Pressure test method of butterfly valve：
The strength test of the pneumatic butterfly valve is the same as that of the globe valve. The sealing performance test of the butterfly valve should introduce the test medium from the end of the medium flow, the butterfly plate should be opened, the other end should be closed, and the injection pressure should reach the specified value; after checking the packing and other seals without leakage, close the butterfly plate, open the other end, and check the butterfly No leakage at the plate seal is qualified. The butterfly valve used to adjust the flow can not be tested for sealing performance.
Pressure test method of plug valve：
During the strength test of the plug valve, the medium is introduced from one end, the remaining passages are closed, and the plug is rotated to the fully open working positions for the test. The valve body is qualified if no leakage is found.
In the sealing test, the straight-through plug should keep the pressure in the cavity equal to that of the passage, 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 valve The pressure in the cavity and one end of the passage should be kept equal, the stopper should be rotated to the closed position in turn, the pressure should be introduced from the right-angle end, and the other end should be inspected at the same time.
Before the plug valve test, it is allowed to apply a layer of non-acid dilute lubricating oil on the sealing surface, and no leakage or enlarged water droplets within the specified time are qualified. The test time of the plug valve can be shorter, generally 1~3min according to the nominal diameter.
The plug valve for gas shall be tested for air tightness at 1.25 times the working pressure.
