Incident information on Accident Caused by Fractured Exhaust Gas Boiler Circulating Pump

This incident occurred while at sea when crewmembers were switching from one circulating pump of the exhaust gas boiler to the other, as part of normal operation. The connected pump fractured and released considerable amount of hot water and steam.

2013.11.08 - Incident information on Accident Caused by Fractured Exhaust Gas Boiler Circulating Pump Figure 1

The incident killed one crew member, and injured/burned two other crewmembers due to the hot water and steam bursting out from the fractured pump, hitting these crew members.

Normal operation pressure for this exhaust gas boiler is about 7 bar and the water through the circulating pump is expected to have been about 170 degrees Celsius.

The fractured pump was a purchased spare pump, which had replaced one of the two original parallel circulating pumps. The fractured spare pump was not the same brand as the original pump and the two pumps looked differently.

The mounted spare pump had been in use for some years and had been mounted by the crew of the previous management company. A crack in the pump casing finally propagated to such extent that a large piece of the casing broke loose and released the hot water under pressure, which rapidly converted to steam in atmospheric pressure.

The feed for the economiser’s (exhaust gas boiler’s) circulating pump comes from the main boiler pressurised water side, which means that once damage has occurred, a large volume of hot water will be released before the system can be isolated.

A second identical purchased spare pump was subsequently found on board. No certification / documentation was found for any of these purchased spare pumps.

It is suggested that the probable cause was that the fractured pump was neither designed nor suitable for the selected use.

2013.11.08 - Incident information on Accident Caused by Fractured Exhaust Gas Boiler Circulating Pump Figure 2

Photo above: Example of not identical parallel circulating pumps

Lessons to be learned

  • Pumps and other components in safety critical systems are normally required to carry a Class Certificate. The objective of such documentation is to provide sufficient safeguards for the intended use.
  • Even in “low” pressurised parts of a system, a rupture or damage to the system may release vast amount of water/steam mixture, which can cause serious injury to personnel.
  • Ship’s crew should ensure that certified components are replaced only by equally certified components, during maintenance and repair of the vessel. If there is any doubt, the Class surveyor should be consulted.
  • Be particularly observant if two pumps in the same system do not look the same (especially in a redundancy system with main+backup) and double check status of certificates/documentation in relation to intended use.

Source: DNV

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