Diesel Engines

Question 1

State the three speed ranges of a marine diesel engine.

Answer 1

Low speed(0-200RPM), Medium speed(201-1000RPM), High speed(1000+ RPM)

Question 2

What is turbo charging?

Answer 2

When an exhaust gas driven turbine to pressurise air flow into the engine cylinders.

Question 3

What is the purpose of lubricating oil in the main engine.

Answer 3

To minimize the amount of friction between moving components.

Question 4

What is the purpose of piston rings?

Answer 4

Sealing the combustion chamber so that there is minimal loss of gases to the crank case.

Question 5

Describe symptoms that would indicate a scavenge fire

Answer 5

hot combustion gases and sparks which by-passed the piston rings into the scavenge space.

Question 6

How would a Scavenge fire like this be extinguished?

Answer 6

Reduce engine power, cut fuel supply to indicated cylinder, increase oil lubrication, prime C02 system, wait 15-20 minutes.

Question 7

What is the flash point of oil?

Answer 7

between 200-280 Degrees C

Question 8

What is a stuffing box and its function ?

Answer 8

Separates the Scavenge space from the crank case.

Question 9

What is the minimum number of air stars on a 2 and 4 stroke engine?

Answer 9

2 Stroke - 12
4 Stroke - 6

Question 10

Fill in the blank
When the engine is running, the lube oil ——— supplies oil to the main
bearings, ——- end bearings piston, camshaft and in the case of 4 stroke
engines, splash lubrication is taking place to the cylinder liners, gudgeon
pin etc.

Answer 10

System, Bottom

Question 11

Fill in the blank
Two stroke engines have separate cylinder lubrication. The main lube oil
system supplies lubrication to the ——head bearings and main ——

Answer 11

Crankcase, Bearings

Question 12

Fill in the blank ( HT & LT)
—— Fresh water to cool the cylinder heads and turbochargers

Answer 12

Filtered

Question 13

What are the two methods of slow speed propulsion in two stroke engines?

Answer 13

fixed gear and CPP

Question 14

what problems are faced when using seawater for cooling.

Answer 14

there can be a buildup of weed and or silt which can build up in the strainers and filters.

Question 15

Give 4 reasons why we need to use purifier for heavy fuel oil. or why dose
the fuel purification is needed ?

Answer 15

It separates light liquid fuel form solids and sediments.

Question 16

List 4 safety features of air starting system and explain each of the items.

Answer 16

• Flame Trap
• Spring loaded safety valve or bursting disc
• Staring airline drain valve
• Turning gear interlock (pip-pin)

Question 17

Describe the two water cooling circuits are used in an auxiliary diesel
engine

Answer 17

The propulsion system is cooled by 2 centrifugal pumps maintaining 4 bar.
Main engine is cooled by fresh water generated from the boiler.

Question 18

What are the step (Before, during and after) you will follow for carrying
out the inspection of the scavenge space on a large two stroke diesel
engine

Answer 18

Check condition of cylinder liner wall through scavenge ports using mirror.
Slowly bring the piston up from BDC.
Inspect piston top land and piston skirt.
When piston rings are visible through scavenge ports, move piston up and down several times to ensure that rings are freely moving in the piston grooves.

Question 19

What pressure does the air start require?

Answer 19

20-30 Bar

Question 20

The downcomer pipes in a water tube boiler are situated between the:

Answer 20

Steam and water drums inside the furnace.

Question 21

A water tube boiler requires soot-blowing to be carried out:

Answer 21

On a regular and frequent basis.

Question 22

In a direct drive slow-speed marine diesel engine, how is the propulsion changed from ahead to astern?

Answer 22

By reversing the engines direction of rotation.

Question 23

Which type of marine engines do scavenge fires occur?

Answer 23

Low speed, large bore 2 stroke diesel engines.

Question 24

In a steam system water tube boiler, the feed pump…

Answer 24

Pumps the boiler feed water before it enters the steam drum.

Question 25

What is the temperature for both HFO and DMO

Answer 25

HFO - 130’C
MDO - 25’C

Question 26

what is the 1-7 of 2 stroke combustion

Answer 26

1-2 Completion of scavenge
2-3 Post scavenge
3-4 Compression
4-6 Fuel injection
6-7 Expansion
7-8 Exhaust blow-down
8-1 Scavenge