ejector.
Preservation of 1 m volume requires at least 300 g of linasil, the protective concentration of the inhibitor in the air is 0.015 g/dm.
Linasil is placed in cartridges, which are pipe sections, to both ends of which flanges are welded. Both ends of the pipe with flanges are tightened with a mesh with a mesh size that does not allow spillage of linasil, but does not interfere with the passage of air. The length and diameter of the pipes is determined by the amount of linasil required for conservation.
Linasil is loaded into cartridges with a spatula or gloved hands.

6.3.4. Before the start of conservation, to exclude possible accumulation of condensate in the turbine, pipelines and valves, they are drained, the turbine and its auxiliary equipment are devaporated, disconnected from all pipelines (drains, steam extractions, steam supply to seals, etc.).
To remove possible accumulation of condensate in non-drained areas, the turbine is dried with air. To do this, a cartridge with calcined silica gel is installed at the inlet and the ejector sucks in air along the circuit "cartridge-high pressure cylinder - low pressure cylinder - low pressure cylinder - collector for suctioning the vapor-air mixture from the seals - ejector - atmosphere".
After the turbine metal has cooled down to approximately 50 °C, it is sealed with asbestos packing impregnated with sealant at the air inlet from the turbine hall to the suction chamber of the vapor-air mixture of the end seals.
After drying the turbine, cartridges with linasil are installed at the inlet, and cartridges with pure silica gel are installed at the outlet, the ejector is switched on and air is sucked in along the circuit "cartridge - pipeline for supplying steam to the seal - HPC - collector for suctioning the steam-air mixture - cartridges with silica gel - ejector - atmosphere". When the protective concentration of the inhibitor equal to 0.015 g/dm3 is reached, conservation is terminated, for which the ejector is turned off, a plug is installed at the air inlet to the cartridge with linasil and at the inlet of inhibited air into the cartridges with silica gel.

6.3.5. During the period when the turbine is in reserve, the concentration of the inhibitor in it is determined monthly (Appendix 2).
When the concentration falls below 0.01 g/dm3, represervation is carried out with fresh linasil.

6.3.6. To depreserve the turbine, the cartridges with linasil are removed, the plug at the inlet of inhibited air into the cartridge with silica gel, the ejector is turned on, and the inhibited air is drawn through silica gel to absorb the remaining inhibitor during the same time that it took to preserve the turbine.
Since the conservation is carried out in a closed circuit, there are no effluents or emissions into the atmosphere.
Brief characteristics of the chemicals used are given in Appendix 3.

4.1.1. It is prohibited to decommission steam and hot water boilers without taking the necessary measures to protect the metal of the boilers from corrosion.

4.1.2. Preservation of boilers must be carried out in one of the following ways: for a period of up to one month - filling the boiler alkaline solution; for a period of more than one month - the use of desiccants or sodium nitrate solutions.

4.1.3. During dry conservation of boilers, desiccants should be used: calcium chloride (CaCl2), silica gel grade MCM, quicklime, as a result of which relative humidity The internal environment in the boiler must be maintained below 60%.

4.1.4. The following preliminary measures must be carried out before boiler conservation:

a) install plugs on the steam, feed, drain and vent lines of the boiler;

b) drain the water from the boiler;

c) clean the inner surface of the boiler;

d) acid wash the water economizer if its mechanical cleaning is not possible;

e) clean the outer heating surfaces of the boiler and gas ducts from fly ash and slag;

f) dry the heating surface of the boiler with a fan through the open hatches of the drums and boiler collectors.

4.1.5. The amount of desiccant per 1 cu. m of the internal volume of the preserved boiler must be at least (in kg):

calcium chloride - 1 - 1.5;

silica gel - 1.5 - 2.5;

quicklime - 3 - 3.5.

Quicklime is used as an exception in the absence of other desiccants.

4.1.6. Upon completion of all work, a certificate of conservation of the boiler must be drawn up.

4.1.7. In case of alkaline conservation, the water volume of the boiler must be filled with deaerated condensate with the addition of up to 3 g/l sodium hydroxide (NaOH) or 5 g/l trisodium phosphate (Na3PO4).

4.1.8. When adding softened deaerated water to the condensate up to 50%, the addition of caustic soda should be increased to 6 g/l, and trisodium phosphate to 10 g/l.

Performing a represervation

During storage, responsible services periodically inspect the equipment, assessing its condition. If traces of corrosion or other defects are found on the surfaces of the equipment, re-preservation is carried out. This event also involves the implementation of primary surface treatment in order to remove traces of damage to metal or other materials. In some cases, repeated conservation also takes place - this is the same set of preventive measures, but in this case it has a planned implementation. For example, if a protective composition is applied with a certain service life, then after this period the technical service must update the product as part of the same re-preservation.

1. Schematic diagram of the preparation and dosing of the preservative using a gear pump.

For the preparation and dosing of the preservative is used
compact dosing system, the diagram of which is shown in fig. 6.1.1.

