EN 15839: Testing for Acceptance of Freight Wagons – Derailment under Longitudinal Compressive Forces

What is EN 15839?

EN 15839 is a safety-critical European Standard titled “Railway applications – Testing for the acceptance of running characteristics of railway vehicles – Freight wagons – Testing of trackkeeping ability under longitudinal compressive forces.”

In long Freight Wagons consists, when the brakes are applied or when the train is being pushed, the wagons are subjected to massive Longitudinal Compressive Forces (LCF). If a wagon is not designed correctly, these forces can cause the vehicle to “jackknife” or lift, leading to a derailment. This standard provides the rigorous testing framework to ensure a wagon’s Structural Integrity and stability under these specific conditions.

The “Jackknife” Phenomenon

When a wagon is compressed between two other vehicles, the Buffing and Draw Gear creates a lateral force component, especially in curves. EN 15839 focuses on preventing two primary failure modes:

• Wheel Climb: The lateral force pushes the wheel flange against the rail until the wheel “climbs” over the rail head.
• Track Shifting: The combined lateral force from the wagons exceeds the resistance of the Wheel/Rail Interface and the ballast, moving the entire track structure.
• Vehicle Overturning: Excessive lateral force causing the wagon body to tilt beyond its stable limit.

Testing Methodologies

The standard requires two main types of assessment to validate the Running Characteristics of a wagon:

• Static Tests: Measuring the characteristics of the buffers and the geometry of the underframe to calculate the theoretical lateral force.
• On-Track Tests: A real-world test where the candidate wagon is placed between two “barrier” wagons in a S-curve track configuration. A locomotive then applies a controlled compressive force (often exceeding 200-300 kN) to measure the wheel unloading ($ΔQ/Q$) and lateral forces ($Y$-forces).

Relationship with EN 14363

While EN 14363 is the general standard for running behavior, EN 15839 is a specialized supplement specifically for freight wagons equipped with side buffers. It ensures that the interaction between the buffers, the chassis stiffness, and the bogie rotation is optimized to dissipate energy safely rather than converting it into lateral movement.

Comparison: Standard Running Tests vs. EN 15839