Overview - ISO 24033:2009 (PE-RT pipes)
ISO 24033:2009 specifies how to determine the expected long‑term strength of pipes made from polyethylene of raised temperature resistance (PE‑RT) types I and II as a function of time and temperature. The standard provides reference lines - mathematical relationships between time, temperature (K) and hoop stress (MPa) - and tabulated values for use in strength and lifetime calculations for PE‑RT piping materials. Type II PE‑RT (extended in this edition) is noted for higher hoop‑stress performance at elevated temperatures (up to 110 °C).
Key topics and technical requirements
- Reference lines and equations: Logarithmic equations relate time to fracture (hours) with temperature and hoop stress. These reference lines are used for interpolation and controlled extrapolation.
- Material coverage: PE‑RT type I (reference lines valid 20 °C–95 °C) and type II (20 °C–110 °C).
- Tabulated expected strengths: Table 2 provides hoop stress (MPa) values for specific times and temperatures (no design safety factors included).
- Extrapolation limits: Based on an Arrhenius model with an activation energy of 110 kJ/mol, the standard gives extrapolation factors (K) from 110 °C to lower temperatures (e.g., K = 100 acceptable up to 50 °C).
- Conformity testing: Annex A requires testing per ISO 1167‑1 and ISO 1167‑2 at specified temperatures and time intervals, with at least three failure times in each interval and at least 97.5% of results on or above the reference line. For type II, tests must show no brittle‑failure knee up to 110 °C within 8 760 h.
- Normative references: ISO 1167‑1/‑2 (pressure‑failure tests), ISO 9080 (long‑term hydrostatic strength extrapolation), ISO 1043‑1 (polymer terminology).
Practical applications and users
Who uses ISO 24033:2009:
- Pipe and material manufacturers validating long‑term hydrostatic performance of PE‑RT compounds
- Product qualification and certification bodies demonstrating conformity to reference lines
- Design engineers and specifiers calculating allowable hoop stress and service life for hot‑water and raised‑temperature piping systems
- Test laboratories performing long‑term pressure/creep‑rupture testing
Typical applications:
- Hot and cold water distribution and heating systems where raised temperature resistance is required
- Material selection and lifetime prediction during product development and quality control
Related standards
Keywords: ISO 24033:2009, PE‑RT, polyethylene of raised temperature resistance, reference lines, expected strength, hoop stress, long‑term hydrostatic strength, ISO 1167.
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