Boiler pressure relief valve Boiler is a kind of energy conversion equipment. The energy input to the boiler includes chemical energy and electric energy in the fuel. The boiler outputs steam, high temperature water or organic heat carrier with certain heat energy. The original meaning of the…
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Boiler pressure relief valve
Boiler is a kind of energy conversion equipment. The energy input to the boiler includes chemical energy and electric energy in the fuel. The boiler outputs steam, high temperature water or organic heat carrier with certain heat energy.
The original meaning of the pot refers to the water container heated on the fire, and the furnace refers to the place where fuel is burned. The boiler consists of two parts: the pot and the furnace. Hot water or steam generated in boilers can directly provide the necessary heat energy for industrial production and people’s lives. It can also be converted into mechanical energy through steam power devices or into electrical energy through generators. Boilers that provide hot water are called hot water boilers. They are mainly used in daily life and also in industrial production. Boilers that produce steam are called steam boilers, often referred to as boilers, and are mostly used in thermal power plants, ships, locomotives and industrial and mining enterprises.
Operation Method of Boiler Pressure Reducing Valve
Adjustment of opening pressure:
Before the safety valve leaves the factory, the opening pressure should be adjusted step by step to the setting value required by the user. If the user puts forward the spring working pressure level, the lower limit value of the pressure level should be adjusted to leave the factory.
(2) Before installing the safety valve on the protected equipment or before installing it, the user must readjust it at the installation site to ensure that the setting pressure of the safety valve meets the requirements.
(3) Within the working pressure level of the spring indicated in the nameplate, the opening pressure can be adjusted by rotating the adjusting screw to change the compression of the spring.
(4) Before rotating the adjusting screw, the inlet pressure of the valve should be reduced to less than 90% of the opening pressure to prevent the disc from being driven to rotate when rotating the adjusting screw, so as to damage the sealing surface.
In order to ensure that the opening pressure is accurate, the medium conditions, such as the type of medium, temperature and so on, should be adjusted as close as possible to the actual operating conditions. When the type of medium changes, especially when the accumulation state of the medium is different (e.g. from liquid to gas), the opening pressure often changes. When the working temperature rises, the opening pressure generally decreases. Therefore, when it is adjusted at room temperature and used at high temperature, the setting pressure value at room temperature should be slightly higher than the required opening pressure value. To what extent is related to the valve structure and material selection, it should be based on the manufacturer’s instructions.
_Conventional safety valves are used to fix additional back pressure. When the opening pressure is adjusted after inspection (when the back pressure is atmospheric pressure), the setting value should be the required opening pressure value minus the additional back pressure value.
Adjustment of discharge and backup pressure:
To adjust the discharge pressure and return pressure of the valve, it is necessary to carry out the action test of the valve reaching the full open height. Therefore, it is only possible to carry out the test on a large capacity test device or after the safety valve is installed on the protected equipment. The adjustment method varies according to the valve structure.
For the structure with recoil disc and seat adjusting ring, the seat adjusting ring is used to adjust. By unscrewing the fixing screw of the adjusting ring and extending a thin iron rod from the exposed screw hole, the gear teeth on the adjusting ring can be moved to turn the adjusting ring left and right. When the adjusting ring rotates counterclockwise to the left, the position of the adjusting ring rises, and the discharge pressure and the return pressure will be reduced. On the contrary, when the adjusting ring rotates clockwise to the right, the position of the adjusting ring decreases, and the discharge pressure and the return pressure will increase. When adjusting each time, adjust: the rotating range of the circle should not be too large (the number of teeth can be rotated in general). After each adjustment, the fixed screw should be screwed up so that the end of the screw is located in the groove between the two teeth of the adjusting ring, which can prevent the rotating of the adjusting ring and generate no radial pressure on the adjusting ring. In order to be safe, the inlet pressure of the safety valve should be reduced appropriately (generally less than 90% of the opening pressure) before the adjusting ring is moved to prevent the sudden opening of the valve during the adjusting process and cause accidents.
(3) For the structure with upper and lower adjusting rings (one adjusting ring on the guide sleeve and one adjusting ring on the valve seat), the adjustment is more complicated. The seat regulating ring is used to change the size of the passage between the disc and the regulating ring, thereby changing the degree of pressure accumulation in the chamber between the disc and the regulating ring when the valve is initially opened. When the seat regulating ring is raised, the degree of pressure accumulation increases, so that the proportional opening stage of the valve decreases and achieves sudden and rapid opening. Therefore, raising the seat regulating ring can reduce the discharge pressure. It should be noted that the seat adjustment ring should not rise too close to the disc. In that case, leakage at the sealing surface may cause the valve to suddenly open prematurely, but because the medium pressure is not enough at this time to keep the disc in the open position, the disc then closes, so the valve occurs frequent jumps. Seat adjustment: The ring is mainly used to reduce the valve proportion, open the stage and adjust the discharge pressure, but also has an impact on the return pressure.
The adjusting ring is used to change the angle of the flow medium bending after reflection on the lower side of the valve disc, thereby changing the magnitude of the fluid force, so as to adjust the return pressure. When the adjusting ring is raised and raised, the bending angle decreases, and the fluid force decreases accordingly, so that the return pressure increases. On the contrary, when the adjusting ring is lowered, the backing pressure decreases. Of course, while changing the backup pressure, the upward adjustment ring also affects the discharge pressure, that is, the upward adjustment ring increases the discharge pressure, and the lower adjustment ring reduces the discharge pressure, but its impact is not as obvious as the backup pressure.
Safety valve lead seal:
When the safety valve is adjusted, it should be sealed with lead to prevent any change in the adjusted condition. When repairing the relief valve, the position of adjusting screw and adjusting ring should be noted before removing the valve so as to facilitate the adjustment after repairing. Lead seal should be applied again after readjustment.
Common faults
Disc does not return after discharge: This is mainly caused by spring bending stem, incorrect installation position of disc or stuck. It should be reassembled.
Leakage: Under the normal working pressure of the equipment, leakage occurs between the disc and the sealing surface of the valve seat beyond the allowable level. The reasons are: there is dirt between the valve disc and the sealing surface of the valve seat. The lifting wrench can be used to open the valve several times to wash away dirt; the sealing surface is damaged. It should be repaired by grinding or grinding after turning according to the degree of damage; the valve stem is bent, inclined or the lever and fulcrum are deflected, so that the spool and disc are dislocated. It should be reassembled or replaced; spring elasticity is reduced or lost. The spring should be replaced and the opening pressure should be readjusted.