PTFE Seal for Cryogenic Service — sealing force when everything shrinks
A cryogenic seal has a problem a cryogenic ball does not: it must maintain a continuous sealing force while the polymer contracts away from the surface it is sealing against. That is why cryogenic PTFE seals are almost always spring-energised rather than relying on interference alone.
Where PTFE Seal for Cryogenic Service is used
Glass-filled PTFE is generally preferred over unfilled for the seal body because it contracts less and resists the cold flow that assembly loads cause at ambient. Where the service is also oxygen, the filler restrictions of oxygen duty override that preference.
Failure is usually loss of sealing force after repeated thermal cycles rather than abrasion. Count cool-down cycles, not running hours.
Key properties
Service
LNG, liquid nitrogen and oxygen transfer, cryogenic valves
Design driver
maintaining sealing load through contraction
How it behaves here
PTFE contracts markedly more than the metal housing around it. An interference-fit seal loses that interference on cool-down, so the load has to come from somewhere else — a stainless spring or a metal energiser that keeps pushing the lip against the counterface as the polymer shrinks.
Where it does not belong
Unenergised PTFE seals should not be assumed to work cryogenically simply because the material tolerates the temperature. The material survives; the seal geometry is what fails. This distinction is the most common cryogenic sealing mistake.
Specifications
| Property | Value |
|---|---|
| Service condition | Cryogenic transfer and valve sealing |
| Design requirement | Spring or metal energiser, not interference alone |
| Seal body | Glass-filled PTFE typical; unfilled where contraction is designed for |
| Governing factor | Contraction mismatch between polymer and housing |
| Form supplied | Machined to seal drawing |
| Confirm | Housing material and energiser specification |
Manufacturing process
Machined from sintered billet to the seal drawing, with the energiser fitted to specification.
Material selection notes
PTFE contracts markedly more than the metal housing around it. An interference-fit seal loses that interference on cool-down, so the load has to come from somewhere else — a stainless spring or a metal energiser that keeps pushing the lip against the counterface as the polymer shrinks.
How to specify your order
Glass-filled PTFE is generally preferred over unfilled for the seal body because it contracts less and resists the cold flow that assembly loads cause at ambient. Where the service is also oxygen, the filler restrictions of oxygen duty override that preference.
Quality checks and inspection
Dimensions are verified on CMM against your drawing. Filler content and sintered density are checked per ASTM D792, with tensile and elongation per ASTM D4894. A mill test certificate stating the lot, filler content and measured values ships with the order.
Ordering and export documentation
Verify the energiser specification as carefully as the seal dimensions, and confirm the housing material — a stainless housing and an aluminium housing produce very different contraction mismatches with the same seal.
Export packing and lead time
HEMSUN is a DGFT IEC registered exporter (Government of India). Commercial invoice, packing list and certificate of origin accompany international despatch.
Storage and handling
Failure is usually loss of sealing force after repeated thermal cycles rather than abrasion. Count cool-down cycles, not running hours.
Compliance & Standards
HEMSUN is a DGFT IEC registered exporter (Government of India). Filler content and sintered density are verified per ASTM D792 on each batch, with tensile and elongation checked per ASTM D4894.
Frequently Asked Questions
What PTFE Seal for Cryogenic Service options does HEMSUN manufacture?
A cryogenic seal has a problem a cryogenic ball does not: it must maintain a continuous sealing force while the polymer contracts away from the surface it is sealing against. That is why cryogenic PTFE seals are almost…
Can you supply PTFE Seal for Cryogenic Service for OEM and export orders?
Yes. We support prototype lots, recurring OEM programmes, and export packing with material certificates and dimensional inspection reports on request. Typical RFQ response is within one business day when drawings are complete.
How do I request a quote for PTFE Seal for Cryogenic Service?
Send material grade, dimensions or drawing, quantity, application media, and operating temperature/pressure via https://hemsun.com/contact. Our engineering team confirms manufacturability, lead time, and pricing.
