Watermist fire fighting MV electrical safety

Ask the system makers.

Info:

Hi David,

Have you considered systems such as Firetrace? These can be interfaced with the main fire alarm system etc. These are Co2 based and is basically an extinguisher with a pressurised tube that is routed through the protected area. It is a totally self contained system that is not affected by power loss etc where the extinguishant is concerned. 

If this is an area you would like to explore as an alternative for the switch boards etc drop me a pm. 

Regards TS

Water mist works on the basis that the droplets of water are too fine to provide a conductive path, would not like to use this in a confined space as I would imagine this may have a detrimental effect on the size/dispersion of droplets and thereby become conductive. 

Regards TS

Hi TS, this is indeed the view that is put forward to make it safe in electrical switchboard rooms. However, with an MV convertor running at 6.6KV and the potential for the droplets to start ‘pooling’ does this then create the situation where a ‘charged coil’ with a decay of over 6 minutes once isolated  becomes a hazard to fire fighters? Hence my question to ask if there is any testing available to validate the ‘generic’ claims thats it's OK to use on switchgear rather than subjective comments from the makers??

I am not sure that this is the appropriate forum for such a specialised question and of course ships are out of the scope of BS 7671, but I am interested in the idea of a hybrid ship. Is that like, e.g. HMS QE with diesel engines and electric motors on the propellers? I feel sure that the damage control provisions are state of the art.

Hi David,

The Fire Trace system would actually be installed within the electrical panels as to speak, this way the fire is extinguished at source. If such a system is installed what perceived risks remain?

Regards TS

David Gorshkov: 
 

Hi TS, this is indeed the view that is put forward to make it safe in electrical switchboard rooms. However, with an MV convertor running at 6.6KV and the potential for the droplets to start ‘pooling’ does this then create the situation where a ‘charged coil’ with a decay of over 6 minutes once isolated  becomes a hazard to fire fighters? Hence my question to ask if there is any testing available to validate the ‘generic’ claims thats it's OK to use on switchgear rather than subjective comments from the makers??

I don't think that the manufacturer's would be testing with your location specifics in mind, if this is the preferred route it may be best to open dialogue with a specialist manufacturer of water mist systems. I'm sure you are aware you will also need sufficient space for the holding tank.

Regards TS

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!

David Gorshkov: 
… enabling us to use battery power in port …

David, thank you - that is interesting. I live on the Solent and I am aware of the concerns about cruise ship emissions in port.

Of course, like the ULEZ in London, it just shifts the problem away from the city centre - in this case hopefully well out to sea.

I hope you make yourself available to your local ET a branch, David. I could see you delivering a vey interesting technical walkthrough of your new vessels!

As an aside, are shore connections completely out of the question as an alternative to lugging big batteries every trip?