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Watermist fire fighting MV electrical safety

David Gorshkov

I am reviewing the fixed watermist fire fighting installations in a new fleet of hybrid ships we are building . The water mist based fixed fire fighting appliances (FFFA) we are using extends into the main propulsion areas as well as the power generating areas.

Water Mist heads are used instead of sprinklers these days as these are more effective, however I can find no definitive tests or regulations that state water mist is safe to use in Medium Voltage switchboard areas?  Appreciate that if I have a fire the main objective is to extinguish it but it is not unusual for FFFA to be set off accidentally in a technical space so I must then consider IP ratings of equipments in these spaces in order that equipment is not damaged during an accidental discharge and that engineers investigating the incident are not at risk of electrocution from the MV systems which may still be live or charged!

Does anyone have any reference information regarding any testing done on Watermist systems to validate their safety levels with LV, MV and indeed HV systems?

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    Hi Chris, yes thats the idea although HMS QE is an Integrated Electrical propulsion (IEP)  ship not hybrid as she does not have a battery configuration for propulsion. Most Cruise ships are  (IEP) using Diesels (plus Gas Turbines - GTs - sometimes ) driving large alternators which in turn drive Propulsion Electric Motors (PEMs) . These  can drive a shaft line (inside the ship) or PODs (under the ship) via frequency convertors - harmonics are a real challenge! 

    HMS QE has 4 x Diesels and 2 x GT's giving 110MW at 11KV (CODAG) combined diesel and gas configuration with tandem PEMs on 2 shaft lines. New cruise ships have 4 or 6 DG's driving 2 or  PEMs or 2 PODs (sometimes more - RMS QM2 has 4) . 

    Our new Hybrid super ferries have 4 x DG's and 4 x 2MWH battery packs , expandable to 8 x 2 MWH , enabling us to use battery power in port and driving 4 x PODs (unique for a passenger RORO vessel). We also have full dual bridges , again a first for a 230M ferry. These will be in service on Dover Calais in 2022 so we're getting close to seeing them launched!

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    Hi Chris, yes thats the idea although HMS QE is an Integrated Electrical propulsion (IEP)  ship not hybrid as she does not have a battery configuration for propulsion. Most Cruise ships are  (IEP) using Diesels (plus Gas Turbines - GTs - sometimes ) driving large alternators which in turn drive Propulsion Electric Motors (PEMs) . These  can drive a shaft line (inside the ship) or PODs (under the ship) via frequency convertors - harmonics are a real challenge! 

    HMS QE has 4 x Diesels and 2 x GT's giving 110MW at 11KV (CODAG) combined diesel and gas configuration with tandem PEMs on 2 shaft lines. New cruise ships have 4 or 6 DG's driving 2 or  PEMs or 2 PODs (sometimes more - RMS QM2 has 4) . 

    Our new Hybrid super ferries have 4 x DG's and 4 x 2MWH battery packs , expandable to 8 x 2 MWH , enabling us to use battery power in port and driving 4 x PODs (unique for a passenger RORO vessel). We also have full dual bridges , again a first for a 230M ferry. These will be in service on Dover Calais in 2022 so we're getting close to seeing them launched!

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