Question 551Steam Plants - Assistant Engineer

The correct answer is B) maintain oil supply for several minutes to bearings should the lube oil service pump fail. The gravity tank in a gravity lube oil system serves to provide a temporary supply of lube oil to the bearings in the event that the main lube oil service pump fails. This ensures that the bearings continue to receive lubrication for a limited time, preventing damage until the main pump can be restored or an auxiliary pump can be engaged. The other options are incorrect because: A) the purifier, not the gravity tank, is responsible for settling the lube oil; C) the gravity tank does not store heated oil; and D) the gravity tank's purpose is to provide a positive suction head, not to supply the service pump directly.