Safety valves for steam and hot water boilers. Technical requirements. Trial furnace and commissioning of the boiler Safety valves on the steam boiler
10.1.1 In boiler rooms with steam boilers with a steam pressure of more than 0.07 MPa (0.7 kgf / cm 2) and hot water boilers with a water temperature of more than 115 ° C (regardless of pressure), pipes, materials and fittings must comply.
10.1.2 In boiler rooms with steam boilers with a steam pressure of not more than 0.07 MPa (0.7 kgf / cm 2) and hot water boilers with a water heating temperature of not more than 115 ° C, the choice of pipes and fittings, depending on the parameters of the transported medium, must be made in accordance with the requirements of state standards.
10.1.3 The main pipelines to which steam boilers are connected should be provided as single sectional or double in boiler rooms of the first category. In other cases, sectioning is determined in the design task.
The main feed pipelines of steam boilers with a pressure of over 0.17 MPa should be designed double for boiler houses of the first category in accordance with. In other cases, these pipelines may be provided as single non-sectioned.
The main supply and return pipelines of heat supply systems, to which hot water boilers, water heating installations and network pumps are connected, should be provided as single sectional or double for boiler houses of the first category, regardless of heat consumption and for boiler houses of the second category - with a heat consumption of 350 MW or more. In other cases, these pipelines must be single, non-sectioned.
Main steam pipelines, feed pipelines, supply and return pipelines of heat supply systems for boiler houses with steam boilers with steam pressure up to 0.17 MPa and water temperature up to 115 ° C, regardless of category, are accepted as single non-sectional.
10.1.4 When installing boilers with individual feed pumps, the feed pipes must be single.
10.1.5 Pipelines of steam and water from pipelines to the equipment and connecting pipelines between the equipment shall be single.
10.1.6 The diameters of the steam pipelines should be taken based on the maximum hourly calculated coolant flow rates and allowable pressure losses.
In this case, steam speeds should be taken no more than:
- for superheated steam with pipe diameter, mm,
up to 200 - 40 m/s; over 200 - 70 m/s;
- for saturated steam with pipe diameter, mm,
for 200 - 30 m/s; over 200 - 60 m/s.
10.1.7 Horizontal sections of pipelines in boiler rooms must be laid with a slope of at least 0.004, and for pipelines of heat networks a slope of at least 0.002 is allowed.
10.1.8 The sampling of the medium from the steam pipelines shall be carried out in the upper part of the pipeline.
10.1.9 The disconnected sections, as well as the lower and end points of the steam pipelines, must have devices for periodic purging and condensate removal: fittings with valves, condensate traps. A non-return valve should be installed downstream of the trap to prevent backflow when the system is shut down.
10.1.10 For periodic draining of water or periodic blowdown of the boiler, drainage of pipelines, steam pipelines and condensate pipelines, devices for draining water (bleeders) and common collecting drain and purge pipelines should be provided in the lower parts of the pipelines, and devices for air venting at the highest points of the pipelines ( air vents) in accordance with Appendix B.
10.1.11 The minimum clear distances between the surfaces of the thermal insulation structures of adjacent pipelines, as well as from the surface of the thermal insulation of pipelines to the building structures of buildings should be taken in accordance with Appendix D.
10.1.12 The connection of all pipelines, except for rubber-lined ones, must be provided for by welding. On flanges, it is allowed to connect pipelines to fittings and equipment.
The use of coupling joints is allowed on pipelines of steam and water of the fourth category with a nominal bore of not more than 100 mm, as well as for boiler rooms with boilers with steam pressure up to 0.17 MPa and water temperature up to 115 ° C. For pipelines located within the boilers, with a steam pressure of more than 0.17 MPa and a temperature of more than 115 ° C, the use of coupling connections according to.
10.1.13 For the installation of measuring and selection devices on pipelines, straight sections with a length determined by the device manufacturer's instructions should be provided.
10.1.14 Equipping the locking devices of boiler rooms with electric drives should be carried out depending on the degree of automation technological process, requirements for remote control and safety of operation according to the design assignment.
10.2 Safety devices
10.2.1 Each element of the boiler, the internal volume of which is limited by shut-off devices, must be protected by safety devices that automatically prevent an increase in pressure beyond the allowable by releasing the working medium into the atmosphere.
10.2.2 The following may be used as safety devices:
- lever-load safety valves of direct action;
- spring-loaded safety valves of direct action;
- throw-away safety devices (hydraulic locks).
10.2.3 Safety valves are installed on branch pipes directly connected to the boiler or pipeline without intermediate shut-off devices.
When several safety valves are located on one branch pipe, the cross-sectional area of the branch pipe must be at least 1.25 of the total cross-sectional area of the valves installed on this branch pipe.
The selection of the working medium through the branch pipe, on which the safety valves are located, is prohibited.
10.2.4 The design of safety valves shall provide for the possibility of checking their operation in working condition by forced opening of the valve.
The weights of lever safety valves must be fixed on the lever in a way that excludes their arbitrary movement. Do not attach new weights after adjusting the valve.
If two safety valves are installed on the boiler, one of them must be a control valve. The control valve is provided with a device (for example, a casing that is locked with a lock) that does not allow the operator to adjust the valve, but does not interfere with checking its condition.
10.2.5 Safety valves must have devices (branch pipes) to protect operating personnel from burns when the valves actuate. The medium leaving the safety valves is diverted outside the room. The configuration and section of the outlet must be such that there is no back pressure behind the valve. The discharge pipelines must be protected from freezing and equipped with devices for draining condensate, and both the discharge pipelines and the drain devices must not have shut-off devices.
10.2.6 Hot water boilers with drums, as well as boilers without drums with a heat output of more than 0.4 MW (0.35 Gcal / h) are equipped with at least two safety valves with a minimum diameter of 40 mm each. The diameters of all installed valves must be the same.
Hot water boilers without drums with a heat output of 0.4 MW (0.35 Gcal/h) or less can be equipped with one safety valve.
The number and diameter of safety valves is determined by calculation.
