Cryogenic valves are installed at room temperature and work at low temperatures, and the temperature varies widely. If the design and installation are improper, it is easy to produce thermal stress or deformation. At the same time, the operating part of the valve is at room temperature and the flow part is at low temperature. In order to reduce cold damage, the valve rod is often made too long, so it becomes deformed and stuck easily. 

Cryogenic valves often rotate flexibly at room temperature, but are tight at low temperature and even cannot be opened. The main reasons for the valve stuck at low temperature are:

In installation, unreasonable valve and pipeline configuration cause prestress; pipeline cold compensation ability is poor, valve position changes at low temperature; the valve lacks a bracket and deforms at low temperatures; improper fixing of the valve, deformation of the cold storage box at low temperatures, which affects the concentricity of the valve rod and the valve body.

In the design, because the linear expansion coefficient, valve rod and valve sleeve materials are different, the valve rod is generally made of stainless steel, with a linear expansion coefficient of 1.73×10-6 ° C-1; the valve sleeve is brass, with the coefficient of linear expansion is 19.9×10-6℃-1, that is, brass shrinks more than stainless steel, therefore, low temperature may bite the screw. Especially when using the dark rod structure and fine thread, the temperature of the screw is wide and the thread clearance is small, which makes it easier to bite.

In operation, the valve heating is not complete or valve packing with water, it will cause freeze in low temperature, or close the valve so tight at room temperature that the screw thread bite.

In order to prevent the phenomenon of valve sticking, it is advisable to adopt the structure of rising bar and trapezoidal thread of coarse teeth in design. The valve shall be firmly supported on the installation to prevent the valve from bending due to pipe displacement. The valve and the cold box can be fixed with an elastic connection to prevent the valve rod from deforming and being different from the valve body; During naked cooling, check and adjust the installation of the valve under cold condition. When it is found that the valve is stuck after cooling, adjust the fixed flange of the valve on the barrel shell to make it open and close freely.  

In operation, the heating before starting should be thorough, do not leak and overexert when closing the valve.