② When leaving the factory, the valve was not dried and anti-corrosion treated after water pressure was applied, resulting in rust on the sealing surface and internal leakage;

③ Insufficient protection at the construction site, no blind plates installed at both ends of the valve, and impurities such as rainwater and sand entering the valve seat, resulting in leakage;

④ During installation, lubricating grease was not injected into the valve seat, causing impurities to enter the back of the valve seat or internal leakage caused by 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, resulting in internal leakage;

⑥ Welding slag and other construction residues causing scratches on the sealing surface;

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 common reason is that operation managers do not maintain valves due to expensive maintenance costs, or lack scientific valve management and maintenance methods to prevent valve maintenance, 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 may cause damage to the sealing surface and result in internal leakage;

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

⑥ Inadequate valve opening and closing can cause internal leakage. Any ball valve, regardless of its opening or closing position, can generally tilt by 2 ° to 3 °, which may cause leakage;

⑦ Many large-diameter ball valves have valve stem stop blocks. If used for a long time, rust, dust, paint, and other debris will accumulate between the valve stem and valve 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, extending the valve stem will produce and drop more rust and impurities, which will hinder the valve ball from rotating in place and cause valve leakage;

⑧ General actuators are also limited in position. If they cause corrosion, hardening of lubricating grease, or loosening of limit bolts for a long time, the limit will be inaccurate and cause internal leakage;

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

⑩ Lack of periodic maintenance and upkeep results in the sealing grease becoming dry and hard. The dried sealing grease accumulates behind the elastic valve seat, hindering valve seat movement and causing seal failure.

Method for Judging Internal Leakage of Natural Balloon Valves

The commonly used fixed shaft ball valve on natural gas pipelines is to rotate the valve to the fully open or fully closed position, and check for leakage through the discharge nozzle of the valve body. If it can be drained clean, it proves that the seal is good. If there is always pressure discharge, it can be considered that the valve is leaking, and corresponding measures should be taken for the valve.

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