MDE Unit 6 crank case Quiz

MDE 6 Q1

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Circumstances Causing Relief Valves to Operate in Diesel Engine Crankcases

Question: Under what circumstances might relief valves in a diesel engine crankcase operate?

B) When there is excessive blow-by gas pressure or high crankcase pressure

D) During routine engine maintenance and servicing

A) During normal engine startup and shutdown

C) When the engine oil temperature is within the normal operating range

Answer: B) When there is excessive blow-by gas pressure or high crankcase pressure
Explanation: Relief valves in diesel engine crankcases operate when there is excessive blow-by gas pressure or high crankcase pressure. These conditions can occur due to high engine load, worn piston rings, or inadequate ventilation, and the relief valves help to prevent damage by releasing excess pressure.

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Purpose of Relief Valves in Diesel Engine Crankcases

Question: Why are relief valves fitted to diesel engine crankcases?

C) To prevent excessive pressure buildup and avoid crankcase damage

A) To regulate the temperature of the engine oil

B) To control the pressure of the engine coolant

D) To filter out impurities from the engine air

Answer: C) To prevent excessive pressure buildup and avoid crankcase damage
Explanation: Relief valves are fitted to diesel engine crankcases to prevent excessive pressure buildup. This pressure can result from blow-by gases and can lead to crankcase damage or oil leaks. The relief valve helps maintain proper pressure levels within the crankcase, ensuring safe and efficient engine operation.

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Safety Detection System in Diesel Engine Crankcases

Question: What is a common safety detection system that may be fitted to diesel engine crankcases?

C) Crankcase pressure sensor

D) Turbocharger speed monitor

B) Exhaust gas temperature gauge

A) Oil temperature sensor

Answer: C) Crankcase pressure sensor
Explanation: A crankcase pressure sensor is a common safety detection system fitted to diesel engine crankcases. It monitors the pressure within the crankcase and provides alerts if the pressure exceeds safe levels, helping to prevent potential damage or failure.

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MDE 6 Q2

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Actions After Crankcase Oil Mist Detector Activation

Question: What actions should the on-watch engineer take when the engine crankcase oil mist detector activates?

C) Check the fuel level and adjust as necessary

A) Increase engine speed to reduce pressure

D) Perform a routine check of the engine’s air intake system

B) Shut down the engine immediately and investigate the cause

Answer: B) Shut down the engine immediately and investigate the cause
Explanation: When the crankcase oil mist detector activates, it indicates a potential problem such as excessive oil mist or pressure in the crankcase. The on-watch engineer should shut down the engine immediately to prevent further damage and investigate the cause of the activation to address any underlying issues.

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Further Actions After Crankcase Oil Mist Detector Activation

Question: After shutting down the engine due to activation of the crankcase oil mist detector, what additional actions should the on-watch engineer take?

C) Clean the engine’s fuel injectors and replace the air filter

A) Immediately restart the engine to clear the fault

D) Monitor the engine oil level and top it up if necessary

B) Check for signs of oil leaks and inspect the crankcase ventilation system

Answer: B) Check for signs of oil leaks and inspect the crankcase ventilation system
Explanation: After shutting down the engine, the on-watch engineer should check for signs of oil leaks and inspect the crankcase ventilation system. These steps help to identify and address any issues that may have caused the oil mist detector to activate, ensuring that the engine is safe to restart and operate.

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Crankcase Explosion Relief Door Components

Question: Which of the following lists the MAIN components of a crankcase explosion relief door?

C) Relief door, blast shield, hinge mechanism, and latch

D) Relief door, control lever, inspection window, and sealing ring

A) Relief door, pressure spring, locking pin, and gasket

B) Relief door, pressure sensor, actuator, and safety valve

Answer: A) Relief door, pressure spring, locking pin, and gasket
Explanation: The main components of a crankcase explosion relief door typically include the relief door itself, a pressure spring that helps the door open under excess pressure, a locking pin to hold the door in place, and a gasket to ensure a proper seal when the door is closed. These components work together to allow for controlled release of pressure in the event of an explosion, helping to protect the engine and surrounding areas.

