(A) pressure test of the valve:
1. Pressure test method of electric gate valve
The strength test of electric gate valve is the same as that of globe valve. There are two methods for testing the tightness of gate valves.
The gate is opened so that the pressure in the valve rises to the regulation value; then the gate is closed and the gate valve is immediately taken out to check whether there is leakage at the seals at both ends of the gate. The test medium may be injected directly into the valve plug to the regulation value Check the seals on both ends of the ram. The above method is called intermediate pressure test. This method is not suitable for sealing tests on gate valves with a nominal diameter below DN32mm.
Another method is to open the gate to increase the valve test pressure to the required value; then close the gate and open the blind plate at one end to check whether the sealing surface is leaking. Turn down and repeat the test until it is qualified.
The tightness test at the packing and gasket of the pneumatic gate valve shall be carried out before the tightness test of the gate.
2. Pressure test method of diaphragm valve
Diaphragm valve strength test. Introduce medium from either end, open the valve disc, and close the other end. After the test pressure rises to the required value, see that the valve body and valve cover are leak-free. Then reduce the pressure to the tightness test pressure, close the clapper, and open the other end for inspection. No leakage is acceptable.
3. Pressure test method of electric butterfly valve
The strength test of pneumatic butterfly valve is the same as that of globe valve. The sealing function test of the butterfly valve should be introduced into the test medium from the flowing end of the medium, the butterfly plate should be opened, the other end should be closed, and the injection pressure should reach the required value. No leakage at the disc seal is acceptable. The butterfly valve used for regulating the flow may not be tested for sealing function.
4. Pressure test method of ball valve
The strength test of the pneumatic ball valve should be carried out with the ball half-open.
Floating ball valve sealing test: Put the valve in a half-open condition, introduce test medium at one end, and close the other end; roll the ball several times, open the closed end when the valve is closed, and check the sealing function of the packing and gasket together. There must be no leakage. Then introduce the test medium from the other end and repeat the test.
Fixed ball valve sealing test: Before the test, roll the ball a few times with no load, the fixed ball valve is closed, and draw the test medium from one end to the regulation value; check the sealing function of the lead-in with a pressure gauge, and use the accuracy of the pressure gauge to 0.5 ～ Level 1, measuring range is 1.5 times the test pressure. Within the time of compliance, no pressure drop is acceptable; the test medium is introduced from the other end and the above test is repeated. Then, place the valve in a half-open condition, with both ends closed, and the internal cavity filled with medium. Check the packing and gasket under the test pressure for no leakage.
Three-way ball valves shall be tested for leak tightness in all orientations.
5. Pressure test method of check valve
Check valve test conditions: The lift check valve flap axis is in a vertical orientation; the swing check valve channel axis and the flap axis are in an orientation approximately parallel to the horizontal line.
In the strength test, the test medium is introduced from the inlet end to the specified value, and the other end is closed. It is acceptable to see that the valve body and valve cover have no leakage.
For the leak test, the test medium is introduced from the outlet end, and the sealing surface is checked at the inlet end, and there is no leakage at the packing and gaskets.
6. Pressure test method of plug valve
During the strength test of the plug valve, the medium was introduced from one end, the remaining passages were closed, and the plug was sequentially rotated to the full open operating position for testing. The valve body was found to be qualified.
During the tightness test, the straight-through plug should insist that the pressure in the cavity is equal to the passageway. Rotate the plug to the closed position, check from the other end, and then rotate the plug 180 ° to repeat the above test; Keep the pressure in the cavity equal to the pressure at one end of the channel, rotate the plug to the closed position in turn, the pressure is introduced from the right-angle end, and check from the other end together.
Before the test of the plug valve, it was agreed to apply a layer of non-acid thin lubricating oil on the sealing surface. No leakage or expansion of water droplets was found to be acceptable within the compliance time. The plug valve test time can be shorter, generally according to the nominal diameter of l ~ 3min.
Gas stopcocks shall be tested for air tightness at 1.25 times the operating pressure.
7. Pressure test method of globe valve and throttle valve
For the strength test of the shut-off valve and the throttle valve, the assembled valve is usually placed in a pressure test frame, the valve flap is opened, the medium is injected to the specified value, and the valve body and the valve cover are checked for sweat and leakage. A single piece can also be used for strength testing. The tightness test is only done for globe valves. During the test, the stem of the shut-off valve is vertical, the disc is opened, and the medium is introduced to the regulation value from the bottom end of the disc. Check the packing and gasket; when it is qualified, close the disc and open the other end to check for leakage. If both the valve strength and tightness test are to be done, the strength test can be performed first, then the pressure is reduced to the tightness test value, and the packing and gasket are checked; then the valve flap is closed, and the outlet end is opened to check whether the sealing surface is leaking .
2. Rules for pressure test of valve electric device :
1. All valves should be visually inspected after unpacking, including the complete nameplate on the valve body, product quality certification documents, the valve is closed, no other damage such as blue surface, no dirt, and protective covers at both ends.
2. The operator should understand the operation of the test bench.
3. The JHA of valve pressure test is perfect. Operators should be aware of the safety hazards of valve pressure test and reverse process and have corresponding preventive measures.
4. Valve pressure test process is: valve housing strength test, upper seal test, seal test.
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