10.2.7 On any boilers (including those with one safety valve), instead of one safety valve, it is allowed to install a bypass with a check valve that allows water from the boiler to bypass the shut-off device at the hot water outlet. In this case, there must be no other shut-off valve between the boiler and the expansion vessel, other than the specified non-return valve.
It is allowed not to install safety valves on hot water boilers operating on gaseous and liquid fuel, equipped with automatic devices according to 15.9, and on boilers with mechanical fireboxes, equipped with automatic devices according to 15.10.
10.2.8 The diameter of the connecting and atmospheric pipelines of the expansion vessel must be at least 50 mm. To prevent freezing of water, the vessel and pipeline should be insulated; the expansion vessel must be tightly closed with a lid.
10.2.9 If the boilers are connected to the heating system without an expansion vessel, it is not allowed to replace the safety valves on the boilers with bypasses.
10.2.10 For hot water boilers operating on a hot water supply system, instead of safety valves, it is allowed to install a separate exhaust pipe connecting the upper part of the boilers with the upper part of the water tank. There should be no shut-off devices on this discharge pipe, and the tank should be connected to the atmosphere. The outlet pipe diameter must be at least 50 mm.
10.2.11 If there are several sectional or tubular hot water boilers in the boiler rooms without drums operating on a common hot water pipeline (if, in addition to shut-off devices on the boilers, there are shut-off devices on the common pipeline), instead of safety valves on the boilers, it is allowed to install bypasses with reverse valves at the shut-off devices of the boilers, and on the common hot water pipeline (within the boiler room) - two safety valves between the shut-off devices on the boilers and the shut-off devices on the common pipeline. The diameter of each safety valve should be taken according to the calculation for one of the boilers with the highest heat output, but not less than 50 mm.
10.2.12 Diameters of bypasses and check valves should be taken according to the calculation, but not less than:
- 40 mm - for boilers with heat output up to 0.28 MW (0.24 Gcal/h);
- 50 mm - for boilers with a heat output of more than 0.28 MW (0.24 Gcal / h).
10.2.13 The total capacity of the safety devices installed on the steam boiler must be not less than the nominal hourly steam output of the boiler.
10.2.14 The number and dimensions of safety valves are calculated using the following formulas:
a) for hot water boilers with natural circulation
ndh=0.000006Q; (10.1)
b) for hot water boilers with forced circulation
ndh=0.000003Q, (10.2)
where n is the number of safety valves;
d - valve diameter, cm;
h - valve lift height, cm;
Q - the maximum productivity of the boiler, kcal / h.
The lift height of the valve when calculating according to the indicated formulas for ordinary low-lift valves is assumed to be no more than 1/20d.
Pipes from the safety devices of steam boilers must be led outside the boiler room and have devices for draining water. The cross-sectional area of the exhaust pipe must be at least twice the cross-sectional area of the safety device.
Pipes from safety valves for hot water boilers below 100°C are discharged into the sewer, for boilers up to 115°C - through a steam separator - into the atmosphere and into the sewer.
10.2.15 Safety valves must protect the boilers from exceeding the pressure in them by more than 10% of the calculated (allowed).
10.2.16 Safety valves must be installed:
- in steam boilers with natural circulation without a superheater - on the upper drum or dry steamer;
- in hot water boilers - on the outlet manifolds or drum;
- in disconnected economizers - at least one safety device at the outlet and inlet of water.
10.2.17 Checking the serviceability of the safety valves should be carried out at least once per shift on boilers with a working pressure of up to 1.4 MPa (14 kgf / cm 2) inclusive and at least once a day on boilers with a working pressure of more than 1.4 MPa (14 kgf / cm 2).
10.2.18 On steam boilers, instead of safety valves, a discharge safety device (hydraulic seal) can be installed, designed so that the pressure in the boiler does not exceed the excess working pressure by more than 10%. Shut-off devices must not be installed between the boiler and the safety device and on the device itself.
The vented safety device must have an expansion vessel with a pipe in the upper part for the removal of steam, which must be led to a place safe for people. The expansion vessel is connected to the bottom manifold of the blowout safety device by an overflow pipe.
The diameters of the pipes of the discharge safety device must be at least those given in Table 10.1
Table 10.1
| Boiler steam capacity, t/h | Pipe inner diameter, mm | |
|---|---|---|
| Higher | Before | |
| 0,124 | 0,233 | 65 |
| 0,233 | 0,372 | 75 |
| 0,372 | 0,698 | 100 |
| 0,698 | 1,241 | 125 |
| 1,241 | 2,017 | 150 |
| 2,017 | 3,103 | 173 |
| 3,103 | 4,654 | 200 |
| 4,654 | 6,982 | 225 |
The diameter of the pipe that discharges steam from the discharge safety device must not be less than the diameter of the pipes of the device itself. When installing several discharge devices, it is allowed to install a common outlet pipe with a cross-sectional area of at least 1.25 of the sum of the cross-sectional areas of the pipes of the connected devices.
To fill the water seal with water, it should be connected to a water pipe with a shut-off valve and a check valve, and equipped with devices for controlling the water level and draining the water.
The discharge safety device must be protected against freezing of water in it. Operation of boilers with an inoperative safety discharge device is prohibited.
10.3 Water level gauges in the boiler
10.3.1 The hot water boiler must be equipped with a water test cock installed in the upper part of the boiler drum, and in the absence of a drum, at the outlet of water from the boiler into the main pipeline (up to the locking device).
10.3.2 On the steam boiler for continuous monitoring of the position of the water level in the drums, at least two direct-acting water-indicating instruments should be installed.
10.3.3 For cast-iron and steel tubular boilers with a heating surface area of less than 25 m 2, it is allowed to install one water-indicating device.
A cast-iron boiler with a drum (steam collector) must be equipped with circulation pipes connecting the lower part of the drum with the sections of the boiler.
10.3.4 Direct-acting water-indicating instruments should be mounted in a vertical plane or tilted forward at an angle of no more than 30°. They must be located and lit so that the water level is clearly visible from the workplace of the driver (fireman), operator.
