ISO 3601-2:2016

Overview

ISO 3601-2:2016 - "Fluid power systems - O-rings - Part 2: Housing dimensions for general applications" specifies recommended housing (gland/groove) dimensions for ISO 3601 O-rings used in general hydraulic and pneumatic systems. It covers Class A O-ring housings for general industrial use and selected Class B housings for metric hardware (e.g., cylinder bores and piston rods). The standard addresses housings for dynamic, static and axial (face) sealing, with provisions for use with and without anti‑extrusion (back‑up) rings.

Key technical topics and requirements

• Housing (gland) geometry - nominal widths, depths and clearances for piston, rod and face seals; drawings and tables define typical cross‑sections and dimensions.
• O-ring size codes and tolerances - uses O-ring diameters, cross‑sections, size codes (SC) and tolerances referenced from ISO 3601‑1.
• Compression and stretch calculations - formulae and guidance for percent inside‑diameter stretch (S), percent cross‑section reduction (R) and effective compression (C) to ensure reliable sealing across hydraulic/pneumatic and static/dynamic use.
• Surface finish and run‑out - surface roughness requirements (see Table 1), material ratio Rmr guidance (50–80 % at specified cut depths) and run‑out tolerances for mating bores.
• Lead‑in chamfer and corner radii - chamfer angle (15°–20°) to protect O-rings during assembly, plus edge rounding and permissible corner radii.
• Anti‑extrusion (back‑up) ring accommodation - groove widths and options for zero, one or two back‑up rings; references to ISO 3601‑4 for back‑up ring selection.
• Illustrative figures and annexes - detailed figures for housings and informative Annex A (aerospace correlation) and Annex B (custom housing sizing).

Practical applications and users

ISO 3601-2:2016 is applied where reliable sealing is critical in fluid power systems:

• Design engineers and OEMs developing hydraulic/pneumatic cylinders, pistons, rods, valves and fittings
• Seal and elastomer manufacturers specifying O‑ring and gland geometry
• Maintenance, quality and procurement teams selecting replacement seals and verifying groove dimensions
• System integrators and testing labs ensuring compatibility with ISO 3601‑1 size codes

Practical benefits include reduced leakage risk, predictable seal life, easier interchangeability of O‑rings, and clear guidance when using back‑up rings or designing custom housings.

Related standards

• ISO 3601‑1:2012 - O‑ring diameters, cross‑sections, tolerances and codes
• ISO 3601‑4 - Anti‑extrusion (back‑up) rings
• ISO 3601‑3, ISO 3601‑5 - quality criteria and material specifications
• ISO 5598, ISO 8015 - vocabulary and tolerancing principles

Keywords: ISO 3601-2:2016, O-ring housing dimensions, gland dimensions, fluid power systems, hydraulic seals, pneumatic seals, back-up rings, O-ring groove dimensions, surface roughness.