Overview
ISO 16031-1:2002 - "Aerospace fluid systems - O-rings, inch series: Inside diameters and cross sections, tolerances and size-identification codes - Part 1: Close tolerances for hydraulic systems" defines inch-series O-ring dimensions and close tolerances for aerospace hydraulic applications. The standard specifies inside diameters, cross-sections, tolerances and size-identification codes for toroidal (O‑ring) seals, and is intended for use with nitrile (NBR) and ethylene propylene (EPDM) materials in high‑pressure hydraulic fluid systems when suitable tooling is available.
Key topics and technical requirements
- Dimensional specifications: Lists standardized inside diameters and cross-section sizes for inch-series O-rings.
- Close tolerances: Establishes high‑precision tolerances appropriate for hydraulic systems where leakage risk and pressure demands require tighter control.
- Size-identification codes: Provides a dash-number coding system (e.g., -001 to -475 and a 900 series) that maps each code to a specific inside diameter and cross-section. Example: -025 corresponds to a 0.070 in (1.78 mm) cross-section and an internal diameter range of 1.170–1.182 in.
- Configuration: Confirms the toroidal shape (commonly called an O‑ring) is the specified geometry.
- 900 series: Includes standardized O-rings for sealing straight thread tube fitting bosses; dash numbers in this series often indicate tube size in sixteenths of an inch.
- Normative references and terms: Uses ISO 5598 (Fluid power systems and components - Vocabulary) for terminology.
- Material suitability: Recommended for nitrile and ethylene propylene elastomers intended for high‑pressure hydraulic service, subject to tooling and manufacturing capability.
- Notes on IP and tooling: The standard highlights the need to consider possible patent rights and suitable tooling to achieve specified tolerances.
Applications
- Designing and specifying O-rings for aerospace hydraulic systems (actuators, valves, pumps, landing gear, flight controls).
- Sourcing and procurement of inch-series O-rings with traceable size codes.
- Manufacturing and tooling setup for precision O-ring production.
- Quality control, inspection, and component verification in aerospace maintenance and overhaul operations.
- Sealing straight-thread tube fittings using the 900-series O-ring dimensions.
Who uses this standard
- Aerospace design and systems engineers
- Hydraulic system designers and integrators
- O-ring manufacturers and molding/tooling suppliers
- Quality assurance and inspection teams in aerospace supply chains
- Procurement specialists specifying replacement seals
Related standards
Keywords: ISO 16031-1, aerospace O-rings, inch series O-rings, O-ring tolerances, hydraulic systems, nitrile O-rings, ethylene propylene O-rings, size identification codes, O-ring dimensions.
Open preview (PDF)Aerospace fluid systems — O-rings, inch series: Inside diameters and cross sections, tolerances and size-identification codes — Part 1: Close tolerances for hydraulic systems