10.3.5 On water-indicating devices, against the maximum permissible lower water level in the boiler, a fixed metal indicator with the inscription "Lowest level" should be installed. This level must be at least 25 mm above the lower visible edge of the transparent plate (glass) of the water indicator. Similarly, a pointer of the highest permissible water level in the boiler should be placed, which should be at least 25 mm below the upper visible edge of the transparent plate (glass).
10.3.6 Water gauges or test taps should be installed on the boiler drum separately from each other. Joint placement of two water-indicating devices on a connecting pipe (column) with a diameter of at least 70 mm is allowed.
If water-indicating devices are connected to the boiler with pipes up to 500 mm long, then the inner diameter of these pipes must be at least 25 mm, and more than 500 mm long - at least 50 mm.
Pipes connecting water gauges to boilers must be accessible for internal cleaning. Installation of intermediate flanges and locking elements on them is not allowed. The configuration of the pipes connecting the water-indicating device with the boiler drum must exclude the possibility of the formation of air and water bags in them.
10.3.7 Pipes connecting water-indicating devices with the drum (casing) of the boiler must be protected from freezing.
10.3.8 Flat transparent glasses should be used in direct-acting level indicators of steam boilers. Water-indicating devices with cylindrical glasses can be used on steam boilers with a capacity of not more than 0.5 t / h.
10.3.9 Water-indicating instruments must have external protective devices that ensure the safety of service personnel in case of glass breakage. Protective devices should not obstruct the observation of the water level.
10.3.10 Water-indicating devices must be equipped with shut-off valves for disconnecting from the steam and water space of the boiler, which makes it possible to replace glasses and the body during operation of the boiler, as well as purge valves. It is allowed to use cork taps for these purposes. To drain water when purging water-indicating instruments, funnels with a protective device and a drain pipe for free draining should be used.
10.3.11. Fully automated boilers must be equipped with automatic devices for pointing and maintaining the water level in the boiler drum.
10.4 Pressure gauges
10.4.1 Pressure gauges installed on boilers and feed lines must have an accuracy class of at least 2.5.
10.4.2 Pressure gauges must be selected with such a scale that, at operating pressure, their pointer is in the middle third of the scale.
10.4.3 A red line should be put on the scale of the pressure gauge according to the division corresponding to the permitted pressure in the boiler, taking into account the additional pressure from the weight of the liquid column.
Instead of a red line, it is allowed to attach or solder to the pressure gauge body a metal plate, painted red and tightly attached to the pressure gauge glass, above the corresponding division of the scale. Putting a red line on the glass with paint is prohibited.
10.4.4 The pressure gauge should be installed so that its readings are visible to the operating personnel, while the dial of the pressure gauge should be in a vertical plane or tilted forward up to 30°.
10.4.5 The diameter of pressure gauge cases installed from the level of the pressure gauge observation platform at a height of up to 2 m must be at least 100 mm, at a height of 2-5 m - at least 160 mm and at a height of 5 m - at least 250 mm.
10.4.6 Each steam boiler must be equipped with a pressure gauge that communicates with the steam space of the boiler through a connecting siphon tube or through another similar device with a hydraulic seal.
10.4.7 For liquid fuel boilers, pressure gauges must be installed on the fuel supply pipeline to the nozzles (burners) after the last shut-off valve in the fuel flow, as well as on the common steam pipeline to the oil burners after the control valve.
10.4.8 Pressure gauges are not allowed to be used in cases where:
- there is no seal or stamp on the pressure gauge about the inspection;
- the period for checking the pressure gauge has expired;
- the arrow of the pressure gauge, when it is turned on, does not return to the zero reading of the scale by an amount exceeding half of the permissible error for this pressure gauge;
- the glass is broken or there is other damage that may affect the correct reading.
10.4.9 Pressure gauges should be placed on hot water boilers:
- at the water inlet to the boiler after the shut-off valve;
- at the outlet of heated water from the boiler to the shut-off body;
- on the suction and discharge lines of circulation and make-up pumps.
10.4.10 For each steam boiler, a pressure gauge should be installed on the feed line before the body that regulates the boiler feed.
If there are several boilers in the boiler room with a steam capacity of less than 2 t / h, it is allowed to install one pressure gauge on a common feed line.
Pressure gauges on the feed lines of steam and hot water boilers must be clearly visible to the operating personnel.
10.4.11 If a water supply network is used instead of the second feed pump, a pressure gauge must be installed on this water supply line in the immediate vicinity of the boiler.
10.4.12 Boilers operating on gaseous fuels must be equipped with control and measuring devices in accordance with.
10.5 Temperature measuring instruments
10.5.1 For hot water boilers, to measure the water temperature, it is necessary to install thermometers at the water inlet to the boiler and at the outlet from it.
At the outlet of water from the boiler, the thermometer must be located between the boiler and the shut-off device.
If there are two or more boilers in the boiler room, thermometers are also placed on the common supply and return pipelines. In this case, it is not necessary to install a thermometer on the return pipe of each boiler.
10.5.2 Thermometers should be installed on the feed pipes of steam boilers to measure the temperature of the feed water.
10.5.3 When operating boilers on liquid fuel requiring heating, the fuel line should be equipped with a thermometer that measures the temperature of the fuel in front of the nozzles. For boilers with a capacity below 50 MW, it is allowed to measure the temperature at the inlet to the boiler room.
10.6 Boiler fittings and piping
10.6.1 Fittings installed on boilers and pipelines must be marked, which should indicate:
- conditional diameter;
- conditional or working pressure and temperature of the medium;
- medium flow direction.
Valve handwheels must be marked with directions of rotation for opening and closing.
10.6.2 A shut-off valve or gate valve is installed on the steam pipeline from the boiler. Shut-off bodies on the steam pipeline are located as close as possible to the boiler.
