单项选择题
（） are mounted in pairs to protect the boiler against overpressure.
A.Safety valves
B.Water tubes
C.Steam stop valves
D.Blow down valves
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相关考题
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单项选择题
In a （） boiler the hot gases from the furnace pass through the tubes while the water is on the outside.
A.water-tube
B.fire-tube
C.exhaust gas
D.None of the above is true -
单项选择题
In a （） boiler the water flows through the inside of the tubes while the hot gases pass around the outside.
A.water-tube
B.fire-tube
C.exhaust gas
D.none of the above -
单项选择题
The tube in a boiler should be blinded if found （）.
A.scaled
B.informed
C.leaky
D.deformed
