单项选择题

Mechanical lubricators for diesel engine cylinders are usually small reciprocating pumps which are （）.

A.operated manually once an hour
B.operated until the engine has started
C.placed into operation only at maximum load
D.adjustable to meet lubrication requirements

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单项选择题

Bottom blow valves are installed on auxiliary water-tube boilers to （）

A.remove suspended and precipitated solids from the boiler water
B.completely drain the boiler in an emergency situation
C.prevent hardened scale deposits in the water drum
D.remove floating impurities from the oily water surface

单项选择题

A three-way thermostatic control valve regulates the diesel engine cooling water temperature by passing a portion of the water （）.

A.around the engine
B.around the cooler
C.to the expansion tank
D.overboard

单项选择题

The concentration of total dissolved solids in the water of an auxiliary boiler can increase as a result of （）.

A.seawater contamination
B.frequent surface blows
C.dissolved oxygen deaeration
D.frequent bottom blows