Protective Devices in Locomotives
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Questions and Answers

What does the low water detecting portion of the EPD primarily monitor?

  • Oil temperature
  • Engine noise levels
  • Water pressure (correct)
  • Airbox pressure

    • What action does the low water detection device take when it detects low water pressure?

  • Releases oil to prevent overheating
  • Activates a warning light
  • Increases engine throttle
  • Shuts down the engine (correct)

    • Which protective device does NOT contribute to the EPD's function?

  • Engine overspeed protection
  • Crankcase pressure monitoring
  • Low water detection
  • Oil level sensing (correct)

    • When the engine is shut down, what pressure must act against spring pressure to keep the low water device latched?

    <p>Static water pressure</p> Signup and view all the answers

    What happens to the EPD when there is no airbox pressure?

    <p>It cannot function</p> Signup and view all the answers

    Which condition does the EPD primarily protect against?

    <p>Engine overspeed</p> Signup and view all the answers

    What is required for the protective device to remain latched when the engine is not running?

    <p>Water pressure against spring pressure</p> Signup and view all the answers

    What is the first step in testing the hot oil detector?

    <p>Connect a 50 psi air line to the hot oil detector inlet port</p> Signup and view all the answers

    At what temperature should the hot oil detector valve open during testing?

    <p>258°F</p> Signup and view all the answers

    What component has replaced the hot oil detector on locomotives equipped with EMDEC fuel injection?

    <p>Lube Oil Temperature Sensor</p> Signup and view all the answers

    Which of the following is NOT a step involved in testing the hot oil detector?

    <p>Place the detector in an ice bath</p> Signup and view all the answers

    What does the low lube shutdown system protect the engine against?

    <p>Failure of the mechanical support systems</p> Signup and view all the answers

    What condition does the crankcase pressure detector sense to signal the engine to shut down?

    <p>Positive crankcase pressure</p> Signup and view all the answers

    How does the crankcase pressure detector indicate a positive pressure condition?

    <p>By tripping a switch</p> Signup and view all the answers

    What mechanism is used by the crankcase pressure detector to operate the shutdown signal?

    <p>A large diaphragm</p> Signup and view all the answers

    What keeps the long stem of the crankcase pressure detector in a latched position?

    <p>Normal negative pressure</p> Signup and view all the answers

    What is the primary purpose of the EMDEC master Electronic Control Module (ECM)?

    <p>To shut the engine down during malfunctions</p> Signup and view all the answers

    What does negative crankcase pressure help to maintain?

    <p>Ventilation equipment functionality</p> Signup and view all the answers

    Which component is responsible for sensing the crankcase pressure?

    <p>Crankcase pressure detector</p> Signup and view all the answers

    What happens to the contacts in the switch mechanism when the crankcase pressure detector responds to positive pressure?

    <p>They close to send a shutdown signal</p> Signup and view all the answers

    What indicates a malfunction within the engine's crankcase pressure system?

    <p>A buildup of positive crankcase pressure</p> Signup and view all the answers

    What is the initial condition that the crankcase pressure detector relies upon to function correctly?

    <p>Normal negative pressure</p> Signup and view all the answers

    What should be done immediately after starting the engine to ensure proper functioning of the device?

    <p>Reset the device</p> Signup and view all the answers

    At what intervals should the operation of the low water shutdown device be checked?

    <p>At the intervals in the Scheduled Maintenance Program</p> Signup and view all the answers

    What is the correct position to place the test cock when testing the low water detecting device?

    <p>Horizontal position</p> Signup and view all the answers

    How long should it take for the low water button to pop out once the test cock is opened?

    <p>No more than 5 seconds</p> Signup and view all the answers

    What action should be taken if the low water shutdown reset pushbutton does not pop out freely?

    <p>Remove and replace the device</p> Signup and view all the answers

    What is the role of the low oil plunger during the testing process?

    <p>To shut down the engine</p> Signup and view all the answers

    What should be monitored to ensure the low water button stays in the set position?

    <p>The rack positioning lever</p> Signup and view all the answers

    What indicates a faulty operation of the low water detecting device during a test?

    <p>The button pops out after hesitation</p> Signup and view all the answers

    What is the first step to take if the low water shutdown does not function as expected?

    <p>Reset the low water button and plunger</p> Signup and view all the answers

    What can cause a crankcase pressure detector to trip due to blocked pathways?

    <p>Excessive oil level in the crankcase</p> Signup and view all the answers

    Which of the following conditions is NOT associated with cylinder compression leaking into the oil pan?

    <p>Clogged fuel filter</p> Signup and view all the answers

    What is a possible danger of an engine condition indicated by the crankcase pressure detector?

    <p>Overheated bearing igniting oil vapours</p> Signup and view all the answers

    Which component's improper installation may lead to crankcase pressure detector trip?

    <p>Lube oil pressure relief valve</p> Signup and view all the answers

    What should you NOT do after an engine shutdown caused by a crankcase pressure detector trip?

    <p>Restart the engine to check for issues</p> Signup and view all the answers

    What could contribute to crankcase pressure due to air leaks?

