What are the test pressure methods of commonly used industrial valves?

In general, industrial valves are not tested for strength when in use, but the body and cover of the valve after repair or corrosion damage should be tested for strength. For the safety valve, its fixed pressure and back seat pressure and other tests should be in accordance with its instructions and the provisions of the relevant regulations. Valve should be installed before the valve hydraulic test bench for the valve strength test and valve sealing test. Low-voltage valve sampling 20%, such as failure should be 100% of the inspection; medium and high pressure valves should be 100% of the inspection. Valve test pressure commonly used media are water, oil, air, steam, nitrogen, etc., all types of industrial valves including pneumatic valves test pressure methods are as follows: <p

1, the test pressure method for globe valves and throttle valves

1, the test pressure method for globe valves and throttle valves

Strength test of globe valve and throttle valve, usually the assembled valve is placed in the pressure test frame, open the valve flap, inject the medium to the specified value, check whether the valve body and cover sweat and leakage. Strength test can also be done for a single piece. Sealing test is done only for shut-off valves. Test the stem of the globe valve into a vertical state, the valve flap open, the media from the bottom end of the valve flap introduced to the specified value, check the packing and gasket; to be qualified to close the valve flap, open the other end to check whether there is leakage. If the valve strength and sealing test are to be done, you can do the strength test first, then lower the pressure to the specified value of the sealing test, check the packing and gasket; then close the valve flap and open the outlet end to check whether the sealing surface is leaking.

2. Gate valve pressure test method

The strength test for gate valves is the same as that for globe valves. There are two methods for testing the sealability of gate valves.

① Open the gate and let the pressure inside the valve rise to the specified value; then close the gate and immediately take out the gate valve to check if there is any leakage at the seal on both sides of the gate or directly inject the test medium into the plug on the valve cover to the specified value and check the seal on both sides of the gate. The above method is called the intermediate test pressure. This method is not suitable for sealing test in gate valves with nominal diameter DN32mm or less.

② Another method is to open the gate and bring the valve test pressure up to the specified value; then close the gate and open the blind plate at one end to check whether the sealing surface is leaking. Then reverse the head, make the above repeated tests until qualified.

The sealability test at the packing and gasket of the pneumatic gate valve should be performed before the gate sealability test.

3. Pressure test method for ball valves

The strength test for pneumatic ball valves shall be conducted with the ball valve body half open. The strength test for pneumatic ball valves shall be performed with the ball valve body half open.

① Floating ball valve sealing test: put the valve in the half-open state, one end of the test medium, the other end closed; turn the ball several times, the valve is closed, open the closed end to check, and check the packing and gasket sealing performance, there should be no leakage phenomenon. Then introduce the test medium from the other end. Then introduce the test medium from the other end and repeat the above test.

② Fixed ball valve sealing test: Turn the ball unloaded several times before the test, with the fixed ball valve in a closed state, and introduce the test medium from one end to the specified value; check the sealing performance at the introduced end with a pressure gauge, using a pressure gauge with 0.5 to 1 level of accuracy and a range of 1.6 times the test pressure. 1.6 times the test pressure. In the specified time, no pressure drop phenomenon for qualified; and then introduce the test medium from the other end, repeat the above test. Then, the valve is in a half-open state, both ends closed, the cavity is full of media, check the packing and gasket at the test pressure, there should be no leakage.

③ The three-way ball valve should be tested for tightness in all positions.

4. Test method for plug valves

① For strength testing of plug valves, the medium is introduced from one end, closing the rest of the pathway

The plug is rotated to the fully open working position for testing, and the valve body is not found to be leaking as qualified.

② For the seal test, the straight-through plug should be kept equal to the pressure in the cavity and the pathway, rotate the plug to the closed position and check from the other end, then rotate the plug 180° and repeat the above test; the three-way or four-way plug valve should be kept equal to the pressure in the cavity and the pathway. equal pressure at one end, rotate the plug to the closed position in turn, the pressure is introduced from the right-angle end, and check from the other end at the same time.

A layer of non-acidic dilute lubricant is allowed on the sealing surface before the plug valve test bench, and no leakage or expanding water droplets are found within a specified time period for passing. The test time for plug valves can be shorter, generally l to 3min according to the nominal diameter.

Plug valves for gas should be tested for air tightness at 1.25 times the working pressure.

5. Butterfly valve pressure test method

The strength test for pneumatic butterfly valves is the same as that for globe valves. Butterfly valve sealing performance test should be introduced from the media flow end of the test medium, the butterfly plate should be open, the other end closed, inject pressure to the specified value; check the packing and other seals without leakage, close the butterfly plate, open the other end, check the butterfly plate seal without leakage for qualified. Butterfly valve used as a flow control may not do the sealing performance test.

6. Diaphragm valve pressure test method

Diaphragm valve strength test from either end of the introduction of media, open the valve flap, the other end closed, test pressure up to the specified value, see the valve body and valve cover no leakage is qualified. Then lower the pressure to the sealing test pressure, close the valve flap, open the other end for inspection, no leakage for qualified.

7, check valve pressure test method

Check valve test state: lift check valve valve axis is in the horizontal vertical position; swing check valve position; swing check valve channel axis and valve axis is in the position of approximately parallel to the horizontal line.

For the strength test, introduce the test medium from the inlet end to the specified value, close the other end, and see that the valve body and cover do not leak.

For sealing test, introduce the test medium from the outlet end, check the sealing surface at the inlet end, and see that there is no leakage at the packing and gasket to pass.

8. Pressure test method of safety valve

① The strength test of safety valve is the same as other valves, which is tested with water. When testing the lower part of the valve body, the pressure is introduced from the inlet I = I end, the sealing surface is closed; when testing the upper part of the valve body and the valve cover, the pressure is introduced from the outlet El end, the other end is closed. In the specified time valve body and valve cover no leakage is qualified.

② Sealing test and constant pressure test, the general use of media are: steam safety valve with saturated steam as the test medium; ammonia or other gas valves with air as the test medium; water and other non-corrosive liquid valves with water as the test medium. For some important positions of the safety valve commonly used nitrogen as the test medium.

The seal test is performed at a nominal pressure, no less than twice, with no leakage within a specified time period. There are two methods of leak detection: one is to seal the connections of the safety valve, with butter to seal the thin paper paste in the out El flange, thin paper bulging for leakage, not bulging for qualified; two is to seal the thin plastic plate or other plate with butter in the lower part of the export flange, water seal valve flap, test water does not bubble for qualified. Safety valve pressure setting and back to the seat pressure test not less than three times, in line with the provisions of the qualified.

Safety valve performance tests are described in GB/T 12242 "Safety Valve Performance Test Methods".

9, pressure reducing valve test method

① The strength test of pressure reducing valve is generally assembled after the test of individual pieces, or assembled after the test. test. Strength test duration: DN

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