單項(xiàng)選擇題A shallow dish positioned at the normal water level is connected to the（）This enables the blowing down or removal of scum and impurities from the water surface.

A.main stern stop valve
B.auxiliary steam stop valve
C.scum valve
D.blow down valve


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1.單項(xiàng)選擇題The（）enables water to be blow down or emptied from the boilerIt may be used when partially or completely emptying the boiler.

A.main stem stop valve
B.auxiliary steam stop valve
C.feed check or control valve
D.blow down valve

2.單項(xiàng)選擇題The（） is fitted in pair one is the main valve, the other the auxiliary or standby.

A.main stem stop valve
B.auxiliary steam stop valve
C.feed check or control valve
D.blow down valve

3.單項(xiàng)選擇題The（） is a smaller valve fitted in the auxiliary steam supply line, and is usually of the non-return type.

A.main stem stop valve
B.auxiliary steam stop valve
C.feed check or control valve
D.blow down valve

4.單項(xiàng)選擇題The（）is fitted in the main steam supply line and is usually of the non-return type.

A.main steam stop valve
B.auxiliary steam stop valve
C.feed check or control valve
D.blow down valve

5.單項(xiàng)選擇題The lifting pressure of （） is set in the presence of a Surveyor it is locked and cannot be changed.

A.fuel valves of main engine
B.injector pump of main engine
C.safety valves of marine boiler
D.safety valves of a reciprocating pump