• Pressure Tests for Gate Valves, Throttle Valves, and Globe Valves

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Pressure Tests for Gate Valves, Throttle Valves, and Globe Valves

  • Oct 11, 2019
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In general, industrial valves are not tested for strength during use, but the valve body and bonnet after repair or corroded body and bonnet should be tested for strength. For safety valves, the constant pressure and return pressure and other tests shall comply with the specifications and relevant regulations. Valve strength test and valve tightness test shall be performed on the valve hydraulic test board before valve installation. The low pressure valve is checked by 20%. If it is not qualified, it should be 100% inspection; the medium and high pressure valves should be checked 100%. Commonly used media for valve pressure test are water, oil, air, steam, nitrogen, etc. The pressure test methods for various industrial valves, pneumatic valves included, are as follows:

01. Pressure tests for globe valves and throttle valves

The strength test of the globe valve and the throttle valve is usually to place the assembled valve in the pressure test frame, open the valve flap, inject the medium to the specified value, and check whether the valve body and the valve cover are sweating and leaking. The strength test can also be carried out in one piece. The sealing test is only performed for a globe valve. During the test, the valve stem of the globe valve is in a vertical state, the valve flap is opened, the medium is introduced from the lower end of the valve flap to the specified value, and the packing and the gasket are inspected; no leakage is acceptable; after being qualified, the valve flap is closed, and the other end is opened to check for leakage. If both the valve strength test and the tightness test are to be done, the strength test may be performed first, then the pressure is reduced to the specified value of the sealing test, and the packing and the gasket are inspected; then the valve flap is closed, and the outlet end is opened to check whether the sealing surface leaks.

02. Pressure tests for gate valves

The strength test of the gate valve is the same as that of the globe valve. There are two methods for the sealing test of the gate valve.

① The gate is opened to raise the pressure inside the valve to the specified value; then close the gate, immediately take out the gate valve, check whether there is leakage at the seals on both sides of the gate or directly inject the testing medium into the plug on the valve cover to the specified value. Check the seals on both sides of the gate. The above method is called intermediate pressure test. This method is not suitable for sealing tests on gate valves with nominal diameters below DN32 mm.

② Another method is to open the gate to raise the valve testing pressure to the specified value; then close the gate, open the blind plate at one end, and check whether the sealing surface leaks. Then go back and repeat the above test until it is qualified.

The sealing test of the pneumatic gate valve packing and gasket shall be carried out before the sealing test of the gate.