The first cause of valve internal leakage is the improper valve design and selection.

The designer did not comprehensive consider oil and gas pipeline transport medium, transport medium temperature and environmental temperature, flow, pressure and other factors, resulting in the selection of the valve pressure class. Structure does not conform to the actual medium of oil and gas pipeline transport, resulting in the leakage of the valve in the process of use.

Second, the valve manufacturer production unqualified. The purchased sealing ring does not meet the requirements of design and selection, and the material technical indicators do not meet the requirements of the technical specifications; Improper sealing ring installation or use of defective sealing ring, and the valve pressure test was not found, resulting in valve leakage in the pipeline; The size of valve and bonnet is out of tolerance and assembly is not in place; The valve switch position is not adjusted in place, so that the valve cannot be fully closed when all the indicating positions are closed, resulting in internal leakage of the valve; When the valve leaves the china ball valve factory, it is not adjusted to the full open position, or the two ends of the valve are not protected, leading to impurities entering the valve cavity.