Rice. 6.1. Scheme of the dosing plant

1 - tank; 2 - pump; 3 - circulation line; four -
heater;
5 - electric drive with gearbox; 6 - branch pipes;
7 - sampler; 8 - drain valve

To the tank 1 where the heat exchanger is installed 4 ,
loaded preservative. By heating the tank with feed water ( t = 100
°C) a preservative melt is obtained, which is pumped 2 fed into the line 9
on the suction of the PEN feed pump.

As a dosing pump, you can use pumps of the type
NSh-6, NSh-3 or NSh-1.

Line 6 connected to the pressure pipe of the pump
PEN.

The pressure in the circulation line is monitored by a manometer.

Tank temperature 1 should not fall below 70 °C.

The unit is easy to operate and reliable. compact
the dosing system takes up little space, up to 1.5 m2 and is easily remounted
from one object to another.

What is reopening

When the time allotted for conservation expires, the equipment is subjected to a reverse process, which involves preparation for operation. This means that preserved parts must be freed from temporary protective compounds and, if necessary, treated with other means designed for use on working equipment.

It is worth noting the need for precautionary measures. As well as technical preservation, depreservation must be carried out under conditions that meet the requirements for the use of degreasing, anticorrosive and other compositions that are sensitive to temperature and humidity.

Also, when performing such procedures, special ventilation standards are usually observed, but this depends on the specifics of the particular equipment.

Conservation of hot water boilers with gas

Reducer for argon.

First, we will analyze the conservation of boilers with gas. The bottom line is that a gas is pumped into the heater, which, when in contact with wet metal surfaces, does not start oxidation processes, that is, corrosion. The gas completely squeezes out the air, which contains oxygen. Can be used:

• argon;
• nitrogen;
• helium;
• ammonia.

The instructions for the conservation of hot water boilers have a clear algorithm of actions. First you need to fill the heater with deaerated water - this is water from which air has been removed. But in principle, you can fill in ordinary water. Then a gas cylinder is connected to the upper branch pipe of the heater.

The pressure in the gas cylinder is huge, about 140 atmospheres. If you give such pressure directly to it, then it will break. Therefore, a reducer is screwed onto the cylinder.

It has two gauges. One pressure gauge shows the pressure that comes from the cylinder, and the second pressure gauge shows the pressure that is supplied to the boiler. On the gearbox, you can install required pressure and when this value is reached, the gas supply from the cylinder stops. Thus, it is possible not only to safely fill the boiler with gas, but also to build up pressure to the required value (recommended 0.013 MPa).

The process goes something like this:

• gas slowly squeezes water out of the boiler (the lower pipe must be open);
• after all the liquid has come out, the lower pipe is blocked;
• when the pressure in the boiler reaches 0.013 MPa, the gas stops flowing;
• the upper branch pipe to which the reducer is connected is blocked.

The gas pressure should be checked from time to time and adjustments made if necessary. The main thing is to prevent air from entering the boiler.

Instructions for the conservation of steam and hot water boilers with gas

Scheme of a gas boiler.

This method is intended for the conservation of boilers during downtime with a decrease in pressure to atmospheric pressure. It is used for conservation of steam and hot water boilers. During the proposed conservation, the boiler is emptied of water and filled with gas (for example, nitrogen), after which excess pressure is maintained inside the boiler, at the same time, before gas is supplied, it is filled with deaerated water.

The steam boiler conservation method involves filling the boiler with gas at an overpressure in the heating surface of 2-5 kg/cm² while simultaneously displacing water in the drum. In this case, the ingress of air inside is excluded. According to this scheme, gas (nitrogen) is supplied to the outlet collectors of the superheater and into the drum. The low overpressure in the boiler is due to the consumption of nitrogen.

This method cannot be used for the conservation of boilers in which the pressure has decreased to atmospheric pressure after shutdown and the water has been drained. There are cases of emergency shutdown of the boiler. During repair, it is completely emptied, respectively, air gets inside. The specific gravity of nitrogen and air is not significantly different, therefore, if the boiler is filled with air, it is impossible to replace it with nitrogen. In all areas where the air is located and where the humidity exceeds 40%, the metal of the equipment will be subject to oxygen corrosion.

The small difference in specific gravity is not the only reason. The displacement of air from the boiler and the uniform distribution of nitrogen over it is also impossible due to the lack of hydraulic conditions caused by the nitrogen supply system (via the superheater and drum outlet headers). Also in the boiler there are so-called non-draining areas that are impossible to fill. Therefore, such a method is applicable only after the boiler has been operating under load while maintaining excess pressure in it. This is the disadvantage of such a technical solution.

The task of the boiler conservation method with gas is to increase the reliability and efficiency of boilers that are put into reserve by completely filling the steam-water path with gas, regardless of the shutdown mode. The described preservation method is illustrated by a diagram (image 1).
Boiler conservation scheme with indication of boiler equipment:

Steam boiler diagram.

1. Drum.
2. Airmen.
3. Superheater.
4. Airmen.
5. Capacitor.
6. Airmen.
7. Superheater outlet manifold.
8. Portable cyclone.
9. Airmen.
10. Screens of the boiler circulation panels.
11. Economizer.
12. Drainage of the lower points of the boiler.
13. Air outlet chamber of the superheater.
14. Nitrogen supply line with valve.
15. Air vent line with valve.
16. The line of drainage and supply of water with a valve.

