In order to meet more challenging European engine
emissions regulations, the client (a locomotive manufacturer) modified
the engine and cooler group of their standard locomotive design. The
changes were relatively minor but a larger cooler group generated more
noise, which must be absorbed in order to meet the dosage requirements
of GM/RT2160. This was achieved by fitting noise-absorbant materials in
various locations around the cab. The materials were initially
selected based on compliant (non-UK) fire tests and their ubiquitous
use, not only in the domestic market (the materials are fitted to
locomotives, plant equipment, motor homes, trucks etc) but also in the
UK – and verified as being previously approved for use in the cab of
the standard design locomotives.
Through the use of a comprehensive and robust
quantified risk assessment using relevant service data it was
demonstrated that there was sufficient mitigation in place to
demonstrate that the risk that the non-RGS compliant materials present
to the railway infrastructure is as low as reasonably practicable
(ALARP). The full analysis was presented in report ESG-R-R001(01).
The fault tree analysis (shown below) was just one element of a 7-stage quantified risk assessment process:
- Hazard Identification - System
boundaries, scope, interactions with other systems (e.g. sources of
heat or ignition), review of mandatory requirements & test results -
establish delta
- Causal Analysis - Factors contributing to the hazard, measures that reduce likelihood (risk mitigation)
- Fault Tree Analysis - Quantified assessment of likelihood of Top-Hazard
- Consequence Analysis - Specifically, an event tree analysis to establish likelihood of failure, possible effects of the hazard
- Options Analysis - Required by ALARP to investigate and quantify possible alternative methods (risk reduction)
- Risk Mitigation - Relevant issues that
use a Fire TCA comparative assessment basis ie comparing Class 66
incident data to Class 66 UIC-II fire performance
- Demonstration of ALARP - Used to ultimately establish the elimination of importation of Risk.