Bulletin No.: 01/1982

Date (Y-M-D): 1982-03-26
 

Subject: Shipboard Fires Caused by Heating Systems with Electric Re-Heat Elements

It has recently been brought to our attention that a fire on board the CCGS "Louis S. St. Laurent" may have been caused by a combination of excessive heat in the air reheater box and dust laden ducts. This type of heating system is fitted in approximately 85 Canadian registered vessels.

During the past several years, a number of similar incidents involving reheat type heating systems have been brought to our attention. In one specific case, during a preliminary enquiry on a shipboard fire, a situation was encountered where several overheat safety thermal cut-outs were missing and "jumpers" installed to bypass the missing overheat safety cut-outs. The vessel in question had a requirement for 24 new thermal over heat cut-outs. A second incident involved extremely filthy duct trunking and reheater boxes in which the filter system had not been properly maintained. The overheat cut out did not function properly and a fire ensued which caused severe damage to the vessel. Heating systems of this type, employing air "reheater boxes", have been provided with safety features such as overheat safety thermostats and interlocking arrangements to prevent heater operation if the supply fan is stopped or if the fan is belt driven, by belt failure or belt slippage.

Accidents involving faulty electric air reheat systems have not as yet caused loss of life, however, the fact that they were the direct cause of shipboard fires indicate that a very dangerous situation existed in the ships in question and probably, to some degree, exists in many vessels in which regular cleaning and maintenance routines are not followed.

Every vessel in which electric air reheat systems are fitted should have regular maintenance and inspection routines promulgated to ensure that hazardous conditions are eliminated. Inspection and maintenance routines should include the recommendations as published by the system's manufacturer with particular attention being paid to the following:

1. each safety overheat cut-out should be checked for proper operation and temperature rating and defective or missing overheat cut-outs should be replaced immediately.
2. regular filter changes and maintenance in accordance with the manufacturers instructions should be carried out to prevent ducts and re-heat boxes, which contain electric elements, from becoming dust laden and a prime source of ignition.
3. regular cleaning routines should be established, which together with filter changes and planned maintenance, will prevent a build-up of flammable dusts, and
4. all internal electrical connections in re-heat boxes should be checked to ensure tight connections and covers for all boxes should be in place and properly secured.

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