Scroll necessary tools, devices, fixtures:

1. Manometers are U-shaped.
2. Gas analyzer.
3. Set of wrenches.
4. Combined pliers.
5. Screwdrivers.
6. Files.
7. Stairs.
8. Bucket.
9. Solidol.
10. Paronite pads.
11. Plugs, bolts, nuts, washers.
12. Means and medicines of the first pre-medical aid.
13. Fire extinguisher.

The process of conservation of the boiler with gas is carried out as follows (an example of conservation of a steam drum boiler is given):

Schemes of separation devices in the boiler drum.

The boiler is released from water after it stops, opening all its lower points. After emptying, in some places there remains a vapor-air mixture containing oxygen, which causes corrosion of the metal of boiler equipment. In order to displace the steam-air mixture, all elements of the boiler (1, 3, 5, 7, 8, 10, 11) are filled with deaerated water. Filling occurs through the lower points (12). Complete filling is controlled by the valve (15), after which they close and supply nitrogen through the valve (14), then through the air vents (9, 2, 6, 4, 13).

When supplying nitrogen to the boiler, it is necessary to open the drains of the lower points of all its components. Next, the water is forced out and the boiler is filled with nitrogen. The nitrogen pressure in the boiler is adjusted on the supply line 14 and (if necessary) on the discharge line 16. After the water is completely displaced and the boiler is filled with nitrogen, the overpressure necessary for conservation is set (25-100 mm of water column). Despite the presence of a small amount of deaerated water in some parts of the boiler, the metal of the equipment does not corrode, this has been proven by research.

Consequently, the proposed method significantly increases the reliability of conservation due to the absolute disposal of the boiler from air, filling it with deaerated water and nitrogen with parallel displacement of water.

Wet method for heating conservation

The wet method is suitable both for the preservation of boilers and the heating system as a whole. The method is to fill the circuit with a special liquid that will prevent the metal from rusting. If the house is not heated at all and there is a risk of freezing, then only antifreeze (antifreeze liquids based on propylene glycol). Concentrates do not freeze even at -60, but at the same time they strongly thicken. They can be diluted to the desired consistency, thereby adjusting the minimum operating temperature. The disadvantage of antifreezes is that they are expensive, they dry out rubber, they have a high degree of fluidity, and when overheated, they turn into acid.

If you do not plan to use the Buderus gas boiler for several months, then it must be mothballed.

The same applies to Buderus solid fuel boilers. According to reviews, this significantly prolongs their life.

If you need to preserve the boiler and there is no risk that the liquid in it will freeze, then in addition to antifreeze, you can use water with the addition of sodium sulfate. Its concentration should be at least 10 g/l. After that, the liquid is heated to remove air from it and all pipes are clogged. The liquid is pumped using a pressure test pump. They are different: manual, automatic, household and professional. About that, we already wrote.

2. FLOW BOILERS

4.2.1. Preparation for conservation

4.2.1.1. Stop the boiler and drain.

4.2.1.2. The boiler conservation scheme is shown in fig. 4.2.1. (on the example of the boiler TGMP-114). For
conservation, a circulation circuit is organized: deaerator, nutrient and
booster pumps, boiler itself, BROW, condenser, condensate pump, BU,
HDPE and HPH are bypassed. During the period of pumping the preservative through the PPP of both buildings
the boiler is discharged through SPP-1,2.

4.2.1.3. The dosing unit is connected to the suction unit.

4.2.1.4. The circulation circuit is being filled.

4.2.1.5. Included in the work of BEN.

4.2.1.6. The working medium is heated to a temperature
150 - 200 ° C by periodically turning on the burners.

Rice. 4.2. Scheme of conservation of once-through boiler SKD

4.2.2. List of controlled and registered
parameters

4.2.2.1. During the conservation process

- temperature feed water;

— temperature and pressure in the boiler.

4.2.2.2. Indicators according to clause 4.2.2.1. register every hour.

4.2.2.3. Record start and end times of dosing
preservative and its consumption.

4.2.2.4. Periodicity and scope
chemical control in the process of conservation are given in the table.

4.2.3.1. Proceed to dosing the preservative on the suction of the PEU.

4.2.3.2. In the process of conservation, produce 2 times per shift
intensive blowing of the boiler for 30 - 40 seconds.

4.2.3.3. Maintaining the required temperature range
the circulating medium is provided by periodically turning on the burners.

4.2.3.4. After the preservation process is completed, the steam supply to
the deaerator stops, the circulation circuit is in operation until reaching
the average temperature of the environment is 60 °C. After that, all activities are carried out
provided for in the operating manual when the boiler is stopped (drainage
steam path, vacuum drying of preserved elements, etc.).

2. Principal diagram of preservative dosing according to the extrusion method

On fig. 6.2.1.
shows a schematic diagram of a dosing unit based on the principle
extrusion.

Rice. 6.2.
Schematic diagram of preservative dosing according to the extrusion method

This setting can be used for conservation
and cleaning of hot water boilers in a closed circulation circuit.

The unit is connected bypass to the recirculation pump.

The estimated amount of preservative is loaded into the tank 8
with level gauge and working fluid heat (boiler water, feed water)
the preservative is melted to a liquid state.

