202545 Green patina crashes the fire drill

30 Oct 2025 MARS

As edited from USCG Safety Alert16-25

A passenger vessel was undergoing a US Coast Guard inspection, including a test of the high pressure water mist nozzles (part of the HI-FOG fire suppression system). The high-pressure water mist nozzles are designed to hold the standard line pressure of 25 bar (363 PSI). When the glass bulb thermal actuator reaches a certain temperature, it breaks, activating the release mechanism which allows water to flow through the nozzle at the standing pressure. The system then senses the drop in pressure and automatically activates the high pressure pumps, increasing the pressure to 140 bar (2,031 PSI). This increased pressure is required for the system to achieve an effective release of water as a mist.


Due to past failures, the manufacturer (Marioff) released a Service Bulletin (001/2012) recommending that if a nozzle fails to release at the standing pressure of 25 bar after the glass bulb is broken, the high-pressure pumps must be manually energised to raise the pressure to 140 bar. This should activate the release mechanism, allowing water to flow through the nozzle. During the examination this recommended action was taken, but did not activate the release mechanism of the nozzles as expected.

Upon closer inspection, it was found that the high-pressure water mist nozzles had accumulations of green patina, a sign of corrosion, which rendered them unable to release water after the glass bulb broke, even with 140 bar pressure.

Lessons learned

  • Does your vessel have high-pressure water mist nozzles? Check for green patina!
  • Sprinklers at the highest risk of corrosion include sprinklers more than 10 years old and those located in high moisture and corrosive atmospheres. Areas of high moisture could include outer decks, spas, pool areas, galleys, or even normal passenger and crew areas close to external doors.
  • Contact the manufacturer if any signs of green patina build-up are observed on high-pressure water mist nozzles. Consider replacing the affected nozzles.
As edited from USCG Safety Alert 16-25:

 

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