單項選擇題Fins are installed on the generating tube surfaces in waste heat boilers to （）.

A.prevent soot fires in the exhaust system
B.prevent exhaust gas erosion of the tubes
C.increase the velocity of exhaust gas flow
D.increase the rate of heat transfer


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1.單項選擇題On a medium-speed main propulsion diesel engine, the crank-pin or crank journal bearings receive lubricating oil from （）.

A.a spindle lubricator
B.an oil jet
C.internal splashing
D.drilled passages in the crankshaft

2.單項選擇題The rate of cylinder lubricating oil metered to each cylinder of a large low-speed main propulsion diesel engine is （）

A.the same, whether at sea, or during maneuvering
B.adjusted during each hour of operation while at constant RPM
C.higher at sea than while maneuvering
D.lower at sea than while maneuvering

3.單項選擇題The crankcases of many diesel engines are kept under a slight vacuum to （）

A.improve fuel economy
B.increase the air charge velocity
C.reduce the risk of explosion
D.all of the above

4.單項選擇題Which of the following conditions could cause the feed pump for an auxiliary boiler to lose suction?（）

A.Increased suction head pressure
B.Decreased feedwater temperature
C.Pump recirculating line being open too much
D.Excessive feedwater temperature

5.單項選擇題In readying an auxiliary water-tube boiler for a routine hydrostatic test, which of the following procedures should be undertaken prior to filling the boiler with fresh water?（）

A.The safety valve escape piping should be disconnected from the valve body and a blank inserted
B.The boiler vent valves should be opened
C.All handhole/manhole covers should be tightened up as much as possible to preclude any leaks
D.All of the above