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Old 09-28-2022, 07:56 PM   #1
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Auto fire extinguisher size

Hi

I need to buy an automatic fire extinguishing system.

They are sold by cabin volume.

Do I calculate the size of the engine room or by the free volume excluding the displacement of the engine?

My engine room is approx 500 cubic feet but the engines and associated mechanics probably take 200 cubic feet of that.

I’m thinking that the net free volume is 300 cubic feet, so I should over spec to 500 cubic feet. If that’s wrong then maybe I should overspec to 600? The price jumps quite a bit once you get over 500.

I don’t want to scrimp on a vital piece of safety equipment but I don’t want to waste money either.

Thoughts?
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Old 09-28-2022, 08:50 PM   #2
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Give Fireboy a call and they can help you figure out the right system for the size of your ER.

This is not a go cheap situation.

https://www.fireboy-xintex.com/
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Old 09-28-2022, 08:55 PM   #3
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The advantage of modern halon and its replacements over CO2 is that they can put out fires at concentrations that won’t kill you if you are in the space when they are released. In this case more is not better. Of course that doesn’t answer your question. I think there is a new member in the group who installs fire systems for a living. Hopefully he’ll see this and respond.
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Old 09-28-2022, 11:39 PM   #4
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Quote:
Originally Posted by Tang View Post
Hi

I need to buy an automatic fire extinguishing system.

They are sold by cabin volume.

Do I calculate the size of the engine room or by the free volume excluding the displacement of the engine?

My engine room is approx 500 cubic feet but the engines and associated mechanics probably take 200 cubic feet of that.

Iím thinking that the net free volume is 300 cubic feet, so I should over spec to 500 cubic feet. If thatís wrong then maybe I should overspec to 600? The price jumps quite a bit once you get over 500.

I donít want to scrimp on a vital piece of safety equipment but I donít want to waste money either.

Thoughts?
You are thinking correctly. No need to go up to 600.
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Old 09-29-2022, 05:55 AM   #5
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Keep in mind that the automatic system is only effective if the engine(s) and vent fans are shut off IMMEDIATELY on fire bottle discharge. Otherwise the running engine and vent fans will just suck all the fire suppressant out of the ER. All the automatic system I've seen require an automatic shutdown system to accomplish this. It's a pain to install, but essential if you want the fire system to actually do anything.
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Old 09-29-2022, 06:37 AM   #6
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The Fireboy-Xintex website says the gross volume of the space must be used unless the builder has attached a nameplate deducting the volume of fixed tanks. It also says, if in doubt choose the next larger size.
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Old 09-29-2022, 07:27 AM   #7
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I would rather go over in cubic feet than go under. But it sound like 500ft would do it. But I would call FireBoy. They maybe including everything in the E.R. to a degree.
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Old 09-29-2022, 07:38 AM   #8
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Each of the available agents has 2 important specs: the concentration where it's effective, and the concentration where it's lethal. The wider the gap between those 2, the more you could safely over-size. IIRC, Novec 1230 has a wider spread than FM-200, for example.



Unfortunately I've never seen it available for marine use, but ideally, a system would have 2 bottles. 1 that dumps immediately (and triggers the shutdowns), then unless manually stopped, another that starts deploying a few minutes later and slowly deploys over 15 - 30 minutes to maintain the agent concentration while things cool (to prevent a re-flash). Airplane fire suppression is typically done that way, for example.
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Old 09-29-2022, 07:50 AM   #9
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ď Selecting Your System
1. Determine the volume of your engine compartment in cubic feet or cubic meters, L x W x H. Do NOT deduct for engines, fixed tanks, or other equipment.

2. Choose your model from the Model/Size Chart:

HFC-227ea Clean Agent | FK-5-1-12 Fire Protection Fluid

Example: CG20950227 = automatic discharge with optional manual discharge, 950 cubic feet coverage.

