The recent APTA Expo brought the seal and wire protection needs of transit OEMs worldwide into sharp focus.

OEMs told us they need three core parameters: performance, safety, and reliability.

All three combine to drive decisions on materials and suppliers.

City Bus


Digging deeper we found that this could be distilled into 3 specific product features

  1. Metal Reinforcement
  2. Silicon or Thermo-Plastic Elastomers (TPE)
  3. Flame, Smoke, Toxicity (FST) Compliance

DTi offers seals and grommet edging that meet all three.

Metal Reinforced for Performance/Reliability

For performance, they required seals and grommets to have metal embodied into the design.  They know that it gave the products resilience and longevity that drives strong performance characteristics.

  • Spring-Fast Grommet Edging features an encapsulated spring steel core that outperforms plastic grommets and as a significant plus it lowers install costs by 49% vs. grommets with glue – due to far fewer workflow steps.
  • Seal-Fast Silicone seals are reinforced with steel/stainless steel wire, improving strength and grip.


Silicone or TPE for Performance/Reliability/FST:

a) Silicone Seals embody these key performance features:

  • Steel reinforced: making it flexible, durable, and easy to apply, with a high tear strength and a stronger grip
  • Low compression set recovers its original shape post compression e.g. doors that open/close many times a day.
  • Environment resistant to adverse weather, UV, & ozone. Ideal for external use at high speeds.

(See related post Silicone and Rail – the Perfect Match for Effective Seals)

b) Thermo-Plastic Elastomers (TPE)

Spring-Fast® Grommet Edging SL-FST is encapsulated with TPE

  • TPE Encapsulation material is resistant to weather conditions, UV, & ozone.
  • FST compliant with EN 45545-2 & US NFPA standards.  Flame retardant, low smoke & low toxicity,
  • Steel core creates best-in-class performance and 49% installation savings


Flame, Smoke, Toxicity FST Compliant

In transit environments, fire and toxic smoke are a major danger so safety is a critical issue and has become the focus of specific regulation.

a) Silicone seals improve the overall fire safety envelope due to:

  • High fire resistance and self-extinguishing characteristics,
  • Resistance to smoke development,
  • A high-temperature range diminishes the chance of a potential fire outbreak.
  • FST compliant with EN 45545-2, E662, E162, and SMP-800 certificated test results

b) Spring-Fast SL-FST grommet edging is fully encapsulated in a TPE that is flexible but is also:

  • Flame retardant,
  • Low smoke-producing
  • Low toxicity producing.
  • FST compliant with EN 45545-2 (within requirement sets R22 and R23 for small critical components it is certified for Smoke Density, Oxygen Index, and Toxic Gas for Hazard Levels, 1, 2, and 3.)

More and more OEM design engineers have added these materials to their e-books or internal design guides for seals and wire protection to ensure they are available to their engineers.   We are making inroads into more and more transit projects in North America and Europe precisely because we meet OEM needs.

SL-FST was added to the tried and tested Spring-Fast line specifically to meet the needs of FST standards like EN45545-2 – as well as other US and worldwide certifications like the ASTM FST requirements. This dual compliance allows transit OEMs worldwide to implement unified design specifications with this product regardless of the end-use track system.

Spring-Fast is used widely in high-performance arenas like commercial /military aircraft interiors/avionics, medical, IT, power/energy, robotics, and military vehicles.

Find out more about Spring-Fast SL-FST

Find out more about Seal-Fast Silicone

Request free samples here