ISO 2505:2023

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.