Stainless ORFS Fittings

The O-ring face seal is the one connection here that does not seal on metal. A captive O-ring in the face of the male fitting is squeezed flat against the machined face of the female, and the 316 body only holds the faces together. That inverts the usual problem: the elastomer, not the alloy, decides what the joint can be used in.

Nitrile is the default and fine in mineral oil, but it is what limits temperature and chemical range; FKM covers hotter oil and many solvents; EPDM is the compound for phosphate esters and steam, where FKM is not. Bodies follow SAE J1453 and ISO 8434-3, so the flat-face geometry that shrugs off vibration in steel behaves the same here — the grade simply removes the plating that would corrode away around the seal groove.

Where it's specified

• Phosphate ester and water-glycol systems — an EPDM O-ring stays serviceable in fluid that swells nitrile
• Vibrating machines in coastal air — the face seal takes shake and 316 keeps the face free of pitting
• Food, beverage and washdown lines — bodies clean down and the elastomer is specified against whatever contact rules apply
• High-purity and pharmaceutical plant — no zinc or chromate on the wetted path to shed into the fluid

Range and materials. Straight adapters, elbows, run and branch tees, bulkheads, swivels, unions and plugs in 316/316L, with ORFS ends converting to JIC 37°, NPT, SAE ORB, BSPP and metric across the common ORFS thread sizes. O-rings ship fitted; name the compound with the order.

Ordering notes. Because the seal is a crushed O-ring rather than a torqued metal seat, this is the most forgiving stainless joint to assemble — but the threads still gall, so lubricate them and stop when the faces meet. Check the groove and mating face for nicks first: a scratch there leaks in a way a thread scratch does not.