This panel containing main engine cooling water pump supply fuses was periodically opened for visual inspection as part of planned maintenance but there were no visible signs of overheating, in fact, from the front all the fuses looked like new. However, as shown below, it was actually very close to failure.
Installed during a major refit, these cooling water pump starters were mounted on a steel frame that shook violently when the vessel was underway. This had led to a high resistance interface developing at the fuse clip which resulted in the clip springs annealing with associated loss of tension. The fault was spotted during the first thermal imaging inspection to be conducted on this vessel.
As she was a diesel-electric vessel and all electrical power at sea was derived from the main engines a failure on passage would have most likely led to a loss of propulsion and all electrical power.
100A HRC fuse supplying main engine HT cooling water pump.