Testing of Electrical Switch and Pneumatic Valve Quiz

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What triggers an alarm in the atmosphere according to the text?

Vapourised oil condensing and forming white mist

What does the oil mist detector do in terms of levels of white mist?

Triggers an alarm when mist levels are below those of an actual explosive condition

What is the purpose of a crankcase relief valve in the event of a crankcase explosion?

To deal with pressure wave and flames

What are the elements resulting from an initial crankcase explosion?

Pressure wave and flames Signup and view all the answers

What material is the valve disc of a crankcase relief valve typically made of?

Aluminium alloy Signup and view all the answers

What is the purpose of the large diameter spring in a crankcase relief valve?

To provide sensitivity and allow the valve to float Signup and view all the answers

What is the function of the external deflector in the construction of a crankcase relief valve?

To redirect external elements away from the valve Signup and view all the answers

What is the purpose of fitting a test weight to an overspeed device?

To make it trip at a lower speed Signup and view all the answers

How do many diesel engines utilize compressed air in starting the engine?

By using compressed air to operate air start valves direct into individual cylinders Signup and view all the answers

What advantage do air start valves direct into individual cylinders provide in starting diesel engines?

Delivers timed air into cylinders to sequentially turn the engine over Signup and view all the answers

What is the risk associated with air start valve systems if key equipment fails?

Potential for explosions Signup and view all the answers

Why is it preferable to trip an overspeed device at a lower speed?

To avoid running a large engine in overspeed conditions Signup and view all the answers

Explain how an overspeed trip of the centrifugal type operates.

It trips at a lower speed when fitted with a test weight Signup and view all the answers

What is the common use of compressed air in starting diesel engines?

To start the engine Signup and view all the answers

State TWO methods of detecting a potential crankcase explosion.

Oil mist detector, relief valves Signup and view all the answers

When the engine crankcase oil mist detector activates, what actions must be taken by the on-watch engineer?

Immediately stop the engine and investigate the cause. Signup and view all the answers

Sketch a crankcase explosion relief door and label the MAIN components.

The main components are: Door, Hinge, Latch, Relief Valve Signup and view all the answers

Explain why crankcases may have relief valves fitted.

To release excess pressure in case of an explosion. Signup and view all the answers

Outline the circumstances which may cause the relief valves to operate.

Excessive pressure buildup inside the crankcase. Signup and view all the answers

What does the 'Gain' represent in governors?

How much the governor will react for a change in the engine speed Signup and view all the answers

State a safety detection system that may be fitted in diesel engine crankcases.

Oil mist detector Signup and view all the answers

State the implications of a much higher value on the engine crankcase pressure gauge and the immediate actions to be taken.

High pressure indicates a potential issue. Immediately stop the engine and investigate the cause. Signup and view all the answers

How do electronic governors differ from mechanical governors?

Electronic governors provide a finer degree of control and can be interlinked with specific load profiles. Signup and view all the answers

Outline the checks and investigations to ascertain the cause of increased crankcase pressure.

Check oil levels, inspect for leaks, examine relief valves, assess engine performance. Signup and view all the answers

What is the role of the comparator in an electronic governor system?

The comparator uses 2 signals to determine the final output speed to the control unit by comparing the actual speed with the desired speed. Signup and view all the answers

What are some of the sensors used in an electronic governor system?

Speed sensors, emergency stop sensors, overspeed sensors, engine flywheel sensors, low lubricating oil sensors, high temperature sensors. Signup and view all the answers

How does the electronic governor system control the speed of the engine?

By issuing a signal to the actuator based on power and speed sensing, as well as digital speed sensing. Signup and view all the answers

How does the speed sensing unit of the hydraulic governor respond to an increase in engine speed?

The two weights on the sensing unit move outwards due to centrifugal force. Signup and view all the answers

What happens to the pilot valve when the speed sensing unit moves the weights outwards?

The pilot valve moves up and drains oil from the servo cylinder. Signup and view all the answers

How does the downwards movement of the servo piston affect the fuel supplied to the engine?

The downwards movement reduces the fuel supplied to the engine by adjusting the fuel rack. Signup and view all the answers

What role does the feedback link play in controlling the engine speed?

The feedback link moves down and increases the tension of the speeder spring. Signup and view all the answers

How does the pilot valve react to the movement of the weights back inwards?

The pilot valve moves down, allowing oil to lift the servo piston, thus increasing fuel and engine speed. Signup and view all the answers

What is the aim of the hydraulic governor in response to load changes affecting speed?

The aim is to ensure that any load change affecting speed can be met by the governor. Signup and view all the answers

What is another term used to describe 'amplification' in the context of the hydraulic governor?

Gain. Signup and view all the answers