ISO 16031-2:2003

Overview

ISO 16031-2:2003 - Aerospace fluid systems - O-rings, inch series: Inside diameters and cross-sections, tolerances and size-identification codes - Part 2 - defines standard inside diameters, cross-sections, tolerances and size-identification codes for inch-series O-rings intended for non-hydraulic aerospace fluid systems. The standard applies to O-rings made from elastomeric materials other than nitrile and ethylene propylene (EP), and it adopts the toroidal (O-ring) configuration. Tables in the document list the standardized inside diameters, cross-sections and associated dash size codes (e.g., -001 to -475 and a 900 series for tube-fitting bosses).

Key topics and technical requirements

• Scope: Inch-series O-rings for non-hydraulic aerospace fluid systems; applies when suitable tooling is available.
• Dimensions and tolerances: Standardized combinations of inside diameter and cross-section are specified in tabular form; tolerances are provided for each size.
• Size-identification codes: Dash numbers map to specific inside diameter / cross-section pairs; groups of 100 dash numbers indicate the cross-section family. A separate 900-series addresses O-rings for sealing straight thread tube-fitting bosses.
• Configuration: O-rings are defined as toroidal sealing rings (note: ISO uses the term “O-ring”).
• Normative references and terminology: Uses ISO 5598 vocabulary; prepared by ISO/TC 20 SC 10 (Aerospace fluid systems and components).

Practical applications and users

ISO 16031-2:2003 is used to ensure interchangeability, quality and reliable sealing performance in aerospace systems that are not hydraulic (for example pneumatic circuits, fuel venting seals, environmental seals and low-pressure fluid lines). Typical users include:

• Aerospace design and systems engineers selecting seal sizes for non-hydraulic components.
• O-ring manufacturers and mold/tooling designers producing inch-series elastomeric seals.
• Procurement teams and suppliers specifying dash-code parts for inventory and replacement.
• Quality, inspection and maintenance personnel verifying dimensional conformity during acceptance testing and repair.

Using the standardized inside diameters, cross-sections, and tolerances streamlines sourcing, reduces mismatch risk and simplifies maintenance logistics for aerospace operators and OEMs.

Related standards

• ISO 16031-1 - Part 1: Close tolerances for hydraulic systems; covers nitrile and EP materials and small diameters (≤ 12.7 mm) referenced in Part 2.
• ISO 5598 - Fluid power systems and components - Vocabulary (terminology used in ISO 16031-2).

Keywords: ISO 16031-2:2003, O-rings, aerospace fluid systems, non-hydraulic systems, inch series, inside diameters, cross-sections, tolerances, size-identification codes.