What Is an ORFS Fitting? O-Ring Face Seal Connection and Sizes
An ORFS (O-Ring Face Seal) fitting uses an O-ring in its end face so the joint does not leak even under vibration. Size table, working pressures and a comparison with JIC.
5 min read · 8-row dimension table · 5 frequently asked questions
How an ORFS fitting works
ORFS stands for O-Ring Face Seal. The end of the male part is not a cone but a flat face with an O-ring groove machined into it. As the nut is tightened the O-ring is compressed between two flat faces and makes the seal.
The standard is SAE J1453, with ISO 8434-3 as its international equivalent. Threads are inch-based UN/UNF straight threads; the thread plays no part in sealing at all — it only generates the clamping force.
Why it is considered the safest connection
On metal-to-metal joints (JIC, 24° metric) vibration gradually works the seating face and the joint starts to weep. In an ORFS joint the seal is made by an elastic element, so the O-ring absorbs the vibration. That makes it first choice:
- on breakers, hydraulic hammers and any line under impulse loading,
- on the constantly moving booms of mobile plant,
- anywhere a leak is simply unacceptable (food production, clean rooms, enclosed spaces).
Working pressure reaches 420 bar in the smaller sizes.
ORFS size table
One point to note with ORFS: the thread size is always one step larger than the tube it connects to. For 1/2" tube, for instance, the thread is 13/16"-16. Ordering by dash number is the safest approach.
ORFS or JIC?
The two are not interchangeable — both the threads and the sealing faces are different. Choose as follows:
- Vibration present, pressure high, leaks unacceptable → ORFS.
- Joint broken and remade often, cost matters, existing machine is JIC → JIC.
If you need to change type on an existing machine, a JIC–ORFS adaptor will do it; bear in mind though that every extra joint is another potential leak point, so having the hose made up with the required ends from the start is preferable.
Looking after the O-ring
- Every time you break the joint, inspect the O-ring; replace it if it is crushed, nicked or hardened.
- The standard O-ring material is NBR, good for –30 °C to +100 °C. Higher temperatures or different fluids call for an FKM (Viton) O-ring.
- Lightly oil the O-ring with system fluid before assembly; fitted dry it can pop out of its groove.
- If the O-ring has come out of its groove the joint will definitely leak — adding torque will not cure it.
ORFS sizes and thread equivalents (SAE J1453)
| Dash | Tube OD | Thread (UN/UNF) | O-ring size | Approx. working pressure |
|---|---|---|---|---|
| –4 | 1/4" | 9/16" – 18 | 8.92 × 1.83 mm | 420 bar |
| –6 | 3/8" | 11/16" – 16 | 11.89 × 1.98 mm | 420 bar |
| –8 | 1/2" | 13/16" – 16 | 15.08 × 1.78 mm | 420 bar |
| –10 | 5/8" | 1" – 14 | 18.64 × 1.78 mm | 350 bar |
| –12 | 3/4" | 1.3/16" – 12 | 23.39 × 2.62 mm | 350 bar |
| –16 | 1" | 1.7/16" – 12 | 29.74 × 2.62 mm | 275 bar |
| –20 | 1.1/4" | 1.11/16" – 12 | 35.10 × 2.62 mm | 210 bar |
| –24 | 1.1/2" | 2" – 12 | 43.82 × 2.62 mm | 210 bar |
The table scrolls horizontally. Values are for guidance; we recommend confirming the size before ordering.
Frequently Asked Questions
What does ORFS mean?
ORFS is short for O-Ring Face Seal. The flat end face of the male part carries an O-ring which is pressed against the flat face of the mating part to make the seal.
What pressure does an ORFS fitting hold?
Up to 420 bar in the smaller sizes (1/4"–1/2"). At 1" it is around 275 bar and at 1.1/2" around 210 bar. Those figures make ORFS the safest connection type for high-pressure lines.
Can an ORFS fitting replace a JIC one?
Not directly. The thread sizes and sealing faces differ, and forcing them together damages both the thread and the face. Use a JIC–ORFS adaptor if you must, though having the hose made up with the required ends from the outset is better.
What should I do if an ORFS joint leaks?
Slacken the nut and inspect the O-ring. Replace it if it has come out of its groove, or is crushed or nicked. Adding torque will not stop the leak — it crushes the O-ring further and makes matters worse.
Which material should the ORFS O-ring be?
NBR is sufficient for standard hydraulic oil and a –30 °C to +100 °C range. For higher temperatures, brake fluid or special fluids, use an FKM (Viton) O-ring.