单项选择题
A.backwards B.forwards C.upward D.downwards
When installed for bilge pumping or ballast duty, centr...
单项选择题When installed for bilge pumping or ballast duty, centrifugal pumps require a （） to remove air from the suction pipe.
A.air chamber B.head lank C.primer D.prime mover
Water enters the rotating impeller through the entry, k...
单项选择题Water enters the rotating impeller through the entry, known as “（）”, at the centre.
A.eye B.hole C.balance holes D.opening
Which one is not the normal operation for boiler shutdo...
单项选择题Which one is not the normal operation for boiler shutdown?（）
A.Carry out soot blowing if permissible B.Change fuel supply to diesel oil C.Close steam stop valves on boiler when pressure is reduced D.Drain boiler empty when it has cooled down
