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Six ways to relieve safety valve failure

The safety valve is a valve that protects the system from being damaged due to high pressure. Once the pressure in the system piping or device exceeds the set value, it will automatically release the pressure, so as to achieve the purpose of safety protection.
The main cause of failure of a safety valve is caused by improper design, manufacture, selection, or use. If these failures are not eliminated in time, the effectiveness and life of the valve will be affected, and even safety protection will not be available.
Safety valve common failures and elimination methods:
(1) The valve flap does not return to seat after discharge. This is mainly caused by the spring bending valve stem, the valve disc mounting position being incorrect or being stuck. Should be re-assembled.
(2) Leakage. Under the normal operating pressure of the device, leakage beyond the allowable level occurs between the disc and the sealing surface of the valve seat. The reasons are: There is dirt between the valve flap and the sealing surface of the valve seat. Use a lifting wrench to open the valve a few times to flush away the dirt; the sealing surface is damaged. Should be based on the degree of damage, grinding or grinding after grinding method to repair; valve stem bending, tilting or deflection of the lever and fulcrum, so that the spool and valve disc misalignment. Should be reassembled or replaced; spring elasticity reduced or lost elasticity. Replace the spring and readjust the opening pressure.
(3) Does not turn on when pressure is specified. The reason for this situation is that constant pressure is not allowed. The amount of spring compression or the position of the weight should be readjusted; the valve flap sticks to the valve seat. The safety valve shall be manually deflated or drained periodically; the leverage of the lever-type safety valve is jammed or the hammer is moved. The weight position should be readjusted and the lever should move freely.
(4) The pressure continues to rise after exhausting. This is mainly due to the safety discharge volume of the selected safety valve displacement level equipment. The appropriate safety valve should be selected again; the stem centerline is not correct or the spring is rusted, so that the valve disc cannot be opened to the proper height. The valve stem should be reassembled. Or replace the spring; exhaust pipe cut enough, should be taken to meet the safety discharge area of the exhaust pipe.
(5) Valve flap or vibration. This is mainly due to the high spring stiffness. Should use a spring with appropriate stiffness; improper adjustment of the adjustment ring will make the pressure in the seat back too high. The position of the adjusting ring should be readjusted; the discharge pipe resistance is too large, resulting in excessive discharge back pressure. The discharge pipe resistance should be reduced.
(6) The pressure is less than the prescribed pressure. The main reason is that the constant pressure is not accurate; the elasticity of the spring is reduced. Tighten the adjusting screw or replace the spring properly.

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