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WorksheetsPASGT LEC MIDTERM QUIZ 1 - 2631
Total questions: 20
Worksheet time: 15mins
The turbine completed slow turning but trial run shows high vibration only at certain RPM ranges. The likely analysis is:
Fuel quality causing intermittent misfires related to rotor dynamics
Cooling water overcapacity causing shaft contraction and smooth rotation
Rotor natural frequency or resonance causing amplification at that speed range
Excessive pre-lubrication time causing uniformly low vibration across speeds
A gradual decline in oil pressure during trial run with rising temperature suggests:
Fuel system purge releasing trapped air into bearings intentionally
Normal behavior requiring no corrective action before full-load operation
Improved lubrication film leading to reduced pump outlet pressure readings
Leak, pump degradation, or viscosity change impacting lubrication effectiveness
If start attempts fail but turning gear runs smoothly, analysis points to:
Ignition system failure, fuel delivery problem, or control logic preventing ignition
Exhaust backpressure being too low to allow flame propagation to occur
Lubrication system overpressure preventing fuel valves from opening correctly
Bearing seizure preventing rotation during motoring but not detected visually
During trial run, inconsistent EGT with stable fuel flow likely means:
Combustion instability due to nozzle fouling, injector fault, or airflow irregularity
Cooling system flow excessive, dropping exhaust temperature artificially low
Turning gear misengaged and interfering with combustion dynamics directly
Bearing temperature drift misreported by sensors unrelated to combustion
Multiple trips during trial runs after maintenance indicate:
That the turbine is ready for immediate full-power operation with no issues
Potential sensor faults, interlock misconfiguration, or unresolved mechanical issues
Successful repairs made too thoroughly, causing unfamiliar alarm triggers
Normal behavior when validating safety systems under test conditions of newly maintained component
A persistent knocking noise during slow turning best indicates:
Normal turbine harmonics that require no remedial action before trial run
Excessive cooling water flow causing lubrication turbulence in bearings
Proper operation of fuel injection timing and combustion cycles later on
Loose internal components, misaligned bearings, or mounting structure defects
If differential pressure across intake filter rises during turning, analysis shows:
Fuel injectors blocked and causing reduced atomization only at ignition
Bearing seals leaking and causing internal contamination of the intake path
Filter blockage reducing airflow and risking compressor performance during trial run
Starter motor slipping, creating the impression of airflow restriction and rise of differential pressure
Trial run shows acceptable temperatures but intermittent control panel alarms. Most plausible analysis is:
Complete overhaul required due to catastrophic mechanical failure imminent
That fuel quality is excellent and alarms are unrelated to turbine condition
That temperatures must be ignored because alarms are always false positives
Faulty sensor wiring, calibration drift, or intermittent electrical faults in control logic
The turbine trips on overspeed during a partial load increase; analysis would suspect:
Governor or control system malfunction or sensor feedback error causing false reading
Lubrication system failure causing increased friction and thus speed rise
Ignition system misfire causing uncontrolled rotational acceleration consistently
Fuel viscosity too high to allow proper acceleration control by governors
If post-trial inspection reveals small metal particles in bearing drains, the likely cause is:
Foreign object inflow from the intake causing external contamination
Normal lubricant breakdown expected after every successful trial run
Overcorrection by the lubrication pump causing harmless metallic flakes formation
Bearing wear, misalignment, or early-stage component degradation needing repair
If the turning gear shows intermittent engagement, the engineer should:
Stop turning and inspect clutch, drive coupling, and electrical supply
Bypass the turning gear and proceed to immediate ignition sequence
Continue turning and plan inspection after full trial run completion
Increase rotational speed hoping the clutch will engage consistently
While slow turning, sight glasses show interrupted oil flow. The correct action is:
Proceed to trial run and monitor oil flow during ignition stage only
Stop turning and investigate pump operation, filters, or possible air entrapment
Increase turning speed slightly to restore continuous oil flow automatically
If temperatures appear normal overall, ignore the sight glass reading
If a foreign object is found in the intake during inspection, the operator must:
Close the intake and proceed with turning to see if noise persists
Remove the object, re-check for further debris, and secure intake before motoring
Record the object in the log and continue procedures even without removal
Start ignition cautiously to blow the object out through exhaust path
During the trial run, oil pressure drops below limit. What should be done?
Reduce load, shut down if needed, and investigate pump and seals immediately
Continue trial run and schedule a maintenance after arrival at next port
Increase fuel flow to raise temperature and restore oil viscosity quickly
If bearing temperatures appear stable during monitoring, minor pressure drops may be ignored
If vibration increases suddenly during slow turning, the technician should:
Reduce lubrication flow to change damping characteristics immediately
Stop rotation and inspect for misalignment, imbalance, or foreign debris
Continue turning and log vibration trend for future diagnostic review
Increase turning speed to allow balancing forces to stabilize rotor dynamics
When performing the trial run, a sensor reads out-of-range intermittently. The proper step is:
Continue run and average readings to compensate for intermittent spikes
Disable the alarm temporarily and proceed to complete the trial run
Halt trial run, isolate the fault, and verify sensor calibration before continuing
Replace the sensor only after completing a full-power test at sea
If exhaust backpressure is high during trial run, the engine room team should:
Ramp to full power to create higher exhaust velocity and clear obstruction
Identify and clear downstream restriction before continuing with additional tests
Ignore backpressure if temperatures and RPM appear normal during monitoring
Increase fuel flow to attempt to force gases through the restriction
During slow turning, oil filter differential pressure increases. What is the correct action?
Inspect and replace or clean filters before proceeding to trial startup
Reduce turning speed and ignore filter differential trends temporarily
Bypass the filtration system to allow uninterrupted motoring operation
Increase turning duration to attempt self-cleaning of the filter assembly
While monitoring trial run parameters, TIT spikes briefly but returns. The best action is to:
Lower lubrication pressure to try and dampen thermal fluctuations quickly
Stop increase in load, investigate causes and inspect fuel control system closely
Immediately increase load to smooth out temperature transients naturally
Ignore single spike because parameters are still not stable during trial run
If the turning gear cannot be disengaged after slow turning, the operator should:
Apply a temporary manual override and proceed to quick ignition sequence
Log the condition and continue with other related engine room checks
Keep turbine secured, do not attempt ignition, and diagnose the disengagement mechanism
Force starter engagement and proceed cautiously into the trial run phase
