ISO 5735-1:2024

Overview - ISO 5735-1:2024 (Ultrasonic testing on rails in track)

ISO 5735-1:2024 specifies requirements for continuous ultrasonic testing (UT) of rails in track to produce comparable results for the location, type and size of internal discontinuities. The standard applies to flat-bottom (Vignole) rail profiles of 43 kg/m and above, using UT systems fitted to dedicated test vehicles or manually propelled devices. It covers testing principles, reference reflector design and evaluation principles, but does not provide guidance on managing inspection results, vehicle acceptance or UT in production plants.

Key topics and technical requirements

• Scope limits: Continuous in-track testing only; welded joints treated as plain rail; excludes production-plant UT and result management.
• Frequency range: UT systems use sound in the 2 MHz to 5 MHz range.
• Reference reflectors: Definition and construction of reference reflectors (FBH - flat-bottomed holes, SDH - side-drilled holes, EDM notches or water-jet cuts) with tight manufacturing tolerances (accuracy ±0.1 mm, angle ±0.1°).
• Reference rails and installation: Reference rails must be new or prepared running surfaces; reflectors recorded at normal operational speeds and plugged with synthetic compound to prevent contamination.
• Signal evaluation:
  • A-scan: minimum signal-to-noise ratio ≥ 3 for detection.
  • B-scan: should avoid spurious or multiple-echo artefacts.
  • Systems use gate threshold levels and gain control to define detection criteria and relate the number of responses to reflector size.
• Performance factors: Beam width, transducer size, frequency, sampling frequency, required number of responses and rail geometry determine maximum testing speed and non-tested zones.
• Verification and maintenance: Infrastructure managers must verify UT devices to specified intervals and may need risk assessments for reference rails that carry traffic.

Applications - who uses ISO 5735-1:2024

• Railway infrastructure managers specifying and validating continuous ultrasonic testing regimes.
• Maintenance contractors and providers of UT test vehicles or manually propelled inspection trolleys.
• NDT equipment manufacturers designing probes, probes angles and data acquisition systems for rail inspection.
• Safety and asset-management teams using standardized detection capabilities to plan repairs and interventions. Practical uses include routine rail integrity monitoring, validation of UT vehicle performance, and establishing comparable detection thresholds across networks.

Related standards

• ISO 5577:2017 (Ultrasonic testing - Vocabulary) - normative reference cited in ISO 5735-1.
• Other parts of the ISO 5735 series (see ISO website for the full list) cover complementary aspects of non-destructive testing on rails.

Keywords: ISO 5735-1:2024, ultrasonic testing, non-destructive testing, rails, continuous testing, reference reflectors, rail inspection, railway infrastructure.