10.6.3 A non-return valve and shut-off valves are installed on the steam boiler feed pipe.
10.6.4 A check valve and a shut-off valve (valve) are installed on the supply pipeline.
10.6.5 If there are several feed pumps having a common suction and discharge pipeline, shut-off devices are installed for each pump on the suction side and on the discharge side. A non-return valve is installed on the pressure pipe of the feed or circulating centrifugal pump up to the shut-off body.
10.6.6 The supply pipeline must have branch pipes for air release from the upper point of the pipeline and drains for draining water from the lower points of the pipeline.
10.6.7 For each hot water boiler connected to the common pipelines of network water, one shut-off device (valve or gate valve) is mounted on the supply and return pipelines of the boiler.
10.6.8 To prevent overheating of the boiler walls and increase in pressure in it in case of accidental shutdown of network pumps in a system with forced circulation, a pipeline with a shut-off device must be installed between the boiler and the valve (valve) to drain water to a safe place.
10.6.9 On the drain, purge and drainage lines of pipelines of steam boilers with a steam pressure of not more than 0.07 MPa (0.7 kgf / cm 2) and hot water boilers with a water heating temperature of not more than 115 ° C, one shut-off valve should be installed ( valves); on pipelines of steam boilers with a steam pressure of more than 0.07 MPa (0.7 kgf / cm 2) and hot water boilers with a water temperature of more than 115 ° C according to.
Safety valves provide automatic release of steam or water from boilers, superheaters and economizers that can be switched off (by water) in which the pressure has risen above the norm. They are divided into lever-load, spring and impulse.
At each steam and hot water boiler, economizer, switched off by the working environment, at least two safety valves (operating and control) must be installed. Safety valves protect boilers and water economizers when their pressure is exceeded by more than 10% of the calculated (allowed) pressure.
Figure: Safety valves:
a - lever cargo; b - spring; 1 - safety valve casing; 2 - chain for undermining the valve; 3 - load; 4 - lock; 5 - stock; 6 - body; 7 - saddle; 8 - plate; 9 - lever; 10 - pressure screw; 11 - spring; 12 - handle for opening the valve; => — flow direction.
In the lever cargo safety valve (Fig. 1a), the steam outlet from the valve is closed by a plate (8), which is pressed against the seat (7) inserted into the body (6) by a load (3) attached to the lever (9). The guide ribs of the plate do not allow it to warp relative to the saddle. The lever control valve after adjustment is enclosed in a casing (7) and closed with a lock (4). To check the operation of the valve, a chain (2) is attached to the lever, which is passed through the casing cover. There is a hole in the body for steam to escape.
The method and frequency of regulation of safety valves on boilers, superheaters and economizers and the pressure at which they begin to open must be specified by the manufacturer in the instructions for installation and operation of the boiler.
In spring-loaded safety valves (Fig. b), the pressure on the plate (8) is created by the spring (11). Pressure screws (10) are used to set the safety valves to actuate at the required pressure.
Pulse safety valves are installed on steam boilers with an operating pressure of more than 3.9 MPa.
Safety valve adjustmentboilers type DE
Safety valves are adjusted:
1. When starting the boiler, after installation.
2. When starting the boiler after being in reserve.
3. During the technical examination of the boiler.
4. According to the results of checking the serviceability of the safety valves.
5. When the operating pressure in the boiler changes.
The safety valves can be adjusted on the stand, during hydraulic tests or in the alkaline process when steam is discharged through the auxiliary line and installed steam outlet pipelines.
Safety valves should be inspected before installation. Lubricate the thread of the pressure sleeve (silver graphite - 20%, glycerin - 70%, copper powder - 10%), check the condition of the sealing surfaces, the presence of stem seals.
In normal operation, the valve is closed, the poppet is pressed against the seat by the force of the spring. The force of the spring on the plate is regulated by the amount of its compression, produced by means of a threaded pressure sleeve.
The pressure rises slowly and the safety valves are adjusted to the opening start pressure indicated in Table 3.
If it is necessary to operate the boiler at a reduced pressure (but not lower than the values specified in paragraph 1 of the section “Maintenance of the boiler”), the valves are adjusted according to this operating pressure, according to section 6.2. Boiler rules.
The safety valves are adjusted one by one in the following sequence (see P. II):
- set the required pressure in the boiler;
- remove the manual release lever (4) and protective cap (11);
- unscrewing the pressure sleeve (8) to achieve the beginning-undermining of the valve;
- reduce the pressure in the boiler until the valve is seated, while the difference between the pressure of lifting and seating the valve should be no more than 0.3 MPa. By turning the damper sleeve (9) clockwise, the difference is increased, counter-clockwise, it is reduced. To rotate the damper sleeve, it is necessary to loosen the locking screw (7), after completing the adjustment, lock the specified screw;
- measure the spring tightening height with an accuracy of 1 mm and write it down in a removable journal;
- at the end of the adjustment, reinstall the protective cap and the manual release lever;
- seal the protective cap.
To check the correct adjustment of safety valves, increase the pressure until the valve opens, then reduce the pressure until the valve closes.
If the valve actuation pressure does not correspond to the opening start pressure indicated in the table, and the difference between the pressure of lifting and seating the valve is more than 0.3 (3) MPa (kgf/cm 2 ), repeat the adjustment.
Brick drying, alkalizingboilers type DE
1. After the installation of the boiler is completed, it is recommended to dry the lining for 2-3 days with electric heaters, for wood or using steam from working boilers, which is fed into the boiler filled with water to the lower level through the heating line of the lower drum. The process of heating water in the boiler must be carried out gradually and continuously; at the same time, it is necessary to monitor the water level in the boiler using direct-acting level indicators. During the drying period, the water temperature in the boiler is maintained at 80-90°C.
2. Alkalinization of the boiler is carried out to clean the internal surfaces from oily deposits and corrosion products.
It is desirable to use chemically purified water to fill the boiler during alkaline and make-up during alkaline. It is allowed to fill the boiler with raw clarified water with a temperature not lower than + 5°С.
The superheater cannot be alkalized and is not filled with an alkaline solution.
It is cleaned from oily contaminants and rust by a steam flow, for which the superheater purge valve is opened before alkalizing.
