Investigation of the isolation and frictional properties of hydrophobic products on the rail head, when used to combat low adhesion

• Hydrophobic products as a combatant for low adhesion at the wheel–rail contact were assessed using laboratory tests.
• Twin disc and pendulum testers were used to measure traction/adhesion and isolation effects at different dilutions and compared to dry and wet conditions.
• Products did not cause isolation of the wheel–rail contact although low adhesion was caused by one product at high concentrations.
• Adhesion was increased in low water conditions when a dried filmed of hydrophobic solution applied prior to water application.
• Current tests did not show a convincing case for use of products to combat low adhesion.

Low adhesion affects rail networks around the world. A recent unpublished study by Network Rail has shown a strong correlation between low adhesion incidents and the occurrence of the dew point. It is hypothesised that at or below the dew point water vapour from the air condenses onto the railhead forming a fluid film that leads to a loss of traction within the wheel/rail contact. It has been proposed that this formation of dew on the rail could be prevented by treating rails with commercially available hydrophobic products. In this work laboratory based trials of the hydrophobic products were carried out in order to test their suitability for field use. Traction and impedance properties of the products in a twin disc wheel/rail contact simulation were compared with dry and pure water conditions. Tests were also carried out using a pendulum friction measurement device with the products applied to a railhead.At present there is not a convincing case for applying hydrophobic products to help reduce low adhesion incidents, but pendulum tests with a layer of moisture applied to a dried product film indicated that an increase in friction over moisture on a clean rail may be possible.