Introduction

Cryogenic equipment operates at temperatures far below those encountered in conventional industrial systems. Applications include liquefied natural gas (LNG) handling, liquid nitrogen storage, cryogenic valves, gas transfer equipment and specialized laboratory systems.

Sealing at low temperatures presents several engineering challenges. Materials may become less flexible, dimensional clearances can change due to thermal contraction, and differences in thermal expansion between components can affect sealing contact.

A sealing material that performs well at room temperature may not maintain the same properties when exposed to cryogenic conditions.

Why Low-Temperature Sealing Is Challenging

Material contraction: Components contract as temperature decreases. Differences between the seal, shaft and housing materials may alter the installation clearance.

Elasticity changes: Some elastomers become harder and less flexible at low temperatures, potentially reducing their ability to maintain contact.

Pressure fluctuations: Cryogenic systems may experience pressure changes during filling, storage, transfer and shutdown.

Thermal cycling: Repeated cooling and warming can place additional stress on the sealing interface.

Media compatibility: The material must be compatible with the actual cryogenic fluid and any associated cleaning or operating media.

Common Material Considerations

PTFE and selected modified PTFE compounds are often considered for low-temperature sealing because of their broad thermal capability and chemical resistance. However, the exact design must account for creep, thermal contraction and the need to maintain sealing contact.

Specialized elastomers may also be suitable for certain low-temperature applications if their verified material properties meet the operating requirements.

No material should be selected based on temperature range alone. The complete sealing assembly and its operating cycle must be evaluated.

Important Engineering Parameters

For reference, LNG is commonly stored and handled at temperatures around -162°C, while liquid nitrogen boils at approximately -196°C at atmospheric pressure. These temperatures illustrate why cryogenic sealing requires application-specific engineering.

Industry Applications

Cryogenic seals may be used in LNG filling nozzles, transfer couplings, cryogenic valves, liquid nitrogen equipment and specialized gas-handling systems.

In energy infrastructure, reliable sealing helps control leakage and supports safe fluid transfer. In laboratory and industrial gas systems, the seal must also remain compatible with the pressure, fluid and maintenance procedures.

Conclusion

Cryogenic sealing requires more than selecting a material with a sufficiently low temperature rating. Designers must consider thermal contraction, pressure, leakage requirements and the complete operating cycle.

GUOHAO SEALS can review low-temperature sealing requirements based on drawings, operating parameters and material specifications. Suitability for LNG or liquid nitrogen service should be confirmed for the specific product design before use.