Before alkalizing the boiler, the boiler is prepared for kindling (see the section “Inspection and preparation for kindling”).
In order to save time and fuel, the introduction of reagents and the start of alkalizing of the boiler should be carried out 1 day before the end of the lining drying.
The input of reagents can be carried out by means of a dosing pump with a capacity or through a tank with a capacity of 0.3-0.5 m3, installed above the platform of the upper drum. From the tank, enter the reagent solution through a flexible hose through the valve of the “steam for own needs” branch pipe.
For alkaline reagents are used: caustic (caustic soda) or soda ash and trisodium phosphate (table 4).
Reagents before entering dissolve to a concentration of about 20%. Solutions of soda and trisodium phosphate must be introduced separately to avoid crystallization of trisodium phosphate in the boiler pipes. It is possible to introduce a solution of reagents from the tank into the boiler only in the absence of pressure in the latter. Personnel working on the preparation of the solution and putting it into the boiler must be provided with overalls (rubber aprons, boots, rubber gloves and masks with goggles).
When loading solid reagents into the tank, it is not recommended to break them into pieces, but it is better to dissolve them in boiling water or heat the jar of reagents with an open end above the tank opening with steam.
Before the first fire-up of the boiler after installation, the springs of the safety valves are loosened if the valves have not been adjusted on the bench. With each rise in pressure during alkalizing (0.3; 1.0; 1.3 MPa), by tightening the pressure bushings, the spring pressure on the valve is matched to the steam pressure.
In case of alkalizing, after adding the reagents, fire up the boiler, in accordance with the requirements of the "Firing up" section, increase the pressure in the boiler to 0.3-0.4 MPa (3-4 kgf / cm 2) and tighten the bolted connections of hatches and flanges. Alkalinization at this pressure should be carried out for 8 hours with the boiler load not exceeding 25% of the nominal one.
Blow out the boiler at all points for 20-30 seconds. each and feed to the top level.
Reduce pressure to sub-atmospheric.
Raise the pressure to 1.0 MPa (10 kgf / cm 2 ) and alkalize at a load of not more than 25% - 6 hours.
Purging and make-up of the boiler is carried out at a pressure reduced to 0.3-0.4 MPa (3-4 kgf / cm 2 ).
New pressure rise to 1.3 MPa (13 kgf / cm 2), and for boilers for excess pressure of 2.3 MPa (23 kgf / cm 2) to a pressure of 2.3 MPa (23 kgf / cm 2) and alkalinization under load no more than 25% within 6 hours.
Boiler water is changed by repeated blowing and filling the boiler.
During the alkaline process, do not allow water to enter the superheater. The superheater purge valve is open all the time. The total alkalinity of the boiler water during alkalization must be at least 50 mg.e q/l. When it drops below this limit, an additional part of the reagent solution is introduced into the boiler, while the pressure in the boiler should not exceed atmospheric pressure.
The end of the alkalinization is determined as a result of the production of analyzes for the stability of the content of P 2 O 5 in water.
The consumption of reagents is shown in table 4. ¦
Table 4
|
Boiler size |
Name of reagents |
|
|
NaOH (caustic soda), kg |
Na 3 PO 4 x12 H 2 O (trisodium phosphate), kg |
|
|
DE-4-14GM |
26-40 |
15-25 |
|
DE-6.5-14GM |
30-50 |
20-25 |
|
DE-10-14(24)GM |
43-70 |
25-40 |
|
DE-16-14(24)GM |
70-110 |
|
|
DE-25-14(24)GM |
85-140 |
|
Note. Weight is for 100% reagent. Lower reagent value for clean boilers, higher for boilers with a large layer of rust.
After alkalization, the pressure is reduced to zero, and after the water temperature drops to 70-80°C, water is drained from the boiler.
The hatches of the drums and the hatches of the collector are opened, the drums, intra-drum devices, pipes are thoroughly washed from a hose with a fitting with a water pressure of 0.4-0.5 MPa (4-5 kgf / cm 2), preferably with a temperature of 50-60 ° C.
The condition of the heating surfaces is recorded in the HVO log.
After alkalizing, it is necessary to revise the purge and drain valves and direct-acting water level indicators.
If the period between alkalinization and start-up of the boiler exceeds 10 days, then the boiler must be put into conservation.
3. After alkalizing, warm up and blow out the steam pipeline from the boiler to the points of connection to the operating sections of the steam pipelines or to the steam consumers.
During heating and purge, the following operations are performed:
- the pressure in the boiler rises to the working one;
- the water level rises above the average by 30 mm;
- the air vent and drain valves open on the steam line;
- gradually open the steam shut-off valve, reaching the highest steam flow within 5-10 minutes, while monitoring the water level in the boiler.
Note: The procedure for purging the steam line may be different. It is regulated by the requirements of the production instructions, depending on the schemes of steam pipelines, purge pipelines and valve control automation.
Comprehensive testing of boiler units and adjustment during complex testingboilers type DE
Comprehensive testing is the final stage installation work.
Generaland subcontractors that carried out the installation of the boiler, instrumentation, auxiliary equipment, electrical installation and other works, during the period of comprehensive testing of the boiler unit, ensure that their personnel are on duty to promptly eliminate the identified defects in construction and installation works in accordance with the requirements of SNiP-3.05.05-84.
Before performing a comprehensive testing, the customer, together with the commissioning organization, draw up a testing program. Comprehensive testing is carried out by the customer's personnel with the involvement of service technicians.
The procedure for comprehensive testing of the boiler and adjustment at the same time must be brought into line with the requirements of SNiP 3.01.04-87 and GOST 27303-87.
Loads for complex testing are determined in the program (as a rule: nominal, minimum possible and intermediate).
Testing of the boiler operation in combination with an economizer, draft mechanisms, a piping system, ancillary equipment of the boiler room, and an instrumentation and control system is carried out within 72 hours. During this period, the commissioning organization performs commissioning of the furnace and water-chemical regime, the instrumentation and automation system with the issuance of temporary regime cards. After the end of the comprehensive testing, defects and malfunctions identified during its implementation are eliminated (if necessary, the boiler stops); an act of comprehensive testing and commissioning of the boiler is drawn up.
