ORFS Hydraulic Fittings
O-Ring Face Seal — the modern standard for leak-free hydraulics
ORFS (O-Ring Face Seal) fittings provide a leak-free seal in high-pressure hydraulic systems. Learn how ORFS works, how to identify ORFS fittings, male vs female types, and O-ring compatibility.
How to Identify an ORFS Fitting
ORFS fittings have very distinctive visual features that make them easy to identify once you know what to look for.
Look for the Flat Face with O-Ring Groove
The defining feature of ORFS. The face of the fitting has a machined groove (called the face seal) that contains an O-ring. When the fitting is tightened against a flat surface (the port), the O-ring compresses to form a leak-proof seal. This is NOT like BSP or JIS fittings that seal on a cone or thread.
Check for Three-Hole or Four-Hole Flange Pattern
ORFS tube fittings ( swivel nut type ) have a flat face with 3 or 4 bolt holes around the O-ring groove — similar to a small SAE flange. The bolt holes align with matching ports on equipment manifolds. This distinguishes ORFS from BSP or JIS fittings which use threaded connections.
Identify Male vs Female ORFS
ORFS Male: the fitting with the O-ring on its face connects to a port (female port). ORFS Female: the swivel nut type — the O-ring is on the fitting face that mates with the port. In hose assemblies: ORFS male fittings are crimped onto the hose and seal against the port face; ORFS female (swivel) fittings have a nut that swivels for easy connection.
Check the O-Ring Type
ORFS O-rings are typically NBR (Nitrile/Buna-N, colour-coded black) for petroleum-based hydraulic fluid, or EPDM (Ethylene Propylene, colour-coded black or green) for phosphate ester fluid (Skydrol). Using the wrong O-ring material causes rapid swelling or hardening and leaks.
Identify the Size Designation
ORFS fittings are designated by tube OD: -4 (1/4" OD), -6 (3/8" OD), -8 (1/2" OD), -10 (5/8" OD), -12 (3/4" OD), -16 (1" OD), -20 (1-1/4" OD), -24 (1-1/2" OD). Note: ORFS size is based on tube OD, not thread size — this differs from BSP sizing which is based on pipe bore.
Look for the Hex or Nut
ORFS swivel female fittings have a hexagonal nut (flat wrench faces) that tightens against the port face. The fitting body or nut is usually marked with the size and "ORFS" or "SAE". Common brand markings: Parker (Parkrimp), Eaton (Aeroquip), Gates.
Technical Specifications
| Seal Mechanism | O-ring on flat face — no thread sealing. The O-ring (not the threads) carries the pressure and prevents leaks. |
| Working Pressure | Up to 6,000 PSI (414 bar) depending on size and material. Larger sizes have lower pressure ratings. |
| Temperature Range | NBR O-ring: -40°C to +120°C. EPDM O-ring: -40°C to +150°C (for Skydrol / phosphate ester fluid). |
| Common O-Ring Material | NBR (Nitrile/Buna-N): petroleum-based hydraulic oil. EPDM: phosphate ester fluid (Skydrol). Never mix EPDM with petroleum oil. |
| ORFS Tube (Male) Fitting | Crimped onto hose. O-ring on face seals against the port. Non-swivel — orientation set at crimping. |
| ORFS Swivel (Female) Fitting | Nut swivels. O-ring on face seals against port. Allows orientation adjustment during assembly. |
| Sizes Available | -4 (1/4") to -24 (1-1/2") OD. Most common in mobile hydraulics: -6, -8, -10, -12, -16. |
| Common Standard | SAE J1453 (primary standard). Also ISO 8434-3. Supersedes older 4-bolt flange fittings in many modern applications. |
| Port Type Required | ORFS ports require a flat-face port (SAE J1926 or ISO 11926). Cannot connect ORFS to BSP or NPT ports without an adapter. |
Why ORFS Has Become the Modern Standard
ORFS fittings solve three major problems that plagued older fitting types: 1. Thread leakage: BSP and NPT fittings rely on thread engagement and sealant (PTFE tape, paste) to seal — any over-tightening, under-tightening, or vibration can cause leaks. ORFS seals with a precision O-ring — no thread sealing required. 2. Assembly orientation: Swivel ORFS fittings can be oriented by hand before tightening, making routing easier than BSP fittings. 3. Vibration resistance: The O-ring absorbs vibration-induced movement without degrading the seal. ORFS is now standard on most new mobile hydraulic equipment worldwide. The main limitation: ORFS requires a flat-face port. You cannot thread an ORFS male directly into a BSP or NPT tapered port — you need an adapter. This is why many older machines still use BSP throughout.
ORFS Fitting Types at a Glance
Type | Description | Hose End? ORFS Male (Tube) | O-ring on face, crimped to hose, non-swivel | Yes — hose end ORFS Swivel Female | Nut swivels, O-ring on face | Yes — hose end ORFS Port (Straight Thread) | Male fitting with O-ring for flat-face port | No — port connection ORFS Elbow / Tee | 90° or 45° elbow with ORFS ends | Yes — hose end ORFS to BSP Adapter | Converts ORFS port connection to BSP thread | Adapter Always specify: fitting type + ORFS size + hose type (R1AT or R2AT) + hose length when ordering.
Related Products
Shop the products mentioned in this guide
Full range of ORFS fittings in stock — male, female, elbows, tees
Replacement NBR and EPDM O-rings for ORFS fittings
ORFS to BSP adapters for connecting ORFS to BSP systems
R2AT preferred for ORFS assemblies at higher pressures
Need ORFS fittings or O-rings?
Tell us the ORFS size, fitting type (male/female/elbow), and hose type — or send a photo of what you need. We stock common ORFS fittings in Johor.