The Pressure Testing Methods for Plug Valve
Plug valve is a kind of sanitary valve that uses holed plug as its opening and closing member. The plug rotates with the valve stem to achieve the opening and closing movements.
The use of plug valve:
Plug valves are best suited for shutting off and connecting the medium as well as for shunting. However, according to the applicable properties and the erosion-resistance of the sealing surface, it can sometimes also be used for throttling.
Plug valve is widely used in oil field mining, transportation and refining equipment, as well as in petrochemicals, chemicals, gas, natural gas, liquefied petroleum gas, HVAC industry and general industry.
Plug valve is also suitable for the delivery of liquid containing suspended solids and particles. Straight-through plug valve with insulation measures can transmit materials containing crystals.
Pressure testing method:
When plug valve undergoes strength test, medium is introduced from one end, and other remaining access is closed. Turn the plug to various positions for testing. If there’s no leakage at the valve body, it is considered qualified.
For sealing performance test, the pressure inside the chamber and on the channel should be kept equal. Turn the plug to the closing position. Check from the other end. Then rotate the plug for 180 degrees and repeat the above steps. For three-way or four-way plug valve, the pressure inside the cavity should be kept equal to the pressure on the end of the channel. Turn the plug to the closing position. Pressure is introduced from the right angle end. And check simultaneously from other ends.
Before test, it is allowed to apply a layer of non-acidic thin lubricant on the sealing surface of the plug valve. Within a specified period of time, if there is no leakage or enlarged water droplets, it is considered qualified. The test time of plug valve can be short. According to nominal diameter, usually it takes one to three minutes. Plug valve for gas should undergo air tightness test at 1.25 times the operating pressure.