Marine Auxillary 2007 Objective Paper

Q- It is a known fact that centrifugal pumps require priming for pumping liquids , as they cannot handle air and will lose suction due to air entry . But on the other hand T/Cs use centrifugal compressors for supercharging . Which of the following do you think makes a centrifugal compressors to pump air and behave differently than the centrifugal pumps?

A.Presence of air cooler

B.Presence of Labyrinth seal

C.High speed of rotation , very fine internal clearences and large impeller diameters

D.Difference in principle of operation


Q- Modern marine turbochargers use a ___________ type of compressor

A.Radial flow

B.Axial flow

C.Mixed flow

D.Turbulent flow


Q- What do you mean by surge limit of a turbocharger?

A. Characteristic curve of a turbocharger

B. Portion of compressor characteristic curve which lies on the left side of the point of maximum pressure

C. A line joining all the points of maximum pressure on compressor characteristic curves , drawn at various speeds of operation

D. Maximum rpm limit of T/C above which surging will start


Q- With full load on the main engine, the RPM for the turbocharger is too low. What may cause this?

A The diffuser ring is damaged.

B Exhaust temperatures on the main engine are too high.

C Dirty nozzle ring.

D The lubricating oil pump is malfunctioning.

Answer-Not Sure

Q- A partial opening of which of the following kinds of valves can lead to wire -drawing of its seat?

A.Globe Valve

B.Butterfly valve

C.Gate Valve

D.Full bore angle valve


Q- Scale formation in a fresh water generator evaporator can lead to ____________________

A.Impaired heat transfer

B.Reduced capacity

C.Increased shell temperature

D.All of the above


Prepare for MMD Class 4 Objective