Sparks and Signals: The Legacy of EN 50199 in Railway Maintenance

What was EN 50199?

EN 50199 was the specialized European Standard (CENELEC) titled “Electromagnetic compatibility (EMC) – Product standard for arc welding equipment.” Although now withdrawn and superseded, it established the foundational requirements for emission and immunity in arc welding processes used extensively in railway workshops and track maintenance.

In the railway sector, where sensitive signaling and telecommunication cables run parallel to tracks, the high currents and arcs generated by welding equipment pose a significant risk of Electromagnetic Interference (EMI). EN 50199 defined the limits to ensure that welding operations (such as flash butt welding of rails or bogie repairs) did not disrupt adjacent electronic systems.

Transition to EN 60974-10

As standards harmonized globally, EN 50199 was replaced by EN 60974-10 (Arc welding equipment – Part 10: Electromagnetic compatibility requirements). While the core objective remains the same, the new standard introduces more rigorous testing methods and aligns with the broader IEC framework.

• Scope: Covers power sources, wire feeders, and ancillary equipment (e.g., cooling systems).
• Environment: Distinguishes between equipment used in industrial zones (railway depots) and residential areas.
• Risk Management: Critical for preventing “noisy” welding currents from coupling into track circuits and causing “Ghost Trains” or false occupancy signals.

Why Welding EMC Matters in Railways

Using non-compliant welding equipment in a railway environment is dangerous. The electromagnetic field generated by an arc weld can induce voltages in nearby conductors.

Trackside Risks: During rail maintenance, if a welding machine lacks proper EMC filtering (as defined in EN 50199/EN 60974-10), the noise can be interpreted by the interlocking system as a train, potentially turning signals red unexpectedly.
Workshop Risks: In depots, high-frequency emissions from TIG/MIG welding can interfere with the diagnostic electronics of the Rolling Stock being repaired.

Comparison: Legacy vs. Current Standard