Sizing Automatic FireBoy for our Engine Room

[davidrossboyer]

Need some help in selecting the correct automatic FireBoy Halon System for our GB42 MY engine room. We presently have an external very outdated Halon fire extinguisher that is clearly inappropriate. Also plan to have the remote panel and automated engine shutdown accessory. I’ve calculate the approximate cubic capacity of our engine room with the two CAT 3208’s, fuel & water tanks, the NL Generator, battery banks, etc. and it looks like the 500 cu. ft. model appears to be the one we need. My question is that overkill and we can get away with a smaller system? 300 cu. ft? Would appreciate your input as the cost difference is significant.

 

[Larry M]

What's the difference in the cost between the two sizes? I'd think the installation cost would be the same so the incremental cost for the larger size would minimal in the big picture. Plus I'm not sure for fire protection, if there really is overkill?

 

[rslifkin]

The only risk of overkill with a clean agent system is that over-sizing too much will lead to an agent concentration high enough to kill a person that's in the space when it discharges (most clean agent systems take more to kill a person than is required for effective extinguishing). But a too-small system may be completely ineffective.



Personally, I'd love to see a 2 stage system, but I don't know of anything off the shelf like this for marine use. 1st bottle dumps all in one shot, second releases slowly over the next 20 minutes to maintain extinguishing agent concentration while things cool down to prevent a re-flash. That's basically how airplane cargo fire suppression works.

 

[Portage_Bay]

I was on the edge, the upper limit the installed bottle would handle when I purchased. On the surveyors recommendation I went with next size up. Most recreational boats don't have automatically closing ventilation. Most have bilges open from one end to the other. Both of those things will dilute the extinguishing agent. If the engines are not auto shut down on release of the agent they act as very effecient air pumps removing the agent. Go big.

On a small boat with a small crew nothing scares me more than fire. Small in that sense means too small to muster a fire team without the necessary gear.

 

[Comodave]

I believe you want one system that is large enough not two. Because one of them may not go off in in a fire and with a too small system it may not be enough to put the fire out.

 

[sbu22]

David - I went through a similar exercise with my boat. It had (has) a vintage halon system - removed the wired controls, left the bottles and fusible links. May or may not work.

In sizing the new system, noticed that all of the "sizing calculations" seem to assume that the engineering space(s) are isolated. As Portage noted, my engine room communicates with the rest of the hull volume through open bilges, a few bulkhead openings, and exterior vents. My take was "more is better" and oversized considerably.

The fact is that a fire on a plastic rec boat, unless defeated in the very, very, early stages of development, will probably be disastrous. Based on my marine and industrial firefighting experience, in the event of an ER fire, I will pull the red T handle on my way over the side following my pax.

 

[fgarriso]

I would rather have too much fire protection than just enough. Engine rooms are not sealed tightly, and there will be some delay in getting the system activated.
Remember you "CAN NOT" get of the boat and walk home, unless you can walk on water.

 

[Unclematt]

I went one size up, one in the engine room one in the lazerette for the genset, both hooked to an automatic shut down system. Then I added 4 hand held in different locations around the boat. No such thing as to many. My wives car caught fire in our garage a few years ago, we had enough now I have plenty.

 

[sbu22]

Good point, Unclematt. In addition to the ancient Halon and the newer HFC, I have an assortment of dry chem and CO2 handhelds to augment the installed. However, there is no plan to attempt to use them to battle an ER fire unless it's in the very incipient stages.