The DIN EN 45545-2 standard sets fire protection requirements for materials used in rail vehicles. For designers of injection-moulded components, this is far from an exotic topic - quite the opposite. Every material decision in a rail project comes back to this standard.
In this article we clarify the three things that most often cause confusion: R requirement classes, HL hazard levels and product categories. Without going into the full apparatus of test methods - those are the domain of the laboratory, not the designer.
R requirement classes
The R sets describe what is actually tested. For plastic components in rolling stock, the most common are:
- R1 - large-surface interior trim parts
- R22 - small components (e.g. clamps, clips, housings)
- R23 - related to R22, but with an additional flame spread test
- R24 - plastic parts inside the passenger compartment
For the MS-PROGRESS rolling stock portfolio, R22 and R23 are key - they come up in 90% of customer briefs.
HL hazard levels
HL (Hazard Level) describes the degree of stringency imposed by the application:
- HL1 - lowest. Local passenger services, short distances.
- HL2 - medium. Conventional long-distance vehicles.
- HL3 - highest. Tunnels, metro, vehicles without automatic evacuation.
HL3 imposes the strictest parameters: low heat release (MARHE), low smoke density, low toxicity of combustion gases. A material compliant with HL3 will also comply with HL2 and HL1 - not the other way round.
How to read a material data sheet
The material supplier's data sheet usually declares a specific combination, e.g. “compliant with EN 45545-2 R22 / HL3”. Three things to check straight away:
1. Does the compliance cover the required thickness
The data sheet usually states the minimum thickness at which the test was carried out. A component with 1.8 mm walls will not automatically inherit compliance from a data sheet based on a 4 mm sample.
2. Does the compliance cover the colour
Colour (or more precisely, the added pigment) can push a toxicity test result beyond the permissible values. The standard declaration covers natural / black; other colours require separate confirmation.
3. Report number and laboratory
It sounds trivial, but in discussions with the customer it is this number that ultimately settles the matter - and it goes into the PPAP documentation.
“In rail projects, most time is lost not on calculations but on misunderstandings when reading a two-page material data sheet.” - PM · MS-PROGRESS rolling stock projects
The most common materials in our portfolio
In series production for rolling stock, we most often work with:
- PA6.6 GF30/GF50 in an FR (self-extinguishing) grade - R22, R23 / HL2
- PBT GF, FR grade - R22 / HL3
- PC+ABS with an FR modifier - selected R sets / HL2
What to check before you send a request for quotation
Three questions that will save weeks:
- Exactly which R and HL does the end customer (the infrastructure manager) require?
- What is the minimum required colour / colour range?
- What is the thinnest wall in the design?
Without answers to these three questions, every material calculation is work done just in case. If you don't know - get in touch; a 30-minute conversation is usually enough to settle it.
