Dynamic positioning (DP) is a computer-controlled system designed to maintain a ship’s position and heading by making use of its own propellers and thrusters.
DP first came into use in the 1960s by the offshore oil industry as it began operating in deeper waters, where it was not possible to use anchors to maintain position. There are over 2,000 vessels fitted with DP technology operating worldwide.
The global market for marine dynamic positioning technology is expected to increase from $1,594 million in 2015 to 2,127 million by 2022, according to Allied Market Research “Marine Dynamic Positioning System Market” report.
The growth in this market is because of several factors including an increasing demand for offshore patrol vessels, a growing need for offshore wind construction vessels and a rise in deployment of research vessels.
How it works
The vessel’s DP software uses a mathematical model of the vessel that includes information relating to the wind and current drag of the vessel and the location of the thrusters. This knowledge, combined with the sensor information, allows the computer to calculate the required steering angle and thruster output for each thruster. This allows operations at sea where mooring or anchoring is not workable because of deep water, congestion on the sea bottom (pipelines, templates) or other problems.
DP can maintain a vessel’s absolute position at a fixed point on the globe, or relative to a moving object like another ship or an underwater vehicle. One may also position the ship at a favourable angle towards wind, waves and current, this is called Weathervaning.
Dynamic Positioning systems users
An increasing number of vessels are making use of DP systems for maintaining position and accurate manoeuvring. Here are a few examples of different types of vessels that make use of DP technology. For instance:
- Drilling ships and Semi-submersibles. A Drilling vessel will use DP to remain in a fix location while drilling in deep water.
- Offshore support vessels: Platform supply vessels, Well intervention vessels, Diving Support Vessels, offshore wind construction vessels etc., make use DP to stay in a safe distance from offshore platforms and drilling rigs. For example the Gusto MSC’s NG-20000X offshore wind construction vessel.
- Pipe-laying and offshore construction vessels. Pipe-laying vessels use DP for position keeping and track keeping.
- Dredging vessels. Suction Hopper dredgers, Rock-dumping vessels, Trenching vessels
- Pleasure craft such as the 64-metre superyacht Atomic and Quark Expeditions new expedition ship Ultramarine.
How vessels determine their position when using Dynamic Positioning systems
There are several means to determine a ship’s position at sea. Most traditional methods used for ship’s navigation are not exact enough for some modern requirements. Several positioning systems have been developed during the past few decades. These include DGPS, Hydro acoustic position reference, Taut wire, Laser-based systems and Artemis
The advantages of Dynamic Positioning technology
Making use of DP technologies is a good option for vessels in deep water operations and where vessels need to move often:
- Quick and easy positioning and manoeuvrability of the vessel. No need for mooring lines, tugs boats and time consuming anchor handling operations.
- Offshore operations can take place in ultra-deep waters where mooring lines are difficult to instal.
- Easy to change location or weathervaning to avoid the effects of bad weather. Quick disconnect and sail away in case of emergency.
- Safe when working in congested sea beds with many pipelines, mooring lines from other vessels or sub-sea structures such as manifolds, wellheads, risers, etc.
The disadvantages of Dynamic Positioning technology
Dynamic Positioning is not always the best of the most economical option. Mooring lines are a better choice for shallow waters or for an operation that does not need frequent relocation of the vessel as with drilling or diving in shallow waters,
- Great Capital expenditure for designing and installing DP systems.
- High fuel consumption and increased maintenance cost.
- It poses limitations in swallow waters and situations were diving operations must take place close to the thrusters
- Severe consequences in case of equipment failure during pipe-laying or during operations near fixed platforms.
DP class requirements
Based on the International Maritime Organization publication 645 the various classification societies have issued the following regulations for Dynamic Positioned Ships. These are Class 1, Class 2 and Class 3.
Equipment Class 1 – has no redundancy. Loss of position may occur in the event of a single fault.
Equipment Class 2 – has redundancy so that no single error in an active system will cause the system to fail. Loss of location should not occur from a single fault of an active component or system such as generators, thruster, switchboards, remote controlled valves etc., but may occur after catastrophe of a static component such as cables, pipes, manual valves etc.
Equipment Class 3– which also has to survive fire or flood in any one compartment without the system failing. Loss of location should not occur from any single disaster including a completely burnt fire sub division or flooded watertight section.
Leading providers of DP technology
Amongst the key providers of DP technologies include ABB, General Electric Co., Kongsberg Gruppen, Marine Technologies LLC, Moxa Inc., Navis Engineering Oy, AB Volvo Penta, Praxis Automation Technology B.V., Rolls Royce, and Wartsila Corporation.
New developments in DP technology
Keeping pace with technological and operational developments has always been a challenge for industry regulators tasked with producing industry guidance and best practice. Recent years have seen several updates to important guidance documents from IMO, IMCA, The Marine Technology Society and The Oil Companies International Marine Forum, etc. For instance, Key updates to IMCA documents include the February 2017 Rev 3 of IMCA M103–Guidelines for the Design and Operation of Dynamically Positioned Vessels and the September 2016 Rev 2 of IMCA M117–Guidelines for the Training and Experience of Key Dynamic Positioning Personnel.