Fire aboard vehicle carrier probably caused by insufficiently tightened pipe plug

The National Transportation Safety Board (NTSB) has released its report on the fire aboard vehicle carrier Alliance St. Louis (IMO 9285500) which occurred on January 16th 2017 while the vessel was travelling from Port Arthur, Texas, to Jacksonville, Florida.

A pipe plug on the fuel pump for the main engine’s no. 6 cylinder came loose, resulting in fuel spray onto the engine’s hot exhaust gas pipe manifold. The atomized fuel quickly ignited. The fire was contained to the main engine room and extinguished by the CO2 fixed fire-suppression system. No injuries were reported, but the property damage exceeded $3.75m.

The NTSB said that the pipe plug was probably insufficiently torqued into the top cover during the last inspection, because the crew did not recognize this as a crucial step in maintaining the reliability of the fuel oil system.

The instruction book’s section Overhaul of Top Cover Complete contributed to the crew’s lack of awareness about this hazardous situation because it did not depict the fuel oil return passages or describe the purpose of the pipe plugs, said the NTSB.

The engineers on board the Alliance St. Louis had never previously experienced a situation where a pipe plug vibrated out of a pump’s top cover. The aft pipe plug on the no 6 cylinder fuel pump top cover likely loosened over time due to normal main engine vibration, fuel oil pressure acting on the plug, and switching of fuels.

The missing pipe plug would have provided a path for MGO to spray out of the top cover at an approximate pressure of 7–8 bars (101–116 psi). Several engineering crewmembers stated in their interviews that they had experienced an increased number of fuel oil system leaks and seepages from gaskets, flanges, seals, o-rings, and other fittings due to thermal expansion or contraction of the components and material when changing from heated heavy fuel oil to ambient and sometimes cooled MGO.

During the post-accident inspection the spray shield on the no 6 cylinder’s top cover was found hanging off the air pipe next to the pump housing. NTSB said that it was probably knocked off the top cover by the pipe plug and spraying MGO because it was not properly secured with two screws.

A properly secured spray shield would have kept the MGO from spraying directly into the air and contacting the no 6 cylinder exhaust gas pipe/receiver.

2005-built, USA-flagged, 52,780 gt Alliance St. Louis is owned by Wilmington/Hoegh Autoliners care of manager Maersk Line Ltd-USA of Norfolk, Virginia. It is entered with Standard Club (UK & Americas Division) on behalf of Wilmington Trust Co. It is entered for hull & machinery with Norwegian Hull Club, with Gard having a subscription position (RDC 4/4), on behalf of Höegh Autoliners Management AS.

https://www.ntsb.gov/investigations/AccidentReports/Reports/MAB1808.pdf