Which lubricants are used for railway tracks? This article provides a concise introduction to the various lubricants used in the industry, including curve rail lubricants, fishplate lubricants, switch plate and switch blade lubricants, and Top of Rail (TOR) Friction Control Materials.

By Frans Pienaar, Technical Sales Manager

When I started in the lubricant business in 1997, my boss handed me a technical manual with over 1,000 pages of finely printed text, illustrations, and diagrams. “After I have read this book, will I know everything about lubricants?” I asked. “When you have read this book, you will know one-eighth of everything there is to know about lubricants.” he replied.

Almost 30 years later, I still don’t know everything. But, like me in 1997, we all must start somewhere. This article is an introduction for those new to the industry or anyone seeking a high-level overview. It is just the beginning—your journey into the fascinating world of rail lubricants starts here!

The importance of lubricants for higher rail safety and lower costs

There are four primary lubricant categories for rail tracks: Curve rail lubricants, fishplate lubricants, switch plate & switch blade lubricants, and Top of Rail Friction Control Materials. In every instance, lubrication is essential to ensure longevity, high performance, noise reduction, and lower maintenance costs.

The benefits can be summarised as follows:

• Reduced Friction: Whenever two metal surfaces interact—such as a train wheel and a rail—friction is generated. While a specific amount of friction is necessary (to prevent wheels from sliding), lubricants control these levels, so the train moves with minimal wear, noise, and lower fuel consumption.
• Lower Maintenance: Significant wear occurs when friction is too high. Lubricants mitigate this wear, extending the intervals between maintenance cycles. Consequently, operators experience fewer service disruptions and lower costs related to equipment and man-hours.
• Noise Reduction: Noise is a byproduct of metal-on-metal interaction. Lubricants dampen this sound by lowering the friction between the two surfaces.
• Reduced Risk of Derailment: Although rare, a train or carriage can run off the rails. While many derailments are minor, all lead to disruption, and some can result in serious accidents. By minimising wear, lubricants are essential in preventing wheels from “climbing” the rails, especially around curves and junctions.

What is a Curve Rail?

Curve rail grease is perhaps the most common rail lubricant, applied wherever a rail line bends. To understand why it is necessary, one must understand the basics of the wheel-rail interface.

Rail lines consist of two parallel rails. On straight track, the force from the train is vertical pressing down equally on both rails. However, when the line curves, lateral forces apply. Most curves utilise a Cant angle (a high rail and a low rail) to mitigate these forces. Additionally, train wheels are cone-shaped; this allows the wheel on the high rail to travel a longer distance than the wheel on the low rail as the train negotiates the curve.

The role of the lubricant

The Cant angle of each curve is designed based on the expected weight and speed of the trains. If a train exceeds these criteria, the flange of the wheel on the high rail will push against the gauge face of the rail, causing significant wear.

Beyond simple wear, should the lateral force from the wheel flange on the rail’s gauge corner exceed the wheel’s ability to slide or relocate, the wheel can “climb” the rail, leading to a derailment. Curve rail grease is applied to the rail gauge face to reduce this friction. This not only reduces maintenance requirements on curved rails but also ensures the flange can glide rather than grip and climb, significantly lowering the risk of accidents.

(Curve rail grease is applied to the gauge face of the rail.)

The ideal curve rail grease must:

• Possess Extreme Pressure (EP) properties to resist the forces applied by the train wheel.
• Feature High Adhesion to ensure the product stays in place.
• Remain stable across all operating temperatures.
• Resist extreme weather, including heavy rain, snow, and heat.

You can read much more about curve rail greases.

What is a Fishplate?

Put simply, fishplates are two metal plate bolted to the sides of two rails where they meet, holding the sections together. Different fishplates are used depending on whether the rails profiles are the same or require electrical insulation.

The Role of the Lubricant

Fishplate grease is applied underneath the plate before it is bolted to the rail. It is vital for extending the lifetime and reliability of the joint. The lubricant allows the rails and fishplate to move slightly, accommodating load fluctuations as a train passes or the expansion/contraction caused by temperature changes. It also prevents corrosion and seizing.

The ideal fishplate grease must:

• Offer superior anti-corrosive properties.
• Be exceptionally long-lasting, ideally extending maintenance intervals to a minimum of two years.
• Not interfere with electrical conduction.
• Remain stable in all weather conditions.

You can read much more about fishplate greases.

What is a Switchplate?

A switch (or points) enables a train to change direction. It is typically a Y-shaped piece of track where one line splits into two. By moving the switch blade, the operator directs the train to the left or right line. The switch plate or sliding chair is the horizontal metal plate sitting beneath these moving parts.

The Role of the Lubricant

Switch plate lubricant is applied to the top of the plate. Its job is to enable the foot of the switch blade to slide freely with minimal force. This is critical; if a switch blade sticks, it can cause severe delays or derailments.

The ideal switch plate grease must:

• Have extreme adhesion so it stays in place during the sliding movement.
• Be highly resistant to UV light and rain wash-off.
• Withstand the heat from switch heaters, which are used in colder climates to mitigate ice and snow.

You can read much more about switchplate greases.

Top of Rail (TOR) Friction Control Materials

Top of Rail Friction Management is a relatively new field with significant recent innovation. These materials are applied directly to the top (running surface) of the rail to ensure the “ideal” amount of friction exists between the wheel and the track.

What do Top of Rail Friction Control Materials do?

Top of Rail Friction Management is a relatively new field with significant recent innovation. These materials are applied directly to the top (running surface) of the rail to ensure the “ideal” amount of friction exists between the wheel and the track.

(As the name suggests, Top of Rail Friction Control Materials are applied to the top of the rail.)

What do they do?

On a rail track, you need some friction to prevent the wheels from spinning or sliding. However, excessive friction requires more energy to move the train. TOR materials ensure an ideal friction coefficient—typically between 0.3 and 0.4, whereas dry, untreated rail is around 0.7. The result is optimised performance, lower wear, significantly reduced fuel consumption, and superior noise control at the Wheel-Rail Interface (WRI).

Managing the “Stick-Slip” Effect

When a train navigates a curve, mechanical systems are in place to ensure the wheels (connected to a solid, rigid axle) travel through the curve safely. However, when the physical limits of these steering mechanisms are reached, TOR friction control materials are used to manage a phenomenon known as stick-slip.

Because the wheels are on a fixed axle, the wheel on the low rail (the inner rail of the curve) must travel a shorter distance than the wheel on the high rail. When the mechanical steering reaches its limit, the wheel on the low rail begins to exceed the required rotational speed for the distance available.

This creates a buildup of energy that is released when the wheel momentarily “slips” to compensate for the speed difference. Once the energy is released, the wheel “sticks” again, and the cycle repeats: stick-slip-stick-slip. This continues until the train navigated the curve and returns to a straight line. By applying TOR friction control materials, we stabilise the friction levels, eliminating this erratic cycle and reducing the associated vibration, wear, and noise.

Other Considerations: Environment, Heavy Haul, and Weather

The exact lubricant or friction control material required depends on several factors:

• Environmental Compliance: Environmentally Acceptable Lubricants (EALs) are increasingly required as residue can seep into the water table.
• Heavy Haul: Tracks carrying heavy goods may require specialised gauge face grease formulated for extreme loads.
• Fire Safety: In tunnels and urban areas, lubricants often require fire-resistant properties to reduce the risk of smoke and flames.

Getting Started

Choosing the right lubricant and friction control material ensures lasting performance and reliability for your network. If you would like advice on selecting the best product for your specific needs, get in touch with us at RS Clare. We would be happy to help.