    <p>Hardened liner seals</p> Signup and view all the answers

    Which condition must be resolved before operating the engine again?

    <p>Unable to reset crankcase pressure detector</p> Signup and view all the answers

    What might happen if air enters the engine after a pressure detector trip?

    <p>Crankcase explosion risk increases</p> Signup and view all the answers

    Which of the following is a cause of crankcase pressure detector tripping that involves physical damage?

    <p>Extreme cylinder scoring</p> Signup and view all the answers

    What action is critical to ensure safety after a tripping event?

    <p>Allowing the engine to cool down</p> Signup and view all the answers

    What condition leads to a 'true' low lubricating oil pressure scenario?

    <p>Insufficient oil flow from the pump.</p> Signup and view all the answers

    Which of the following determines the delay in shutting down the engine when at idle?

    <p>The throttle position of the engine.</p> Signup and view all the answers

    How does the shutdown system respond when oil pressure drops below the speed setting oil pressure?

    <p>It shuts down the engine immediately.</p> Signup and view all the answers

    What mechanism prevents immediate shutdown of the engine during the initial startup?

    <p>A built-in delay mechanism in the oil pump.</p> Signup and view all the answers

    What effect does a positive crankcase pressure have on the low lubricant pressure monitoring system?

    <p>It can cause a false low lubricant pressure reading.</p> Signup and view all the answers

    What should be checked immediately after starting the engine to ensure proper function of the EPD?

    <p>The reset button on the low water shutdown device</p> Signup and view all the answers

    How should the low water button react during the operation test after opening the test cock?

    <p>It should pop out smoothly without hesitation</p> Signup and view all the answers

    What is the maximum time allowed for the low water button to pop out after the test cock is opened?

    <p>Four seconds</p> Signup and view all the answers

    What indicates a malfunction during the low water detection device test?

    <p>The reset pushbutton requires force to pop out</p> Signup and view all the answers

    What should be done if the low water shutdown device fails to function as expected during testing?

    <p>Remove and replace the device with a functioning one</p> Signup and view all the answers

    During testing, what should be monitored as the engine begins to shut down?

    <p>The low water button's stability</p> Signup and view all the answers

    What should occur when the low oil plunger operates correctly during testing?

    <p>The engine should be shut down within approximately 5 seconds</p> Signup and view all the answers

    What is the primary function of the special apparatus mentioned for testing the crankcase pressure detector?

    <p>To apply suction to trip the upper button.</p> Signup and view all the answers

    What is the air box-to-water diaphragm area ratio for turbocharged engines?

    <p>1:1</p> Signup and view all the answers

    What condition would NOT cause the low water shutdown to activate?

    <p>High water temperature.</p> Signup and view all the answers

    Which diaphragm in the low water device senses water pressure into the engine?

    <p>The water pressure diaphragm.</p> Signup and view all the answers

    What mechanism is triggered when water pressure is within 1/2 psi of air box pressure?

    <p>The low water reset button.</p> Signup and view all the answers

    What does excessive air box pressure due to turbine surging indicate?

    <p>Turbocharged engines only.</p> Signup and view all the answers

    What happens to the combination low water and crankcase pressure detector in case of pump cavitation due to water temperature approaching boiling point?

    <p>The detector will trip.</p> Signup and view all the answers

    What is a consequence of overfilling the water tank?

    <p>Low water shutdown.</p> Signup and view all the answers

    Which factor is critical for maintaining the functionality of the low water device under normal operating conditions?

    <p>Water pressure exceeding air box pressure.</p> Signup and view all the answers

    What can cause the crankcase pressure detector to trip due to issues with oil management?

    <p>Blocked oil separator or aspirator tube</p> Signup and view all the answers

    Which condition is likely to occur due to a cracked component in the engine?

    <p>Oil vapor ignition</p> Signup and view all the answers

    What critical action should NOT be performed immediately after a crankcase pressure detector trip?

    <p>Open the top deck covers for inspection</p> Signup and view all the answers

    What is a potential consequence of operating an engine with a tripped crankcase pressure detector that cannot be reset?

    <p>Risk of diaphragm backup plate damage</p> Signup and view all the answers

    Which of the following issues can lead to pressurized air leaking from the air box into the crankcase?

    <p>Hardened liner seals</p> Signup and view all the answers

    What could potentially elevate crankcase pressure due to mechanical failure?

    <p>Loose fuel injectors</p> Signup and view all the answers

    What environment factor could aggravate the chances of crankcase explosion?

    <p>Overheated parts in the crankcase</p> Signup and view all the answers

    What common problem can occur due to the incorrect installation of an engine component?

    <p>Lube oil pressure relief valve malfunction</p> Signup and view all the answers

    What catastrophic event is indicated by a tripping crankcase pressure detector?

    <p>Possibility of an overheated bearing</p> Signup and view all the answers

    What should be done to prevent oil spray when testing the hot oil detector?

    <p>Attach a return line to the outlet port</p> Signup and view all the answers

    At what temperature is the oil bath initially set during the hot oil detector test?

    <p>$235°F$</p> Signup and view all the answers

    What indicates that the hot oil detector needs to be replaced during testing?

