Pilot gas detector is there a leak or not ??

[rogersimms]

Hi All

I know there have been various discussions regarding leaks but this one is giving me a headache where to start so here goes.

I have a Pilot gas detector which works extremely well. It will detect anything from gassing batteries, all sorts of cleaning products, and of course gas.

Recently the gas alarm randomly goes, off maybe after a few days, sometimes a couple of times a day.

My concern is gas and to test if it really is a gas problem or is it just using to much deodorant. the batteries are not overcharging and there has been no excessive cleaning So how do I do this. I do not have access to corgi registered engineers or specialised equipment although if there was some detector that could test for just gas propane or butane I think I would buy one.

Looking at other posts someone mentioned a bubble test which I presume replicates a pressure test. How do I make one. Are there any simple diagrams on how to do this.

Just to let you know it is a long run from the aft gas locker going to the gas solenoid which is by the cooker, not the ideal setup which I really would like to change but first things first. I should also mentioned the lowest sensor in the boat which is in the engin room is the one setting of the alarm every time. which makes me think that something is setting it off. This of course doesnt aliminate that it could also be a faulty sensor. Cant smell gas either

Thanks

 

[Cliveshep]

Making a bubble tester is not on, seriously, but you can buy one cheaply from ASAP. Fit it into the pipework close to the bottle in the gas locker and you can test at any time. Testing is done with appliances turned off. All craft should have one, no excuses here, and if you have to undergo a BSS test it's about the best way of carrying out a system integrity test without a manometer (u-gauge) and a lot quicker. BSS examiners love them, makes their job so much easier.

Re: your engine room sensor, if a bubble test shows nothing but alarm still goes off - change the detector head or get it to an air-line and blow it clean if you can. Generally, change the detector.

 

[Skyva_2]

The detector heads have a finite life, and 'fail safe' as if detecting gas. Sounds as if changing it will be worth trying at least.

A bubble detector will give added security.

Or there might be someone local with a manometer?

 

[Dipper]

[ QUOTE ]
I should also mentioned the lowest sensor in the boat which is in the engine room is the one setting off the alarm every time. which makes me think that something is setting it off.

[/ QUOTE ]

My gas alarm kept going off. When I sent it back to Technisol (Pilot) they said the sensors were contaminated with diesel. I did have a slight diesel leak from one of the banjo joints and the fumes must have permeated the bilges. Unfortunately with diesel, it 'condenses' on surfaces including the sensors and will set off the alarm even after the fumes have dissipated. At least, that was my understanding.

Fitting a new washer to the banjo joint and replacing the sensors seems to have cured it.

 

[bluedragon]

For what it's worth, I've found my nose is at least as good as these detectors (actually I think better). If you can't smell gas when it goes off, it really sounds like it's something else. But as you say, best to be safe and find some means of checking the system.

 

[Cliveshep]

You must have a nose like a super-retriever 'cos detectors detect gas in concentrations of one to zillions!

 

[VicS]

[ QUOTE ]
You must have a nose like a super-retriever 'cos detectors detect gas in concentrations of one to zillions!

[/ QUOTE ] To set the record straight the gas detectors such as the Pilot ones are set to alarm at a maximum of 25% of the "lower explosive limit" (LEL)

The LEL of butane is 1.5% (by volume) and of propane 2.1% . We are therefore talking about approx 0.4% and 0.5% respectively for the concentrations at which the instrument will alarm. Not concentrations as low as parts per million, billion, trillion etc.

The sensitivity of the human nose does of course vary but the concentrations at which a "typical nose" will detect a strong smell of LPG gases is quoted at about 5% of the LEL. Significantly lower than the alarm setting of the typical gas detectors. It would however be folly to rely on the sense of smell as the smell of the gas could easily be masked by another or affected in some other way.

Bluedragon is therefore probably quite correct in claiming that his nose is more sensitive than the gas detectors.

 

[claudio]

The smell test is Ok in the UK, however most propane or butane gas in Europe does not have any smell added. Aerosols also use inflammable propellants. I would say that the nose is an unreliable detector. Gas detectors generally detect the gas by a heated wire, when gas is present the wire burns hotter. This changes the resistance and triggers the alarm.

If the detector keeps going off, there is either gas in the bilge or the detector is faulty. You can use a gas cigarette lighter to test the sensor.

 

[Laysula]

So where can I buy a replacement detector head?

 

[Skyva_2]

Technisol, the manufacturer, very helpful:

http://www.technisolltd.co.uk/gas-alarms.html

 

[PembrokeshirePromise]

Just asked:

new sensor (PDH/3) is £24.06 including postage and vat.