The flow rate of the working fluid through the heat exchanger 9
adjustable by valves 3 and 4 .

The required amount of preservative melt through the valve 5
passed into the dosing container 10 and further valves 1 and 2
the required flow rate and speed of movement of the working fluid through
dosage container.

The flow of the working fluid, passing through the preservative melt,
captures the latter in the boiler circuit.

The inlet pressure is controlled by a pressure gauge 11 .

For venting the dosing container during filling and
drainage serve as gate valves 6 and 7 . For better mixing
melt, a special diffuser is mounted in the dosing tank.

2. Option 2

5.2.1. Turbine conservation can be carried out separately from
boiler using auxiliary steam CH ( R= 10 - 13 kg/cm2,
t= 220 - 250 ° С) with the turbine rotor spinning with a frequency in the range of 800
- 1200 rpm (depending on critical frequencies).

5.2.2. To the devaporation line before the check valve
steam saturated with preservative is supplied. The steam passes through the flow path of the turbine,
condenses in the condenser, and the condensate is discharged through the emergency line
plum for HDPE. In this case, the preservative is adsorbed on the surfaces of the flow part
turbines, pipelines, fittings and auxiliary equipment.

5.2.3. During the whole period of turbine conservation
the following is supported temperature regime:

- in the steam inlet zone at the beginning of conservation, the temperature
is 165 - 170 ° C, by the time the conservation is completed, the temperature drops
up to 150°С;

— the temperature in the condenser is maintained at the level
the maximum possible within the limits determined by the manufacturer's instructions.

Preparing for conservation of boilers

Gas boilers (steam and hot water) are disconnected from the main gas and water supply with special plugs, which are completely cooled, after which water is removed from them through the drainage systems. Then specialists in the repair of boiler equipment proceed to the internal cleaning of boilers from scale. Scale significantly reduces the shelf life of boilers and reduces their efficiency by an average of 40%, therefore, a thorough cleaning of the internal elements of boilers is carried out annually. Despite the fact that boiler water undergoes preliminary chemical purification from heavy calcium and magnesium salts, during the heating season a significant part of these salts is deposited on the internal heating surfaces of boiler units.

mechanical; manual; chemical.

With the mechanical cleaning method, the inner surfaces of the drums and collectors are cleaned first, and then the screen pipes. Cleaning is carried out using blunt chisels, as well as special heads powered by an electric motor on the principle of a drill.

In places inaccessible to mechanical cleaning, manual cleaning is carried out, for which special scrapers, wire brushes, abrasive tools and blunt mild steel hammers are used. For manual cleaning, it is forbidden to use chisels and other sharp tools to prevent damage to the metal surface.

The fastest and effective method cleaning - chemical, which, in turn, is divided into acidic and alkaline. Alkaline cleaning is carried out by boiler room specialists on their own, using soda ash or caustic soda. Acid cleaning is carried out by a representative of a special organization. In this case, solutions of hydrochloric or sulfuric acid are used.

Boiler conservation methods

Preservation is necessary* to prevent the corrosion process. Preservation of boilers for the summer period can be done by any of four methods:

• wet;
• dry;
• gas;
• overpressure method.

During the conservation of boilers by the wet method, the boilers are filled with a special liquid that forms a protective film on the internal heating surfaces, which prevents the penetration of oxygen.

With the dry method, water is removed from the boilers, and stainless steel trays are installed inside the drums and collectors, which are filled with desiccants (granular calcium chloride or quicklime). After that, the boilers are sealed.

The gas method involves filling the boilers with any inert gas, which also prevents corrosion.

The overpressure method is used in cases where the boilers need to be stopped for a short period of time (up to 10 days). In all other cases, the first three methods are used.

By following the rules for cleaning and preserving boiler equipment during the summer period, it is possible to achieve a high efficiency of boilers during the heating season, as well as significantly reduce the cost of their repair.

*) excerpt from PUBE:

3. WATER BOILERS

4.3.1. Preparation for conservation

4.3.1.1. The boiler is stopped and drained.

4.3.1.2. Selection of conservation process parameters (temporary
characteristics, concentration of the preservative at various stages) is carried out
based on a preliminary analysis of the state of the boiler, including the determination
values ​​of specific pollution and chemical composition of deposits of internal
boiler heating surfaces.

4.3.1.3. Before starting work, analyze the scheme
conservation (revision of equipment, pipelines and fittings used in
conservation process, instrumentation systems).

4.3.1.4. Assemble a scheme for conservation,
including boiler, preservative dosing system, auxiliary
equipment, connecting pipelines, pumps. The diagram should represent
a closed circulation loop. In this case, it is necessary to cut off the circulation circuit
boiler from the network pipelines and fill the boiler with water. For emulsion supply
preservative in the preservation circuit, an acid line can be used
boiler flushing.

4.3.1.5. Pressurize the conservation system.

4.3.1.6. Prepare the required for chemical
analyzes of chemicals, utensils and instruments in accordance with the methods of analysis.

4.3.2. List of controlled and registered
parameters

4.3.2.1. During the conservation process
control the following parameters:

— boiler water temperature;

- when the burners are turned on - the temperature and pressure in the boiler.

