Processes of Valve Pressure Tests (2)
As for the one-way ball valve and the one-way butterfly valve, the intake’s pressure of the valve is supposed to be increased according to the mark on the valve. When the liquid such as suds is smeared on the sealing surface of the valve, the leakage condition can be known by observing the bubbles from the valve opening which is opened.
With the consent of users and manufacturers, other devices which are used for the leakage test and have the same leakage as that this regulation specifies are able to be adopted.
Except the single-wedge-disc gate valve, the pressure of most gate valves’ valve bodies can be increased through nipples between the two sealing surfaces. Meanwhile, in accordance with the previous regulation, the leakage of two sealing surfaces can be checked simultaneously or individually.
The leakage condition of the gate’s intake can be known by increasing the pressure of every sealing surface individually and checking the leakage between sealing surfaces.
Except the single-wedge-disc gate valve, the pressure of every gate valve with the pipe thread whose diameter is larger than two inches, can be increased simultaneously. In such a case, the leakage of the sealing surfaces can not exceed the allowed leakage of the sealing surfaces which are individually tested.
For the test in accordance with the regulation above, the nipple of the valve body is not supposed to be larger than the 1/2 inch pipe thread.
Moreover, before shipment, the solid plug screw, which is made of the material similar to the valve body’s material or with corrosion resistance greater than or equal to the corrosion resistance of the valve body’s material, needs to be installed according to ANSI B16.11.
The high pressure sealing test
The process of the high pressure sealing test is the same as the low pressure sealing test’s.
During the high pressure test of the gate valve, the bonnet should be fully filled with the liquids if the liquid media are adopted.
The load of the valve end in the test
In the process of the sealing test, the external force which effects the leakage of sealing surfaces should not be exerted on the valve openings.
It should be noticed that human factors are very essential to the result of the valve pressure test, so inspectors must comply with the standard operation requirement and ensure that the test pressure and the time of keeping up the test pressure do satisfy the requirement. The staff who inspect the valve need to take the responsibility for the test result.
Source: China Ball Valves Manufacturer – Yaang Pipe Industry (www.ugsteelmill.com)