ISO 22074-5:2021

Overview

ISO 22074-5:2021 specifies a laboratory test method to determine the electrical resistance (wet conditions) between running rails provided by a rail fastening system fitted to steel or concrete sleepers, bearers, elements of ballastless track, or embedded rail. The procedure assesses rail-to-rail resistance that is relevant to signalling (track circuit) currents, not traction currents. The standard includes a reference procedure (three specimens) and an alternative procedure (repeated single-specimen tests).

Key topics and technical requirements

• Scope: Complete fastening assembly tested as mounted on a typical support (surface-mounted, ballastless or embedded rail).
• Test principle: Measure rail-to-rail resistance while spraying the support and fastenings with controlled water to simulate wet conditions.
• Water quality: Potable water adjusted to a conductivity of (50 ± 5) mS/m, measured per ISO 7888 and corrected to 25 °C; optional polluted conditions may be specified by the requesting authority.
• Spray equipment: A movable spray frame with four nozzles (3.6 mm diameter, 100°–125° cone); flow controlled and measured for each nozzle.
• Spray conditions: Water temperature 10–20 °C, sprayed at (7 ± 1) L/min per nozzle for 2 minutes, with resistance recorded during spraying and for at least 10 minutes after.
• Electrical supply and instruments: Alternating current representative of operational conditions (default 30 ± 3 V RMS, 50 ± 15 Hz when unspecified); instruments with 1% accuracy and logging/printout capability.
• Specimens and repetition: Reference method uses three sleepers/bearers tested individually; alternative method repeats the single specimen test three times with at least 120 h drying between tests.
• Reporting: Test report must reference ISO 22074-5:2021 and include laboratory details, test procedure used, specimen descriptions, water conductivity and temperature, resistance-time plots and the arithmetic mean result.

Applications and users

ISO 22074-5:2021 is used for:

• Railway infrastructure owners and operators validating signalling performance of track components.
• Fastening-system manufacturers for product development, type testing and quality control.
• Independent testing laboratories performing compliance and acceptance tests.
• Signalling and track engineers assessing rail-to-rail electrical continuity to reduce false track-circuit occupancy.

Practical benefits include improved track-circuit reliability, informed procurement specifications, and documented compliance with international test methods.

Related standards

• ISO 22074-1 (Vocabulary for rail fastening systems)
• ISO 7888 (Water quality - Determination of electrical conductivity) - referenced for water conductivity measurement.

Keywords: ISO 22074-5:2021, rail fastening systems, electrical resistance test, track circuits, rail-to-rail resistance, signalling currents, ballastless track, embedded rail, railway infrastructure standard.