4.3.2.2. Indicators according to clause 4.3.2.1. register every hour.

4.3.2.3. Record the start and end times of input and
preservative consumption.

4.3.2.4. Frequency and scope of additional chemical control
in the process of conservation are given in the table.

4.3.3. Instructions for carrying out work during conservation

4.3.3.1. By means of an acid wash pump (NKP)
circulation is organized in the boiler-NKP-boiler circuit. Next, heat the boiler up to
temperature 110 - 150 °C. Start dosing preservative.

4.3.3.2. Set the calculated concentration in the circuit
preservative. Depending on the results of the analyzes, carry out periodic
preservative dosing. Periodically (every 2-3 hours) purge
boiler through the drains of the low points to remove the sludge formed during the
preservation of equipment. Stop dosing during purge.

4.3.3.3. Periodic kindling of the boiler is necessary
maintain in the working circuit the parameters required for conservation
(temperature, pressure).

4.3.3.4. Switch off the system after the end of conservation
dosing, the recirculation pump remains in operation for 3 to 4 hours.

4.3.3.5. Turn off the recirculation pump, switch the boiler to
natural cooling regime.

4.3.3.6. In case of violation of technological parameters
stop the conservation process and start conservation after restoration
boiler operating parameters.

Dry method of preservation of boilers

Boiler outlet diagram.

The release of the boiler from water at a pressure above atmospheric pressure occurs after emptying due to the heat accumulated by the metal, lining and isolation while maintaining the temperature of the boiler above the temperature of atmospheric pressure. At the same time, the inner surfaces of the drum, collectors and pipes are dried.

Dry shutdown is applicable to boilers with any pressure, but provided that there are no pipe-to-drum flare joints in them. It is carried out during a planned shutdown in reserve or for the period of equipment repair work for a period of not more than 30 days, as well as during an emergency shutdown. In order to prevent moisture from entering the boiler during downtime, it is necessary to monitor its disconnection from the pressurized water and steam pipelines. Must be tightly closed: plug installations, shut-off valves, inspection valves.

Displacement of water is carried out at a pressure of 0.8-1.0 MPa after the boiler has been stopped and cooled naturally. The intermediate superheater is devaporated onto a heat exchanger. At the end of drainage and drying, the valves and valves of the steam-water circuit of the boiler, the manhole and gate of the furnace and gas duct must be closed, only the revision valve remains open, if necessary, plugs are installed.

During the conservation process, after the boiler has completely cooled down, it is necessary to periodically monitor the ingress of water or steam into the boiler. Such control is carried out by probing the spaces of their probable entry into the area stop valves, opening drains of the lower points of collectors and pipelines, valves of sampling points for a short period.

In case of detection of water ingress into the boiler, it is necessary to take necessary measures. After that, the boiler is subject to kindling, raising the pressure in it to 1.5-2.0 MPa. The specified pressure is maintained for several hours, and then nitrogen is produced again. If the ingress of moisture cannot be eliminated, a conservation method is resorted to by maintaining excess pressure in the boiler. A similar method is still used if, during the shutdown of the boiler, equipment was repaired on the heating surfaces and there was a need for pressure testing.

Legal registration of the procedure

Preparation for the conservation process begins with the implementation of formal procedures. In particular, the preparation of documentation is necessary so that in the future it remains possible to recognize all the costs of the activity. The conservation initiator may be a representative of the service personnel who submits an appropriate application addressed to the head. Next, an order is drawn up to allocate funds for the procedure and an instruction is given to develop a project in which the requirements for conservation from the side will be noted. technical services. As for legal requirements, representatives of the administration, the management of the department responsible for facilities, economic services, etc. should control the process of transferring equipment to a state of storage. the feasibility of the project and make an estimate for the maintenance of facilities.

wet preservation technology

When carrying out wet conservation of the boiler, it is necessary to ensure the dryness of its surface and masonry, close all hatches tightly. Monitor the concentration of the solution (the content of sodium sulfate should be at least 50 mg / l). The use of the wet preservation method during repair work or in the presence of leaks in the boiler is unacceptable, since compliance with tightness is the main condition. If the leakage of steam is unacceptable with the dry and gas method of preservation, then with the wet method it is not so dangerous.

Scheme of a double-turn steam superheater.

If it is necessary to stop the boiler for a short period, a simple wet preservation method is used, filling the boiler and the steam heater with deaerated water while maintaining excess pressure. If the pressure in the boiler drops to 0 after it has been shut down, filling it with deaerated water is no longer effective. Then you need to boil the boiler water with open air vents, this is done in order to remove oxygen. After boiling, if the residual boiler pressure is not lower than 0.5 MPa, conservation can be carried out. This method is used only when the oxygen content in deaerated water is low. If the oxygen content exceeds the allowable value, corrosion of the metal of the superheater is possible.

Boilers with shutdown immediately after operation can be subjected to wet preservation without opening the drums and headers.

Ammonia in gaseous form can be added to the feed water. A protective film is formed on the surface of the metal, protecting it from corrosion.