They serve to prevent the destruction of boilers and vessels when the operating pressure is exceeded. They are divided into cargo, spring and impulse.
lever valve (see fig. 7) has a lever with a load, under the action of which it closes. At normal pressure in the boiler, this weight presses the valve disc to the seat, that is, the pressure of steam and weight on the valve is balanced. When the pressure rises, the valve rises, the excess pressure is removed to the atmosphere, and the valve, under the action of the weight of the load, lowers onto the seat. Suspension of an additional weight on the lever or jamming of the valve in order to eliminate leaks is not allowed. They are produced single-cargo with DN = 25,32,40,80,100 mm and two-cargo with Du = 80,100,125,150,200 mm. The valves are adjusted by moving the load along the lever.
a - single-lever
b - double lever
1 - body
2 - housing cover
3 - valve
4 - valve seat
8 - rack
9 - restrictive bracket
10 - locking bolts
IN spring valves (see fig. 8b) pressure in the apparatus is balanced by the force of compression of the spring. These valves are used on receivers, mobile boilers, and in Lately they began to be used for installation on boilers of type E and DE. They are produced with DN = 25,40,50,80,100 mm.
Fig.8. Safety valves:
a - cargo:
1 - cover
2 - lever with load
4 - body
5 - spindle
6 - valve seat
7 - plate
b - spring valve:
1 - fitting
2 - valve
3 - body
4 - spring
6 - locknut
7 - adjusting screw.
Pulse valves are installed on steam boilers with an operating pressure of more than 39 kgf / cm 2 ( 3,9 MPa).
At least two valves must be installed on each steam and hot water boiler and economizer that is switched off due to the working medium and the superheater. One of them - the control one - must be in a metal casing, closed with a lock or sealed and have a device for undermining it, and the second one must be working.
The safety valves of steam boilers are adjusted to start opening at a pressure that does not exceed the following values:
On hot water boilers, they must be adjusted to start opening at a pressure of not more than 1.08 R working pressure in the boilers.
Equipment Check Valves They allow the medium to flow in only one direction and serve to protect equipment from damage due to reverse flow of the medium. They are produced in two types: lifting (see fig. 9a) And rotary (see fig. 9b) . According to the type of case material, they are produced: cast iron, steel and bronze. According to the method of connection with the pipeline, they are coupling and flanged.
Check lift valve consists of a body, in the round through hole of which a seat is pressed, closing with a valve disc. For tight closing, the valve disc is lapped against the seat. The body is closed with a lid, where the guide rod of the plate enters. When the water moves in the opposite direction, the valve disc drops and the reverse movement of water stops.
Rice. 9. Check valves:
a - lifting
b - rotary
Check valve (see fig. 10) consists of a body with a hinged damper, which rises under the pressure of the moving medium and the valve opens. When the pump is turned off or there is an emergency pressure drop after the valve, the valve closes and the reverse flow of water stops.
Rice. 10. Swing check valve:
2 - body
3 - valve
4 - valve seat
5 - valve axis
Lift check valves are installed only on horizontal pipelines, while rotary check valves are installed on horizontal and vertical pipelines.
Check valves must be installed on the shut-off device in the direction of water flow. Check valves with coupling connection are manufactured for small nominal diameters DN = 15,20,25,32,40,50,80 mm, and with flange - Du = 20-200 mm.
Cranes with nominal bore up to 50 mm are made with a threaded cover, and more than 50 mm with studded lid.
fusible plugs(see fig. 11) are designed to prevent damage to DKVR boilers when draining water. They have a conical shape with an external thread and are screwed into the lower part of the upper drum from the firebox side (2 pcs.).
Rice. 11. Control fusible plug:
1 - stamp
3 - body
The plug hole is filled with a low-melting alloy (90% lead and 10% tin), the melting point of which is 280-310 o C.
At a normal water level in a steam boiler, the fusible alloy is cooled by water and does not melt. When the water is drained, the plugs are not cooled, but at the same time, from the side of the furnace, they continue to heat up with the products of fuel combustion and the low-melting alloy melts. Through the hole formed, the steam-water mixture under pressure enters the furnace with noise, which serves as a signal for an emergency stop of the boiler.
For reliable operation, the plugs must be replaced or refilled at least once a quarter. when replacing, a stamp is applied with the date.
Requirements of the Rules (PB-10-574-03):
Each boiler must be equipped with at least two safety valves.
The total capacity of the safety devices installed on the steam boiler must be at least the nominal steam output of the boiler
The use of lever-weight safety valves is not allowed
Only safety valves of the fully closed type are allowed to be used.
The nominal passage of the safety valve must be at least 25 and not more than 150 mm.
Safety valves must protect boilers, superheaters and economizers from exceeding the pressure in them by more than 10% of the calculated (allowed).
The design of spring valves should exclude the possibility of tightening the spring beyond the specified value. The valve springs must be protected from direct influence of the escaping steam jet.
STATE STANDARD OF THE UNION OF THE SSR
SAFETY VALVES
STEAM AND WATER BOILERS
TECHNICAL REQUIREMENTS
GOST 24570-81
(ST SEV 1711-79)
USSR STATE COMMITTEE ON STANDARDS
STATE STANDARD OF THE UNION OF THE SSR
|
SAFETY VALVES FOR STEAM AND WATER BOILERS Technicalrequirements Safety valves of stream and hot-water boilers. |
GOST (ST SEV 1711-79) |
Decree of the USSR State Committee for Standards dated January 30, 1981 No. 363 established the deadline for introduction
from 01.12.1981
Checked in 1986. By the Decree of the State Standard of 06/24/86 No. 1714, the validity period was extended
until 01.01.92
Non-compliance with the standard is punishable by law
This standard applies to safety valves fitted to steam boilers with absolute pressure above 0.17 MPa (1.7 kgf / cm2) and hot water boilers with a water temperature above 388 K (115 ° WITH).
