Update 06 Jan 2013

By Mas Edy


Abandon Dive:
Equivalent to red alert when divers return to the bell immediately and bell is brought back to the surface.

Radio system used to measure vessels position. System operates using a microwave frequency and measures the range and bearing of the vessel from a fixed station that is generally installed on a platform.

Back-up DP:
A physically separate DP control system that will be available in the event of a total failure of the main DP control system.

Free running device on seabed that generates acoustic pulses that are received by the HPR system and used to establish the vessels position.

Loss of all main electrical power.

Capability Plot:
A theoretical polar plot of the vessels capability for particular conditions of wind, waves and current from different directions. These can be performed for different thruster combinations and should be produced in accordance with IMCA document (Ref. 3 Specification of Capability

Closed Circuit Television.

GPS plus a differential correction supplied by one or more receivers at a known fixed location, accurate enough for Dynamic Positioning.

Dynamic Positioning: automatic control of vessel’s location with respect to one or more fixed references.

DP Blackout:
Loss of electrical power that prevents the DP control system operating.

DP Control System:
The part of the DP system that calculates position and provides thruster commands.

DP Incident:
A DP incident is a loss of position to the surprise of the operator.

Operator of the DP Control System.

DP System:
All equipment that supports automatic position control.

Diving support vessel: a vessel from which divers are deployed.

Duplex DP:
DP control system with full redundancy and a smooth automatic changeover between the two systems.

A graphic illustration of a set of real observations of a vessel’s DP station keeping ability in particular environmental conditions.

Global Positioning System using satellites to establish a vessel’s position.

Green Alert:
Normal Operational Status; adequate DP equipment is on line to meet the required performance within the declared safe working limits.

Any Hydroacoustic Position Reference system.

Independent Joystick:
A joystick that is independent of the DP control system.

Positioning facility that uses a single lever for surge, sway and yaw control.

Limit alarms:
Selectable values of position and heading excursion at which the operator wants an alarm.

Manual Control:
Use of thruster controls other than those associated with the DP Control System.

Radio system used to measure a vessels position using range/range techniques. System operates using a microwave frequency to measure the ranges of the vessel to a number of fixed stations.

Any member of the vessel’s compliment involved with DP equipment, e.g. DP operator, Master, Duty Engineer, Chief Engineer, Electrician, Taut Wire Operator, Radio Operator.

Printed Circuit Board (an assembly of mounted electronic components that form part of a system that can be quickly repaired by replacement).

Any structure that is fixed relative to the DP vessel.

Towed unit generally used to bury communications cable.

Expression used when a position measurement system is interfaced to a DP control system as another position reference.

Red Alert:
DP Emergency Status, i.e. there is a loss of position, or position loss is inevitable.

A transponder except the interrogation is by an electronic pulse sent down a cable. This is generally fitted to an ROV and interrogated down the ROV’s umbilical.

Remotely Operate Vehicle that is launched to operate sub-sea from a vessel.

Safe Working Limits:
The environmental limits that a vessel sets for safely working on DP taking into account specified equipment failures.

Single board computer.

Shallow Water:
Less than 50m water depth.

Simplex DP:
DP control system with no redundancy.

Radio system used to measure vessels position that uses range/range techniques from fixed stations.

Taut wire:
A position reference using a tensioned wire to a seabed weight (vertical) or to a fixed object nearby (horizontal).

Device on the seabed that responds to acoustic interrogation from the HPR on the vessel. The timing and phase of the acoustic reply is used to calculate vessel position.

Sub-sea vehicle used for pipe or control line burial.

Triplex DP:
A triple DP control system that is able to vote on all inputs and all outputs and processors to identify a faulty unit.

Any propulsion device used by the DP system.

Connection carrying life support and communication systems between a support vessel and a diving bell, an ROV or similar device (also divers umbilical between diver and bell).

Uninterruptible Power Supply – unit to provide electricity continuously to DP control system in the event of a blackout of the main ship’s power.

Worst Case Failure:
The worst-case failure of a DP system is the failure that has been the basis of the design and proved by the FMEA. In static terms this usually relates to a number of thruster and generators that are also used in consequence analysis.

Yellow Alert:
Degraded DP Operational Status for which the DP vessel has a preplanned response to prepare for the risks associated with a DP red alert.