Fire extinguishers

[Westie11]

What size fire extinguishers do I need for the engine compartments on a lagoon 450

[GordMay]

Greetings and welcome aboard the CF, Westie.

Fire Extinguisher (46 CFR 25) requirements:
For a 40’ to 65’ boat with no fixed system:
(3) B-I or (1) B-II + (1) B-I

➥ https://www.law.cornell.edu/cfr/text/46/25.30-20

➥ https://www.uscgboating.org/images/420.PDF

[Pete7]

Is this for a UK flagged vessel? if so you should consider the SOLAS regulations:

General exemption in relation to Fire Protection on Class XII vessels | Pleasure Craft Regulations | Regulations | Knowledge & Advice | Knowledge & Advice | RYA

[Bean Counter]

The engine compartment on a L450 can be accessed via a through bulkhead fitting in the rear cabins. This is so you don't need to open the engine hatch and possibly have a rush of flame come up at you. The extinguisher will need to have a hose/nozzle that fits through the hole. The one that came with this boat is a 2Kg Halocarbon for class B and C fires (fuel and electrical). We have 3 other 1.5Kg chemical B/C one in each hull and one in the cockpit. (We still have 3 older ones out of date but still showing pressure in the green) and a fire blanket.

[mikereed100]

If you are using hand held extinguishers, just get the biggest you can manage. We use automatic extinguishers mounted inside the compartments. These are rated for a certain volume of space. Simply measure the compartments and estimate the volume. Bigger is better!

[Bean Counter]

Originally Posted by mikereed100

If you are using hand held extinguishers, just get the biggest you can manage. We use automatic extinguishers mounted inside the compartments. These are rated for a certain volume of space. Simply measure the compartments and estimate the volume. Bigger is better!

I like the idea of an automatic one.
Which brand/model automatic ones do you recommend?

[mikereed100]

Originally Posted by Bean Counter

I like the idea of an automatic one.
Which brand/model automatic ones do you recommend?

We are using Sea-Fire, but I don't think the brand is as important as size. As the saying goes; "go big or go home". We also have a 10 lb dry chemical extinguisher in a locker outside each engine compartment and an automatic behind the Nav station where the solar controller, batteries and most of the electrical connections are.

[sy_gilana]

Go BIG!
Extinguishers rated for a specific volume are all well and good but.....

In my experience, you need more. The initial inrush of Halides or CO2 is a very temporary solution. It will knock down the actual flame, but the other 2 sides of the triangle still exist, namely heat and fuel. After your gas replacement system is empty, the fire is out but the components are merely waiting to get some oxygen to restart, and sometimes will do so explosively as flammable gasses will be releasing. Ideally, boundary cooling and direct cooling will be needed, then ventilation.

The best system is the HiFog, where flame suppression and cooling happen simultaneously.

To answer your initial question, size it according to specs, then increase it.

It might all be completely useless anyway, as your bulkheads and access hatch are plastic and will burn. Your internal hoses should be in steel up to above waterline, otherwise they will burn through and admit water, (thus helping with the cooling, but adding another problem.)

Do you have external fuel shut off valves? Is there a battery in the same compartment? Is fuel, gas, propane, cans of spray, lubes stored in the same compartment?

Fire is my biggest fear on board.

Maybe look up Lloyds 100/A1 requirements for an idea.

[Badsanta]

In regards to hand held extinguisher, every year take it off rack, turn it upside down and shake it, if you can't feel the powder shift wack it with a rubber mallet on the base, if you can't feel the weight shift, just trash it. To be safe just replace them every few years. That powder will get hard from sitting and won't work even if still under pressure.