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Country: UK | ||
Location: OFFSHORE : Other offshore | ||
Release Date: — | Time incident occurred: — | |
Type of Activity: — | ||
Type of Injury: null | Function: null | |
Applicabale Filter Categories: Electrical,Human error,System/Equipment failure | ||
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In a recent incident on an offshore installation, there was an explosion in an open drains tank containing oily water. The tank contained an electric heater which was Ex certified. However, the sheath on the electric heating element had corroded, exposing the conductor. Although the incident is still being investigated, it is thought that this fault led to ignition of flammable material in the tank.
It has also been found that duty holders do not necessarily have a complete list of such heaters, and so cannot be in a position to manage their inspection and maintenance.cted to the TEMPSC, the craft will almost certainly fall to the sea. |
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What Went Wrong?:The contents of a drains tank are likely to be somewhat unpredictable but:
Where a flammable atmosphere may be present in the tank, its interior should be regarded as a hazardous area, and any relevant apparatus in the interior of the tank should be appropriately Ex certified and maintained. |
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Corrective actions and Recommendations:Duty holders should ensure that they are aware of all Ex certified electric heaters on their installations and should ensure that the purpose of each heater is understood. Redundant heaters should be decommissioned [as this is the inherently safer option] and the risks associated with those remaining in service should be appropriately managed in order to reduce those risks to a level which is as low as is reasonably practicable.
Duty holders should ensure that the interior of tanks has an appropriate hazardous area classification if it can contain a potentially flammable atmosphere and has any potential source of ignition.
Duty holders should ensure that any relevant apparatus in a tank whose interior is classified as a hazardous area is appropriately Ex certified. Note that some Ex certified products have special conditions for safe use [indicated by an X on the certificate number]. Duty holders should address any such special conditions for the safe use of Ex certified electric heaters on their installations. For example, the heated part of the element may require to remain immersed when energised; in order to guarantee this, it may be necessary to provide an automatic interlock on tank level to isolate the heater supply when liquid level falls, and appropriate interlocks for start-up and shutdown conditions, in order to prevent violation of the heater T rating and to avoid damage to the heater sheath. Also, a separate over temperature trip function may be required in addition to any temperature control function. Orientation of the heater may be an issue – a horizontally mounted heater is more likely to remain immersed and so be (a) less likely to experience corrosion associated with conditions around the liquid surface, (b) less likely to overheat, and (c) less likely to expose any damaged section of the element to any potentially explosive atmosphere.
Duty holders should address the routine inspection and maintenance activities of:
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Relevant legal requirementsThe Offshore Installations (Prevention of Fire and Explosion, and Emergency Response) Regulations 1995, Regulation 9(2)(d) requires measures to control electrical or other sources of ignition; and the Provision and Use of Work Equipment Regulations 1998, Regulation 12(2)(e) requires measures to control unintended explosions. References1 BS EN60079-17:2007 Explosive Atmospheres: Electrical installations inspection and maintenance BSI 2007 ISBN 978 0 580 55823 8
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Source Contact:Any queries relating to this notice should be addressed to: |