STORM Lok-Dieselmotorenservice

It overhauls the internal combustion engines of locomotives: general overhauls, repairs, sourcing spare parts, and complete replacement with a more modern unit. The STORM group, headquartered in Spelle in the Emsland, works independently of manufacturers and services engines not only in locomotives but also in ships, construction machinery and stationary plant.

The original engine of a vehicle is replaced with a newer one, while the frame, running gear and body are kept. This isn't a conversion in the sense of a new design, but it noticeably changes power, emissions behaviour and sound. For shunting and main-line diesel locomotives, this has been common practice for decades – for instance with vehicles of the LEW V 100 family.

For three reasons: spare parts for very old engines become scarce, modern units use less fuel, and emissions regulations for mobile machinery have been considerably tightened over the years. A vehicle with an up-to-date engine stays usable where an original unit loses fields of application.

Yes, this is one of the few reliable acoustic features in spotting. Older locomotive diesel engines have a characteristic, deeper and rougher sound; modern units sound smoother and often run in different rev bands. Once you've heard a Class 294 in original and converted form side by side, you won't confuse them again.

By the periphery of the engine, not the engine itself. Look for the exhaust routing, additions for exhaust after-treatment, altered radiator grilles, and new cut-outs or hatches in the engine bonnet. Panel joints and rivet patterns in that area are also often different from the original vehicle – comparing against the standard-production condition helps, see Identifying older-generation diesel locomotives.

Often, yes. Converted vehicles frequently get a new class designation so the changed technical status is reflected in the operating records. That's why, on such machines, the number sometimes doesn't match the visual impression. For you that means: note the number, don't infer it from the appearance – how to do that is covered in the guide to the UIC number.

Generally not. At most, the vehicle carries small notices about the engine type or emissions standard, usually near a door or the engine compartment. Who overhauled the engine can't be determined from outside. So in your sighting, note what you saw – such as "altered exhaust routing" – not who might have worked on it.

No. Even current shunting and main-line diesel locomotives need major engine work after a few thousand operating hours. The difference is that newer vehicles are more often overhauled, while older ones are more often fully replaced. Modern shunting locomotives such as the Voith Gravita 10 BB are designed for regular engine work.

At freight hubs and marshalling yards. Maschen marshalling yard is the classic place for this, and in the north-west there's Bad Bentheim, a border station with plenty of diesel traffic. What to expect at places like these is covered in the guide to marshalling yards.

Legally and in the fleet register, yes – the frame and vehicle identity are preserved. Technically, it's a different machine. This dual nature is exactly what makes the subject interesting for documentation: two vehicles of the same class can differ considerably in power, consumption and sound without the design designation reflecting that.