The Common Faults and Choose Principle of safety valve

In the last article we learned the basic operation knowledge of the safety valve, but how to solve the problems encountered during operation? How do we choose a suitable safety valve? 

Common faults of safety valves

1. The safety valve disc does not return to the seat after discharge. This is mainly caused by the spring bent valve stem, the valve disc installation position is incorrect or it is stuck, so it should be reassembled. 

2. The safety valve does not open when it reaches the specified pressure. The reason for this is the inaccurate constant pressure. In this way, the compression amount of the spring or the position of the weight should be readjusted, and the valve disc and the valve seat are stuck. We should conduct manual air release or water release tests on safety valves; 

3. After the safety valve exhausts, the pressure continues to rise. This is mainly because the displacement of the selected safety valve is less than the safety relief of the equipment. A suitable safety valve should be selected again; the centerline of the valve stem is incorrect or the spring is rusted, so that the valve flap cannot be opened to the desired height, and the valve stem should be reassembled Or replace the spring; 

4.Safety valve flaps flutter or vibrate. It is mainly due to the stiffness of the spring. This should be replaced with a spring with appropriate stiffness; improper adjustment of the adjustment ring makes the return pressure too high. The position of the adjusting ring should be readjusted; the resistance of the discharge pipe is too large, causing excessive discharge back pressure. The discharge pipe resistance should be reduced.

Selection principle of safety valve

1. For steam boiler safety valve, the open full-open spring safety valve 0490 series is generally selected; 

2. The safety valve for liquid medium is generally selected as the micro-opening spring safety valve 0485 series; the air or other gas medium safety valve is generally selected as the full-open spring safety valve; 

3. LPG tank trucks or LPG railway tankers generally use full-open safety valves; safety valves for oil well exits are generally pilot-operated safety valves; 

4. The high pressure bypass safety valve of steam power generation equipment is generally a pilot safety valve with dual functions of safety and control. 

5. When the safety valve is tested regularly, we should choose a safety valve with a lift wrench. When the medium pressure reaches more than 75% of the opening pressure, the valve disc can be slightly lifted from the valve seat by using a lift wrench to check the flexibility of the safety valve opening; 

6. If the temperature of the medium is high, in order to reduce the temperature of the spring chamber, generally when the temperature of the closed safety valve exceeds 300 ° C and the temperature of the open safety valve exceeds 350 ° C, a safety valve with a radiator should be selected;  

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