Overview
ISO 13480:1997 - "Polyethylene pipes - Resistance to slow crack growth - Cone test method" - specifies a laboratory test to quantify the resistance of polyethylene (PE) pipe to slow crack growth (SCG). The method measures the rate of crack propagation from a single notch in a notched pipe ring held at a constant hoop strain while immersed in a surface-active solution at elevated temperature. The standard was prepared by ISO/TC 138 (Plastics pipes) and applies to pipe wall thicknesses up to and including 5 mm.
Key topics and technical requirements
- Test principle: Notched pipe rings are expanded by a conical mandrel (cone) to impose a constant hoop strain, notched, then immersed vertically in a surfactant solution at 80 °C ± 1 °C. Crack growth is measured over time.
- Surface-active solution: Uses an ethoxylated nonylphenol detergent (nonyl-phenoxy(ethyleneoxy)ethanol) with n = 11, prepared at an equivalent concentration of 5% by weight in deionized water. Solution life at 80 °C is limited to 100 days.
- Specimen and tooling:
- Rings cut to specified length (different lengths for OD ≤ 40 mm and > 40 mm).
- Mandrel (cone) with specified dimensions and groove (e.g., groove ~20 mm × 1 mm by 2 mm deep); mandrel materials must not affect the solution.
- Notch created with a commercial razor blade (blade changed after ≤ 20 notches); recommended blade penetration/cutting speed around 10 mm/min.
- Mandrel insertion rate example 100 mm/min ± 50 mm/min.
- Measurements and acceptance:
- Measure outer diameter before and after cone insertion to calculate percent hoop strain.
- Measure notch length from the pipe end every 24 hours to ±0.5 mm precision.
- Calculate crack growth rate (v, mm/24 h) from the slope of crack length vs. time (linear regression); unless otherwise specified, the highest measured rate of the three specimens is reported.
- If no crack growth in three specimens after one week, the pipe is deemed resistant to SCG.
- Recommended limit (informative): Annex A suggests a maximum allowable crack growth rate of 10 mm/day for the specified detergent type.
Applications and users
ISO 13480:1997 is used by:
- Pipe manufacturers for material qualification and product development.
- Independent test laboratories and quality control teams for batch verification and performance testing.
- R&D and materials engineers evaluating additives, resin grades, and processing effects on SCG resistance.
- Specifiers and purchasers assessing long-term durability of PE pipes for conveyance of fluids.
Practical benefits include standardized comparison of SCG resistance, supporting material selection and lifetime assessments for plastic piping systems.
Related standards
- ISO 13479:1997 - Notch test method for slow crack growth (applicable for wall thickness > 5 mm).
- ISO 3126:1974 - Measurement of pipe dimensions.
Keywords: ISO 13480:1997, polyethylene pipes, slow crack growth, cone test method, crack propagation, surface-active solution, nonylphenol ethoxylate, notched pipe ring, hoop strain.