In order to exclude the occurrence of corrosion in boilers that are in reserve for a long time, the wet preservation method is used, maintaining an excess pressure of a nitrogen cushion over the liquid in the boiler, eliminating the possibility of air entering the boiler. In contrast to dry conservation, in which dewatering means operate, dewatering is provided from the mine working, boiler equipment is maintained in a condition suitable for use if necessary. At the time of conservation, the write-off of mineral reserves is not allowed.

Information to be included in the document

The act must contain the following information:

• date of transfer of equipment for conservation;
• list of equipment to be transferred;
• the initial cost of the equipment;
• the reason for the transfer;
• actions that were performed for the transfer;
• the amount of upcoming expenses;
• residual value if conservation is planned for more than three months;
• the amount of expenses already incurred;
• conservation period.

During the inventory accounting, the equipment that is intended for canning, the commission allocates to a separate group. For its accounting, the sub-account "Objects transferred to conservation" is used. In the act, such equipment is prescribed with an indication of the manufacturer, model name and inventory number.

Preservation method by creating excess pressure

Boiler valve connection diagram.

Instructions for the technology of preservation of the boiler by creating excess pressure is applicable regardless of the heating surface of the boiler. Other methods using water and special solutions are not able to protect the intermediate superheaters of boilers from corrosion, since certain difficulties arise during filling and cleaning. Vacuum drying with ammonia gas or filling with nitrogen is used to protect superheaters regardless of downtime. As for the metal screen pipes and other parts of the steam-water path of drum boilers, they are not 100% protected to the same extent.

The proposed conservation technology is suitable for both steam and hot water boilers. Principle this method It consists in maintaining the pressure in the boiler above atmospheric, which will prevent the ingress of oxygen into it, and is used for boilers of any type of pressure. To maintain excess pressure in the boiler, it is filled with deaerated water. This method is used when there is a need to put the boiler on standby or carry out repair work not related to measures on the heating surface, for a total period of up to 10 days.

The implementation of the method of maintaining excess pressure in stopped hot water or steam boilers is possible in several ways:

1. During the downtime of the boilers for more than 10 days, conservation by dry or wet methods is applicable (determined by the presence of certain reagents, gasket materials, etc.).
2. During long downtime in winter time and in the absence of heating of the room, the boilers are preserved by the dry method; the use of the wet method of conservation under these conditions is unacceptable.

The choice of one or another method depends on the operating mode of the boiler house, the total number of reserve and operating boilers, etc.

Error correction

If the specialist accounting notices an error in the act, he has the right to correct it. For example, if the amount was written incorrectly in the document, then it can be edited by crossing out and indicating the correct value. However, do not forget that corrections in the document must be certified correctly. For this it is enough:

• put in the act the date when the corrective entry was made;
• prescribe "Corrected believe";
• put the signature of the employee who is responsible for the correction;
• decrypt this signature.

When filling out a document, it is unacceptable to use stroke correctors, blots, corrections and erasures.

Instructions for the preservation of hot water boilers

Let us examine in detail the most common methods that will help protect equipment from destruction.

Gas Method

Let's get straight to the heart of the process. First of all, the space is supplied with gas. Through interaction with wet surfaces metal creates an obstacle to the formation of corrosion. The mass completely squeezes out the air. For this application, the following elements are excellent:

• Helium.
• Ammonia.
• Nitrogen.
• Argon.

There is a special algorithm by which manipulations are performed:

1. The gas is injected into the water, thereby squeezing out the liquid.
2. Further, the lower branch pipe is blocked.
3. When a pressure of 0.013 MPa is reached, the flow stops.
4. After that, the upper part, which is connected to the gearbox, also overlaps.

REFERENCE! Of course, it is worth periodically checking all the parameters and monitoring the pressure.

Wet preservation method

If we talk about the principle of the method, then it is worth mentioning a special liquid that is deliberately used to prevent the appearance of rust. Excellent for antifreeze manipulations presented. However, it is worth remembering the rather high cost and a considerable degree of fluidity. In addition to this type of concentrate, there is also a mixture of water with a small amount of sodium sulfate.

IMPORTANT! The concentration should not exceed ten grams per liter. . As for the process itself, this is the following scheme:

As for the process itself, this is the following scheme:

1. To begin with, it is worth adding this mixture using a pressure pump.
2. Further, from the reservoir, the liquid lends itself.
3. Thanks to this system, the metal will not be able to rust.

Dry preservation method

Despite all the advantages of the previous methods, this one is no worse in practice. The peculiarity lies in the high-quality drying of all channels from the inside. The process goes like this:

• By using warm air the product is blown.
• Thus, all the moisture inside is evaporated.

ATTENTION! The burner is switched off first. . With the help of slow elimination of moisture, the effect of metal elimination is created

Therefore, small holes should be made so that the substance is absorbed. Quicklime or potassium is excellent as a powder. The main thing is that it should be chloride. But it is worthwhile to understand that periodically it will be necessary to change them to new ones.

By slowly eliminating moisture, the effect of eliminating metal is created. Therefore, small holes should be made so that the substance is absorbed. Quicklime or potassium is excellent as a powder. The main thing is that it should be chloride. But it is worthwhile to understand that periodically it will be necessary to change them to new ones.

