EN 15566: The Standard for Railway Couplings and Draw Gear

What is EN 15566?

EN 15566 is the European Standard titled “Railway applications – Rolling stock – Draw gear and screw coupling.” It specifies the requirements for the mechanical devices that connect railway vehicles to transmit tensile forces (pulling forces) during train operation.

In the standard-gauge European rail network, the majority of freight and passenger trains use the “Buffing and Draw Gear” system, where buffers handle compression and the screw coupling handles tension. EN 15566 ensures that these safety-critical components are interchangeable and strong enough to prevent train partings.

Technical Components of the Draw Gear

The standard covers several specific components that make up the “Draft” system of a vehicle:

• Draw Hook: The massive steel hook mounted to the headstock of the vehicle underframe.
• Screw Coupling: The adjustable link consisting of a screw, handle, and shackles that connects the hooks of two adjacent vehicles.
• Elastic Device (Draft Gear): The internal spring or rubber-element system behind the hook that absorbs shocks and limits the peak tensile forces transmitted to the structural integrity of the wagon.

Mechanical Requirements and Strength

EN 15566 defines the “Breaking Load” and “Yield Strength” for these components. For international interoperability, the standard defines specific classes:

• Standard 850 kN / 1350 kN: Requirements for the breaking strength of the coupling and hook to ensure they can pull heavy freight consists without failure.
• Elastic Characteristics: The draw gear must provide a specific stroke (travel) and energy absorption capacity to protect the vehicle’s frame from fatigue.
• Dimensions: Precise geometric tolerances for the hook profile to ensure that any standard screw coupling can be manually fitted by shunting personnel.

Safety and Human Factors

Because screw couplings are usually operated manually, EN 15566 includes requirements for the Screw Handle weight and the ease of rotation. It also dictates the “Berne Rectangle” clearances to ensure the person coupling the train has enough space to work safely between the buffers.

Comparison: Manual Screw Coupling vs. Automatic Couplers

Regulatory Compliance (TSI)

Compliance with EN 15566 is a mandatory requirement for TSI LOC&PAS and TSI WAG. A vehicle cannot be certified for international service unless its coupling system meets these specifications. This ensures that a locomotive from any manufacturer can safely rescue or haul any wagon or coach in the network.