Oil & Gas Wellhead Sealing: Extending Seal Life from 3 Months to 18 Months
Challenge
A wellhead equipment manufacturer needed FKM O-rings that could handle sour gas (H2S) at 150°C and 300 bar, but standard FKM grades showed compression set after short service intervals.
Solution
We specified a high-fluorine FKM compound with 90 Shore A hardness and supplied back-up rings to prevent extrusion into clearance gaps.
Result
Seal life extended from 3 months to over 18 months, eliminating unplanned wellhead maintenance during production seasons.
Details
The customer operated wellheads in a sour gas field where hydrogen sulfide concentrations reached 15% by volume. Standard FKM compounds were experiencing rapid compression set and hardening at 150°C, leading to leakage during pressure cycling.
Our engineering team reviewed the gland design and recommended a high-fluorine FKM (Type 2) with improved thermal stability and H2S resistance. The 90 Shore A hardness provided the extrusion resistance needed for 300 bar operating pressure.
Because the clearance gap exceeded 0.15 mm, we also supplied spiral PTFE backup rings on the low-pressure side of the O-ring assembly. This combination prevented extrusion while maintaining the flexibility needed for thermal expansion.
After 18 months of continuous service, the seals were inspected during a planned shutdown. The O-rings showed minimal compression set and the backup rings were intact. The customer has since standardized on this specification across all sour gas wellheads.
Related Resources
Oil & Gas Industry Page
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Open resourceFKM Material Page
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