The standard fully complies with ST SEV 1711-79.
The standard establishes mandatory requirements.
1. GENERAL REQUIREMENTS
1.1. To protect boilers, safety valves and their auxiliary devices are allowed that meet the requirements of the "Rules for the Design and Safe Operation of Steam and Hot Water Boilers" approved by the USSR Gosgortekhnadzor.
(Revised edition, Rev. No. 1).
1.2. The design and materials of elements of safety valves and their auxiliary devices must be selected depending on the parameters of the working environment and ensure reliability and correct operation under working conditions.
1.3. The safety valves must be dimensioned and adjusted so that the pressure in the boiler does not exceed the operating pressure by more than 10%. An increase in pressure is allowed if this is provided for by the strength calculation of the boiler.
1.4. The design of the safety valve must ensure free movement of the moving elements of the valve and exclude the possibility of their ejection.
1.5. The design of safety valves and their auxiliary elements must exclude the possibility of arbitrary changes in their adjustment.
1.6. Each safety valve or, as agreed between the manufacturer and the consumer, a group of identical valves intended for one consumer, must be accompanied by a passport and operating instructions. The passport must comply with the requirements of GOST 2.601-68. The section "Basic technical data and characteristics" should contain the following data:
name of the manufacturer or its trademark;
Year of manufacture;
valve type;
conditional diameter at the inlet and outlet of the valve;
design diameter;
calculated cross-sectional area;
type of environment and its parameters;
characteristics and dimensions of the spring or load;
steam flow ratea , equal to 0.9 of the coefficient obtained on the basis of the tests;
allowable back pressure;
the pressure value of the beginning of opening and the permissible range of the pressure of the beginning of opening;
characteristics of the materials of the main elements of the valve (body, plate, seat, spring);
valve type test data;
catalog code;
conditional pressure;
permissible limits of working pressures on the spring.
1.7. The following data must be marked on a plate affixed to the body of each safety valve, or directly on its body:
name of the manufacturer or its trademark;
serial number according to the numbering system of the manufacturer or series number;
Year of manufacture;
valve type;
design diameter;
steam flow ratea;
pressure value of the beginning of opening;
conditional pressure;
conditional diameter;
flow arrow;
body material for fittings made of steel with special requirements;
designation of the main design document and symbol of the product.
The place of marking and the size of markings are established in the technical documentation of the manufacturer.
1.6, 1.7.(Changed edition, Change № 1).
2. REQUIREMENTS FOR DIRECT ACTING RELIEF VALVES
2.1. The design of the safety valve must include a device for checking the correct operation of the valve during operation of the boiler by forcibly opening the valve.
The possibility of forced opening must be ensured at 80% of the opening pressure.
2.1.
2.2. The pressure difference between the full opening and the beginning of the opening of the valve must not exceed the following values:
15% of the opening start pressure - for boilers with a working pressure not higher than 0.25 MPa (2.5 kgf / cm 2);
10% of the opening start pressure - for boilers with a working pressure above 0.25 MPa (2.5 kgf / cm 2).
2.3. Safety valve springs must be protected from impermissible heating and direct exposure to the working medium.
When the valve is fully opened, the possibility of mutual contact of the coils of the spring must be excluded.
The design of spring valves must exclude the possibility of tightening the springs beyond the set value, due to the highest working pressure for this valve design.
2.3. (Revised edition, Rev. No. 2).
2.4. The use of stuffing box seals on the valve stem is not allowed.
2.5. In the body of the safety valve, in places of possible accumulation of condensate, a device must be provided for its removal.
2.6. (deleted , Change No. 2).
3. REQUIREMENTS FOR SAFETY VALVES CONTROLLED BY AUXILIARY DEVICES
3.1. The design of the safety valve and auxiliary devices must exclude the possibility of impermissible shocks during opening and closing.
3.2. The design of safety valves must ensure that the function of protection against overpressure is maintained in the event of failure of any control or regulatory body of the boiler.
3.3. Motorized safety valves must be supplied with two independent power supplies.
In electrical circuits where the loss of energy causes a pulse to open the valve, one source of electrical power is allowed.
3.4. The design of the safety valve must provide for the possibility of manual control and, if necessary, remote control.
3.5. The design of the valve must ensure its closing at a pressure of at least 95% of the working pressure in the boiler.
3.6. The diameter of the pulse valve through passage must be at least 15 mm.
The internal diameter of the impulse lines (inlet and outlet) must be at least 20 mm and not less than the diameter of the outlet fitting of the impulse valve.
Impulse and control lines must have condensate drains.
Installation of locking devices on these lines is not allowed.
It is allowed to install a switching device if, in any position of this device, the impulse line will remain open.
3.7. For relief valves controlled by auxiliary pulse valves, more than one pulse valve is allowed.
3.8. Relief valves must be operated in conditions that do not allow freezing, coking and corrosive effects of the medium used to control the valve.
3.9. When using an external power source for auxiliary devices, the safety valve must be equipped with at least two independently operating control circuits so that if one of the control circuits fails, the other circuit ensures reliable operation of the safety valve.
4. REQUIREMENTS FOR INLET AND OUTLET PIPING OF SAFETY VALVES
4.1. It is not allowed to install locking devices on the inlet and outlet pipelines of safety valves.
4.2. The design of pipelines of safety valves should provide the necessary compensation for thermal expansion.
The fastening of the body and pipelines of safety valves must be calculated taking into account static loads and dynamic forces arising from the operation of the safety valve.
4.3. The supply pipes of the safety valves must have a slope along the entire length towards the boiler. In the supply pipelines, sudden changes in wall temperature should be excluded when the safety valve is actuated.
4.4. The pressure drop in the supply pipeline to direct acting valves must not exceed 3% of the pressure at which the safety valve starts to open. In the supply pipelines of safety valves controlled by auxiliary devices, the pressure drop must not exceed 15%.
When calculating the capacity of the valves, the indicated pressure reduction in both cases is taken into account.
4.4. (Revised edition, Rev. No. 2).
