[单项选择]One of the main functions of wearing rings, as used in a centrifugal pump, is to （）.
A. maintain radial alignment between the pump impeller and casing
B. absorb all impeller shaft end thrust
C. prevent water leakage to the atmosphere
D. prevent wear of the pump casing and/or impeller

[单项选择]The main function of piston compression rings is to （）
A. prevent excessive cylinder liner wear
B. reduce friction losses in the engine
C. seal the space between the piston and the liner
D. limit upward flow of lube oil into the combustion space

[单项选择]The main purpose of the piston oil scraper rings is to （）.
A. seal the space between the piston and the liner
B. reduce the amount of lube oil burned in the combustion chamber
C. transmit heat from the piston to the cylinder liner
D. damp out fluctuations of the piston side thrust

[单项选择]Among the rings of a piston the （） one is subjected to the greatest load and temperature.
A. bottom
B. middle
C. top
D. none of the above

[单项选择]He said that he had turned the main engine one complete revolution with the （）.
A. turning gear
B. steering gear
C. spur gear
D. chain gear

[单项选择]Your company has a main office and one branch office. The main office has a print server named Printer1.The branch office has a print server named Printer2. Printer1 manages 15 printers and Printer2 manages seven printers.You add Printer2 to the Print Management console on Printer1.You need to send an automatic notification when a printer is not available. What should you do？（）
A. Configure an e-mail notification for the Printers With Jobs printer filter.
B. Configure an e-mail notification for the Printers Not Ready printer filter.
C. Enable the Show informational notifications for local printers option on both print servers.
D. Enable the Show informational notifications for network printers option on both print servers.

[单项选择]One of the main differences between the various types of screw pumps is in the （）.
A. stuffing box diameter
B. direction of rotation of the screws
C. pitch of the screws
D. type of driving gears

[单项选择]One of the main purposes of refractories in a boiler furnace is to（）
A. help preheat the air for the furnaces
B. help preheat the feedwater
C. protect economizer from excessive heat
D. prevent excessive furnace heat losses

[单项选择]Fuel oil is thought to be one of the main factors （） the operation and maintenance of an engine.
A. have nothing to do with
B. having nothing to do with
C. have much to do with
D. having much to do with

[单项选择]One of the advantages in the use of a dry liner over a wet liner is（）
A. it is fitted with neoprene O-ring seals
B. the honing process makes it easier to maintain the desired oil film
C. there is likelihood of water leaking into the combustion space
D. it fits more loosely due to a decrease in heat transfer through the composite wall

[单项选择]The（） is fitted in pair one is the main valve, the other the auxiliary or standby.
A. main stem stop valve
B. auxiliary steam stop valve
C. feed check or control valve
D. blow down valve

[单项选择]Broken piston rings manifest themselves during the scavenge port inspection by（）
A. Lack of elastic tension, when the rings are pressed into the groove by means of a stick
B. Blackish appearance
C. Fractured rings and missing rings
D. all off the above

[单项选择]The piston rings are manufactured with a diameter （） the bore of the cylinder.
A. larger than
B. smaller than
C. equal to
D. none of the above

[单项选择]When inspecting piston rings through the ports of a two-stroke/cycle diesel engine, black areas on the sealing surfaces are the result of （）
A. insufficient lubrication
B. improper piston cooling
C. blow-by
D. overload operation

[单项选择]Improperly fitted piston rings in a diesel engine can cause（）
A. excessive lube oil consumption
B. lower than normal lube oil temperature
C. higher than normal exhaust back pressure
D. excessive crankshaft end play

[单项选择]The function of the piston compression rings used in a diesel engine is to （）
A. seal the space between the piston and liner
B. transmit heat from the piston to the cylinder liner
C. reduce the amount of combustion gas blow-by
D. all of the above

[单项选择]If the compression rings on a diesel engine piston become stuck in the ring groove, the cause may be due to（）
A. excessive ring action
B. excessive ring temperature
C. improper ring rotation
D. excessive ring face wear

[单项选择]All the rings are slightly rounded on their external top and bottom edges to keep the oil film on the cylinder liner during （） for new piston rings.
A. the running-in period
B. the running process
C. gas exchange process
D. the boiler firing

[单项选择]Top piston rings are plasma coatedIt gives added safety for the of new lines（）
A. running-in
B. running-out
C. running on
D. running down