Gas Alarm

[tidclacy]

https://www.omnitron.co.uk/gas-leak-alarm-for-caravans-p-541.html

Has anybody got one of these and are they any good. If not what would the forum reccommend

 

[PaulRainbow]

Unless it has a probe at the lowest point within the boat (usually the bilge), a gas alarm is a waste of time on a boat.

 

[VicS]

It looks like good idea ..... but

Are the sensors integral or remote?
A sensor for lpg should be positioned t some low point because lpg is more dense than air
A sensor for CO, which is marginally lighter than air, should be close to the "breathing zone".

Sensors for CO alarms are usually electrochemical devices which have a finite life . Usually 7 or 10 years after which the whole device is discarded.

It would be well worth investigating further before investing £67. Try to find some online installation and operating instructions if you can.

 

[PaulRainbow]

On this page : https://www.omnitron.co.uk/gas-leak-detectors-co-co2-alarms/gas-leak-monitors-alarms-c-113_173.html

they list detectors for various applications, boats/motor homes/caravans/home, but no matter which you click on it takes you to the same product.

If it could be mounted at a suitable height for Co detection, with a remote LPG sensor for fitting in the bilge, it would be good value at £80. If not, it's a high priced Co detector on a boat and dubious in the other applications.

 

[Kinsale373]

Can you afford the power drain? 50mA seems small but over a week its 8.5 A/Hour from your battery if you leave it power up.
It defeats the purpose of having it if you only turn it on when you come back to the boat +if it is not Atex rated it could provide the ignition spark !
As I said some weeks ago , I believe the best solution for a small boat which is not in continuous use is an Atex rated portable gas detector. BW Honeywell are the best from my experience. Check the price of a a unit with Flammable LEL and Carbon monoxide head.

The small cheap Carbon monoxide alarm are definately great value and very useful on a boat to detect exhaust leaks into the cabins.

Kinale 373

 

[ex-Gladys]

Can you afford the power drain? 50mA seems small but over a week its 8.5 A/Hour from your battery if you leave it power up.
It defeats the purpose of having it if you only turn it on when you come back to the boat +if it is not Atex rated it could provide the ignition spark !
As I said some weeks ago , I believe the best solution for a small boat which is not in continuous use is an Atex rated portable gas detector. BW Honeywell are the best from my experience. Check the price of a a unit with Flammable LEL and Carbon monoxide head.

The small cheap Carbon monoxide alarm are definately great value and very useful on a boat to detect exhaust leaks into the cabins.

Kinale 373

I'm looking at Nereus combined CO/LPG with dual sensors (Waterproof LPG one)... not sure that the power drain is an issue (it's similar 60mA) because you'd have it linked to mains switches, as the gas would be off at the bottle when you left the boat, surely?

 

[Kinsale373]

I looked at Nereus some years ago with a view to selling over here in Ireland. They seem to be an excellent system and as far as I know, they are the only manufacturers to have a Waterproof Lel/ Flammable sensor.
My only question mark is the power drain from the Flammable sensor. If you have a Solar Panel or wind generator, or you start the engine a couple of times a week providing top up, then no problem. If you have a marginal electrical system , old batteries, low Amp/ Hours, then be careful with it.
I believe the portable gas detectors are a great alternative in this case as you can safely turn them on and test as you enter the boat . Say you forget to turn off the Valve on the Gas Line and suspect a leaky Jet or connection. You can safely test with a portable unit before you hit any electrical switches. You can also use a portable with CO to test in around the exhaust system for leaks.

Kinsale 373.

 

[LittleSister]

It defeats the purpose of having it if you only turn it on when you come back to the boat +if it is not Atex rated it could provide the ignition spark !

Really?

I would have thought that the chance of a spark from something so low power was remote, and an explosive level of gas at head/wiring height was quite obvious to the nose. The combination of the two, together with turning the gas off at the cylinder when the boat was unattended, would seem a quite safe and practical way of providing a means of warning of gas accumulating in the bilges/around the feet when the boat is in use.

 

[Kinsale373]

Static charge is one very common source of ignition and there is generally a very low amount of power involved so you don't need much to cause a small arc. Turning on your Main Switches to power the distribution panel could be enough if the bilges are with gas.

