Overview
ISO 9080:2012 specifies a statistical method to predict the long-term hydrostatic strength of thermoplastics in pipe form by extrapolation. Developed from pipe stress-rupture test data, the Standard Extrapolation Method (SEM) uses multiple linear regression on log(stress) vs log(time) data to determine a material-specific, conservative design value - the 97.5% lower prediction limit (LPL) - for hoop (circumferential) stress at specified times and temperatures (commonly referenced to 50 years at 20 °C). ISO 9080 is applicable to all thermoplastic pipe types and complements product and testing standards such as ISO 1167 and ISO 12162.
Key topics and technical requirements
- Scope and applicability: Applies only to materials tested in pipe form and is based on stress‑rupture (internal pressure) testing in accordance with ISO 1167‑1/2.
- Standard Extrapolation Method (SEM): Uses statistical extrapolation and multiple linear regression of log(stress) vs log(time) to predict long‑term strength.
- Lower prediction limit (LPL): The method produces the 97.5% LPL (not the mean), used for conservative material classification and design.
- Models supported: SEM accommodates 2‑, 3‑ and 4‑parameter extrapolation models; additional parameters increase fit but can raise prediction uncertainty.
- Knee detection: Procedure for identifying a transition (“knee”) between two failure modes (data type A / B) is included (Annex B).
- Extrapolation controls: Limits on extrapolation time, distribution of pressure levels and test times, and requirements for test-piece uniformity (same batch, dimensions) are specified.
- Documentation and software: Test-report requirements and validated software tools for SEM analysis are described (Annexes A–E).
Practical applications and users
- Material manufacturers use ISO 9080 to classify thermoplastic materials (e.g., determine MRS) and support product data sheets.
- Pipe designers and engineers derive conservative design stresses (CRSθ) for pressure piping systems at different temperatures and design times.
- Testing laboratories apply ISO 9080 together with ISO 1167 to generate stress‑rupture data and perform SEM analysis.
- Standards bodies and certification agencies adopt SEM results for product standards, approvals and regulatory compliance.
- Asset owners and specifiers use the predictions to validate expected long‑term performance and lifetime design inputs.
Related standards
ISO 9080:2012 is essential when you need statistically robust, conservative predictions of long‑term hydrostatic strength for thermoplastic pipes and for generating design values used across the plastics piping industry.
Open preview (PDF)Plastics piping and ducting systems — Determination of the long-term hydrostatic strength of thermoplastics materials in pipe form by extrapolation