NOTE: When in doubt, always select the larger model size for adequate protection.Ē

https://www.fireboy-xintex.com/cg2-fire-extinguisher/
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Old 09-29-2022, 07:54 AM   #10
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As a note to correlate my comments to what Porgy just posted, HFC-227ea = FM200, FK-5-1-12 = Novec 1230 (Fireboy likes to use the technical names rather than the trade names for the agents).
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Old 09-29-2022, 09:59 AM   #11
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I have oversized the bottle. My engine room bulk measurement per fireboy recomendations without allowance for machinery volume is 500 cu ft. I followed fireboy's recommendation and went up to the next bottle size without concerns for 2 reasons.

1 - I don't worry about the lethal effects of being in the engine room when the bottle trips. I don't go in there when underway, I may open the door for a look if I hear something I don't like. I won't go into an engine room on fire, alone, with no protective gear carrying a portable. That's a sure invitation to die. If the fixed system does not extinguish the fire then it will be time to call for help and abandon ship.

2 - Engines are essentially large effecient air pumps that will quickly strip the extinguishing agent to below effective concentrations from the space. PO had his orignal halon fixed system trip when the exhaust hose after the riser blew out and got surrounding flamable materials hot enough to scorch. He heard a "whomp" as the bottle tripped and the engines slowed for a few beats but never stopped running. The halon replacements also will not stop the engines. I want more time to reach for the shutdowns on the mains when the bottle trips. A bottle for 700 cu ft in a 500 cu ft engine room buys me a bit of time to stop the engines and kill the main DC power. Not much mind you but maybe enough.

If you have an automatic fixed system, are concerned about lethal concentration of the extingjishing agent and want to safely be in the space then you might consider a system similar to that used when CO2 is the agent in manned spaces. A small bottle that fires and sets off a siren, not enough to be lethal but more than enough to hear the siren over the engine noise. A short time later the main bottle trips giving you time to exit the space.
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Old 09-29-2022, 11:42 AM   #12
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Thanks to you all for your replies. Engines would shut off quickly after activation of alarm with the option to restart them as a manual override.

I’m looking into some auto closing engine vents to prevent the gas escaping and oxygen coming in. I believe some boats come with this as standard but mine apparently doesn’t.

As a twin diesel then the risk is higher from the batteries rather than the engines so I’m thinking of having a separate manual unit over the battery box, so that I can manually activate that once the main unit has been exhausted.

If 2 dedicated systems plus the 4 handhelds haven’t put the fire out then I’m going to be watching it burn from the life raft and filling out insurance forms when I get back to shore. I’m not risking my life for a hunk of grp and iron.
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Old 09-29-2022, 01:06 PM   #13
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I have oversized the bottle. My engine room bulk measurement per fireboy recomendations without allowance for machinery volume is 500 cu ft. I followed fireboy's recommendation and went up to the next bottle size without concerns for 2 reasons.

1 - I don't worry about the lethal effects of being in the engine room when the bottle trips. I don't go in there when underway, I may open the door for a look if I hear something I don't like. I won't go into an engine room on fire, alone, with no protective gear carrying a portable. That's a sure invitation to die. If the fixed system does not extinguish the fire then it will be time to call for help and abandon ship.“

You still need to be careful. I know of one incident where two men were killed when they were just working in the engine room. They bumped into something and set off a CO2 system. They were dead before they could get out. No fire involved.
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Old 09-29-2022, 10:59 PM   #14
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Quote:
Originally Posted by HopCar View Post
City: Coupeville Wa.
Vessel Name: Pelorus
Vessel Model: Californian 42 LRC
Join Date: Oct 2015
Posts: 1,786
I have oversized the bottle. My engine room bulk measurement per fireboy recomendations without allowance for machinery volume is 500 cu ft. I followed fireboy's recommendation and went up to the next bottle size without concerns for 2 reasons.

1 - I don't worry about the lethal effects of being in the engine room when the bottle trips. I don't go in there when underway, I may open the door for a look if I hear something I don't like. I won't go into an engine room on fire, alone, with no protective gear carrying a portable. That's a sure invitation to die. If the fixed system does not extinguish the fire then it will be time to call for help and abandon ship.ď

You still need to be careful. I know of one incident where two men were killed when they were just working in the engine room. They bumped into something and set off a CO2 system. They were dead before they could get out. No fire involved.
Yes, CO2 is deadly and accidents can be fatal. However the discussion is about halon replacement agents and the concern that they too can be deadly when the concentration is high enough leading some to not want to oversize their bottle. Along that line I suggested the use of a system designed and installed like a CO2 system if it is a concern.