Technical execution of conservation

The whole procedure consists of three stages. At the first stage, all kinds of contaminants, as well as traces of corrosion, are removed from the surfaces of the equipment. If necessary and technically feasible, repair operations can also be carried out. This stage is completed by measures for degreasing surfaces, passivation and drying. The next stage involves processing protective equipment, which are selected based on individual requirements exploitation technical means. For example, conservation of boilers may include treatment with heat-resistant compounds, which in the future will provide structures with optimal resistance to impact. high temperatures. Anti-corrosion powders and a liquid inhibitor can be attributed to universal treatment agents. The final stage provides

8.1. General position

Conservation
equipment is protection against
called parking corrosion.

Conservation
boilers and turbine plants to prevent
metal corrosion of internal surfaces
carried out during shutdowns
and withdrawal to the reserve for a certain and
indefinite period: withdrawal - in the current,
medium, overhaul; emergency
shutdowns, into continuous standby or
repair, for reconstruction for a period above
6 months.

On the
basis production instructions on the
each power plant, boiler house must
be developed and approved technical
conservation solution
specific equipment, determining
preservation methods for various types
shutdowns and downtime
technological scheme and support
equipment.

At
development of a technological scheme
conservation is expedient to the maximum
use default settings
corrective treatment of nutritional
and boiler water, chemical plants
equipment cleaning, tank management
power plants.

Technological
the conservation scheme should be
stationary, reliable
disconnect from working areas
thermal scheme.

Necessary
provide for the neutralization or
disposal of waste water, as well as
reusability
preservative solutions.

B
in accordance with the accepted technical
decision is drawn up and approved
equipment conservation instructions
with instructions for preparation
operations, conservation technology and
re-preservation, as well as measures
safety during conservation.

At
preparation and implementation of work on
conservation and re-preservation is necessary
comply with the requirements of the Rules of Technology
operational safety
thermal mechanical equipment
power plants and heating networks. Also
should be taken if necessary.
additional security measures
related to the properties of the used
chemical reagents.

Neutralization
and cleaning of used preservatives
solutions of chemical reagents should
carried out in accordance with
directive documents.

Conclusion

The conservation procedure undoubtedly has many advantages, and its implementation is mandatory in many cases. Nevertheless, it does not always justify itself from a financial point of view, which leads to the involvement of accounting in the preparation of the corresponding project. Nevertheless, conservation is a set of measures aimed at maintaining the operability of equipment in order to obtain benefits for the enterprise. But if we are talking about unused or unprofitable facilities, then there is no point in carrying out such activities. For this reason, the stage of preparation and development of a project for transferring equipment to a canned state is to some extent even more responsible than the practical implementation of the procedure.

CO - the first stage, further conservation depends on the subsequent repair period, reserve

Notes:

1. For boilers with a pressure of 9.8 and 13.8 MPa without treatment of feed water with hydrazine, maintenance is recommended at least once a year.

2. A - filling the heating surfaces of the boiler with nitrogen.

3. Hydraulic fracturing + CO - hydrazine treatment at the operating parameters of the boiler, followed by a dry shutdown; GO+ZShch, TO+ZShch, FV+ZShch - filling the boiler with an alkaline solution with the previous reagent treatment;

4. TO+CI - conservation with a contact inhibitor followed by trilon treatment;

5. "Before", "after" - before and after repair.

5. Methods of preservation of hot water boilers

5.1. Preservation with calcium hydroxide solution

5.1.1. The calcium hydroxide solution preservative method is based on the highly effective inhibitory abilities of Ca(OH)2 calcium hydroxide solution. The protective concentration of calcium hydroxide is 0.7 g/kg and above.

This method is regulated.

5.1.2. During the conservation of heating surfaces of hot water boilers by filling with a solution of calcium hydroxide, the following effect is achieved by the implementation of the proposed measures:

Formation of a stable protective film upon contact with the metal of calcium hydroxide solution within 3-4 weeks

Preservation for 2 - 3 months protective effect films when emptying the boiler from the solution after contact for 3 to 4 weeks or more.

Complete filling of the boiler with calcium hydroxide solution during conservation

Possibility of draining the solution for repair work after holding in the boiler for 3 - 4 weeks

Application of the method for the conservation of hot water boilers of any type at power plants with water treatment plants with lime economy.

Carrying out conservation with a solution of calcium hydroxide when putting the boiler into reserve for a period of up to 6 months. or withdrawal for repair for up to 3 months.

5.1.3. Preservation of heating surfaces of hot water boilers filled with calcium hydroxide solution is recommended to be carried out by carrying out the proposed measures, maintaining the following options and the maximum realization of the possibilities of the scheme:

Preparation of calcium hydroxide solution in lime wet storage cells with floating suction device (Figure 4)

Settling of milk of lime for 10 - 12 hours until the solution is completely clarified after pouring lime (fluff, building lime, calcium carbide slaking waste) into cells and mixing

Keeping the concentration of calcium hydroxide in solution no more than 1.4 g / kg due to its low solubility at a temperature of 10 - 25 ° C

Control of the position of the floating suction device when pumping the solution out of the cell, preventing the capture of deposits from the bottom of the cell

