Railway Track Crossing

The structural integrity of a railway track crossing, also known as a frog or a diamond crossing, is one of the most critical aspects of track engineering. This is where rails intersect, creating significant stress points that must endure immense dynamic forces from passing trains. The performance of a railway track crossing depends on the precise specifications of its components, particularly the specialized rail profiles and the robust rail clips that form the fastening system. This technical guide focuses exclusively on the specifications for the rails and clips that constitute a safe and durable crossing.

Rail Profile Specifications for a Railway Track Crossing

The rails used in a railway track crossing are not standard continuous rails; they are specially manufactured or fabricated into components like frogs, wing rails, and guard rails. The choice of rail profile and steel grade is paramount to ensure the crossing can handle the high-impact loads it will experience. The profile must match the adjoining track to ensure a smooth transition for the wheel, minimizing wear and tear on both the wheel and the track.

Cast Manganese Steel (CMS) Frogs

For high-traffic and heavy-haul routes, frogs are often manufactured from a single piece of cast manganese steel. This material is chosen for its exceptional work-hardening properties; under the repeated impact of train wheels, the surface of the manganese steel becomes progressively harder and more wear-resistant.

Specification Table: Cast Manganese Steel Frogs

Fabricated Frogs and Crossing Rails

In less demanding applications, a railway track crossing can be fabricated by cutting and bolting standard rail profiles together. The rails used for this must be of a high-strength grade to withstand the forces at the frog’s point and wing rails. The profiles must match the intersecting tracks, with common profiles like UIC60 or AREMA 136RE being used.

Specification Table: Rail for Fabricated Crossings

Railway Track Crossing Rails Frequently Asked Questions

1. What is a “frog” in a railway track crossing?
   The frog is the component that allows the wheel flange to pass through the intersection of two running rails. It is the ‘X’ shaped part in the center of a crossing and is the point of highest impact and wear.
2. Why is manganese steel used for frogs?
   Manganese steel has a unique ability to “work-harden.” The repeated impact from train wheels hardens its surface, increasing wear resistance over time while the core remains tough and ductile, preventing fractures.

Railway Track Crossing Rail Clip Specifications 

The fastening system at a railway track crossing is subjected to higher vibrations and more complex forces than standard track. The rail clips must provide an exceptionally high and consistent clamping force to prevent any movement of the frog, wing rails, or guard rails, which could lead to catastrophic failure.

Heavy-Duty Tension Clamps (SKL Type)

Due to the high-impact environment, heavy-duty tension clamps are the preferred choice for securing the components of a railway track crossing. The SKL system, with its robust design and high fatigue life, provides the reliability needed.

Specification Table: SKL Tension Clamps for Crossings

Pandrol VIPA & VANGUARD Systems

For crossings in urban areas or on bridges where noise and vibration reduction are critical, specialized fastening systems are used. The Pandrol VANGUARD system, for example, uses resilient, encapsulated units to isolate the rail, significantly reducing ground-borne vibration. The clips within these systems are designed to work with the resilient block.

Specification Table: Specialized Crossing Fasteners

Rail Clips for Guard Rails

Guard rails (or check rails) are placed alongside the running rails through a crossing to guide the wheelset and prevent derailment at the frog. These rails are also secured with heavy-duty clips, which must resist high lateral forces.

Guard Rail Clips Specification Table

Railway Track Crossing Clips Frequently Asked Questions

1. Why do crossings require stronger clips than regular track?
   The intersection point (frog) of a railway track crossing creates a discontinuity in the rail, leading to very high impact loads and vibrations. Stronger clips with higher clamping force are needed to prevent components from shifting or loosening under these severe conditions.
2. What is a guard rail and why is it needed in a crossing?
   A guard rail is a short rail placed inside the running rail. It ensures the wheelset is steered correctly through the crossing, preventing the wheel flange from striking the point of the frog and causing a derailment.
3. What does “fatigue life” mean for a rail clip?
   Fatigue life is the number of load cycles (from passing trains) a clip can withstand before it is at risk of breaking. A high fatigue life is especially important for clips used in a railway track crossing due to the constant, high-impact loading.