In its latest Safety Digest, UK MAIB provides lessons learned from an incident where a trawler’s clogged engine fuel filters, resulted in seriously damaging the engine fuel system and causing contamination within the fuel tank.
The incident
A 15m beam trawler suffered engine failure while fishing and had to be towed back to port by a Royal National Lifeboat Institution (RNLI) lifeboat. Nobody on board was injured and there was no external damage to the vessel.
A service engineer’s investigation found that the engine failure was caused by clogged engine fuel filters, serious damage to the engine fuel system and contamination within the fuel tank, which resulted in extensive engine repairs and complete fuel system cleaning.
The trawler’s fuel supplier had recently started to provide fuel containing Fatty Acid Methyl Ester (FAME), commonly known as biodiesel. DfT’s Renewable Transport Fuel Obligation required that certain non-road mobile machinery vehicles burned FAME fuels; this regulation applied to some inland waterway vessels, but not to seagoing vessels. However, some suppliers mistakenly believed it was mandatory to supply seagoing vessels such as pleasure yachts and fishing boats with a marine gas oil fuel that contained up to 7% FAME.
FAME-based marine fuels present certain challenges to safe engine operation:
- FAME is hygroscopic so tends to attract the moisture often found in marine environments;
- FAME and the associated water provide an ideal culture for microbial biological contamination, more commonly known as diesel bug
- Diesel bug can cause expensive fuel system problems, resulting in blocked filters, damaged fuel pumps and injectors, a contaminated fuel tank and, ultimately, engine failure. Modern common fuel rail engines may be especially sensitive to this problem due to high operating fuel pressures and temperatures and large fuel return flow back to tank;
- FAME can be corrosive to rubber and copper and lead to fuel system damage such as leaking seals;
- FAME fuels tend to oxidize quickly and should not be stored for long periods.
Lessons learned
#1 Communicate: Suppliers should inform their customers that their fuel contains FAME
#2 Maintain: Fuel suppliers who choose to supply FAME to seagoing vessels should make sure moisture does not accumulate in their shore tanks and that the fuel is regularly tested for bugs.
#3 Check: Vessel owners should check FAME fuel compatibility with the engine manufacturer.
#4 Procedure: Vessels choosing to burn FAME fuel may require additional fuel filtration.
#5 Action → FAME suppliers and users should use fuel stocks quickly to reduce the risk of oxidization.
