A rail pad protects the sleeper from abrasion and crushing under the rail foot, and it is designed to a specific load-deflection characteristic. Its initial stiffness is deliberately low so that the clip toe load compresses it substantially, which is what gives the fastening its elastic behaviour. If the pad is folded, mis-seated or missing, the fastening loses that designed deflection and the sleeper takes the full impact.
Step 1: Surface Preparation
Clean the concrete sleeper rail seat before laying the pad. In construction and maintenance sites, grit, ballast dust and remnants of old pads accumulate on the seat; under dynamic train loads these particles embed into the new pad and grind against the concrete, rapidly wearing the pad through and damaging the sleeper. The seat must be dry, flat and debris-free, and any old adhesive or pad residue removed. A clean interface also maximizes friction grip, preventing the pad from walking laterally under traffic.
Step 2: Orientation and Geometric Fit
Modern fastening systems use pads with locating tabs, horns or side wings that fit between the insulators or against the shoulder. Install the pad with the correct side facing up, usually the grooved side where grooves are present, and confirm the tabs engage the shoulder as designed. Never force a pad into a position where it does not sit flat: forcing causes buckling and stress concentration that will fail in service. Correctly manufactured pads are made to tight dimensional tolerances so they drop into place without trimming; if a pad needs trimming on site, it is the wrong model for the system.
Step 3: Clamping and Final Inspection
After the rail is lowered onto the pad and the clips are applied, inspect the assembly. The pad should extend slightly beyond the rail foot on both sides, showing full coverage. If the pad is extruded or heavily compressed on one side, the rail is tilted or the cant is wrong; correct the rail position immediately so the pad works within its designed static stiffness range. A properly seated pad lets the fastening develop its specified toe load, which is the clamping force that holds the rail down and resists rail lift.
Technical Parameters of Common Pad Materials
HDPE rail pad
| Parameter | Unit | Typical requirement |
| Density | g/cm3 | 0.95-0.98 |
| Tensile strength | MPa | at least 19 |
| Elongation | % | above 80 |
| Melting point | C | 125-135 |
| Insulation resistance | ohm | at least 1x10^10 |
| Hardness | Shore A | 95-98 |
EVA rail pad (polyethylene 80%, vinyl acetate 20%)
| Parameter | Unit | Typical requirement |
| Density | g/cm3 | 0.95-0.98 |
| Tensile strength | MPa | at least 15 |
| Elongation | % | above 500 |
| Melting point | C | 75-95 |
| Insulation resistance | ohm | at least 1x10^10 |
| Hardness | Shore A | 90-95 |
Rubber rail pad
| Parameter | Unit | Typical value |
| Static stiffness | kN/mm | 90-130 |
| Hardness | Shore A | 72-80 |
| Electrical resistance | ohm | at least 10^6 |
| Tensile strength before aging | MPa | at least 12.5 |
| Elongation before aging | % | at least 250 |
Common Installation Errors
Laying the pad on a dirty or wet rail seat, then wondering why it wears through quickly.
Installing the pad upside down or with the locating tabs against the wrong shoulder.
Forcing a pad that belongs to a different fastening system into the assembly.
Skipping the final visual check and leaving a pad half-covered by the rail foot.
Reusing damaged or permanently compressed pads from an old section.
FAQ
Which side of a rail pad faces up?
Usually the grooved side faces the rail where grooves are fitted; the locating tabs face the shoulder. Confirm with the manufacturer's drawing, because orientations differ between systems.
Why must the sleeper seat be clean?
Grit trapped under the pad acts like sandpaper under dynamic load, wearing through the pad and damaging the concrete. A clean seat also lets the pad develop full friction grip.
How do I know the pad is the right size?
It should cover the rail foot fully and extend slightly beyond it on both sides, with its locating features engaged. If it needs trimming or forcing, it is the wrong model.
What is the static stiffness range of a rubber rail pad?
Typical values are 90-130 kN/mm depending on the fastening system, hardness and formulation. The project specification defines the required range.
Can EVA and rubber pads be mixed on one line?
Mixing materials with different stiffness on the same line creates uneven support and irregular wheel loads. One material and stiffness family should be used per section unless the design deliberately specifies a transition.
How should rail pads be stored before installation?
In a clean, ventilated area away from direct sunlight, heat sources, oil, organic solvents and chemicals. Stored pads should lie flat and unloaded so they keep their shape and elastic properties.