During the installation or operation of a ball valve, leakage may occur due to frequent switching during use, or failure to install according to requirements, etc., making the ball valve not work properly.
In this article, we explain some causes of the floating ball valve, trunnion ball valve, double block, and bleed valve leakage faults and the corresponding troubleshooting methods.
Causes of Leakage in Ball Valves
Causes of leakage in the valve during installation:
① Inadequate transportation and improper lifting can cause damage to the valve, resulting in the leakage of the valve.
② The valve was not treated for corrosion, resulting in corrosion of the sealing surface causing the formation of the leakage.
③ The protection of the installation site was not in place. Blinds were not installed at both ends of the valve. Impurities such as rain and sand entered the valve seat, causing leakage.
④ When installing, no grease is injected into the valve seat, causing impurities to enter the rear of the valve seat or internal leakage caused by burns during welding.
⑤ The valve is not installed in a fully open position, causing damage to the ball. If the valve is not in a fully open position during welding, welding spatter will cause damage to the ball. When the ball with welding spatter is in the switch, it will further damage the valve seat, which leads to endoleaks.
⑥ Welding residue and other installation remnants causing scratches to the sealing surface.
⑦ Leakage caused by inaccurate limits at the delivery or during installation. If the stem drive bushing or other accessories are misaligned with the assembly, the valve will leak.
Causes of leakage in the valve during operation:
① The most common reason is that the operation manager does not maintain the valve in consideration of the relatively expensive maintenance cost, or lacks scientific valve management and maintenance methods, and does not perform preventive maintenance on the valve, causing premature failure of the equipment.
② Improper operation or maintenance according to maintenance procedures, resulting in leakage.
③ During normal operation, construction remnants scratch the sealing surface, causing leakage.
④ Immediate leakage due to seal surface damage caused by improper pigging.
⑤ Long-term no maintenance or inactivity of the valve, causing the valve seat and ball to lock up, and causing leakage damage when the valve is opened and closed.
⑥ Valve leakage caused by incomplete position, any ball valve regardless of the opening and closing position, generally inclined 2 ° ~ 3 ° may cause leakage.
⑦ Many large-diameter ball valves have valve stem stoppers. If they are used for a long time, rust, dust, paint, and other debris will accumulate between the stem and the stem stopper blocks due to corrosion. This debris will cause the valve to fail to rotate into place and cause a leak —If the valve is buried, lengthening the valve stem will produce more rust and impurities, preventing the valve ball from rotating into place and causing the valve to leak.
⑧ The general actuator also has limit bolts. If it is used for a long time, it will cause corrosion. The hardening of the grease or the loosening of the limit bolt will make the limit inaccurate and cause internal leakage.
⑨ The valve position of the electric actuator is set at the front and is not closed to the inappropriate position, resulting in leakage.
⑩ The lack of periodic maintenance and care causes the seal grease to dry and harden. The dried sealant accumulates on the elastic valve seat, hinders the movement of the valve seat, and causes seal failure.
How to determine the leakage of the ball valve
Natural gas pipelines are commonly used trunnion ball valve, the general inspection method is:
Turn the valve in a fully open or fully closed position and check for leaks through the discharge from the valve body drain.
If it can be drained clean, the seal is proven to be good.
If the pressure is always discharged, the valve may be considered to be leaking, and the valve must be treated accordingly.
Troubleshooting methods for the ball valve leakage
① Firstly check the limit of the valve to see if the leakage of the valve can be solved by adjusting the limit.
② Then inject a certain amount of grease to see if it can stop leaking. At this time, the injection speed must be slow. At the same time, observe the change of the pointer of the grease gun outlet pressure gauge to determine the leakage of the valve.
③ If the leakage cannot be stopped, it may be that the early-injection sealant becomes hard or the sealing surface is damaged and the leakage occurs. It is recommended to inject valve cleaning fluid at this time to clean the valve sealing surface and valve seat.
It usually takes at least half an hour to soak, if necessary, it can be soaked for a few hours or even several days. After the cured material is completely dissolved, the next step can be performed. It is best to switch the valve several times during this process.
④ Re-inject grease intermittently and open and close the valve several times, letting the impurities out of the valve seat cavity and the sealing surface.
⑤ Inspect the fully closed position. If there is still leakage, intensified sealing grease should be injected. At the same time, the valve chamber is opened for venting. This can generate a large pressure difference, which helps to seal. Under normal circumstances, it injects the reinforced sealing grease, and endoleak can be eliminated.
⑥If there is still leakage, the valves will need to be replaced completely.