Nabla Insulator for Elastic Rail Fastening System

A Nabla insulator (also known as a railway spacer or rail nylon insulator) is a vital component of the Nabla rail fastening system, commonly used on concrete sleepers in heavy haul, high-speed, and urban transit tracks. It is installed between the rail clip and the steel rail to ensure mechanical stability and electrical isolation. 

The Nabla insulator is a trapezoidal insulating rail pad. It is intended for the rail fastening system on reinforced concrete bi-block sleepers VAX U31 NAG, ensuring maintenance of the 1,435 mm gauge and resistance to a conventional axle load of 22.5 tonnes.

Technical Sharacteristics

• Material: polyamide or thermoplastic material, Nylon 66 (PA66) ;

• Compression resistance (lateral load 80 kN): deformation ≤ 1.6 mm;

• Impact resistance: no breakage or cracking after the fall of a 5 kg mass from a height of 0.40 m;

• Average impact rupture height (on 10 pads): ≥ 0.70 m.

Technical Specifications

Modern Nabla insulators are manufactured from high-performance reinforced polymers to withstand harsh environmental conditions.

Reference Standard

• Compliance with NF F 50-021, defining the characteristics and approval and acceptance conditions of trapezoidal thermoplastic insulating rail pads used in rail fastening systems on concrete sleepers.

Primary Functions

• Electrical Insulation: Prevents electrical current leakage between the rails and the sleeper, which is critical for track signaling systems.

• Gauge Adjustment: Allows for fine-tuning of the track gauge (typically in increments of 1.25mm, up to ±7.5mm per seat) to maintain correct alignment.

• Lateral Force Absorption: Absorbs and distributes lateral forces and vibrations during train operation, reducing wear on assembly components and the sleeper.

• Toe Load Distribution: Helps distribute the clamping force of the rail clip over a larger area of the rail foot.