    <p>If the valve does not open at $235°F$</p> Signup and view all the answers

    What component takes the place of the hot oil detector in locomotives with EMDEC fuel injection?

    <p>Lube Oil Temperature Sensor</p> Signup and view all the answers

    What is the primary function of the low lube shutdown system?

    <p>To protect the engine in case of mechanical failure</p> Signup and view all the answers

    Which procedure is not included in the testing process for the hot oil detector?

    <p>Establishing a vacuum at the inlet port</p> Signup and view all the answers

    What is a necessary step after connecting the air line to the hot oil detector?

    <p>Place the detector in an oil bath</p> Signup and view all the answers

    What specific temperature is the hot oil detector expected to respond and open?

    <p>$258°F$</p> Signup and view all the answers

    Why is a return line needed in the testing setup for the hot oil detector?

    <p>To avoid creating oil spray</p> Signup and view all the answers

    Study Notes

    Protective Devices

    • Locomotives have many devices to protect mechanical and electrical systems
    • Main protective devices safeguard against:
      • Low water
      • Crankcase pressure
      • Hot oil
      • Low oil
      • Engine overspeed

    Engine Protection Device (EPD) - Low Water & Crankcase Pressure Protection

    • EPD has a low water detecting portion (Figure 9.1)
    • Balances water pressure against airbox pressure
    • If water pressure drops, device dumps oil from governor supply line, shutting down engine
    • Air box pressure is not present when the engine is shut down but spring pressure exists
    • Device designed to latch in with water pressure, static water pressure might not be enough when the engine is shut down.
    • The device needs to be reset immediately after engine start in some cases
    • Air-box to water diaphragm area ratios vary, 1:1 for turbocharged and 3:1 for blower (roots)
    • Water pressure exceeding air box pressure is normal operating condition
    • The EPD will trip when water pressure is within 1/2 PSI of the air box pressure

    Testing EPD Operation

    • EPD operation should be checked at intervals specified in the Scheduled Maintenance Program, or whenever faulty operation is suspected.
    • To test the low water detection device, operate the engine at idle and rotate the test cock to the horizontal position.
    •  Water should drain out of the hole (within a few seconds) without hesitation, and then the test cock should be rotated back to the vertical position.
    • Test cocks can be in different locations; one being on the water pump discharge elbow
    • contaminants in the cooling system can plug the small orifice of the test cock reducing the bleed off of water pressure to the diaphragm.

    Low Oil Protection

    • Low oil plunger on the governor is observed as it extends.
    • Engine shuts down after approximately 55 seconds
    •  Reset the low water button and the low oil plunger at the start of restart process when engine is brought back to idle
    • Special apparatus required for testing -Rubber tube over test opening on top of detector and then applying suction for testing

    Crankcase Pressure Protection

    • A mechanically operated, pressure-sensitive device determines abnormal crankcase and coolant pressures
    • Spring-loaded, normally-open, multi-valve system, with two diaphragms, one for water and one for airbox pressure
    • Engine shuts down if positive crankcase pressure is detected
    • Equipment is needed for maintenance and testing
    • Positive crankcase pressure can be caused by:
      • Blocked oil separator or aspirator tube in the exhaust
      • Excessive oil level in crankcase
      • Blockage of oil separator
      • Cylinder compression leak into the oil pan
      • Cracked cylinder head
      • Cracked piston
      • Loose injector
      • Improperly installed or broken rings
      • Broken valves
      • Badly worn valve guides
      • Pressurized air leaking from the air box.
      • Overheated engine parts causing oil vapors to ignite

    Hot Oil Protection

    • Thermostatic valve opens at ~260°F (126°C) oil temperature
    • This may indicate issues with the oil cooler (plugged) or steam pressure preventing shutdown
    • Oil pressure sensor in the engine's governor detects low pressure and shuts down the engine.
    • Valve is non-latching and resets automatically when oil temperature falls
    • Do not add cold water to an overheated engine
    • After a shutdown due to hot oil, do not open any parts for at least 2 hours with the engine off.

    Low Lube Oil Shut Down

    • Shutdown system activates when mechanical support systems fail, creating low lubricating oil pressure
    • Detects "false" low pressure that stems from cooling system failures and hot oil detector
    • Detects positive crankcase pressure and speed-set oil pressure failure

    Engine Overspeed Protection

    • Mechanical safety device stops fuel injection if engine speed exceeds a predetermined limit
    • Flyweight mounted on counterweight activates the trip when excessive centrifugal force overcomes spring tension.
    • Trip pawl rotates trip shaft which prevents further fuel injector actuation
    • Trip speed is usually set a few per cent over normal running speed
    • Adjustments need to be made to the trip-speed mechanism.
    • 16-710G limit revised to 1035-1050 rpm to prevent tripping system during locomotive transition.

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    Locomotive Protective Devices PDF

    Description

    This quiz covers the essential protective devices used in locomotives, focusing on the Engine Protection Device (EPD) for low water and crankcase pressure. Participants will learn about the operation, testing, and importance of these devices in maintaining engine safety and functionality.

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