Deutsche Bahn AG
If there is fine dust on the contact, it does not close properly and malfunctions occur.Stefan Schlottbom, Control and safety technology specialist
Setting the course
Setting the course – for the new year, for social policy, for pension models, for holiday planning. The term is everyday language, used without thinking about where it comes from. It comes from the railway industry, where traffic control centres (former signal boxes) ensure that track switches are set so that the train arrives where it is supposed to and not somewhere else or on the siding (another expression).
3842 signalling centres in operation
In March 2022, there were 3842 signal boxes in Deutsche Bahn’s network, with different technologies – mechanical, electromechanical, relay or electronically controlled. A signal box is the “command centre” for many points and signals within a route area. From the signal box, switches are set and all trains are put on their correct path. At the signal box, employees of railway infrastructure companies – more than 13,000 across Germany – control the entire train traffic of a region.
Relay interlocking (RSTW for short) is a type of interlocking for controlling railway operations in which safety-related dependencies are set entirely electrically by signal relays. The track plans of stations and adjacent track sections are schematically displayed on so-called control panels. Here, all operations are performed and operating states are displayed. Almost half of all signal boxes are relay signal boxes.
How a relay works and why it cannot handle dust
A relay – a brief refresher from physics class – is a remote-controlled switch operated by electric current, usually with two switching positions. The relay is activated via a control circuit and can switch other circuits.
As an example, you see here a hinged armature relay with a normally open contact (also called a normally closed contact). The left image shows the relay at rest; the coil is de-energised, the normally open contact is open. In the right image, voltage is applied to the coil, which attracts the armature of the coil’s iron core and closes the normally open contact.
Fine dust affects electronics
Relays work extremely reliably; what they don’t “like” is fine dust. It is a well-researched fact that dust particles and smoke not only damage the airways, but also electronics. That server rooms are attacked by fine dust is common knowledge. Microscopic pollution particles corrode the electronics of IT technology, causing overheating, interruptions, failures, short circuits or malfunctions, thus reducing reliability, life expectancy and long-term value retention. It is much less known that relay interlocks are also sensitively disrupted by microscopic dust particles.
Image: User:Bisgaard, language neutral version by Teslaton, CC BY-SA 3.0, via Wikimedia Commons
When a small dust particle burns away on the relay contact
Operating disruptions due to fine dust – that was the challenge facing Stefan Schlottbom. He has worked at DB Netz AG since 2010 and is a specialist in control and safety technology in training RB West / installation and maintenance management RB West – the area includes North Rhine-Westphalia and parts of Rhineland-Palatinate. His area of responsibility also includes the large relay signal boxes in Düsseldorf, Essen and Cologne.
Stefan Schlottbom describes the process in a way that even non-experts can understand: The relays control the processes according to a binary system; the contact is open or closed, current flows through it or not. If the finest dust is on the contact, it does not close properly and information processing does not work. It is clear: such a process prevents the urgently needed safe information at the right time. This means: stop. Interruption of the business process, for the sake of safety.
Colleagues already use air cleaners
Stefan Schlottbom drew on the experience of colleagues in Bremen’s signal boxes. Since mid-August 2019, six fine dust air cleaners from Euromate’s Vision Air Blue Line product line have been installed there and the experiences are good.
“The advice from Euromate’s consultant was very good,” says Stefan Schlottbom. “He answered all questions and if something was not clear, I could always ask. He gave us the opportunity to use air cleaners on a trial basis, we took air measurements and we saw that the dust levels went down.”
Flexible due to wheels
A total of 18 VisionAir BlueLine DustFree were commissioned between May and November 2022 – first in Brake near Bielefeld, then in Düsseldorf and now in Cologne-Mülheim. Measurements are still being carried out at the sites. Particulate matter levels are falling sharply, says Stefan Schlottbom, to less than half of what they were before the air cleaners were commissioned.
The biggest challenge, says Schlottbom, was finding a place for the air cleaners, “because the corridors in the signal box are very narrow. But the air purifier fits right in.” Some staff initially complained that they took up space and were in the way. Thanks to the wheels, the units could easily be pushed back. “The units are not very noisy in use, air conditioning is much louder,” says Schlottbom. “They are not disruptive in terms of noise at all.
Less fine dust means less disruptions
And most importantly: There is measurably less, much less particulate matter in the air and thus a source of disturbance has been eliminated. Measurable in concrete terms: on Brake’s data sheet, you can see how the lines for particles of size PM10 (brown line) and the size between 0.3 and 10.0 µ drop by using the air cleaners – from more than 40 per cm³ to less than 10 per cm³.
Impressive is also the measurement in Düsseldorf between 14 and 16 December (figure above). When the air cleaners were commissioned on 15 December, the blue line (particles between 0.3 µ and 10 µ) dropped very significantly – from 120 /cm³ to less than 20 / cm³.
Stefan Schlottbom: “As far as I know, colleagues from other signal boxes now want to buy air cleaners too!”
Vision Air Blue Line DustFree
The term fine dust covers many different types of particles. Fine dust is dust with a particle size of 10 micrometres or less, i.e. 0.001 centimetres. But not all types of fine dust are the same size or have the same effect. The slightly larger particles, which are between 5 and 10 micrometres in size, are inhaled by humans only superficially. One cough or sneeze and the particles are gone from our bodies. The smaller particles, however, cause more serious health problems and interfere with sensitive electronics.
An air purifier against fine dust protects against diseases and against operational failures due to electronic malfunctions caused by fine dust.
- Filters 99.96% of all particles from 0.1 µ
- Available with different filter packages
- Filters particulates, viruses, odours, smoke, etc.
- Options: Space-saving installation on wall or ceiling or mobile on the floor (wheels)
- Low-noise and user-friendly
- Energy-efficient
More information
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