If you are happy to rely on turning off the Gas Valve and sniffing for Gas when you come back to the boat then why bother with the cost of installing a Gas Alarm. I believe that this is a reasonable approach.
But if you do install one, do it correctly and it should be powered up all the time to be effective and safe,

Kinsale 373

 

[Momac]

If concerned about gas escape while the boat is unoccupied..............
When leaving the boat light a cooker hob burner then turn the gas off at the cylinder . Allow the flame to extinguish then close the valve to the burner. This way there will be little gas in the pipework an whatever gas remains will not be under pressure.
.

 

[Minchsailor]

Really?

I would have thought that the chance of a spark from something so low power was remote, and an explosive level of gas at head/wiring height was quite obvious to the nose......

NO. I used to be involved in the design of electrical/electronic equipment for use in flammable atmospheres (think oil refineries, natural gas processing plants - what is now refereed to as ATEX). The characteristics of an electrical spark that can ignite gases is quite complex, but the spark across a 12V switch could have the possibility.

The best way is passive protection. I've seen no mention of fitting a bubbler leak detector after the regulator. Regular use of one to check integrity of the system is probably the first thing to do, then consider a gas alarm.

 

[LittleSister]

If you are happy to rely on turning off the Gas Valve and sniffing for Gas when you come back to the boat then why bother with the cost of installing a Gas Alarm.

As I suggested in my post - it's to give warning of an emerging problem when the gas is on and the boat is in use. It is not a substitute for common sense. It doesn't need to be on when the boat is not in use - that's what gas shut off valve and overboard draining gas locker are for.

 

[PaulRainbow]

As I suggested in my post - it's to give warning of an emerging problem when the gas is on and the boat is in use. It is not a substitute for common sense. It doesn't need to be on when the boat is not in use - that's what gas shut off valve and overboard draining gas locker are for.

I agree, the gas alarm is to warn you when you are onboard. With a portable "sniffer" how often are we supposed to lift the sole boards and crawl through the bilges to check for leaks ?

When leaving the boat, bottles and 12v isolators off, sea cocks closed etc. When returning, reverse the process.

 

[PaulRainbow]

There's been a few mentions of CO alarms in this thread. I'd suggest treating them as a separate item. A decent battery one doesn't cost much and has a 10 year battery life, at which point you throw it away and fit a new one.

I'd want my gas alarm (yes, i haven't got around to fitting one yet) to be 12v powered with a probe in the bilge. On when the domestic isolator is on only.

 

[Kinsale373]

In a boat you are most at risk when you return after a day or a week and have left the Gas Valve open or it leaks a bit. If you have any leaks in the supply line or the cooker itself them you may have built up a dangerous amount of Gas which is heavier than air and fills the bilges and above . So when you turn on your main electrical switches you generate an ignition spark and up you go! You might not get a chance to turn on your Gas Detector !
Leave it powered up or you are wasting your money !

What does Minchsailor think of the idea of using an Atex rated portable Gas detector on a small boat instead of fixed Gas Detection. I use mine regularly, If I have left the Valve on by mistake, I check around the bilges before I turn on electrical power. I also use the CO head around the the engine compartment to test for exhaust leaks.

Kinsale 373

 

[VicS]

In a boat you are most at risk when you return after a day or a week and have left the Gas Valve open or it leaks a bit. If you have any leaks in the supply line or the cooker itself them you may have built up a dangerous amount of Gas which is heavier than air and fills the bilges and above . So when you turn on your main electrical switches you generate an ignition spark and up you go! You might not get a chance to turn on your Gas Detector !
Leave it powered up or you are wasting your money !

What does Minchsailor think of the idea of using an Atex rated portable Gas detector on a small boat instead of fixed Gas Detection. I use mine regularly, If I have left the Valve on by mistake, I check around the bilges before I turn on electrical power. I also use the CO head around the the engine compartment to test for exhaust leaks.

Kinsale 373

Surely your main isolator switches are ignition protected?

If not change them to a type that are ......... but remove all gas cylinders from the boat before you start any work on the electrical system!

 

[LittleSister]

In a boat you are most at risk when you return after a day or a week and have left the Gas Valve open

Then don't!

In a boat you are most at risk when you return after a day or a week and have left the Gas Valve open or it leaks a bit.

