Nabla Blade for Railway Fastening System

The Nabla Blade (also known as a Nabla clip or Nabla plate) is a critical elastic component used in the Nabla railway fastening system to secure rails to sleepers. It is widely recognized for its use on high-speed lines, such as the French TGV, as well as in metro, tram, and heavy-haul networks across Europe and Africa. 

Key Features and Specifications

• Design: It is shaped like a thick trapezoidal shovel with a central round hole for a mounting bolt. This unique shape generates a stable toe load on the rail when the nut is torqued.

• Material: Typically manufactured from high-quality alloy spring steel(In China it is named as 60Si2MnA or 60Si2CrA), following standards NF F50-015.

• Performance:

• Toe Load: 11 kN (or up to 2500 DaN).

• Static Stiffness: Around 70 kN/mm.

• Hardness: Usually ranges between HRC 51-55.

• Adjustment: Allows for height adjustment of -8 to +4 mm and lateral gauge tuning in 1.25 mm increments. 

System Components

The Nabla blade works as part of an assembly that includes: 

• Nabla Blade: Provides the clamping force.

• Insulator: The insulator is also known as bumper. It is specially designed to sit between the blade and the rail to provide electrical insulation and absorb lateral forces.

• High-Strength Bolt & Nut: A double-ended bolt often anchored into concrete sleepers to secure the blade.

• Rail Pad: A resilient layer placed under the rail foot to reduce vibration and protect the sleeper. 

Primary Advantages

• Durability: Offers high resistance to wear from lateral loads, which reduces maintenance costs.

• Stability: Effectively prevents rail roll and maintains precise track gauge, especially in tight radius curves.

• Electrical Insulation: Provides superior insulation compared to many other systems, making it suitable for electrified tracks.

• Installation: Designed for "pre-assembled" delivery on sleepers, allowing for faster and more efficient track laying.