單項選擇題Black areas on the sealing surfaces of piston rings indicate（）

A.lube oil pumping
B.rotating rings
C.gas pressure behind the ring
D.passage of hot gases


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1.單項選擇題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

2.單項選擇題Visual inspection of chrome-plated piston compression rings reveals a black ring face at the position of the cylinder liner portsThis condition indicates a ring which（）

A.has a crown-face
B.exceeds wear limits through normal wear
C.has excessive blow-by
D.is in good condition

3.單項選擇題A bright shiny appearance of the sealing surfaces on diesel engine compression rings indicates（）

A.combustion gas blow-by
B.excessive lubrication
C.properly functioning rings
D.insufficient cylinder cooling

4.單項選擇題Following the failure of one turbocharger on a large, crosshead, main propulsion diesel engine, fitted with multiple turbochargers, which of the following actions should be taken prior to further operation of the engine? （）

A.Blank off the exhaust gas inlet to the damaged turbocharger
B.Secure cooling and lubrication to the damaged turbocharger
C.Lock the rotor of the damaged turbocharger
D.All of the above

5.單項選擇題Which of the following conditions may contribute to the formation of deposits on the blades of the turbocharger turbine?（）

A.Poor combustion
B.High cylinder oil consumption
C.Leaking exhaust valves
D.All of the above