 Leakage between the ball and the valve seat
Reason:
Damage of the valve seat sealing material is a common situation. For example, for ball valves using rubber valve seats, the rubber may age, deform or crack after being eroded by the medium for a long time, temperature changes or chemical erosion. For example, in ball valves that transport corrosive liquids in chemical pipelines, chemicals may gradually corrode the rubber valve seat, resulting in a decrease in sealing performance.
Solution:
In the case of damaged valve seat sealing materials, the valve seat needs to be replaced. When selecting a new valve seat, factors such as the nature, temperature and pressure of the medium should be considered. If it is a high-temperature environment, a metal valve seat may need to be selected; for general water media, a high-performance rubber valve seat may be sufficient.
When the surface of the ball is worn, slight scratches can be repaired by grinding with abrasive paste. If the wear is severe, the ball needs to be replaced.

 Unable to open
Reason:
One of the common reasons is that the ball is stuck by impurities in the medium. For example, in a water pipe containing mud and sand, mud and sand may enter the inside of the ball valve and get stuck in the gap between the ball and the valve body, hindering the rotation of the ball.
Damage to the connecting parts between the valve stem and the ball can also cause the ball to be unable to rotate. For example, the connection key is broken or loose, so that the valve stem cannot effectively drive the ball.
Solution:
If the ball is stuck by impurities, you can first close the upstream valve, empty the medium in the pipeline, and then disassemble the ball valve to clean the impurities. For some situations where the medium cannot be completely emptied, you can try to remove impurities by flushing with fluid.
When the connecting parts are damaged, it is necessary to replace the damaged connecting keys and other parts, and after installation, check whether the connection between the valve stem and the ball is firm and whether the rotation is flexible.

Reason:
One of the main reasons is that the friction between the valve seat and the ball is too large. This may be due to the excessive elasticity of the valve seat material or the tight seal between the valve seat and the ball. For example, if the seat preload is adjusted too high during the initial operation of a newly installed ball valve, the operating torque will be too large.
The friction between the valve stem and the packing will also affect the operating torque. If the packing is installed too tightly or has hardened, the resistance to the rotation of the valve stem will increase.
The rough surface of the ball or the small gap between the ball and the valve body will also increase the friction during rotation, thereby increasing the operating torque.
Solution:
For the case where the friction between the valve seat and the ball is too large, the preload of the valve seat can be adjusted appropriately. During the adjustment process, pay attention to ensure the sealing performance of the valve.
For the friction problem between the valve stem and the packing, it is necessary to check the installation of the packing. If the packing is too tight, the packing gland nut can be slightly loosened; if the packing is hardened, the packing needs to be replaced.
When the surface of the ball is rough or the gap is too small, the surface of the ball can be ground to increase the gap between the ball and the valve body to reduce friction.