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Tuesday, June 27, 2017

Dynamic positioning

Posted to Maritime Musings (by on December 18, 2012

A vital technology for modern ship handling

Dynamic positioning developed in the 1960s in the offshore oil and gas drilling industry when efforts began entering waters too deep for use of either jack-up rigs or anchor spreads as a means of keeping the rig precisely located over the drill site.  It consists of a computer-controlled system for maintaining a vessel’s position and heading using propellers and thrusters.  Use of dynamic positioning has spread to cable-layers, dredgers, shuttle tankers, oceanographic survey vessels, and other ships that require precise positioning.  Data from gyro compasses, motion sensors, anemometers, and highly precise GPS receivers are integrated by the ship’s computer to control the propellers and thrusters so as to keep the ship as stationary as possible.  Classification societies generally rate dynamically positioned ships into three classes.  Class 1 is the most basic, having no redundancy so that loss of position may occur the event of a single fault.  Class 2 has some redundancy, so that no single fault in an active system will cause the system to fail.  Class 3 has multiple redundancies and will also withstand fire or flooding in any one compartment.  A Class 1 DP vessel would normally be used in situations where loss of position is not likely to endanger life or cause significant property damage or pollution.  A Class 2 DP vessel would normally be used in situations where loss of position could cause personnel injury or significant property damage or pollution.  A Class 3 DP vessel would normally be used in situations where loss of position could cause fatalities or major property or pollution.  The DP operator position has transitioned from a status acquired solely through experience to one involving a combination of experience and specialized training.  The Nautical Institute has taken a leading position in developing DP operator training programs and accreditations and in certification of individual mariners.

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