Fuel Bloom Investigation for South Western Railway

Background

In April 2023, several diesel units operated by South Western Railway (SWR) experienced sudden and unexpected faults. The root cause was identified as microbial contamination within the vehicle fuel, leading to fuel filters becoming blocked by sludge. Further investigation revealed that the fuel storage tanks at Sailsbury Depot were contaminated by micro-organisms, predominantly fungal.

Overview

Whilst SWR successfully resolved this fuel contamination incident, they asked DB ESG to conduct an independent investigation. The objective was to determine the causes of the contamination and to provide a comprehensive list of preventative measures that SWR could implement to avoid future occurrences.

Work Undertaken by DB ESG

Incident Analysis:

• Conducted a thorough analysis of the incident, including staff interviews to establish the event timeline, incident specifics and actions taken, Information was also gathered on the fuel supplier, fuel composition, any antimicrobial additives used, the storage tank and maintenance activities performed.
• A report was submitted outlining this analysis, highlighting fuel quality issues, actions taken to manage the problem, the root cause of the contamination and reasons for the incident occurring in April.

Broader Investigation:

• Investigated the wider context of microbial contamination events and explored available options for prevention and management
• Provided a report containing a comprehensive list of strategies to prevent and manage any future contamination incidents.

Investigation Summary

• The main cause of the microbial contamination was the build up of water in the bottom of the fuel storage tanks.
• The recent introduction of diesel with a bio-diesel component significantly increased the water absorption and precipitation of the fuel.
• The weather conditions in previous months exacerbated the precipitation of water from the fuel and the promoted the microbial growth.
• The addition of treatment chemicals to the fuel caused the large active microbial colony to die, then to break-up and contaminate the fuel distribution system with colony debris.