ISO 9631:2018

Overview

ISO 9631:2018 - Rubber seals - Joint rings for pipelines for hot‑water supply up to 110 °C - Specification for the material - defines material requirements for vulcanized rubber joint rings used in hot drinking and non‑drinking water systems up to 110 °C. The standard covers elastomeric material properties, classification by hardness and application class, general requirements for finished seals, testing methods and quality assurance. It is intended to be used together with product standards that set joint performance criteria.

Key Topics

• Scope and applicability: Applies to elastomeric components of seals for pipelines made of metals, concrete, plastics, glass‑reinforced plastics, etc. Cellular rubber joint rings are excluded.
• Classification:
  • Hardness classes (nominal IRHD): 50, 60, 70, 80, 90 (specified hardness ranges).
  • Service classes: T1, T2, T3 - increasing severity for hot‑water and district‑heating applications.
  • Seal types: Type A (EPM, EPDM, NBR, SBR or equivalents) and Type B (IIR, CIIR, BIIR butyl rubbers).
  • Drinking‑water designation adds the letter D.
• Material requirements and tests (examples): tensile strength, elongation at break, hardness tolerance, compression set (air and in hot water), accelerated ageing, stress relaxation, volume change in water, ozone resistance, tear strength. Test methods reference ISO standards (e.g., ISO 37, ISO 48, ISO 815‑1, ISO 188).
• Design life: Material requirements target long‑term performance with a potential design lifetime of 50 years, noting actual life also depends on joint design, assembly quality and operating conditions.
• Composite seals: For components with hardness 76–95 IRHD, some tests (elongation, compression set, stress relaxation) apply only if that component contributes to sealing or long‑term stability.

Applications

Who uses ISO 9631:2018 and why:

• Seal and gasket manufacturers - to specify compound formulations and verify testable properties for hot‑water joints.
• Piping system designers and OEMs - to select compatible joint rings for potable and non‑potable hot‑water pipelines.
• Water utilities, plumbing specifiers and contractors - to ensure compliance with long‑term sealing performance for hot‑water distribution and district heating secondary systems.
• Testing and certification labs - to apply standardized test methods and quality assurance procedures.

Practical benefits: ensures material compatibility with water quality, predictable aging behavior at elevated temperatures, and standardization across pipeline materials and installation contexts.

Related Standards (if applicable)

Relevant references cited by ISO 9631:2018 include:

• ISO 37 (tensile testing), ISO 48 (hardness), ISO 815‑1 (compression set), ISO 188 (accelerated ageing), ISO 1817 (effect of liquids), ISO 1431‑1 (ozone resistance), ISO 3384‑1 (stress relaxation), ISO 10508 (hot/cold water piping guidance).

Keywords: ISO 9631:2018, rubber seals, joint rings, hot‑water supply, elastomeric seals, pipeline seals, compression set, hardness IRHD, tensile strength, water quality compliance.