Overview
ISO 2505:2023 - Thermoplastics pipes - Longitudinal reversion - Test method and parameters describes a standardized test for measuring the longitudinal reversion (length change) of thermoplastic pipes when exposed to heat. The method can be performed in a heated liquid bath or an air oven (heated liquid is the reference in disputes) and applies to smooth-walled thermoplastic pipes of constant cross‑section with wall thickness ≤ 16 mm. Annex A gives material-specific parameters and recommended maximum reversion limits.
Keywords: ISO 2505:2023, longitudinal reversion, thermoplastics pipes, test method, heated liquid, air oven, reversion parameters.
Key topics and requirements
- Scope and applicability
- Applies to smooth internal/external walls and constant cross‑section pipes; excludes non‑smooth structured‑wall systems.
- Wall thickness limit: ≤ 16 mm.
- Principle
- Measure a marked length before and after heat exposure; reversion expressed as percentage: R = (ΔL / L0) × 100.
- Apparatus
- Heated liquid bath (thermostatically controlled) or air oven with specified temperature control.
- Suggested liquids: glycerine, glycol, mineral oil (aromatic-free), or calcium chloride solution.
- Measurement tools: calliper (uncertainty ±0.1 mm), thermometer (±0.5 °C), scriber for marks.
- Preparation and conditioning
- Test pieces: nominal 200 ± 20 mm length, three specimens per sample (large pipes may be segmented).
- Conditioning at (23 ± 2) °C for times based on wall thickness (e.g., 1 h for e ≤ 3 mm up to 6 h for e > 8 mm).
- Small-diameter coiled pipes must be straightened before testing.
- Test parameters
- Temperature and exposure time vary by material (see Table 1 in the standard); e.g., PVC and some polymers use 150 °C, PE classes use 100–110 °C, PP variants differ.
- Acceptance criteria (Annex A)
- Recommended maximum reversion limits (examples): PVC-U ≤ 5%, PE (all classes) ≤ 3%, PP / PB ≤ 2%, ABS/ASA ≤ 5%. Stricter limits may be adopted where required.
Applications and users
- Who uses it
- Pipe manufacturers for quality control and product development.
- Independent test laboratories for compliance and certification.
- Designers, specifiers and procurement teams setting acceptance criteria.
- Contractors and asset owners for material selection and fitness-for-service assessments.
- Practical uses
- Validate thermal stability and dimensional performance of thermoplastic pipes.
- Support warranty, performance claims and dispute resolution (heated liquid as reference).
- Inform material selection when heat-induced dimensional change is critical (e.g., buried services, hot-water systems).
Related standards
- ISO 1043-1 (Plastics - Symbols and abbreviated terms - Part 1) is normative in ISO 2505:2023 and useful for polymer identification and abbreviations.
- Users should consider complementary ISO/CEN piping standards for full system performance and installation requirements.