System Components & Functions Flashcards
7 cards from real DPO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 System Components & Functions flashcards as text
What is the primary purpose of a motion reference unit (MRU) in a DP system?
Answer: Measure vessel roll, pitch, and heave for motion compensation
An MRU uses accelerometers and gyroscopes to measure the vessel's rotational and translational motion, providing heave, roll, and pitch data used by the DP system to compensate for wave-induced motion.
In a DP electrical power system, what is 'harmonic distortion' and why is it a concern?
Answer: Non-sinusoidal current waveforms from VSDs that can overheat equipment
Variable speed drives generate harmonic currents that distort the power supply waveform, which can cause overheating in transformers and cables and interfere with sensitive electronic equipment.
What is the significance of the 'yellow watchcircle' alarm on a DP system?
Answer: An operator-set position warning indicating the vessel is approaching the outer limit
The yellow (inner) watchcircle is an operator-defined warning zone; when the vessel drifts beyond it, the alarm alerts the operator to take action before reaching the critical red watchcircle.
Which component allows a DP operator to manually command individual thrusters independently of the DP controller?
Answer: Joystick panel in manual thruster mode
In manual thruster mode, the joystick or individual thruster levers allow the operator to directly command each thruster's thrust and direction without the DP controller's automated position-keeping algorithms.
What is the function of shaft encoders fitted to azimuth thruster drive units?
Answer: Measure the azimuth angle of the thruster for feedback to the DP controller
Shaft encoders on azimuth thrusters provide precise feedback of the thruster's rotational angle to the DP controller, ensuring commanded and actual azimuth directions match.
In the context of DP systems, what does 'FMEA' stand for and what is its purpose?
Answer: Failure Mode and Effects Analysis — identifies how failures impact DP capability
Failure Mode and Effects Analysis (FMEA) is a systematic study that identifies every possible component failure and evaluates its effect on the overall DP system to verify the design meets the required redundancy class.
What is the effect of thruster-thruster interaction (hydrodynamic interference) during DP operations?
Answer: Reduced effective thrust when thruster wash impinges on another thruster's inlet
When the thrust wash from one thruster passes through another thruster's inlet, it reduces that thruster's effective thrust output, a phenomenon the DP thruster allocation algorithm must account for.