The humidifier’s valve of air-condition should be （）, when the temperature is lower than 0℃.

A . below B . in C . of D . under

A . remove any air that may accumulate in the system B . take out unpleasant fumes from the refrigerant C . vent off excess refrigerant in an emergency D . permit opening the refrigerating system for cleaning and inspecting

A . The profile of the valve is like a globe B . The valve seat is set into the bulbous body C . The plug or disc of the valve is made vertical to the axis of the pipe D . The valve seat is located at right side of the plug or disc

A . increase the capacity of the coil B . increase the superheat at the bulb C . deliver more refrigerant to the coil D . decrease the capacity of the coil

A . Holding the valve open for a long period B . Increasing the starting air pressure used C . Opening the stating air valve quickly D . Reducing the starting air valve size

A . Lube oil passing through the system B . Moisture or foreign matter collecting at the valve seat and orifice C . Variable spring tension caused by the changing temperature D . Frost on the liquid line

A . Special tools are required for lapping or grinding B . It is impossible to throttle flow with a butterfly valve C . To close the valve, it is only necessary to turn the handle a quarter of a turn D . The butterfly valve should never be used in a freshwater system

A . Pressure-reducing valve B . Unloading valve C . Counterbalance valve D . Pressure-relief valve

A . cylinder exhaust valve B . air starting valve C . air inlet valve D . cylinder relief valve

A . bottom-blow valve B . skin valve C . feed-check valve D . feed-stop valve

A . be jammed B . be opened C . be seated D . be broke

A . the direct acting relief valve is used for controlling lower flows and pressure B . the pilot operated relief valve is used for controlling higher flows and pressure C . the pilot operated relief valve is used for controlling lower flows and pressure D . the controlling accuracy of direct acting relief valve is worse than that of the pilot operated relief valve

A . the inlet valve is open B . the exhaust valve is open C . both valves are close D . both valves are ope

A . Regulation of discharge pressure from cargo pumps B . Maintaining constant velocity in cargo lines C . Regulation of suction head on cargo pumps D . To maintain a tank or void at atmospheric pressure

A . the proper back pressure B . the cooling water temperature C . correct timing and proper seating D . accurate metering and the exhaust temperature

A . control the pressure of the oxygen as it enters the body B . allow the wearer to manually give himself oxygen C . release excess heat which would otherwise cause the bottle to explode D . allow exhaled gases to pass outside the bottle

A . decreased B . increased C . fixed D . closed

A . tightened up B . sealed up C . opened up D . unscrewed

A . the air start valve timing gears and rods B . a cylinder check valve C . individual cams and valve gear D . an air manifold poppet valve

A . relieve excess fuel oil pressure during the “off” fire cycle B . admit water to the dry pipe C . throttle the forced draft fan output for proper combustion D . reduce excess steam pressure in the boiler

A . proceeding B . overloading C . collision D . flooding

A . At the designed operating temperature, the liquid refrigerant charge has changed to a vapor B . The liquid refrigerant tends to collect at the bellows or diaphragm and reduces the valve sensitivity C . The sensing bulb is empty of liquid refrigerant charge at the designed operating temperature D . The sensing bulb is never emptied of liquid refrigerant under normal operating conditio

A.decreased B.increased C.fixed D.closed

A:正确; B:错误