202351 - Un-inspected engine mods are a risk

31 Oct 2023 MARS

While departing port, a RoRo vessel suffered a fire in the auxiliary engine room. The fire was contained and subsequently extinguished without injury to the crew, but the equipment in the auxiliary engine room suffered serious damage.

As edited from MAIB (UK) SB1/2023

The fire originated below the outboard turbocharger when a small-bore flexible fuel hose failed, spraying marine gasoil (MGO) onto a high temperature surface, where it ignited.

The auxiliary engines had been modified many years earlier, when low pressure fuel alarm pressure switches and gauges were installed using flexible fuel hoses. This was contrary to MSC/Circ.647 – Guidelines to Minimize Leakages from Flammable Liquid Systems, which states that flexible hose assemblies should only be used where necessary to accommodate relative movement between fixed piping and machinery parts. In this case, flexible hose assemblies were not needed for this purpose. Furthermore, the hoses were routed under the turbochargers covered by the insulation pads, exposing them to the risk of contact with high temperatures and making them difficult to inspect.

The investigation also established that the initial proposal to modify the system was not submitted to the classification society for approval and the installation was not surveyed on completion.

Lessons learned

  • The risks associated with modification to safety critical equipment should be considered before and during the work being completed.