Overview
ISO 6164:2018 specifies four-screw, one-piece square flange connections for hydraulic fluid power systems rated at 42 MPa (420 bar) for nominal sizes DN 25 to DN 80. The standard defines general and dimensional specifications for flanged heads, flange clamps, ports, mounting surfaces, seal dimensions and grooves. These connections are intended where threaded connectors are to be avoided - for example in hose fittings, tube connectors, manifolds and other hydraulic equipment on industrial and commercial products.
Key Topics and Requirements
- Pressure rating and sizes: Rated for use at 42 MPa; covers flange sizes DN 25–80.
- Materials and mechanical properties: Flange clamps and flanged heads are ferrous with specified minimum yield strength and elongation; screws are typically property class 10.9 (ISO 4017 / ISO 4762 per ISO 898-1).
- Seals and O‑rings: O-rings normally NBR, 90 ±5 IRHD, dimensioned per ISO 3601‑1, tolerance class A and quality grade N (ISO 3601‑3). Seal grooves and seal dimensions are specified.
- Pressure/temperature: Carbon-steel connectors suitable for working pressures (see standard) between −40 °C and +120 °C; stainless-steel connectors −60 °C to +100 °C. Assemblies shall not be assembled below −20 °C. Verification via burst and cyclic endurance tests per ISO 19879.
- Corrosion protection & surface finish: External carbon-steel parts normally coated to pass 72 h salt spray (ISO 9227); weld-on heads protected for 16 h. Cadmium plating is prohibited; hexavalent chromates are discouraged. Machined surfaces and sealing faces have specified roughness limits.
- Tolerances, marking and designation: General tolerances per ISO 2768-m; mandatory marking of manufacturer and nominal size on flanged head and clamp; standardized part designations (e.g., Clamp ISO 6164 - FC×32).
- Selection and assembly guidance: Includes sizing rules, recommended hardened washers, screw lengths and assembly torque guidance (Annex A).
- Hydraulic system designers specifying high-pressure, leak-resistant connections
- OEMs producing hydraulic manifolds, hose fittings and tube connectors for industrial and mobile equipment
- Manufacturers and suppliers of flange clamps, flanged heads and compatible O‑rings
- Test labs and quality engineers performing burst/cyclic testing and corrosion screening
- Procurement and maintenance teams seeking standardized, interchangeable flange components
Related Standards
Relevant normative references include:
Keywords: ISO 6164:2018, hydraulic fluid power, four-screw flange, square flange connections, 42 MPa, DN 25–80, O-rings, flange clamp, flanged head, corrosion protection, pressure-temperature requirements.
