1. Globe valve and throttle valve pressure test method
The strength test of globe valves and throttle valves, usually put the assembled valve in the test pressure frame, open the valve flap, inject the medium to the specified value, check whether the valve body and valve cover sweating and leakage. Can also be a single piece of strength test. The sealing test is only done for globe valves. Test the valve stem of the globe valve into a vertical state, the valve is open, the medium from the bottom of the valve flap end of the introduction to the specified value, check the packing and gaskets; 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 should be done, the strength test can be done first, and then reduce the pressure to the sealing test to the specified value, check the packing and gasket; and then close the valve flap, open the outlet end to check whether the sealing surface leakage.
2. Gate valve pressure test method
The strength test of gate valve is the same as that of globe valve. There are two methods for sealing test of gate valve.
① The gate is opened, so that the pressure inside the valve rises to a specified value; then close the gate, immediately remove the gate valve, check the sealing of both sides of the gate for leakage or directly to the plug on the bonnet of the valve into the test medium to the specified value, check the sealing of both sides of the gate. The above method is called intermediate pressure test. This method is not suitable for sealing test in the nominal diameter DN32mm below the gate valve.
② Another method is to open the gate, so that the valve test pressure to the specified value; and then close the gate, open one end of the blind, check whether the sealing surface leakage. And then reverse the head, make the above repeated tests until qualified.
Pneumatic gate valve packing and gasket sealing test should be carried out before the gate sealing test.
3. Ball valve pressure test method
Pneumatic ball valve strength test should be carried out in the ball valve ball half open state.
① Floating ball valve sealing test: the valve in a half-open state, one end of the introduction of test media, the other end is closed; will be a few times to rotate the ball, the valve is closed when the closed end of the open closed end of the inspection, and at the same time to check the packing and gasket sealing performance, there shall be no leakage phenomenon. Then introduce the test medium from the other end, repeat the above test.
② fixed ball valve sealing test: before the test will be unloaded ball rotation several times, fixed ball valve in the closed state, from one end of the introduction of the test medium to the specified value; with a pressure gauge to check the introduction of the end of the sealing performance, the use of the pressure gauge accuracy of 0.5 ~ 1 level, the range of the test pressure of 1.6 times. In the specified time, no pressure drop phenomenon is qualified; and then from the other end of the introduction of test media, repeat the above test. Then, the valve in a half-open state, closed at both ends, the inner cavity is full of media, under the test pressure to check the packing and gasket, there shall be no leakage.
③ Three-way ball valves should be tested for sealing in all positions.
4. Plug valve test pressure method
① plug valve for strength test, the media from one end of the introduction, closed the rest of the access, the plug will be rotated in turn to the full open position for the test, the valve body did not find leakage is qualified.
② sealing test, straight-through plug should be kept in the cavity and access to equal pressure, the plug rotated to the closed position, from the other end of the inspection, and then rotate the plug 180 ° to repeat the above test; three-way or four-way plug valve should be kept in the cavity and access to equal pressure at one end of the valve, the plug rotated in turn to the closed position, the pressure is introduced from the end of the right-angled end, from the other end of the same time to check.
Plug valve test bench before the sealing surface is allowed to apply a layer of non-acidic dilute lubricant, in the specified time no leakage and expansion of water droplets are found to be qualified. Plug valve test time can be shorter, generally according to the nominal diameter of the provisions of 1 ~ 3min.
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 of pneumatic butterfly valve is the same as that of globe valve. Butterfly valve sealing performance test should be introduced from the media inflow end of the test medium, the butterfly plate should be opened, the other end closed, injected pressure to the specified value; check the packing and other seals without leakage, close the butterfly plate, open the other end, check the butterfly sealing without leakage is qualified. Butterfly valve as a flow control may not do the sealing performance test.
6. Check valve pressure test method
Check valve test state: lift check valve valve flap axis is in a position perpendicular to the horizontal; rotary check valve channel axis and flap axis is in a position approximately parallel to the horizontal line.
Strength test, from the inlet end of the introduction of test media to the specified value, the other end closed to see the valve body and valve cover without leakage is qualified.
Sealing test from the outlet end of the introduction of test media, at the inlet end to check the sealing surface at the packing and gasket at no leakage is qualified.
