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    Station keeping incidents trigger DP review at IMCA

    News // May 23, 2003
    Computers, particularly on vessels with integrated control systems, are seen as an increasingly common cause of DP (dynamic positioning) loss of position incidents, according to the International Marine Contractors Association (IMCA), which has just published its annual 'Station Keeping Incidents' report.

    This twenty-second consecutive annual report in the series covers incidents that took place in 2001. It includes 97 incidents with fault trees, including 21 Position Loss 1 (incidents deemed to be of a serious nature); 34 Position Loss 2 (incidents of aless serious nature); and 42 lost-time incidents. All of the vessels reporting incidents were located in Europe, West Africa, the Gulf of Mexico or Brazil. None of the incidents had catastrophic consequences in terms of safety and/or pollution.

    "Computers were found to be the main cause of incidents both in the 'loss of position 1' category and overall, and one of the major causes of incidents for Position Loss 2 incidents," explains IMCA's Technical Director, Jane Bugler.

    "Although no simple explanation is available, vessels now generally have more computers with integrated control systems and over the past 12 years computers have increasingly been a common cause of DP incidents.

    Of the 21 serious incidents, the DP operator was only the primary cause of three of the incidents. "However a case could be made to show that operator error might be a major part of up to 86% of these incidents," added Bugler.

    'Operator' in this context means any person involved from the designer to the DP operator (DPO).

    With safety very much at the heart of all work undertaken on behalf of its members by IMCA, these incidents are a cause for concern and have resulted in a major review of the safety/reliability of DP systems being undertaken by IMCA during 2003.

    This will work through all elements of DP systems and use FMEAs (failure modes and effects analysis) as one of the key tools in the investigation. The work is being carried out in the light of two recent DP incidents, involving single failure modes thatvessel FMEAs had not identified.

    "DP is being used aboard an ever-increasing number and type of vessels around the world and it is important that everything possible is done to understand and remedy position loss incidents," said Bugler.

    One new area that IMCA is investigating is DP use on offshore supply vessels; work is already under way to produce guidelines that will encourage a consistent approach throughout the industry.

    "Currently it is consistent only in its inconsistency," explained Bugler. "Some clients will allow supply vessel operators to use DP; others will not." The study is a collaborative one involving clients, supply vessel operators and IMCA contractors. A working group has been established and the guidelines are due for publication later in the year.

    Copies of the 127-page 'Station Keeping Incidents Reported for 2001' (IMCA M 169) cost 20 for members, 100 for non-members and are available from IMCA at Carlyle House, 235 Vauxhall Bridge Road, London SW1V 1EJ, UK. Tel: +44 (0)20 7931 8171; Fax: +44 (0)20 7931 8935; Email:; Website:

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