單項選擇題Properties of a good refrigeration oil include（）

A.low wax content
B.high pour point
C.high viscosity
D.all of the above


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1.單項選擇題Proper filtering and straining of diesel fuel is important because the（）

A.fuel oil pump will over-speed if dirt is not removed
B.fuel oil transfer pumps cannot tolerate small amounts of grit in the oil
C.fuel injectors may be damaged by foreign particles in the fuel oil dirty
D.fuel will clog the intake air filter

2.單項選擇題Which factor determines the ring dam size for a fuel oil, tubular bowl type, centrifugal purifier?（）

A.The viscosity off the fuel
B.The quantity of water to be removed from the fuel
C.The specific gravity of the fuel
D.The quantity of dirt to be removed from the fuel

3.單項選擇題If the bowl of a disk type centrifugal purifier when operated as a separator is not primed, the（）

A.oil has a tendency to emulsify in the bowl
B.purifier will act as a clarifier at the discharge ring
C.oil will be lost through the water discharge ports
D.oil solids will be deposited only at the intermediate top disk

4.單項選擇題A centrifugal fuel oil purifier should be shut down if （）

A.more sealing water is needed
B.the cover clamp needs tightening
C.the purifier has a bad vibration when started
D.water is discharged from the overflow line

5.單項選擇題If fuel oil were being discharged from the waster outlet of a fuel oil disk type centrifuge, operated as separator, you should（）

A.remove the discharge ring
B.re-prime the purifier
C.the centrifuge to its proper speed
D.install an additional discharge ring