Question 187Steam Plants - Assistant Engineer

The correct answer is C) Relieve all fuel oil service pressure to that boiler. After securing the fires in one boiler of a two-boiler ship, the immediate action that should be taken is to relieve all fuel oil service pressure to that boiler. This is to prevent any potential ignition or explosion due to the presence of fuel oil in the boiler. Maintaining service pressure could lead to a dangerous situation, so it is crucial to relieve the pressure as the first step. The other options are not the correct immediate actions. Opening air registers or draining/refilling the boiler with cold water would not address the critical issue of fuel oil pressure, and securing the main feed pump would not directly address the boiler fire situation.