Methods for Many types valves' Pressure test
Pressure test method for globe valves
Usually, put the assembled valves in the pressure testing rack, open the valve disc, inject the medium to the specified value and check whether the valve body and the valve bonnet leaks. During testing, the stem of the globe valve should be in the upright position. When the disc is open, the medium is imported from the lower end of the valve flap to the specified value. Inspect the packing and the gasket. Once the valve is qualified, turn off the valve disc, open the other end to check if there is leakage. If both the valve strength and the sealing tests are to be done, the strength test can be taken first, then reduce the pressure to the specified value and inspect the packing and the gasket. Next, turn off the disc, open the outlet end to check whether the sealing surface leaks.
Pressure test methods for gate valves
The strength test of gate valves is the same as that of globe valves. And there are two sealing test methods of gate valves.
1. Open the gate to raise the pressure inside the valve, then close the gate, immediately take out the gate valve and check whether there is leakage at the seal on both sides. Or directly inject the test medium into the plug on the bonnet to the specified value then check the seals on both sides. The above method is not suitable for testing gate valves with a nominal diameter below 32 mm.
2. The other method is to open the gate and raise the test pressure to the specified value, then close the gate, open the blind plate at one end, and check whether the sealing surface leaks. Next, repeat the above test until it is qualified. The seal test for pneumatic gate valve packing and gasket should be carried out before the sealing test for the gate.
Pressure test methods for ball valves
1. Floating ball valve sealing test: When the valve is half open, let the medium from one side while the other side is closed. Rotate the ball a couple of times. When the valve is closed, open and check the side which previously is closed, and check the packing and sealing performance at the gasket, where must have no leakage. Next, check the sealing performance of the other side according to the above procedures.
2. Trunnion ball valve sealing test: Before testing, let the zero-load ball rotate several times. The valve should be closed, then import the medium from one side to the specified value. Use the pressure gauge to inspect the sealing performance of the side. If there is no depressurization in the specific time, the product is qualified. Follow the above procedures to check the other side. After that, let the valve be half open while two sides are both closed, fill it with the medium, inspect the packing and gasket under test pressure, make sure that there is no leakage.
3. Every position of three-way ball valves should be tested.
Pressure test methods for butterfly valves
During the sealing performance test of the butterfly valve, the test medium should be imported from the end of the flow. The disc should be opened while the other end closed, and the injection pressure needs to meet the specified value. After checking the packing and other seals to ensure there is no leakage, close the disc and open the other end to check the seal of the disc. No leakage at the plate seal is acceptable. The sealing performance test for butterfly valves used for regulating the flow rate may not be performed.
Pressure test methods for check valves
During the sealing test, the test medium should be imported from the inlet end to the specified value while the other end is closed, and the valve body and the valve cover are qualified if there is no leakage. Another one test methods is the medium should be imported from the outlet end. At the inlet end, the sealing surface is qualified if there is no leakage at the packing and gasket.