gas detectors

[clueless]

hi,

i'm a student doing a bit of research and i was wondering if anyone knows how most gas detectors/alarms used on boats work, and also what the most common problems with them are and how many boats actually have them. (and anything else on the subject you have to offer i guess!). how much does the average detector cost and which are best?

all help is much appreciated, thanks

clueless

 

[webcraft]

Problems I've found are:

They are set low down by necessity and usually well offset from the centre line. A shallow bilged boat with some water in the bilges may, when heeled well over, spill water over the top of the cabin sole which will result in the gas detector getting wet and being set off.

Another problem on at least two boats I've been on is that they are mounted where they are vulnerable to kick damage, and need to be put in a cage.

Costwise a Pilot gas alarm comprising a control box and single station detector head with 4m of cable costs £90 incl vat from Marine Super Store.

I don't know how they work, but will watch this thread in the hope of finding out!

I think insurance companies require them to be fitted - gas on a boat can be a dodgy business. Certainly all coded boats (e.g. charter, training etc) are required to have them fitted.

<font color=blue>Nick</font color=blue> -

BlueMoment.Com
<A target="_blank" HREF=http://www.bluemoment.com/>http://www.bluemoment.com/</A>

 

[celandine]

In my experience gas detectors on a yacht are of limited use since they have to be sited in the bilge, and one splash of bilge water on the detector head does not so much set them off as write them off.

 

[clueless]

thanks a lot! anyone know how they work or is one of the mysteries of the modern world?

 

[dickh]

I have one under the engine and one in the cabin low down - again I understand they get damaged by water, and also the plastic cap gets easily knocked off... - certainly on the Pilot ones.
Also on the Pilot the control box has stupid tiny screws which fix the lid which go in the side of the unit, meaning you cannot mount anything else alongside it, I got over the problem by mounting on a small board and removing the box and board complete if I need to get at the innards. Also in this day of cheap plastic boxes why is it still made of painted steel?

dickh
I'd rather be sailing...

 

[webcraft]

On one boat I've sailed regularly I've had the gas alarm go off at least three times because of water, but it's not been permanently damaged by it. Don't know the make.

I would suggest that a gas alarm on a boat that is destroyed by water is about as much use as a chocolate fireguard.

<font color=blue>Nick</font color=blue> -

BlueMoment.Com
<A target="_blank" HREF=http://www.bluemoment.com/>http://www.bluemoment.com/</A>

 

[gtmoore]

I have a Canary gas detector that cost nearer £50 - it was recommended here some time ago. It's the kind with a seperate sensor to the main alarm. No idea how it works but it went off the other day within about a minute of opening the Evo-stick I was using to affix some sound proofing.

Not sure whether that means it's working properly or not!!

 

[Ray_G]

I have a Pilot and am sick to death of it going off, so much so I have now disconnected it i.e. after checking there is no actual gas leak!!!
My local boatyard tell me that the resin vapours found in lockers are a common cause of setting them off.

 

[AndrewB]

Try this ...

... http://www.biosystems.com/biobull/vol1iss3/lelexp.htm

PS Are you actually interested or are you testing whether anyone here knows? As the author of this article says, it is quite important to have some idea how these things work to install them properly.

 

[clueless]

Re: Try this ...

that was really useful thanks. in answer to your question i am interested in how they work rather than seeing if people know - although it does seem to rather worrying that almost nobody does. i spent a couple of hours trying to find out using various search engines but with no luck which was why i posted my message!

 

[yachtbits]

FROM THE MAKERS OF CANARY GAS DETECTORS

Email me direct for deatils on how the sensors work, its far to boring for a forum!

Yes the sensor heads will be damaged by water. Its a fine line between watertight and gas tight, and a sensor that is gas tight won't detect much. For this reason we make sensor replacement simple.

Evostick and locker paint, the fumes are highly flammable in quantity and very similar in chemical composition to the gas you bought the unit to detect in the first place. Additionally, gas detectors are usually very sensitive to give you plenty of warning before an explosive concentration is reached. typically 10% of the lower explosive limit (LEL), which isn't much at all.

Not much point finding out you are in an explosive atmosphere, and then switching everything off as this is what will cause the spark.

Finally, Canarys come in plastic boxes!

happy, safe sailing


kev
KM Electronics
and

www.yachtbits.co.uk
sales@yachtbits.co.uk
marine electrical/electronics specialists