Encapsulated O-Ring Installation

The FEP or PFA jacket is a thin fluoropolymer film — typically 0.10–0.25 mm — fused or molded around the elastomer core. It provides chemical isolation, not wear resistance. Repeated flexing under pressure cycles causes micro-cracking at the parting line and eventual jacket separation.

Acceptable applications include flanged chemical connections, valve bonnets, sight glasses, tri-clamp fittings, and other face seals where the gland does not move relative to the mating surface after assembly. For dynamic chemical service, specify spring-energized PTFE seals instead.

Remove burrs, sharp corners, and machining marks from groove edges. A radius of 0.10–0.25 mm on all groove corners reduces the risk of cutting the jacket during seating.

Clean the groove with lint-free wipes and compatible solvent. Residual cutting fluid, rust inhibitor, or particulate contamination creates leak paths under the jacket.

Verify groove dimensions against the Compression Calculator. Encapsulated O-rings use the same rectangular groove geometry as standard O-rings but are less tolerant of over-compression that pinches the jacket.

Limit installation stretch to 2–3% of the unmounted inside diameter — less than standard elastomer O-rings. Excessive stretch thins the FEP shell and can expose the core or create stress whitening that becomes a leak path.

Never use screwdrivers, hooks, or sharp tools to pull the seal into the groove. Use gloved hands or a blunt plastic installation cone.

Store encapsulated O-rings in original packaging until installation. UV, ozone, and abrasion from loose handling damage the jacket before the seal reaches the groove.

Any surface the seal must pass during assembly needs a lead-in chamfer: 15–20° angle over a length of at least one cross section. Without a chamfer, the jacket shears at the bore or port edge.

When the seal must travel over a threaded section, keyway, or sharp port opening, machine a thread undercut with depth at least cross section + 0.5 mm, or use a tapered plastic installation sleeve.

For vertical face seals where the O-ring would fall out during bolt-up, consider a dovetail groove or retain the seal with a temporary assembly fixture until flange bolts are partially tightened.

Light lubrication eases installation and reduces jacket scuffing. Use a fluid compatible with both the service media and the elastomer core — silicone fluid for VMQ cores, fluorinated fluid or clean isopropanol for FKM cores.

Do not use petroleum-based grease on VMQ cores intended for food or pharmaceutical service. Residual hydrocarbon grease contaminates the process and may swell the core unevenly.

After installation, wipe excess lubricant from exposed jacket surfaces if the process requires low extractables or visual inspection.

Inspect 100% of encapsulated O-rings before installation in critical service. Reject seals with visible cuts, pinholes, blisters, delamination at the parting line, or permanent set that prevents round cross section.

Verify inside diameter and cross section with calipers. Encapsulated constructions have slightly larger cross sections than nominal molded O-rings because of jacket thickness — confirm against supplier dimensions, not a generic AS568 chart alone.

Document lot number and installation date for regulated applications. Lot traceability certificates are available on request.