What’s Special About Third Generation Dynamic Positioning DP3?
DP3 is a new offshore vessel positioning technology standard set by IMO that will enable a couple of new Farstad offshore vessels on the stocks in Norway to work safely in the most demanding and potentially dangerous situations using systems equipment provided by Rolls Royce.
Basically, to maintain an accurate position determined mainly by satellite navigation system (anchoring is not in itself precise enough) an offshore vessel needs to be equipped with propulsors and thrusters controlled automatically by a dynamic positioning (DP) system in such a way as to oppose the resultant force of wind, waves, tides and currents.
Dynamic positioning, propulsion & thruster schematic: Courtesy of Rolls-Royce
Deep-water drilling for oil or gas (common now as shallower resources deplete) is an operation that often carries with it the need for jack-ups, construction and support vessels to operate in extremely demanding situations where any loss of position might result in fatal accidents, severe pollution or damage with major economic consequences. In such an environment Rolls-Royce’s most advanced DP3 system has been developed in order to help operators circumvent such catastrophes.
System redundancy is key
Icon DP3 is fully integrated with the Rolls-Royce propulsion and thruster (P&T) control system. System architecture features distinctive fault tolerance and positioning performance by combining two diverse and complimentary redundancy schemes. Maximum effect of a single failure in the control system is loss of one thrust device or one sensor group.
Icon DP 3 consists of two separate and diverse DP control systems, a triple redundant DP Main system and a single DP Alternate system, set up in an online / hot standby redundancy scheme.
The combined redundancy schemes of Icon DP 3 enhance system dependability as DP Alternate has no dependencies with DP Main, is ready to accept command and maintain position at any time and increases tolerance to systematic faults as shown below.
DP 3 redundancy: Schematic courtesy of Rolls-Royce
DP Main is the primary system for DP operation and features:
• Dual redundant network
• Triple redundant controllers working in parallel in triple work-by scheme
• Distributed 2-out-of-3 voting
• Graceful degradation and online repair
• Fire tolerance ensuring continuous DP operation in case of fire in one zone
Arnt-Ove Austnes, Rolls-Royce, Sales Manager – Automation and Control, said: "An increasing number of offshore operations are performed with rigs and vessels having to be kept in precise position without using anchoring systems. With an increased focus on risk limitation in the oil and gas sector, we expect a growing demand for DP3 classed vessels."
Source: Rolls Royce