Overview
EN ISO 15363:2025 (adoption of ISO 15363:2017) specifies the tube ring hydraulic pressure test for metallic tubes. The method determines the hoop (circumferential) stress required to produce a specified total circumferential strain by hydraulically expanding a short tube ring between platens. It is typically applied to tubes with an outside diameter greater than 120 mm and an outside-diameter-to-thickness ratio (d/a) of not less than 20.
Keywords: EN ISO 15363:2025, tube ring hydraulic pressure test, hoop strength, circumferential strain, metallic tube testing.
Key topics and technical requirements
- Scope and purpose: Measures hoop strength (hoop stress at a specified total circumferential strain) without influences introduced by flattening standard tensile specimens.
- Test piece preparation: Ring machined from tube (edges fine turned/ground), uniquely identified, and free from heat-affected zones or burrs.
- Dimensional measurement:
- Outside diameter from tube circumference (accuracy ±1 mm).
- Wall thickness: mean of eight measurements taken at ~45° intervals (excluding the weld); thickness gauge accuracy > ±0.025 mm.
- Apparatus:
- Hydraulic testing machine permitting free radial expansion (small gap to top platen).
- Parallel platens with fine-turned or ground finish; contact surfaces lubricated (graphited grease or PTFE sheet) to minimize friction.
- Inner die, rubber seal/gasket and bleed line to remove air.
- Measurement and recording:
- Circumferential extension measured with steel tape or roller-chain extensometer wrapped at ring mid‑point (separation between tape parallels 1.5–3 mm); extension measurement accuracy ±0.25 mm.
- Pressure measurement accuracy within ±1 %; devices verified regularly.
- Strain rate shall not exceed 0.2 % per minute.
- Pressure vs. circumferential-extension record used to determine the pressure at the specified total strain.
- Calculation guidance: The standard provides the method to calculate hoop strength from measured pressure, diameter and thickness for rings with d/a ≥ 20 and warns that results become less accurate for d/a
