单项选择题
A.blow B.clean C.scavenge D.purge
A shallow dish positioned at the normal water level is ...
单项选择题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
The（）enables water to be blow down or emptied from the ...
单项选择题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
The（） is fitted in pair one is the main valve, the othe...
单项选择题The（） is fitted in pair one is the main valve, the other the auxiliary or standby.
