What the Rail Pad Does?
The rail pad sits between the rail foot and the sleeper. It prevents abrasion of the rail–sleeper interface and crushing of the sleeper under the rail foot, and it contributes controlled elasticity to the track superstructure. Rail pads are normally designed to a specified load–deflection characteristic: the initial stiffness is low, so the pad stays in intimate contact with the rail despite vertical rail movement; when the wheel passes, the stiffness must limit deflection so the metal spring (clip) does not become loose. This characteristic is obtained by introducing grooves or studs in the pad. A more elastic track reduces dynamic loads and noise, meeting today's acoustic requirements.
Materials and Types
Rail pads are available in rubber (natural or synthetic), HDPE and EVA, and special crane-rail pads, with grooved or studded patterns. Standard requirements follow TB/T 2626 (China) or ISO 6446 (international), covering stiffness, hardness, electrical resistance and aging behaviour; the stiffness class is matched to the axle load and the fastener type. For concrete sleepers the pad also protects the sleeper from impact and abrasion.
The SKL Fastening Unit
| Component | Typical spec |
|---|---|
| SKL tension clip (SKL1/3/12/14) | 60Si2CrA or 38Si7 spring steel, hardness 42–47 HRC, per DIN 17221 / GB/T 1222 |
| Screw spike | M24×150; grade 4.6 (Q235), 5.6 (35#), 8.8 (45#) per ISO 898-1 / UIC 864-1 |
| Flat washer | U-shaped or flat, Q235 per EN 10025 / EN 10139 |
| Plastic dowel | Anchors the screw spike in the concrete sleeper |
| Rail pad | Rubber or polymer, grooved/studded, per TB/T 2626 / ISO 6446 |
SKL clip variants (SKL1, SKL3, SKL12, SKL14) differ in geometry and clamping force and are selected by the rail section and system requirement.
System Working Principle
In service, the SKL clip presses the rail foot down through the toe load; the rail pad under the foot distributes the load and provides elasticity; the screw spike holds the clip in place and is anchored in the sleeper by the plastic dowel. Together they fix the rail securely while allowing controlled vertical movement - the combination that gives modern fastening systems their stability and damping.
Frequently Asked Questions
Q1. What is the function of a rail pad?
It cushions the rail, prevents rail–sleeper abrasion and sleeper crushing, and adds controlled elasticity and vibration damping.
Q2. Which standard covers rail pads?
TB/T 2626 (China) and ISO 6446 (international); confirm the stiffness class and material.
Q3. What is the SKL clip made of?
Spring steel such as 60Si2CrA or 38Si7, hardened to 42–47 HRC, per DIN 17221 / GB/T 1222.
