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IMCA publishes Guidance on Offshore Vessel High Voltage Safety

Published on 18 December 2012

The International Marine Contractors Association (IMCA) has published guidance on ‘Offshore vessel high voltage safety’ (IMCA SEL 031/IMCA M 217).

“As the demand for electrical power increases on vessels, especially on large offshore construction vessels with diesel electric propulsion installations, the supply current becomes too high for efficient and practical use of the usual shipboard 3-phase voltage supply of 440 Volts (V) AC,” explains IMCA’s Technical Director, Jane Bugler. “To reduce the level of running currents and fault current levels, it is necessary to specify a higher system voltage for the higher power-rated equipment.

“In marine practice, voltages below 1kV AC are considered LV (low voltage); HV (high voltage) is any voltage above 1kV. Typical marine HV system voltages are 3.3kV, 6.6kV and 11kV.”

The guidance, which is available for downloading free of charge to members and non-members alike, sets out the major reasons why vessels have shifted towards high voltage systems; provides a useful list of definitions; and has sections devoted to ‘what is classed as high voltage onboard a vessel?’; HV equipment; advantages of high voltage supply over low voltage supply, ‘how can injuries happen during work on HV equipment?’; HV safety requirements (training; and risk assessment); permit to work system for HV work; additional procedures to be implemented for HV systems (sanction-to-test system; limitation of access form; and earthing down); and finally safety rules that should be implemented by owners or operators with HV equipment onboard their vessels (HV enclosure entry; work on HV equipment; earthing; and general).

Printed copies of the guidance are available at £2.50 for members and £5.00 for non-members (zero VAT, plus 20% for delivery outside Europe), and can be ordered from the IMCA website at; from [email protected]; or from IMCA at 52 Grosvenor Gardens, London SW1W 0AU, UK. Tel: +44 (0)20 7824 5520; Fax: +44 (0)20 7824 5521.