Additional thoughts related to my previouis. Further reasons to consider going up one size. Most of use don't have auto closures on the ventilation. Many of the older boats this would be very difficult to implement. Almost none of use have water tight compartments. There will always be air leaks, often through the bilge from stem to stern. It is important to keep the extingushing agent high enouth long enough to ensure the fire is out. Oversizing the bottle is one way to do that.

As to the incident you mentioned it would be good to know what they bumped that set the CO2 system off. With decades of experince on boats with properly designed and installed CO2 systems I can't envision that happening. Everytihing was well protected. There was nothing to bump in the engine room that would set the system off. If it did go off the siren and delay before the big bottle(s) released would give time to evacuate the space.
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Old 09-30-2022, 02:08 AM   #15
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As to the incident you mentioned it would be good to know what they bumped that set the CO2 system off. With decades of experince on boats with properly designed and installed CO2 systems I can't envision that happening. Everytihing was well protected. There was nothing to bump in the engine room that would set the system off. If it did go off the siren and delay before the big bottle(s) released would give time to evacuate the space.

This happened in the early seventies at the Richard Bertram Marina near where I worked. I don’t remember the details but I was impressed that they couldn’t get out quick enough. I believe that halon and it’s replacements can be deadly too if the concentration is too high. For that reason you don’t want to go way over size on the system.
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Old 09-30-2022, 02:25 AM   #16
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This probably explains why the guys died so quickly.
“ Carbon dioxide does not only cause asphyxiation by hypoxia but also acts as a toxicant. At high concentrations, it has been showed to cause unconsciousness almost instantaneously and respiratory arrest within 1 min [6].”

Here is a link to the complete report: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5380556/
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Old 10-03-2022, 02:11 PM   #17
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It is the volume of the engine compartment less tankage, no other deductions are to be made for engines, equipment etc.

More here https://stevedmarineconsulting.com/w...reEx125_03.pdf

As someone who spends a great deal of time in engine rooms, my personal preference is for a non-lethal agents, even though they are not required for this 'normally unoccupied space'.

CO2 is prohibited if you seek ABYC compliance.
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Old 10-03-2022, 04:55 PM   #18
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So many automatic systems only shut down the main engine(s). I always have the system rewired to shut down the generator too. Just my preference.
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Old 10-03-2022, 04:57 PM   #19
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I'm an instructor at the Cruising Club of America's Safety at Sea Hands on Training courses. We trained 499 people last year -- 2/3 of which were racing to Bermuda and the rest of which are voyaging to a variety of places.


We are strongly recommending FireTKO FST which is a package about the size of a bowling ball that you toss into the engine room. It is said to be effective up to 5,300 cubic feet. Costs a little over $1,000. See https://www.lrse.com/products/firetko-fst


Unlike dry chemical fire extinguishers, the aerosol is non-corrosive. It is also non-toxic.



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Old 10-04-2022, 12:24 PM   #20
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I'm an instructor at the Cruising Club of America's Safety at Sea Hands on Training courses. We trained 499 people last year -- 2/3 of which were racing to Bermuda and the rest of which are voyaging to a variety of places.


We are strongly recommending FireTKO FST which is a package about the size of a bowling ball that you toss into the engine room. It is said to be effective up to 5,300 cubic feet. Costs a little over $1,000. See https://www.lrse.com/products/firetko-fst


Unlike dry chemical fire extinguishers, the aerosol is non-corrosive. It is also non-toxic.



Jim
The aerosol approach is interesting. If it's what I'm thinking of, these lack USCG or UL approval, and they require a battery to work. Can't hurt, but this is not ABYC compliant for a fixed system, and not a replacement for a fixed clean agent gaseous system.
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