4.5. The discharge of the working medium from the safety valves must be carried out to a safe place.
4.6. The discharge pipes must be frost-proof and equipped with a condensate drain.
Installation of locking devices on drains is not allowed.
4.6.(Revised edition, Rev. No. 2).
4.7. The inner diameter of the discharge pipeline must be at least the largest inner diameter of the outlet pipe of the safety valve.
4.8. The internal diameter of the outlet pipeline must be calculated so that at a flow rate equal to the maximum capacity of the safety valve, the back pressure in its outlet pipe does not exceed the maximum back pressure set by the manufacturer of the safety valve.
4.9. The throughput of safety valves should be determined taking into account the resistance of the silencer; its installation must not interfere with the normal operation of the safety valves.
4.10. In the area between the safety valve and the silencer, a fitting must be provided for installing a pressure measuring device.
5. CAPACITY OF SAFETY VALVES
5.1. The total capacity of all safety valves installed on the boiler must meet the following conditions:
for steam boilers
G1+G2 + ...G n³ D;
for economizers disconnected from the boiler
for hot water boilers
n- number of safety valves;
G1,G2,G n- capacity of individual safety valves, kg/h;
D- nominal capacity of the steam boiler, kg/h;
Increase in water enthalpy in the economizer at nominal boiler capacity, J/kg (kcal/kg);
Q- nominal thermal conductivity of the boiler, J/h (kcal/h);
g- heat of vaporization, J/kg (kcal/kg).
Calculation of the capacity of the safety valves of hot water boilers and economizers can be carried out taking into account the ratio of steam and water in the steam-water mixture passing through the safety valve when it is triggered.
5.1. (Revised edition, Rev. No. 2).
5.2. The capacity of the safety valve is determined by the formula:
G = 10B 1 × a× F(P 1 +0.1) - for pressure in MPa or
G= B 1 × a× F(P 1 + 1) - for pressure in kgf / cm 2,
Where G- throughput capacity of the valve, kg/h;
F- estimated cross-sectional area of the valve, equal to the smallest area of the free section in the flow part, mm 2 ;
a- steam flow rate, referred to the cross-sectional area of the valve and determined in accordance with clause 5.3 of this standard;
R 1 - maximum overpressure in front of the safety valve, which should be no more than 1.1 working pressure, MPa (kgf / cm 2);
IN 1 - coefficient taking into account the physical and chemical properties of steam at operating parameters in front of the safety valve. The value of this coefficient is chosen according to the table. 1 and 2.
Table 1
Coefficient values IN 1 for saturated steam
|
R 1, MPa (kgf / cm 2) |
|||||||
|
R 1, MPa (kgf / cm 2) |
|||||||
|
R 1, MPa (kgf / cm 2) |
|||||||
table 2
Coefficient values IN 1 for superheated steam
|
R 1, MPa (kgf / cm 2) |
At steam temperaturet n, ° WITH |
||||||||
|
0,2 (2) |
0,480 |
0,455 |
0,440 |
0,420 |
0,405 |
0,390 |
0,380 |
0,365 |
0,355 |
|
1 (10) |
0,490 |
0,460 |
0,440 |
0,420 |
0,405 |
0,390 |
0,380 |
0,365 |
0,355 |
|
2 (20) |
0,495 |
0,465 |
0,445 |
0,425 |
0,410 |
0,390 |
0,380 |
0,365 |
0,355 |
|
3 (30) |
0,505 |
0,475 |
0,450 |
0,425 |
0,410 |
0,395 |
0,380 |
0,365 |
0,355 |
|
4 (40) |
0,520 |
0,485 |
0,455 |
0,430 |
0,410 |
0,400 |
0,380 |
0,365 |
0,355 |
|
6 (60) |
0,500 |
0,460 |
0,435 |
0,415 |
0,400 |
0,385 |
0,370 |
0,360 |
|
|
8 (80) |
0,570 |
0,475 |
0,445 |
0,420 |
0,400 |
0,385 |
0,370 |
0,360 |
|
|
16 (160) |
0,490 |
0,450 |
0,425 |
0,405 |
0,390 |
0,375 |
0,360 |
||
|
18 (180) |
0,480 |
0,440 |
0,415 |
0,400 |
0,380 |
0,365 |
|||
|
20 (200) |
0,525 |
0,460 |
0,430 |
0,405 |
0,385 |
0,370 |
|||
|
25 (250) |
0,490 |
0,445 |
0,415 |
0,390 |
0,375 |
||||
|
30 (300) |
0,520 |
0,460 |
0,425 |
0,400 |
0,380 |
||||
|
35 (350) |
0,560 |
0,475 |
0,435 |
0,405 |
0,380 |
||||
|
40 (400) |
0,610 |
0,495 |
0,445 |
0,415 |
0,380 |
||||
or determined by the formula for pressure in MPa
for pressure in kgf / cm 2
Where TO- adiabatic index equal to 1.35 for saturated steam, 1.31 for superheated steam;
R 1 - maximum excess pressure in front of the safety valve, MPa;
V 1 - specific volume of steam in front of the safety valve, m 3 /kg.
The valve capacity formula should only be used if: ( R 2 +0,1)£ (R 1 +0,1)b cr for pressure in MPa or ( R 2 +1)£ (R 1 +1)b kr for pressure in kgf / cm 2, where
R 2 - the maximum overpressure behind the safety valve in the space into which steam flows from the boiler (when flowing into the atmosphere R 2 \u003d 0 MPa (kgf / cm 2);
b cr is the critical pressure ratio.
For saturated steam b cr = 0.577, for superheated steam b cr = 0.546.
5.2. (Revised edition, Rev. No. 2).
5.3. Coefficient a taken equal to 90% of the value obtained by the manufacturer on the basis of the tests.
6. CONTROL METHODS
6.1. All safety valves must be tested for strength, tightness, and tightness of stuffing boxes and sealing surfaces.
6.2. The scope of valve testing, their procedure and methods of control must be established in the technical specifications for valves of a specific size.