Processes of Valve Pressure Tests(1)
The pressure test mainly aims at measuring the security capability and the sealing performance of the valve. All devices and the operation process must comply with the test regulation.
During the test, the valve’s loading capability needs to make sure that the valve can be operated with safety under the nominal diameter, which can be known by observing whether the pressure-containing member of the valve is deformed or broken.
The strength test
The strength test of the valve is supposed to be implemented before the painting process.
During the strength test, in order to maintain the test pressure of the valve, two openings of the valve needs to be blocked and the valve should be half closed. Meanwhile, the pressure of the valve assembled should be increased and the packing gland needs to be pressed tightly. The stuffing box can also to be tested during the strength test. In the process of the test, the leakage is not allowed to occur in the stuffing box.
The process of the strength test (hydraulic test)
Discharge air inside the valve after the valve is filled with water.
Open the valve and increase the pressure of the valve to the test pressure.
Keep the test pressure for more than five minutes.
The valve is up to the standard if the packing gland does not leak during the test.
The back seat sealing test
The back seat sealing test should be implemented right after the strength test. When the gate valve is tested, both two openings of the valve need to be blocked and the valve should be fully opened. At the same time, the packing gland is supposed to be loosened and the pressure of the assembled valve needs to be increased.
The low pressure sealing test
During the low pressure sealing test, the sealing surface is supposed to be clean without oil. However, the oil thinner than the kerosene can be added to the sealing surface of the valve in order to prevent scuffing of the sealing surface. But it should be noticed that the regulation is unsuitable for the valve which the lubricant is used at the very beginning to seal.
The methods listed below can be adopted for the low pressure sealing test of the valve.
For the gate valve, the plug valve, the ball valve and the butterfly valve, which adopt the double flow structure, the pressure of the valve’s opening should be increased in sequence. Meanwhile, in order to check the leakage of the other valve’s opening, one opening should be opened to the atmosphere.
Source: China Valves Manufacturer – Yaang Pipe Industry (www.steeljrv.com)