ISO 4075:2025

Overview

ISO 4075:2025 - Polysulfone (PSU) - Effect of time and temperature on expected strength specifies minimum expected-strength reference lines for polysulfone (PSU) homopolymer used in injection‑moulded fittings. The standard defines how hoop stress, time and temperature interact to predict long‑term hydrostatic strength for design calculations and conformity assessment of PSU components used in piping systems.

Key points:

• Applies to PSU homopolymer compounds for injection‑moulded fittings.
• Reference lines are given as a mathematical model (time, temperature, stress) valid between 10 °C and 110 °C.
• Includes tabulated hoop‑strength values, extrapolation limits and procedures to demonstrate conformance.

Key Topics and Requirements

• Reference equation (log t form): the standard provides the formula linking time (hours), temperature (Kelvin) and hoop stress (MPa) and lists PSU coefficients (A, B, C, D) to generate the reference lines.
• Temperature range: reference lines valid 10 °C–110 °C.
• Extrapolation limits: minimum allowable extrapolation times derived from experiments at 110 °C and an Arrhenius approach (activation energy default 110 kJ/mol). Tableed limits range from 100 years (≤ 60 °C) down to experimentally determined values at 110 °C.
• Expected strength tables: example hoop‑strength values for combinations of temperature and time (no design or safety factors included).
• Conformance: Annex A describes test and statistical procedures (testing per ISO 1167‑1/2 and ISO 9080) to show material results meet or exceed the reference lines (97.5 % of results on/above line or LPL comparison).
• Design guidance: Annex B outlines derivation of S (calculated pipe) values, minimum wall thicknesses and design stress for application classes (links to ISO 10508, ISO 13760). Design pressures (4–10 bar) and S-value formulae are referenced.

Applications and Users

Who benefits:

• Manufacturers of PSU injection‑moulded fittings using PSU homopolymers for hot/cold water systems.
• Design engineers performing structural and pressure calculations for piping components.
• Testing laboratories conducting long‑term hydrostatic strength tests and conformity assessments.
• Specifiers and regulators writing product standards, approvals and installation requirements.

Practical uses:

• Predicting long‑term hoop strength for service life and temperature profiles.
• Deriving minimum wall thicknesses and S‑values for pressure‑rating components.
• Harmonizing design calculations across suppliers using a common reference for PSU strength over time.

Related Standards

• ISO 9080 (long‑term hydrostatic strength extrapolation)
• ISO 1167‑1 / ISO 1167‑2 (internal pressure testing)
• ISO 10508, ISO 13760 (service classes and Miner's rule)
• Relevant piping series: ISO 15874 / 15875 / 15876 / 15877 and ISO 21003 for context in hot/cold water systems

Keywords: ISO 4075:2025, polysulfone, PSU, expected strength, reference lines, injection moulded fittings, long‑term hydrostatic strength, extrapolation limits, ISO 9080.