What will happen to ball valves at low temperatures?

In low-temperature environments, the performance of ball valves will be significantly affected, as shown below:

Changes in material properties result in operational difficulties or damage

Low temperature can make the material of ball valves brittle, especially non-metallic sealing materials, whose expansion coefficient is much greater than that of metal materials. During low-temperature shrinkage, the difference in shrinkage between non-metallic seals and metal valve bodies and seals is significant, resulting in a severe decrease in sealing pressure and the inability to seal. For example, rubber will completely lose its elasticity and become glassy, losing its sealing properties when the temperature is below the glass transition temperature; In LNG medium, rubber still has foaming properties and cannot be used for LNG valves. In addition, low temperatures may also cause low stress brittle fracture of materials. For example, austenitic stainless steel, which was originally in a metastable state at low temperatures, transforms into martensite when the temperature drops below the phase transition point. The volume change causes an increase in internal stress, causing the sealing surface to warp and deform, resulting in sealing failure.

Reduced sealing performance leads to medium leakage

If a low-temperature ball valve uses a metal to non-metal material sealing pair, the non-metal material will become hard and brittle at low temperatures, losing its toughness, resulting in cold flow and stress relaxation, and a decrease in sealing performance. However, currently when designing low-temperature valves, non-metallic sealing materials are generally no longer used when the temperature is below -70 ℃, or they are processed into metal and non-metal composite structures. At the same time, uneven shrinkage caused by temperature differences in various parts of the parts or differences in physical properties between different materials can also generate temperature induced stress, causing elastic distortion or irreversible distortion deformation of the sealing surface, which affects the sealing effect.

Specially designed low-temperature ball valve can adapt to low-temperature environments

To cope with the challenge of low temperature, the low-temperature ball valve adopts a special design. If a long neck valve cover is used to protect the packing box and keep it far away from low temperatures to ensure the sealing effect of the packing, cold insulation materials can also be wrapped to prevent cold energy loss; When the operating temperature is below -100 ℃, the valve stem material is treated with chrome plating or nitriding to improve surface hardness and enhance the reliability of the packing seal; Equipped with a structure to prevent abnormal pressure rise, when the pressure in the valve chamber increases, the chamber and inlet are connected or a pressure relief valve is installed at the inlet end to ensure safe use; The gasket used can reliably seal and have resilience at room temperature, low temperature, and temperature changes.