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How often is the safety valve checked?

Under normal circumstances, the safety valve shall be calibrated at least once a year.

The inspection period is once a year, and it is generally carried out under the boiler operation. Pure mechanical spring safety valve can be calibrated and adjusted by hydraulic device, generally at 75% to 80% of rated pressure. For safety valves regulated by hydraulic devices, at least the actual lifting of the safety valve with the lowest lifting value should be checked. In addition, once the safety valve is qualified, it should be locked or sealed with lead, and recorded in the boiler technical register or pressure vessel technical file.

How is the function of safety valve realized?

Safety valve plays a safety protection role in the system. When the system pressure exceeds the specified value, the safety valve is opened, and a part of gas/fluid in the system is discharged into the atmosphere/pipeline, so that the system pressure does not exceed the allowable value, thus ensuring that the system will not have an accident due to excessive pressure.

The working principle of the safety valve is driven or controlled by the medium discharged by the pilot valve. The pilot valve itself is a direct-acting safety valve, and other types of valves are sometimes used.

1, direct-acting safety valve

The direct-acting safety valve is opened under the direct action of the working medium, that is, the mechanical load exerted by the loading mechanism is overcome by the pressure of the working medium to open the valve. This safety valve has the advantages of simple structure, quick action and good reliability. However, because it depends on the structural load, its load is limited, so it can not be used in high pressure and large caliber occasions.

2. Indirect action safety valve

This kind of safety valve can be divided into pilot safety valve and safety valve with power auxiliary device. The pilot safety valve is driven or controlled by the medium discharged from the pilot valve. The pilot valve itself is a direct-acting safety valve, and other types of valves are sometimes used. Pilot safety valve is suitable for high pressure and large caliber occasions.

The main valve of the pilot safety valve can also be designed to be sealed by the working medium, or the mechanical load on the disc can be much greater than that of the direct-acting safety valve, so it has good sealing performance. At the same time, its action is rarely affected by back pressure.

The disadvantage of this kind of safety valve is that its reliability is related to the main valve and pilot valve, and its action is not as fast and reliable as that of direct-acting safety valve, and its structure is also complicated.

With the help of the power auxiliary device, the safety valve with the power auxiliary device is forced to open under the condition of lower than the normal opening pressure. This kind of safety valve is suitable for occasions where the opening pressure is very close to the working pressure, or where it is necessary to open the safety valve regularly to check or blow off stuck and frozen media. At the same time, it also provides a means to forcibly open the safety valve in an emergency.