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Sealing Elements of Cryogenic Ball Valves (Part 1)

May. 26, 2020

1 Overview

Due to its simple structure and small installation space, the ball valve is sealed by medium force and is not affected by the external driving force, so it is widely used in various working conditions. At present, ultra-low temperature ball valves are commonly used in LNG receiving stations, and the number of ultra-low temperature ball valves accounts for 80% of the total number of valves in the LNG receiving station. Low temperature ball valve supplier based on low-temperature valve design guidelines and the basic theory of valve sealing performance, analyzed the factors that affect the ultra-low temperature ball valve sealing.

2 Design guidelines

Due to the extremely low operating temperature, the design and manufacture of ultra-low temperature valves face a series of technical difficulties, such as material selection, low-temperature sealing, structural design, solution treatment, cryogenic treatment, insulation, quality inspection, maintenance, safety, etc. To this end, there are a series of strict standards for the design of cryogenic valves. When designing cryogenic valves, in addition to the general valve design principles, the special requirements of cryogenic valve design should be followed according to the conditions of use.

① Valves should not be a significant heat source for low-temperature systems. This is because the inflow of heat, in addition to reducing the thermal efficiency, will cause the internal fluid to evaporate rapidly, resulting in abnormal pressure increase, resulting in danger.

②Cryogenic medium should not have harmful effects on handwheel operation and packing sealing performance.

③ Valve assemblies that are in direct contact with low-temperature media should have an explosion-proof and fire-proof structure.

④Valve assemblies that work at low temperatures cannot be lubricated, so structural measures need to be taken to prevent friction from scratching.

In the design process of cryogenic valves, in addition to the general requirements such as the flow capacity of cryogenic valves, some other indicators need to be considered in order to better evaluate the technical level of cryogenic valves. The technical level of cryogenic valves is usually evaluated by measuring whether the energy consumption is reasonable.

①Insulation performance of the cryogenic valve.

②Cooling performance of the cryogenic valve.

③ Working performance of low-temperature valve opening and closing seals.

④The condition of low-temperature valve surface without icing.

Low Temperature Ball Valve

Low Temperature Ball Valve

Low temperature ball valve and general valve working environment are very different, in the process of low-temperature valve design, manufacturing and inspection in addition to the general rules of valve design, manufacturing, and inspection, should also pay attention to low-temperature valve Make appropriate adjustments to your environment.

3 Basic theory

The main factors affecting the sealing of the valve are the structure of the sealing pair, the specific pressure of the sealing surface, the physical properties of the medium, and the quality of the sealing pair. However, only when the valve sealing principle is truly understood, and various factors affecting its sealing performance are fully considered, can the leakage be prevented and the sealing guaranteed.


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