The method for judging internal leakage of ball valves

Fixed-shaft ball valves are commonly used on natural gas pipelines. The general inspection methods for them are:

Turn the valve to the fully open or fully closed position and check for any leakage through the discharge port of the valve body. If it can be drained completely, it proves that the seal is good. If pressure is discharged, it can be considered that the valve is leaking. At this time, corresponding treatment should be carried out on the valve. However, it should be emphasized that for GRoVEB-5 and B-7A type ball valves, PBV ball valves, and ROBERTCORT ball valves, inspection can only be carried out in the fully closed position. This is because these types of ball valves have a channel opened on the valve body, which, when fully open, is used to balance the pressure in the pipeline and the valve chamber. But this situation will not occur when all positions are closed.

The handling procedure for internal leakage of ball valves

First, check the limit of the valve to see if adjusting the limit can solve the internal leakage of the valve.

First, inject a certain amount of grease to see if it can stop the leakage. At this time, the injection speed should be slow. Meanwhile, observe the change in the pointer of the pressure gauge at the outlet of the grease injection gun to determine the internal leakage of the valve.

If the leakage cannot be stopped, it may be due to the hardening of the sealing grease injected earlier or the damage of the sealing surface causing internal leakage. It is recommended to inject valve cleaning solution at this time to clean the sealing surface and valve seat of the valve. Generally, soak for half an hour. If possible, soak for several hours or even days. Wait until the solidified substance dissolves before proceeding to the next step. During this process, the movable valve can be opened and closed several times.

④ Re-inject the grease, and intermittently open and close the valve to expel impurities from the rear chamber of the valve seat and the sealing surface.

⑤ Check in the fully closed position. If there is still leakage, inject reinforcing sealing grease and open the valve cavity at the same time to vent. This can create a large pressure difference, which is helpful for sealing. Generally, internal leakage can be solved by injecting reinforcing sealing grease.

If there is still internal leakage, the valve should be repaired or replaced.

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