Railway Dust

Railway dust, also known as industrial fallout, is the fine metal particulates produced any place you have metal rubbing against metal such as between the wheels and rails, the pantograph and power line, or the brake pad and the rotor.

In this article we will focus on brake dust, but be aware that all these sources play a significant role in the production of metal particulates. The graph below shows the concentrations above normal levels in the NYC subway system for a range of metal types.

Enrichment of subway samples as defined by the ratio of air concentration in an 8 hour sample from the NYC subway to the median air concentration measured at 41 home outdoor locations throughout NYC in summer 1999.
Metal particulate factor of NYC subway system. Reference [1]

What is brake dust?

While standing on a platform as a train pulls in, you may have caught a whiff of an odd burnt odour waft up from under the train. What you are smelling is the brake pad grinding away and producing microscopic dust particles. Just like your car, a train uses brake pads to slow itself. Even modern high speed electric trains with regenerative breaking systems rely on the friction of a brake pad to come to a complete stop.

Modern brake pads are complex compounds, but are generally made of metals for heat dissipation, ceramics for durability and high heat resin’s to bind the elements together. When the break pad is heated by contact with a rotor, small particles of the pad material are transferred and turn a dull gray colour by the friction heat.

Disk brakes on a Bombardier commuter train.
Disk brakes on a Bombardier commuter train.

What does it look like?

The easiest place to observe brake dust would be on your car. You may have noticed that your wheels, particularly the front ones, get covered in a black powder that can be difficult to remove. The composition is slightly different from railway brake dust, but visually it is the same.

 

How does brake dust impact electronics?

Brake dust is composed of many elements including metal, ceramic and resin.

  • The build-up of metal dust presents the obvious risk of short circuit between components on a circuit board.
  • The resins used to bind the composite together are corrosive and will eat away at copper traces and solder joins. They also make removal of any particulates difficult.
  • The build-up of ceramic dust can trap moisture and accelerate corrosion, or interfere with the heat dissipation of a part.

 

How can I mitigate it?

Passenger Information Displays (PID’s) are often located in outdoor environments and require screens up to 10 times brighter than your TV at home. This extra brightness comes with a heat penalty. Brighter screens that are viewable outdoors also product a lot of heat. The standard way for PID manufacturers to handle this excess heat is to circulate air through the enclosure. The air filters will filter a lot of the larger particles (5 microns or larger), but require regular cleaning and struggle to stop the fine brake dust particles from entering the enclosure.

As can be seen in the following chart, brake dust particles are tiny. They are grouped around 0.1micron, but can be 0.05micron or smaller.

Brake dust particle size distribution
Brake dust particle size distribution. Reference [2]
At Metrospec we have invested considerable engineering resources into railway dust and other particulates commonly found in industrial environments. Our X and H series passenger information displays are engineered to work without air filters, eliminating both cleaning costs and internal brake dust build up.

For further information on our rugged high bright LCD displays, please contact our sales team on +61 7 3868 4255 or sales@metrospec.com.au

High bright outdoor LCD display used for Passenger Information Display installed in Adelaide, Australia.
Metrospec Passenger Information Display installed in Adelaide, Australia

 

References

[1] Steven N. Chillrud, David Grass, James M. Ross, Drissa Coulibaly, Vesna Slavkovich, David Epstein, Sonja N. Sax, Dee Pederson, David Johnson, John D. Spengler, Patric L. Kinney, H. James Simpson, Paul Brandt-Rauf. 2005. Journal of Urban Health: Bulletin of the New York Academy of Medicine, Vol. 82, No.1

[2] Klaus Augsburg, Hannes Sachse, Stefan Krischok, Rudiger Horn, Marcus Rieker, Uwe Dierks. 2012. Investigation of Brake Wear Particles, Guest Forum English Edition No. 39.

Share

Leave a Reply

Your email address will not be published. Required fields are marked *