Possibilities of using for filling the boilers with a solution of the scheme of acid washing of hot water boilers, shown in Figure 6

Draining water from the boiler before filling it with preservative solution

By pumping the calcium hydroxide solution from the lime cells into the reagent preparation tank

Flushing the pipeline with water before pumping in order to prevent the milk of lime supplied through this pipeline for preliminary cleaning of the water treatment plant from entering the tank

Filling the boiler while circulating the solution along the circuit "tank - pump - solution supply pipeline - boiler - solution discharge pipeline - tank"

Determining the amount of prepared lime mortar, based on ensuring the filling of the preserved boiler and the circulation scheme, including the tank. When filling the boiler with a pump from the tank without organizing circulation through the boiler, the volume of prepared milk of lime depends only on the water volume of the boiler. The water volume of the PTVM-50, PTVM-100, PTVM-180 boilers is 16, 35 and 60 m3, respectively.

Preservation of the preservative solution in the boiler for the entire downtime in reserve, with tight closure of all shut-off valves on the boiler

1 - tank for the preparation of chemical reagents;

2 - pump for filling the boiler with a solution of chemical reagents;

3 - make-up water; 4 - chemical reagents;

5 - milk of lime in pre-treatment mixers;

6 - lime milk cells; 7 - hot water boilers;

8 - to other hot water boilers; 9 - from other hot water boilers.

Figure 6 - Scheme of conservation of hot water boilers.

Possibility of draining the solution if it is necessary to carry out repair work after holding in the boiler for at least 3-4 weeks, with the expectation that the boiler will be put into operation after the repair is completed.

By checking at least once every two weeks the pH value of the solution while maintaining the preservative solution in the boiler during downtime

The organization of the circulation of the solution through the boiler for the selection of control analyzes

Sampling from air vents during circulation

By draining the solution from the entire circuit if the pH value is ³ 8.3 and filling with fresh calcium hydroxide solution

By draining the preservative solution from the boiler with a small flow rate, diluting it with water to a pH value< 8,5

By draining and flushing the boiler with network water to the hardness of the flushing water before start-up, if the boiler was filled with preservative solution.

5.2. Preservation with sodium silicate solution

5.2.1. Sodium silicate (liquid sodium glass) forms a strong, dense protective film on the metal surface in the form of Fe3O4 FeSiO3 compounds. This film shields the metal from corrosive agents (CO2 and O2).

5.2.2. The formation of a protective film occurs when the preservative solution is kept in the boiler for several days or when the solution circulates through the boiler for several hours.

5.2.3. Preservation of heating surfaces of hot water boilers with sodium silicate is recommended by maintaining the following concentrations and implementing the proposed organizational and technical measures:

Complete filling of the boiler with a sodium silicate solution with a SiO2 concentration in the preservative solution of at least 1.5 g/kg

The use of sodium silicate for the preservation of hot water boilers of all types

Preservation with sodium silicate when the boiler is taken into reserve for up to 6 months. or in repair for up to 2 months.

Use for filling the boilers with a solution of the scheme of acid washing of hot water boilers, shown in Figure 6

Possibilities of using the existing tank with a pump for conservation of power boilers (picture 2)

Preparation of a sodium silicate solution with softened water, since the use of water with a hardness above 3 meq/kg can lead to the precipitation of sodium silicate flakes from the solution

Preparation of a preservative solution of sodium silicate in a tank with water circulating according to the "tank-pump-tank" scheme with the pouring of liquid glass into the tank through the hatch

Determination of the approximate consumption of liquid commercial sodium silicate at the rate of not more than 6 liters per 1 m3 of the volume of the preservative solution

Drainage of water from the boiler before filling it with preservative solution

Establishment of the working concentration of SiO2 in the preservative solution at the level of 1.5 - 2 g/kg

Determination of the amount of the prepared solution, based on ensuring the filling of the preserved boiler and the circulation scheme, including the tank. When filling the boiler with a pump from the tank without organizing circulation through the boiler, the volume of prepared milk of lime depends only on the water volume of the boiler. When filling the boiler without organizing circulation, the volume of the prepared solution depends only on the volume of the boiler.

Preservation of the preservative solution in the boiler for the entire downtime in reserve

Possibility of draining the solution if it is necessary to carry out repair work after holding in the boiler for at least 4 - 6 days, with the expectation that the boiler will be put into operation after the repair is completed.

Drainage of the solution from the boiler for repair after circulation of the solution through the boiler for 8 - 10 hours at a speed of 0.5 - 1 m/s

Maintaining an excess pressure of 0.01 - 0.02 MPa with network water by opening the valve on the bypass at the inlet to the boiler while maintaining the preservative solution in it for the entire downtime

Sampling from the air vents during the conservation period once a week to control the concentration of SiO2 in the solution

Adding the required amount of liquid sodium silicate and circulating the solution through the boiler into the tank until the required concentration is reached while reducing the SiO2 concentration to less than 1.5 g/kg

Displacement of the preservative solution into the network water pipelines in small portions (by partially opening the valve at the outlet of the boiler) at 5 m3/h for 5–6 hours for the PTVM-100 boiler and 10–12 hours for the PTVM-180 boiler during depreservation of the hot water boiler before kindling.