- Failure occurs at the connection of various components
1. Packing failure
The valve stem packing is generally in the packing groove where the valve stem is close to the cold box wall. If the packing is uneven, not tight, not round, or the valve stem is not straight, the low-temperature liquid or gas will flow along the packing area. Leaks from gaps. Because of the external transfer of cold energy, the packing will be frozen by the moisture in the air, and the valve stem will also be frozen. When this happens, steam or hot water must be used to heat the packing to open and close the cryogenic valve.
2. Flange leakage failure
The main reasons for flange leakage include insufficient smoothness and smoothness of the sealing surface, insufficient pipeline compensation, uneven bolt tightening, improper bolt material, etc.
- Failures that are prone to occur on the valve top
Since the connection between the valve top and the valve stem is movable, after being used for a long time, titanium, nickel, zirconium, and Monel alloy valves sometimes have damage to the anti-return gasket, causing the locking nut to loosen. In this way, when the valve is opened, The valve top will fall off, and the cryogenic valve will lose its closing function. Another reason is damage caused by improper material of the lock nut. The last reason is that the valve top is not closed tightly, that is, the valve is leaking.
- Failures that are prone to occur on the valve stem
The most common failure on the valve stem is that the threads on the valve stem and thread sleeve are worn, causing the valve to fail to close. The common reason is that if the valve is opened with too much force and the thread is tightened hard, the thread will be bitten. When the screw thread is completely "bitten" and the valve can only be opened but cannot be closed, the valve stem can only be pushed inward with temporary additional bolts and waited for professionals to come for maintenance.