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High Crankcase Pressure Implications and Actions

Question: If the daily engine log shows that the engine crankcase pressure gauge is indicating a much higher value than the normal reading, what are the implications and immediate actions that should be taken?

A) The engine may be operating normally; no immediate action is required. Continue to monitor.

D) The increased pressure is usually due to low oil levels; top up the engine oil and restart the engine.

C) High crankcase pressure typically results from a faulty fuel pump; replace the fuel pump immediately.

B) High crankcase pressure may indicate potential issues such as excessive blow-by or ventilation problems; immediately shut down the engine and inspect the crankcase ventilation system and seals.

Answer: B) High crankcase pressure may indicate potential issues such as excessive blow-by or ventilation problems; immediately shut down the engine and inspect the crankcase ventilation system and seals.
Explanation: A significantly higher crankcase pressure reading suggests potential problems such as excessive blow-by gases or issues with the crankcase ventilation system. Immediate action should include shutting down the engine and inspecting the ventilation system and seals to prevent further damage and ensure safe operation.

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MDE 6 Q3

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Question 4: What tool should be used to check for excessive blow-by gases that might be contributing to high crankcase pressure?

B) Cylinder compression tester

C) Oil temperature sensor

A) Digital pressure gauge

D) Exhaust gas analyzer

Answer: B) Cylinder compression tester
Explanation: A cylinder compression tester helps measure the compression in the cylinders, which can indicate excessive blow-by gases if compression is low, contributing to high crankcase pressure.

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Checks and Investigations for Increased Crankcase Pressure

Question 1: What is the first step an engineer should take when investigating increased crankcase pressure?

D) Verify the engine’s coolant level

A) Inspect the fuel system for leaks

C) Replace the engine oil filter

B) Check the crankcase ventilation system for blockages or malfunctions

Answer: B) Check the crankcase ventilation system for blockages or malfunctions
Explanation: The first step is to check the crankcase ventilation system as blockages or malfunctions can lead to increased crankcase pressure. Proper ventilation is crucial for maintaining normal pressure levels.

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Question 5: What is a potential consequence of not addressing high crankcase pressure promptly?

C) Risk of engine damage and potential failure

D) Reduced engine noise

A) Improved engine efficiency

B) Enhanced fuel economy

Answer: C) Risk of engine damage and potential failure
Explanation: Failing to address high crankcase pressure promptly can lead to engine damage and potential failure due to excessive strain on engine components and improper operation of the crankcase ventilation system.

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Question 3: What additional investigation should be conducted if crankcase pressure remains high despite checking the ventilation system and seals?

B) Examine the piston rings and cylinder walls for wear or damage

A) Inspect the oil pump for malfunctions

D) Check the alternator for faults

C) Test the fuel injectors for proper operation

Answer: B) Examine the piston rings and cylinder walls for wear or damage
Explanation: If pressure remains high, examining the piston rings and cylinder walls is important, as excessive blow-by gases from worn or damaged components can contribute to increased crankcase pressure.

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Question 2: If the crankcase pressure is high, what should be checked to ensure proper sealing and pressure control?

A) Air filter condition

C) Turbocharger operation

B) Engine gaskets and seals

D) Radiator efficiency

Answer: B) Engine gaskets and seals
Explanation: Engine gaskets and seals should be checked to ensure they are properly sealing the crankcase. Worn or damaged gaskets can lead to increased crankcase pressure due to leaks.

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High Crankcase Pressure Implications and Actions

A) The engine may be operating normally; no immediate action is required. Continue to monitor.

B) High crankcase pressure may indicate potential issues such as excessive blow-by or ventilation problems; immediately shut down the engine and inspect the crankcase ventilation system and seals.

D) The increased pressure is usually due to low oil levels; top up the engine oil and restart the engine.

C) High crankcase pressure typically results from a faulty fuel pump; replace the fuel pump immediately.

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