I. causes of valve leakage during construction period:

(1) improper transportation and lifting caused the overall damage of the valve, resulting in valve leakage;

(2) when leaving the factory, the water pressure did not dry treatment and anti-corrosion treatment of the valve, resulting in the sealing surface rust formation of internal leakage;

(3) construction site protection is not in place, both ends of the valve is not installed blind plate, rain, sand and other impurities into the valve seat, resulting in leakage;

(4) installation, not into the valve seat grease, causing impurities into the back of the valve seat, or welding burns cause internal leakage;

(5) the valve is not installed in the full open position, resulting in ball damage, in the welding, if the valve is not in the full open position, welding spatter will cause ball damage, when the ball with welding spatter in the switch will further cause seat damage, resulting in internal leakage;

(6) welding slag and other construction residue cause sealing surface scratch;

(7) delivery or installation time position is not accurate resulting in leakage, if the stem drive sleeve or other accessories and its assembly Angle dislocation, the valve will leak.

Ii. Causes of internal leakage during operation:

(1) the most common reason is that the operation manager to consider the relatively expensive maintenance costs of the valve do not maintain, or lack of scientific valve management and maintenance methods do not carry out preventive maintenance of the valve, resulting in equipment failure in advance;

(2) improper operation or not in accordance with the maintenance procedures for maintenance caused by internal leakage;

(3) in normal operation, construction residue scratches the sealing surface, resulting in internal leakage;

(4) improper pigging causes damage to the sealing surface and causes internal leakage;

(5) do not maintain or do not move the valve for a long time, resulting in the valve seat and ball embrace dead, in the switch valve caused by sealing damage formation of internal leakage;

(6) the valve switch is not in place to cause internal leakage, any ball valve regardless of open, close, generally inclined 2° ~ 3° may cause leakage;

(7) many large diameter ball valves have stem mostly stop block, if you use a long time, due to reasons such as corrosion in the stem and stem between stop blocks will accumulate rust, dirt, paint and other sundry, these stuff will leak valve cannot be rotated due, if the valve is buried, elongated stem yield and falling more rust and impurities hinder valve ball spinning in place, cause the valve leakage;

(8) general actuator is also limited, if long-term cause rust, grease hardening or limit bolt loose will make the limit is not accurate, resulting in leakage;

 (9) electric actuator valve position set forward, not related to the position caused by internal leakage;

Attending lack of periodic maintenance and maintenance, resulting in seal fat dry, hard, dry seal fat accumulation in the elastic seat, block seat movement, causing seal failure.