EN 15427-2-3: Friction Management – Wheel-Rail Contact – Part 2-3: Top-of-Rail Materials

What is EN 15427-2-3?

EN 15427-2-3 is a European Standard titled “Railway applications – Wheel/rail friction management – Part 2-3: Equipment and Application – Friction Modifiers.” This standard is the “chemical” counterpart to Part 2-1 (Equipment). It focuses on the substances applied to the running surface (top) of the rail head.

In Infrastructure Management, the goal of Top-of-Rail (TOR) management is distinct from flange lubrication. While flange lubrication aims for the lowest possible friction, TOR materials aim for Friction Management—stabilizing the friction coefficient to prevent “stick-slip” oscillations which cause squeal and corrugation.

Functional Requirements: The “Intermediate” Friction

The most critical requirement of EN 15427-2-3 is that the material must be a Friction Modifier, not a lubricant. It must provide a “Thin Film” technology that satisfies two conflicting needs:

• Noise and Wear Reduction: It must reduce lateral creep forces to eliminate high-pitched wheel squeal in tight curves and mitigate Rolling Contact Fatigue (RCF).
• Traction and Braking: Crucially, it must maintain a friction coefficient (typically between 0.3 and 0.4) that allows the train to safely accelerate and perform a full Brake Application.
• Non-Insulating Properties: The material must not interfere with electrical Signalling systems or track circuits; it must remain conductive enough to ensure the train is “detected” by the infrastructure.

Technical Delivery Conditions and Composition

The standard sets out the Technical Delivery Conditions for the manufacturers of these materials (water-based, oil-based, or solid sticks):

• Drying Time: For liquid modifiers, the standard defines the maximum time the material can take to “set” on the rail before it becomes effective.
• Temperature Stability: The material must not become too viscous in winter or break down under the high localized heat (flash temperatures) generated by wheel contact.
• Environmental Safety: Like its flange-lubricant counterpart (Part 1-2), it must be non-toxic and biodegradable, as it is eventually ground into dust or washed into the soil.

Testing and Acceptance Criteria

EN 15427-2-3 requires rigorous verification through:

• Twin-Disc Testing: Laboratory simulation of the Wheel-Rail Interface to measure the friction coefficient under varying slip conditions.
• Adhesion Verification: Confirming that a train can still stop within its safety distance even when the rail is heavily treated with the modifier.
• Migration Testing: Checking how far the material travels down the track from the application point (persistence).

Comparison: Flange Grease vs. TOR Friction Modifiers