Pressure Tests for Ball Valves, Butterfly Valves and Other Industrial Valves
01. Pressure test methods for ball valves
The strength test of the pneumatic ball valve should be carried out with the ball half open.
① Floating ball valve tightness test: the valve is in a half-open state; the test medium is introduced at one end, and the other end is closed; the ball is rotated several times, and the closed end is opened for inspection when the valve is in the closed state; the sealing performance at the packing and the gasket is checked. There must be no leakage. The test medium was then introduced from the other end and the above test was repeated.
② Fixed ball valve tightness test: Before the test, rotate the no-load ball several times, and the fixed ball valve is closed; the test medium is introduced from one end to the specified value; check the sealing performance of the inlet with a pressure gauge. The accuracy of the pressure gauge is 0.5 to 1 and the range is 1.6 times the test pressure. In the specified time, if there is no depressurization, it is qualified; then the test medium is introduced from the other end, and the above test is repeated. Then, the valve is in a half-open state, the ends are closed; the inner cavity is filled with the medium, and the packing and the gasket are inspected under tesingt pressure; there must be no leakage.
③ Three-way ball valves should be tested for leaks at every parts.
02. Pressure test methods for plug valves
① When the plug valve is tested for strength, the medium is introduced from one end; the remaining passages are closed, and the plugs are rotated in turn to the fully open working positions for testing. Check the valve body. If there is no leakage, it is qualified.
② In the sealing test, for the straight-type plug valve, the pressure in the cavity should be kept equal to the passage pressure. Rotate the plug to the closed position; check from the other end, and then rotate the plug 180° to repeat the above test; for three-way or four-way plug valve, the pressure inside the chamber should be kept equal to the pressure at the end of the passage. The plug should be rotated to the closed position in turn; the pressure is introduced from the right angle end, and the inspection is performed simultaneously from the other end.
Before the plug valve test, a non-acid thin lubricating oil is allowed to be applied on the sealing surface, and no leaks and enlarged water droplets are found within the specified time, then it is qualified. The test time of the plug valve can be shorter, generally specified as 1 to 3 minutes according to the nominal diameter.
The plug valve for gas should be tested for air tightness at 1.25 times the working pressure.
03. Butterfly valve pressure test method
The strength test of the pneumatic butterfly valve is the same as that of the shut-off valve. The sealing performance test of the butterfly valve is to introduce the test medium from the inflow end of the medium. The butterfly plate should be opened, and the other end is closed. The injection pressure is up to the specified value; after making sure that there is no leakage for the filler and other seals, the butterfly plate should be closed. The other end should be opened, and the butterfly is inspected. No leakage at the plate seal is acceptable. As a butterfly valve for regulating the flow rate, the sealing performance test may not be performed.
04. Pressure test method for diaphragm valves
The strength test of the diaphragm valve is to introduce the medium from either end. Open the valve flap, and the other end is closed. After the testing pressure rises to the specified value, check the valve body and the valve cover. If there is no leakage, it is qualified. Then, the pressure is reduced to the sealing test pressure. The valve flap is closed, and the other end is opened for inspection. There should be no leakage.
The strength test of the pneumatic ball valve should be carried out with the ball half open.
① Floating ball valve tightness test: the valve is in a half-open state; the test medium is introduced at one end, and the other end is closed; the ball is rotated several times, and the closed end is opened for inspection when the valve is in the closed state; the sealing performance at the packing and the gasket is checked. There must be no leakage. The test medium was then introduced from the other end and the above test was repeated.
② Fixed ball valve tightness test: Before the test, rotate the no-load ball several times, and the fixed ball valve is closed; the test medium is introduced from one end to the specified value; check the sealing performance of the inlet with a pressure gauge. The accuracy of the pressure gauge is 0.5 to 1 and the range is 1.6 times the test pressure. In the specified time, if there is no depressurization, it is qualified; then the test medium is introduced from the other end, and the above test is repeated. Then, the valve is in a half-open state, the ends are closed; the inner cavity is filled with the medium, and the packing and the gasket are inspected under tesingt pressure; there must be no leakage.
③ Three-way ball valves should be tested for leaks at every parts.
02. Pressure test methods for plug valves
① When the plug valve is tested for strength, the medium is introduced from one end; the remaining passages are closed, and the plugs are rotated in turn to the fully open working positions for testing. Check the valve body. If there is no leakage, it is qualified.
② In the sealing test, for the straight-type plug valve, the pressure in the cavity should be kept equal to the passage pressure. Rotate the plug to the closed position; check from the other end, and then rotate the plug 180° to repeat the above test; for three-way or four-way plug valve, the pressure inside the chamber should be kept equal to the pressure at the end of the passage. The plug should be rotated to the closed position in turn; the pressure is introduced from the right angle end, and the inspection is performed simultaneously from the other end.
Before the plug valve test, a non-acid thin lubricating oil is allowed to be applied on the sealing surface, and no leaks and enlarged water droplets are found within the specified time, then it is qualified. The test time of the plug valve can be shorter, generally specified as 1 to 3 minutes according to the nominal diameter.
The plug valve for gas should be tested for air tightness at 1.25 times the working pressure.
03. Butterfly valve pressure test method
The strength test of the pneumatic butterfly valve is the same as that of the shut-off valve. The sealing performance test of the butterfly valve is to introduce the test medium from the inflow end of the medium. The butterfly plate should be opened, and the other end is closed. The injection pressure is up to the specified value; after making sure that there is no leakage for the filler and other seals, the butterfly plate should be closed. The other end should be opened, and the butterfly is inspected. No leakage at the plate seal is acceptable. As a butterfly valve for regulating the flow rate, the sealing performance test may not be performed.
04. Pressure test method for diaphragm valves
The strength test of the diaphragm valve is to introduce the medium from either end. Open the valve flap, and the other end is closed. After the testing pressure rises to the specified value, check the valve body and the valve cover. If there is no leakage, it is qualified. Then, the pressure is reduced to the sealing test pressure. The valve flap is closed, and the other end is opened for inspection. There should be no leakage.
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