No. It will be absolutely fine if you just leave the gas on. It will be absolutely fine if there's just a leak. It will only be a problem if you have both left the gas on and have a leak (and don't use common sense when you get back on board).

Risks are about likelihood and severity. The severity is high. The likelihood is low, and can be reduced to very low by simple measures that don't involve having huge battery banks.

I suggest if someone's that worried about the risks of gas they get rid of the gas and fit diesel, paraffin or spirit kit, but they're free to do what they want.

I am curious as to whether those gas alarms left powered up when the boat is not in use have the facility to disable the bilge pump, or does the boat just goes bang unattended when the bilge switch kicks in?

 

[VicS]

Then don't!



No. It will be absolutely fine if you just leave the gas on. It will be absolutely fine if there's just a leak. It will only be a problem if you have both left the gas on and have a leak (and don't use common sense when you get back on board).

Risks are about likelihood and severity. The severity is high. The likelihood is low, and can be reduced to very low by simple measures that don't involve having huge battery banks.

I suggest if someone's that worried about the risks of gas they get rid of the gas and fit diesel, paraffin or spirit kit, but they're free to do what they want.

I am curious as to whether those gas alarms left powered up when the boat is not in use have the facility to disable the bilge pump, or does the boat just goes bang unattended when the bilge switch kicks in?

Neither
Decent bilge pumps, eg the Rule submersible pumps, are ignition protected!

But I guess if the alarm has the facility to shut a gas isolation valve, some do some don't, that could also be wired to disable the bilge pump

 

[Minchsailor]

What does Minchsailor think of the idea of using an Atex rated portable Gas detector on a small boat instead of fixed Gas Detection. I use mine regularly, If I have left the Valve on by mistake, I check around the bilges before I turn on electrical power. I also use the CO head around the the engine compartment to test for exhaust leaks.
Kinsale 373

I'm flattered that my opinion should be sought. I can see no point in having an alarm continuously powered when there is one on board to take action should it respond. I think it has been identified that what the OP is worried about is a build-up of gas when returning to an unoccupied boat. Two possibilities:

1. An installed ATEX rated detector. This is not a simple proposition as it needs an ATEX rated isolated power supply. This would be connected directly to the battery (bypassing the main 1-2/off switch), and switched by an external switch - say in a cockpit cubbyhole. Get on-board, power up the gas alarm, if OK, turn the main battery on.

2. A portable gas 'sniffer'. Get on-board, pull-up the floor boards, have a sniff around, if OK, turn the main battery on. This seems to me to be the more practical option. Expect to pay around £150 for a reliable one. Remember that both options will require the detectors to be recalibrated ever so often, otherwise they are useless.

Mercifully, incidents involving LPG seem to be relatively few and far between, although when they do occur they have tragic consequences. Reading reports they seems so be caused by silly mistakes. Prevention is the best thing to do. I have a check list for leaving the boat in the back of the log book (wallet, keys, glasses, ensign, clean heads,......, gas off, battery off). Regular maintenance of the gas system. New rubber hoses every 3-4 years are pennies. Replace the regulator every 5 years. It is quite likely the seals in the valves of the cooker will get a bit tired; replace after, say 15 years, even the whole cooker.

As my boat is in winter storage a long way from where I live and will be unoccupied for 6 months, I have removed the regulator from the gas bottle.

Perhaps it's my professional training, but what does gives me the heeby-geebies are packed moorings. I know that I may have taken all reasonable precautions, but if the boat next to me hasn't, then all my work is worthless.

We talk about making things 'safe', or doing something as 'unsafe'. We are very bad at quantifying what we mean by 'safe' or 'unsafe'. We can never have something that is 100.00% safe. All we can do is to reduce the risk to that which is acceptable. We are quite happy to drive around in cars at high speed - how many people get killed on the roads each day? - but that is perceived as 'safe'.

Think about it.

For the record - I don't have a LPG alarm (but I do have a bubble leak detector), I do have a CO alarm.

 

[PaulRainbow]

Perhaps it's my professional training, but what does gives me the heeby-geebies are packed moorings. I know that I may have taken all reasonable precautions, but if the boat next to me hasn't, then all my work is worthless.

You could be in a marina next to Nickolas123 :ambivalence::disgust::eek-new: