Marine Diesel Engineering Exam for Small Vessel Second Engineer Certificate

What is the meaning of the diesel engine term 'overlap'?

Overlap refers to the period during which both the intake and exhaust valves are open at the same time, allowing a small amount of the fresh intake charge to escape back into the exhaust system.

What is the purpose of piston ring end clearance?

Piston ring end clearance is necessary to allow for thermal expansion of the rings during engine operation, preventing the rings from binding in the ring grooves.

Describe the procedure for manually testing the set points on a diesel engine lubricating oil low pressure alarm and shut down using a pressure calibrator.

To manually test the set points on a diesel engine lubricating oil low pressure alarm and shut down using a pressure calibrator, the procedure would involve:1. Isolating the oil pressure sensor from the engine's lubricating oil system.2. Connecting a pressure calibrator to the sensor.3. Incrementally decreasing the pressure while monitoring the alarm and shut down set points.4. Verifying that the alarm activates at the correct low pressure set point, and the engine shuts down at the appropriate lower pressure set point.

Sketch and describe a typical distillate fuel supply system for a diesel engine, including all the safety devices.

A typical distillate fuel supply system for a diesel engine would include the following components and safety devices:1. Fuel tank2. Fuel filters3. Fuel pump4. Fuel lines5. Fuel injectors6. Fuel pressure regulator7. Fuel return line8. Fuel level sensor9. Fuel leakage detection system10. Fuel shut-off valveThe safety devices in this system, such as the fuel level sensor, leakage detection system, and shut-off valve, help prevent fuel spills and ensure the safe operation of the diesel engine. Signup and view all the answers

What are three desirable properties of piston rings?

Three desirable properties of piston rings are:1. Good sealing ability to prevent leakage of combustion gases past the piston2. Resistance to wear and heat3. Flexibility to allow for thermal expansion and maintain a tight fit in the ring grooves. Signup and view all the answers

What are the common materials used for piston rings?

The common materials used for piston rings include:1. Cast iron2. Steel3. Chromium-plated steel4. Molybdenum-coated steel5. Composite materials (e.g., carbon-fiber reinforced polymers) Signup and view all the answers

Sketch three different types of piston ring ends.

The three common types of piston ring ends are:1. Butt joint: The ring ends meet in a straight, square joint.2. Stepped joint: The ring ends have a stepped profile, with one end overlapping the other.3. Lapped joint: The ring ends overlap each other, forming a tapered joint. Signup and view all the answers

What is the meaning of cetane number?

It is a measure of the ignition quality of diesel fuel. Signup and view all the answers

Define calorific value.

It is the amount of heat produced by the complete combustion of a specific quantity of fuel. Signup and view all the answers

Explain density.

Density refers to the mass of a substance per unit volume. Signup and view all the answers

What does viscosity mean?

Viscosity is the measure of a fluid's resistance to flow. Signup and view all the answers

Describe a coalescer type distillate fuel oil filter.

A coalescer filter is designed to combine small droplets of water into larger ones for easier removal. Signup and view all the answers

How is large medium speed diesel engine lubricating oil maintained in optimal condition?

By regular monitoring, testing, and changing of the oil as needed. Signup and view all the answers

How can leaking cylinder air start valves be detected while the engine is running?

By observing abnormal air consumption or performance issues during engine start. Signup and view all the answers

What is the procedure when leaking cylinder air start valves are discovered?

The faulty valve should be isolated and replaced during scheduled maintenance. Signup and view all the answers

List four possible causes of leaking cylinder air start valves.

Possible causes include wear, corrosion, improper sealing, and inadequate maintenance. Signup and view all the answers

What precautions should be taken before removing a diesel engine cylinder head?

Ensure the engine is cool, drain coolant, disconnect batteries, and wear appropriate safety gear. Signup and view all the answers

Explain the purpose of the magnetic filter in the lubricating oil system of reduction gearing.

The magnetic filter helps to remove ferrous particles from the oil, preventing damage to components. Signup and view all the answers

Why is the surface finish of gear teeth important in reduction gearing?

A smooth surface finish reduces friction, wear, and noise while increasing efficiency. Signup and view all the answers

State why a flexible coupling is fitted between the engine and gearbox in reduction gearing.

A flexible coupling accommodates misalignment and reduces vibration transmission between the engine and gearbox. Signup and view all the answers