(1) Globe valve and throttle valve
For the strength test of globe valves and throttle valves, the assembled valve is usually placed in a pressure test stand, the valve disc is opened, the medium is injected to the specified value, and the valve body and valve cover are checked for sweating and leakage. Strength testing can also be performed on a single piece.
The sealing test is only conducted on stop valves. During the test, the valve stem of the stop valve is in a vertical state, the valve disc is opened, and the medium is introduced from the bottom end of the valve disc to the specified value. Check the packing and gasket; after passing the test, close the valve disc and open the other end to check whether there is leakage.
If both the strength and sealing tests of the valve are required, the strength test can be done first, then the pressure is reduced to the specified value of the sealing test, and the packing and gasket are inspected; then the valve disc is closed, and the outlet end is opened to check whether the sealing surface is leaking.
(2) Gate valve
The strength test of gate valves is the same as that of stop valves.
There are two methods for gate valve sealing test.
① Open the gate to raise the pressure in the valve to the specified value; then close the gate, take out the gate valve immediately, check whether there is leakage at the seals on both sides of the gate or directly inject the test 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 DN32mm.
② Another method is to open the gate to increase the valve test pressure to the specified value; then close the gate, open the blind plate at one end, and check whether the sealing surface is leaking. Turn the head back again and repeat the above test until it passes the test.
The sealing test of the gate valve packing and gasket should be carried out before the gate sealing test.
(3) Ball valve
The strength test of the ball valve should be carried out with the ball in a half-open state.
① Floating ball valve sealing test: Put the valve in a semi-open state, introduce the test medium at one end, and close the other end; rotate the ball several times, open the closed end for inspection when the valve is in the closed state, and check the sealing performance of the packing and gasket at the same time. There must be no leakage. Then introduce the test medium from the other end and repeat the above test.
② Fixed ball valve sealing test: Before the test, rotate the ball several times without load, keep the valve in a closed state, and introduce the test medium from one end to the specified value; use a pressure gauge to check the sealing performance of the introduction end, and use a pressure gauge with an accuracy of 0.5 ~Level 1, the measuring range is 1.6 times the test pressure. Within the specified time, if there is no pressure drop phenomenon, it is qualified; then introduce the test medium from the other end and repeat the above test.
Then, put the valve in a semi-open state, seal both ends, and fill the inner cavity with medium. Check the packing and gasket under the test pressure to see that there must be no leakage.
③ The three-way ball valve should be tested for sealing at various positions.
(4) Plug valve
① When the plug valve is tested for strength, the medium is introduced from one end, the rest of the passage is closed, and the plug is rotated to each fully open working position for testing. If no leakage is found in the valve body, it is deemed to be qualified.
② During the sealing test, the straight-through plug should keep the pressure in the cavity and the passage equal, rotate the plug to the closed position, check from the other end, and then rotate the plug 180° to repeat the above test; three-way or four-way plug valves The pressure in the cavity and one end of the passage should be kept equal, the plug should be rotated to the closed position in sequence, the pressure should be introduced from the right-angle end, and the inspection should be carried out from the other end at the same time.
Before the plug valve test, it is allowed to apply a layer of non-acidic thin lubricating oil on the sealing surface. If no leakage or expanding water droplets are found within the specified time, it is qualified. The test time of the plug valve can be shorter, generally 1 to 3 minutes according to the nominal diameter.
Plug valves for gas use should be tested for air tightness at 1.25 times the working pressure.
(5) Butterfly valve
The strength test of butterfly valves is the same as that of globe valves.
The sealing performance test of a butterfly valve should introduce the test medium from the medium flow end, the butterfly plate should be opened, the other end should be closed, and the injection pressure reaches the specified value; after checking that there is no leakage in the packing and other seals, close the butterfly plate, open the other end, and check the butterfly valve. If there is no leakage at the plate seal, it is qualified. Butterfly valves used to regulate flow do not need to undergo sealing performance testing.
(6) Diaphragm valve
The diaphragm valve strength test introduces medium from either end, opens the valve disc, and closes the other end. After the test pressure rises to the specified value, the valve body and valve cover are deemed to be qualified if there is no leakage. Then reduce the pressure to the sealing test pressure, close the valve disc, and open the other end for inspection. If there is no leakage, it is qualified.
(7) Check valve
Check valve test status: the lift check valve disc axis is in a position perpendicular to the horizontal; the swing check valve channel axis and valve disc axis are in a position approximately parallel to the horizontal line.
During the strength test, the test medium is introduced from the inlet end to the specified value, and the other end is closed. If there is no leakage in the valve body and valve cover, it is qualified.
In the sealing test, the test medium is introduced from the outlet end, and the sealing surface is checked at the inlet end. If there is no leakage at the packing and gasket, it is qualified.
