DPO DPO Alarms, Fault Diagnosis & System Troubleshooting 1 — Questions and Answers
Question 1: When a DP operator receives a 'position deviation' alarm, what is the immediate priority?
- Shut down all thrusters
- Assess the cause, check reference systems, and determine whether to intervene or disconnect the operation (Correct answer)
- Increase thruster output to maximum
- Sound the general alarm immediately
Correct answer: Assess the cause, check reference systems, and determine whether to intervene or disconnect the operation
The operator must quickly assess whether the deviation is caused by a reference error, environmental change, or thruster fault before deciding to intervene or initiate disconnect.
Question 2: A 'drive-off' in DP terminology refers to:
- Intentionally moving the vessel away from the set point
- An uncontrolled vessel movement away from the set point caused by a DP system malfunction (Correct answer)
- Maneuvering off station at end of operations
- Thruster-assisted anchoring
Correct answer: An uncontrolled vessel movement away from the set point caused by a DP system malfunction
A drive-off is an unintended, uncontrolled movement away from the set point, typically caused by a control system failure generating spurious thruster commands.
Question 3: What distinguishes a 'drift-off' from a 'drive-off' in DP incident classification?
- Drift-off involves higher vessel speed
- A drift-off is a passive positional loss due to thruster/power failure; a drive-off is an active powered excursion due to control failure (Correct answer)
- Both terms describe the same event
- Drive-off only occurs in manual mode
Correct answer: A drift-off is a passive positional loss due to thruster/power failure; a drive-off is an active powered excursion due to control failure
A drift-off results passively when the DP system loses thrust capability and the vessel drifts under environmental forces, while a drive-off involves active erroneous thruster commands.
Question 4: During a blackout on a DP vessel, the first action the DPO should take is:
- Re-start all thrusters manually
- Initiate ASAP disconnect if over a subsea structure and alert the DP watchkeeping engineer (Correct answer)
- Switch all navigation lights to battery backup
- Lock the propulsion shafts
Correct answer: Initiate ASAP disconnect if over a subsea structure and alert the DP watchkeeping engineer
A total blackout removes DP capability and the vessel will begin to drift; if over sensitive subsea infrastructure, ASAP disconnect should be initiated immediately.
Question 5: Which thruster fault type is most likely to cause a sudden unplanned vessel rotation in DP?
- A thruster running at reduced RPM
- A fixed-pitch thruster stuck at full ahead
- A thruster delivering full thrust in the wrong direction (runaway/hardover) (Correct answer)
- A thruster that fails to start
Correct answer: A thruster delivering full thrust in the wrong direction (runaway/hardover)
A hardover or runaway thruster delivering maximum thrust in an unintended direction creates a large moment that can cause rapid, uncontrolled rotation of the vessel.
Question 6: What is the purpose of the 'yellow' exclusion zone alert on the DP operator display?
- To indicate shallow water ahead
- To warn the operator that the vessel is approaching a predefined safety boundary before reaching the red alert limit (Correct answer)
- To indicate a thruster has tripped
- To signal that the gyrocompass is offline
Correct answer: To warn the operator that the vessel is approaching a predefined safety boundary before reaching the red alert limit
Yellow exclusion zone alerts provide an advance warning that the vessel is nearing the defined safety boundary, giving the operator time to intervene before the red alarm triggers.
DPO DPO Alarms, Fault Diagnosis & System Troubleshooting 1
When a DP operator receives a 'position deviation' alarm, what is the immediate priority?