Technical Foundation
What Is a Split Flange Kit?
A split flange kit connects a hydraulic hose or tube fitting to a mating flange head using two identical clamp halves that bolt around the fitting's neck groove, rather than a single rotating flange nut — this design lets the hose end be positioned and clamped without twisting the hose, and allows disassembly in confined spaces where a wrench can't swing a full rotation. The system is standardized under SAE J518, which defines two pressure series: Code 61 (standard pressure, 3000 psi and below depending on size) and Code 62 (high pressure, up to 6000 psi depending on size), each with its own bolt pattern and flange head dimensions at a given tube size.
A complete kit pairs two identical clamp halves with a matched set of socket-head cap screws sized and grade-rated for the code and pressure series, since the clamp bolts are a structural part of the pressure-retaining joint, not just a mechanical fastener — substituting a lower-grade bolt reduces the joint's actual working pressure below the flange head's rating. Code 61 and Code 62 clamp halves are not interchangeable even at the same nominal tube size, since the bolt circle and flange head dimensions differ between the two series.
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| Spec | What It Means | Why It Matters |
|---|---|---|
| SAE Code | Code 61 (standard pressure) or Code 62 (high pressure) | Bolt pattern and flange head geometry differ between codes — not interchangeable at the same tube size |
| Tube/Hose Size | 1/2 in. to 5 in. nominal, per SAE J518 table | Must match the mating flange head's tube size exactly |
| Bolt Grade | Typically SAE Grade 8 or equivalent socket-head cap screws | Bolts are part of the pressure-retaining joint — substituting a lower grade reduces rated working pressure |
| Working Pressure Rating | Code-and-size-specific, per SAE J518 table | Actual system pressure must not exceed the rating for the specific code, size and bolt grade combination |
| O-Ring Seal | Size-specific O-ring seated in the flange head face | Must match the flange head O-ring groove — wrong size leaks even with correctly torqued bolts |
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Applications
Where Split Flange Kits Get Used
Split flange kits are specified wherever a hydraulic hose or tube connection needs to be made or serviced without room to rotate a conventional flange nut.
Mobile Hydraulic Equipment
Split flange connections on excavators, loaders, and cranes where confined space limits clearance for a rotating flange nut.
Industrial Hydraulic Power Units
Code 61 and 62 flange connections on fixed hydraulic power unit manifolds and cylinder ports.
Agricultural Machinery
Split flange hose connections on tractor and implement hydraulic circuits serviced in the field.
Marine Hydraulic Systems
High-pressure Code 62 split flange kits on steering and winch hydraulic circuits aboard vessels.
Steel Mill & Heavy Industrial Equipment
Large-bore split flange connections on high-flow hydraulic circuits for presses and rolling equipment.
FAQ
Split Flange Kits Questions, Answered
What's the difference between SAE Code 61 and Code 62 flanges?
Code 61 is the standard-pressure series, generally rated up to around 3,000 psi depending on tube size, while Code 62 is the high-pressure series rated up to around 6,000 psi at the same nominal sizes. The two use different bolt circle dimensions and flange head thickness even at the same tube size, so a Code 61 clamp half will not fit a Code 62 flange head or vice versa.
Can I mix a Code 61 clamp half with a Code 62 flange head?
No — the bolt hole spacing and flange head geometry differ between the two codes, so the clamp halves won't seat and bolt correctly on the wrong code's flange head. Always match the clamp kit's code to the flange head it's mating with, not just the nominal tube size.
Are the bolts in a split flange kit just standard hardware?
No — the clamp bolts are part of the pressure-retaining joint and must meet the grade specified for that flange code and size (commonly SAE Grade 8 or an imperial/metric equivalent). Substituting a lower-grade bolt reduces the joint's actual safe working pressure even if the flange halves themselves are correctly rated.
Do I need to replace the O-ring every time I disassemble a split flange joint?
It's good practice to inspect the O-ring for nicks, flat spots or compression set every time the joint is opened, and replace it if there's any visible damage or if it's been in service a long time, since the O-ring is the actual sealing element — the clamp halves and bolts only provide the clamping force to hold it compressed.
How much clearance do split flanges save over a standard flange nut?
Because the two clamp halves bolt together from the side rather than requiring a wrench to swing a full nut rotation, split flanges can be installed and removed in much tighter clearances — a common reason they're specified on mobile equipment where the flange sits close to a frame member or another component.
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