Date (Y-M-D): 1989-12-05
Subject: Safety Relief Valves
- Your attention is drawn to a safety hazard which may exist on some electric water heaters.
- Recently one of these heaters exploded, causing extensive damage to the main engine cooling pipes, engine room deckhead, electrical equipment and other items in the vicinity. Fortunately the mishap occured during the night while the vessel was in port and, since no one was on board, there were no casualties. Had it happened when the space was occupied there would, without doubt, have been serious injuries, in all probability some fatal.
- The cause of the explosion was an inoperative safety relief valve which, in conjunction with an electrical fault that allowed the heating element to remain on, raised steam in the body of the heater to its bursting pressure.
- The safety relief valve was found to have been tampered with. The pressure adjusting sleeve had been screwed down to the extent that the discharge opening of the valve was blocked.
- The heater and safety relief valve were of a type manufactured in 1972. It is now possible to obtain non adjustable valves that, in addition to pressure relief, have the added feature of a set point temperature release. The use of this type of safety relief valve is recommended for domestic type water heaters.
- Although this bulletin refers to electric water heaters, the practice of overloading any safety valve is foolhardy in the extreme. In certain circumstances it could become the basis for certificate suspension, withdrawal or possibly prosecution under the provisions of the Canada Shipping Act.
Keywords: Questions concerning this bulletin should be addressed to:
2. Water Safety
3. Safety valve
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Ottawa, Ontario K1A 0N8
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