1、 Reasons for internal leakage of ball valves

1. Reasons for valve leakage during the construction period:

① Improper transportation and lifting can cause overall damage to the valve, resulting in internal leakage of the valve;

② When leaving the factory, the valve was not dried or treated with anti-corrosion measures after being pressurized, resulting in rusting of the sealing surface and internal leakage;

③ The construction site protection is not in place, and blind plates are not installed at both ends of the valve. Impurities such as rainwater and sand enter the valve seat, causing leakage;

④ During installation, lubricating grease was not injected into the valve seat, resulting in impurities entering the rear of the valve seat or causing internal leakage due to burns during welding;

⑤ The valve was not installed in the fully open position, causing damage to the ball. During welding, if the valve is not in the fully open position, welding spatter will cause damage to the ball. When the ball with welding spatter is opened and closed, it will further cause damage to the valve seat, leading to internal leakage;

⑥ Scratches on the sealing surface caused by construction residues such as welding slag;

⑦ If the valve rod drive sleeve or other accessories are misaligned with its assembly angle, the valve will leak.

2. Reasons for valve leakage during operation:

① The most common reason is that the operation manager considers the relatively expensive maintenance costs and does not maintain the valve, or lacks scientific valve management and maintenance methods and does not perform preventive maintenance on the valve, resulting in equipment failure in advance;

② Improper operation or failure to follow maintenance procedures resulting in internal leakage;

③ During normal operation, construction debris scratches the sealing surface, causing internal leakage;

④ Improper cleaning causes damage to the sealing surface and internal leakage;

⑤ Long term lack of maintenance or inactivity of the valve can cause the valve seat and ball to lock, resulting in seal damage and internal leakage when opening and closing the valve;

⑥ Improper valve opening and closing can cause internal leakage, and any ball valve, regardless of its open or closed position, may be prone to leakage if tilted 2-3 degrees;

⑦ Many large-diameter ball valves have stem stop blocks. If used for a long time, rust, dust, paint and other debris will accumulate between the stem and stem stop blocks due to corrosion and other reasons. These debris will cause the valve to fail to rotate in place and cause leakage. If the valve is buried underground, extending the stem will produce and drop more rust and debris, which will hinder the valve ball from rotating in place and cause valve leakage;

⑧ General actuators also have limited positions. If corrosion, hardening of lubricating grease, or loosening of limit bolts occur for a long time, it will result in inaccurate positioning and internal leakage;

⑨ The valve position of the electric actuator is set forward and not closed properly, causing internal leakage;

⑩ Lack of periodic maintenance and upkeep causes the sealing grease to dry and harden, and the dried sealing grease accumulates behind the elastic valve seat, hindering the movement of the valve seat and causing sealing failure.

2、 Method for determining internal leakage of ball valves

Fixed shaft ball valves are commonly used on natural gas pipelines, and their general inspection method is to rotate the valve to the fully open or fully closed position, and check for leaks through the discharge nozzle of the valve body. If it can be completely drained, it proves that the seal is good. If there is always pressure discharge, it can be considered that the valve is leaking, and the valve should be treated accordingly. However, it should be emphasized that the GRoVEB-5 and B-7A ball valves, PBV ball valves, and ROBERTCORT ball valves can only be inspected in the fully closed position, as these types of ball valves have a channel opened on the valve body to balance the pressure in the pipeline and valve chamber when fully open. But when fully closed, this situation will not occur.

3、 Procedure for handling internal leakage of ball valves

① Firstly, check the limit of the valve to see if the internal leakage of the valve can be resolved by adjusting the limit.

② First, inject a certain amount of lubricating grease to see if it can stop the leakage. At this time, the injection speed must be slow, and at the same time, observe the change of the pressure gauge pointer at the outlet of the grease gun to determine the internal leakage of the valve.

③ If the leakage cannot be stopped, it may be caused by the early injection of sealing grease hardening or damage to the sealing surface leading to 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, it should be soaked for at least half an hour. If necessary, it can be soaked for several hours or even days until the solidified material is completely dissolved before proceeding to the next step of treatment. It is best to open and close the movable valve several times during this process.

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

⑤ Check in the fully closed position. If there is still leakage, inject reinforced sealing grease and open the valve chamber for venting. This can create a large pressure difference and help seal. Generally, internal leakage can be eliminated by injecting reinforced sealing grease.

⑥ If there is still internal leakage, the valve needs to be repaired or replaced.