轮机英语单项选择题每日一练(2019.07.26)

单项选择题
The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains （）.
A.a magnetic operating coil
B.normally open line contacts
C.thermal-overload protection
D.a momentary-contact start button
单项选择题
The size of the discharge ring used for the efficient operation of a disk type purifier is dependent upon the（）
A.rated capacity of that purifier
B.viscosity of the oil being purified
C.maximum design speed of that purifier
D.specific gravity of the oil being purified
单项选择题
In order to release CO2 to the machinery spaces from a fixed fire extinguishing system, you must（）.
A.actuate an alarm and open the engine room control valve
B.actuate an alarm and open the engine room CO₂releasing valve
C.open the engine room control valve and shut off engine room ventilation fans
D.open the engine room control valve and then the CO₂releasing valve
单项选择题
A pressure drop in the liquid line of a refrigeration system may cause（）
A.the solenoid valve to seize
B.the compressor to hunt
C.flash gas to form in the liquid line
D.the expansion valve to freeze open
单项选择题
The lowest temperature at which the vapor formed from a liquid ignites and continues to burn steadily in the presence of an ignition source is called the（）.
A.flash point
B.fire point
C.upper explosive limit
D.lower explosive limit