Railway Dust

Railway dust, or industrial fallout, is the fine metal particulates produced when metal rubs against metal.  In fact, the friction between wheels and rails, the panto-graph and power line, or brake pads and a rotors are good example of this.

In this article we will focus on railway dust produced by brake dust.  The graph below shows concentrations at 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 train platform, you’ve probably caught a wiff of an odd burnt odor wafting up from under the train.  That smell is the trains break pads girding 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.

As a consequence to the high pressure placed on them, modern brake pads are complex compounds.  They consist of metals for heat dissipation, ceramics for durability and high heat resin’s that bind the elements together.  The friction heat produced between the break pad and rotor form small small dull grey particles or break dust.

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. For example, you’ve probably noticed a pesky black powder sometimes covering your front wheels.  Although slightly different to railway brake dust, this powder is visually the same.

How does brake dust impact electronics?

Metal, ceramic and resin – the elements that make up break dust can cause the following issues:

  • Metal dust build up can cause short circuiting between components on a circuit board.
  • Corrosive resins will eat away at copper traces and solder joins as well as make the removal of any particulates difficult.
  • Ceramic dust build up 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. As a result, this extra brightness comes with a heat penalty. Brighter screens that are viewable outdoors produce 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.

The following chart depicts break dust particles as tiny in size.  In fact, they have been grouped around 0.1 micron but can also be 0.05 micron or smaller.

Brake dust particle size distribution
Brake dust particle size distribution. Reference [2]
For this reason, we here at MetroSpec have invested considerable engineering resources into railway dust and other particulates commonly found in industrial environments.  That is why our X and H series passenger information displays are engineered to work without air filters.  Thus 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.

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