ORFS stands for O-Ring Face Seal, sometimes written as flat face o-ring or SAE J1453. If you work on modern mobile hydraulics — excavators, skid steers, agricultural equipment — you have handled a lot of these, because the industry moved toward them for one reason: they are very hard to make leak.
How the seal works
The tube end is machined flat, with an o-ring sitting in a groove on that flat face. A swivel nut pulls the flat face against the mating flat face of the fitting. The o-ring is compressed between two parallel flat surfaces.
Because both sealing surfaces are flat and the o-ring is captured in a groove, the joint tolerates vibration and pressure cycling far better than a thread-sealed connection. That is why ORFS dominates high-pressure applications.
Telling ORFS apart from ORB
The quickest visual check: look at the end of the male fitting.
- ORFS — flat face with a groove and an o-ring sitting in the face, straight threads.
- ORB — o-ring sits at the base of the thread against a shoulder. See our ORB guide.
- JIC 37° — no o-ring at all, a machined cone. If there is no groove and no o-ring, it is metal-to-metal and a replacement ring will not help you.
Why ORFS joints leak
Given the design, a leaking ORFS joint almost always means one of four things:
- The o-ring was nicked on assembly — very easy to do dragging it past a thread.
- The o-ring has taken a compression set after long service and no longer springs back.
- The wrong size was fitted — slightly undersized rings will seal briefly, then extrude.
- The flat face is scored. Inspect it. No o-ring will seal against a damaged face.
ORFS o-ring sizes
ORFS uses standard AS568 dash sizes, which is a genuine convenience compared with the 900-series numbering that ORB requires. Dash 4 takes an #011, dash 6 an #012, dash 8 an #014, and so on.
Keep the common sizes on hand
Hydraulic O-Ring Kit for FACE ORFS Fittings — 155 pieces across 8 common sizes, Buna-N 90 durometer, compartmented case with sizing chart.
Contents: 25× dash 4 (#011), 25× dash 6 (#012), 25× dash 8 (#014), 25× dash 10 (#016), 20× dash 12 (#018), 15× dash 16 (#021), 10× dash 20 (#025), 10× dash 24 (#029).
Before you reassemble
Every o-ring in these kits seats better and lasts longer with a food-grade silicone lubricant. Dry o-rings pinch, twist and take a set, which is how a brand-new seal starts weeping within a season. A thin film is all you need.
Aqua Flex Food Grade Silicone Lubricant is what we use and what ships in our kits. Apply it to o-rings only — never to the polished faces of a mechanical shaft seal. Those faces need to run dry and clean against each other, and lubricant on the carbon or ceramic will cause the seal to slip, overheat and leak.
Beaver Island Parts Company is not affiliated with, endorsed by, or sponsored by any equipment manufacturer named on this page. All brand names, model numbers and part numbers are the property of their respective owners and are used here solely to identify the equipment our replacement parts fit.