ISO 22074-7:2021

Overview

ISO 22074-7:2021 specifies a laboratory test method for clamping force and uplift stiffness of complete rail fastening assemblies used in railway infrastructure. The standard defines how to measure the vertical force required to separate the rail foot from its immediate support (the clamping force) and, when required, how to determine the uplift stiffness of the fastening system. It applies to fastening assemblies with or without baseplates on all types of sleepers, bearers or ballastless track elements, but is not applicable to embedded-rail systems or fastening systems that do not act on the rail foot.

Key Topics and Requirements

• Test scope: Applies to a complete fastening assembly; does not assess the security of components fixed into the sleeper.
• Test principle: Measure the vertical load necessary to separate the rail from its support and record load–displacement behaviour.
• Two test methods: A reference method (loading the rail) and an alternative method (loading the sleeper/loading frame), each with specified setup arrangements.
• Instrumentation:
  • Displacement transducers with accuracy ±0.1 mm (typically four around the rail seat).
  • Force-measuring system conforming to ISO 7500-1:2018, Class 1.
  • Recording equipment capable of plotting load–displacement diagrams.
• Loading rate: Approximately 10 kN/min (±1 kN/min) for controlled loading sequences.
• Procedures for assemblies:
  • With rail pad: load until pad just moves, remove pad, then perform controlled loading/unloading cycles and derive clamping force P0 from the load–displacement diagram at displacement d = 0.
  • Without rail pad: insert 4 steel shims (25 × 25 × 0.25 mm) to establish initial gap and identify the clamping load by shim movement.
• Uplift stiffness: Calculated as secant stiffness between load limits 0.9Pc and 1.1Pc (where Pc is the reference clamping load). Record limiting uplift force/displacement where applicable.
• Repeatability: Measurements are repeated (typically three cycles) and mean values reported.

Applications and Who Uses This Standard

• Practical for railway infrastructure engineers, track designers, test laboratories, product manufacturers, and procurement teams.
• Used to validate design and performance of rail fastening systems, to compare products, ensure compliance with technical specifications, and support quality control during development and certification.
• Valuable in research, component selection for switches & crossings, and when evaluating assemblies for different sleeper types or ballastless solutions.

Related Standards

• ISO 22074-1 - Vocabulary for rail fastening systems (terms and definitions).
• ISO 7500-1:2018 - Calibration and verification of static uniaxial testing machines (force-measuring).
• Other parts of the ISO 22074 series (e.g., ISO 22074-4 referenced for repeated load testing) provide complementary test methods and requirements.

Keywords: ISO 22074-7:2021, rail fastening systems, clamping force, uplift stiffness, test method, railway infrastructure, load-displacement diagram, baseplates, sleepers.