Short answer
In a hydraulic four-bolt flange, the hose flange head, clamp parts, O-ring, port face and bolts work together. Merely seeing the flange head diameter or four holes does not mean that the correct series and assembly have been identified.
Technical explanation
ISO 6162-1 covers the port, face and connection elements of flange connections with split or one-piece clamps. Metric and inch bolt options are separate definitions within the scope of the standard. A wrong combination of bolt, seal or clamp can affect the seating of the flange head. Nominal connection size, hose inside diameter and assembly pressure are separate areas. The manufacturer's assembly method for the relevant size and material must be used.
Topic-specific checkpoints
| Item | Description |
|---|---|
| Flange head | Series, diameter and thickness |
| Clamp | Correct one-piece/split part |
| Bolt | Metric/inch and suitable grade and length |
| Sealing | O-ring and port face |
How is it assessed in practice?
On the sample form, record the hole centers, bolt size and port face in addition to the flange head diameter and thickness. Do not mix up clamp halves based on appearance. Instead of selecting the bolt length by looking only at the overall length of the existing part, verify the port thread depth and the assembly design. Add damage in the seal groove and face cleanliness to the acceptance plan. Use the instructions of the manufacturer concerned for the tightening sequence and torque; do not assign a universal value.
Original editorial recommendation; not a clause of a standard.
Frequently asked questions
Do identical-looking four-hole flanges fit each other?
No. Series, hole pattern, flange head geometry, bolts and seal must be verified together.
Source coverage
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S017
Parker Safety Guide, Publication 4400-B.1 Parker Hannifin · accessed 2026-10-20 PDF page 2; 2.8 Routing, 2.10 Mechanical Loads and 2.11 Physical DamagePDF page 3; 3.1 Component Inspection, 3.2 Hose and Fitting Assembly and 3.3 Related Accessories | PDF page 2; 2.7 Size | PDF page 2; 2.13 LengthPDF page 3; 3.1 Component Inspection, 3.2 Hose and Fitting Assembly and 3.3 Related Accessories | PDF page 2; 2.5 Fluid Compatibility | PDF page 2; 2.13 Length
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S095
ISO 6162-1:2012 ISO · accessed 2026-10-19 Public abstract: four-bolt flange connections, metric/inch fasteners; no pressure or torque tables imported