Overview
EN ISO 9967:2016 (Thermoplastics pipes - Determination of creep ratio) is a CEN-endorsed adoption of ISO 9967:2016 that defines a standardized laboratory method to determine the creep ratio of thermoplastics pipes with a circular cross-section. The method records pipe deflection under a constant compressive load for 1 008 hours (42 days), analyses deflection vs. time, and extrapolates a two‑year deflection to calculate the creep ratio relative to the initial (6 min / 0.1 h) deflection.
Key topics and technical requirements
- Scope: Applies to thermoplastic pipes with a circular cross-section for long‑term static calculations and design considerations.
- Test principle: Place a cut length of pipe between two flat horizontal plates, apply and maintain a constant compressive force, record deflection at specified intervals, analyse linearity and extrapolate a two‑year deflection.
- Duration and measurements:
- Test duration: 1 008 h (42 days).
- Reference early measurement: 6 min (0.1 h) deflection.
- Creep ratio = (extrapolated two‑year deflection) / (measured 6 min deflection).
- Apparatus requirements:
- Compressive loading machine capable of maintaining preload and test load to ±1 %.
- Flat, rigid plates sized to cover the test piece contact area.
- Dimensional measuring devices with specified accuracies (length ±1 mm; inside diameter ±0.1 mm or ±0.2 % of dᵢ).
- Timing device accurate for the initial 6 minutes and thereafter.
- Test pieces:
- Three test pieces (A, B, C) cut from a marked pipe.
- Length rules (e.g., (300 ± 10) mm for pipes with nominal diameter ≤ 1 500 mm) and specific provisions for structured‑wall pipes (ribs, corrugations, helical structures).
- Inside diameter measurement in accordance with ISO 3126 (normative reference).
- Data analysis: Linear regression of deflection vs. log(time), correlation assessment and extrapolation to two years; reporting requirements specified.
Applications and users
- Useful for pipe manufacturers, testing laboratories, product designers, specifiers, and standards/certification bodies concerned with long‑term deformation (creep) of thermoplastic piping.
- Applied in product development, quality control, compliance testing, and long‑term structural calculations for buried or otherwise loaded pipe systems.
- Engineers use creep‑ratio data to predict field deflection over installation lifetimes and to inform soil‑pipe interaction designs.
Related standards
- ISO 3126 - Plastics piping systems: referenced for dimensional measurement methods.
- EN ISO 9967:2016 supersedes EN ISO 9967:2007.
- Prepared by ISO/TC 138 and CEN/TC 155 (plastics piping committees).
Keywords: EN ISO 9967:2016, ISO 9967:2016, creep ratio, thermoplastics pipes, thermoplastic pipe testing, creep testing, pipe deflection, plastics piping standards.
