rotrax
Well-Known Member
Quite right-but by pressing a button for a few seconds you are SURE it is not leaking downstream of the tester.
latest gas regs
- Thread starter Scomber
- Start date
Quite right-but by pressing a button for a few seconds you are SURE it is not leaking downstream of the tester.
VicMallows
Well-Known Member
I think we now need to start considering how long it takes for a visible air bubble to appear .... and compare this to a pressure-drop test measured with a manometer.
(my wife would still probably detect an even smaller leakage!).Scomber
Well-Known Member
thanks for the diagrams vics- thanks to all for interesting points to considerUse the BSS chapter 7 as a guide and you wont go far wrong. New version never has been published as far as i know but 2005 version in its entirety at
http://www.boatsafetyscheme.org/media/180428/bss guide 2005 complete web.pdf
Very simple system and a more complex sytem ( PBO Many years ago)
galeus
Well-Known Member
http://www.gaslowdirect.com/epages/...ries/Gaslow_Products/Gaslow_Marine_Regulators
I have a bubble leak detector in my gas locker and also the above marine regulator that has another test device incorporated , so for the 1 foot or so of hose that is untested by the bubble leak tester you can check for leaks via this.
I no longer have a need for a BSC but the last test I had done the tester was happy to use the bubble leak test in place of a manometer test for the tightness of the system. So for Vic who cannot fit the BLD in his gas locker, perhaps with this regulator is as near as you will get.
I have a bubble leak detector in my gas locker and also the above marine regulator that has another test device incorporated , so for the 1 foot or so of hose that is untested by the bubble leak tester you can check for leaks via this.
I no longer have a need for a BSC but the last test I had done the tester was happy to use the bubble leak test in place of a manometer test for the tightness of the system. So for Vic who cannot fit the BLD in his gas locker, perhaps with this regulator is as near as you will get.
VicS
Well-Known Member
Not practical to fit it there.
The place it might go is where the joint is at present but only if its acceptable for it to be outside the gaslocker.
The installation instructions say : "The leak detector shall be fitted after the regulator in the same space as the gas bottle. ......The distance between the detector and the regulator shall be as short as possible."
rotrax
Well-Known Member
I think we now need to start considering how long it takes for a visible air bubble to appear .... and compare this to a pressure-drop test measured with a manometer.
I dont know if you have one, or if you know how they work.
When the button is pressed, there should be no bubbles in the little bowl of vegtable oil. I cracked a joint and bubbles passed through the unit instantly.
If you open the tap or solenoid and press a cooker button or knob in the lighting position all the gas flowing passes through the oil in the bowl-constant bubbles, a fierce stream.
If it is a bit inconvienient to open the tap or solenoid so the gas is under pressure at the cooker, press the button and watch for a few seconds for a bubble-or bubbles-then a scientific instument like a pressure drop manometer could be used. But that sounds like a bit of a faff.
I'll stick to my permanently installed, high quality, Danish made bubble leak tester.
AFAIK nothing else is as practical as one of those on a boat gas system.
If you know better- I'm all ears.
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rotrax
Well-Known Member
That is correct-you will want to test the longest run of pipe and the appliance.
VicS
Well-Known Member
I think we now need to start considering how long it takes for a visible air bubble to appear .... and compare this to a pressure-drop test measured with a manometer.
There are two tests that should be done to a new or modified installation using a manometer.
One to test the pipework and appliances before the gas bottle and regulator are connected. This is done with air ( bicycle pump) at 70mb
The other to test the complete installation which uses gas at 30mb for propane or 20mb for butane ( achieved by pressurising with gas and then burning off a little to get down to those pressures). I guess a system with a 30mb dual fuel regulator would be done at 20mb)
Full details were in the Corgi manual. I guess the same, or maybe revised procedure, in an equivalent Gassafe manual.
VicMallows
Well-Known Member
My point about a few seconds was that a VERY tiny leek would take some time to form a bubble large enough to be obvious. (You may argue that then it is so small it does not matter). Of course a substantial leak - or tap turned on - will cause an obvious stream of bubbles.
Manometer: Yes, it is essential to drop the down-stream pressure a little below the regulator pressure (after turning off the bottle) otherwise the residual up-stream pressure will maintain the pressure for some time even if there is a leak. A common mistake indeed.
Manometer: Yes, it is essential to drop the down-stream pressure a little below the regulator pressure (after turning off the bottle) otherwise the residual up-stream pressure will maintain the pressure for some time even if there is a leak. A common mistake indeed.
rotrax
Well-Known Member
I fully appreciate that. In reality, all gas flowing when the tester's button is pushed must flow through the bowl of vegtable oil.
If ANY gas is flowing due to a tiny leak, it will make a tiny bubble, or bubbles.
That is why it is best to hold it depressed for a few seconds. Also why it should be installed with good visibility.
I hate to think how I would have got a good installation on our previous boat-but the one before would have been a doddle.
vyv_cox
Well-Known Member
Interesting that every Sadler 32 and 34 ever built, unless modified subsequently, do not have a gas drain overboard. Gas leaks are supposed to drain from the cockpit through the water drains but the elbows on these are attached to the forward-sloping transom, forming a reservoir for water. It is therefore impossible for gas to drain away. How many of these boats have suffered gas explosions? I have never heard of one.
KREW2
Well-Known Member
I have a bubble tester in my gas locker. After a long period of being shut down, say 4/6 weeks I turned on the gas and it bubbled for about 2 seconds.
4/5 hours later i tested it again and all was okay.
I am going to check it out as I believe there is no tolerance allowed on LPG.
4/5 hours later i tested it again and all was okay.
I am going to check it out as I believe there is no tolerance allowed on LPG.
Scomber
Well-Known Member
vyv-thats why i moved the gas cylinder to sit by tiller strapped to pushpit so no worries about leaks into cockpit/bilge-the water drains are looped so gas couldnt get out that way-not too sure where leak detector etc would go in our situation
thanks
VicS
Well-Known Member
It would be a very tight system indeed if it maintained the pressure for 4 weeks
Read the instructions for the leak detector and I think you will find that they suggest holding the button on the detector down for 1 minute
nigelmercier
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That's a decision made then...
Can you turn the gas on please darling.
OK, just a minute...
It's not coming on.
I know, just wait a minute.
I'm standing here with my third lit match, what's the problem?
I'm checking something.
Do you want a cup of tea or not?
Just 30 seconds.
Make your own ****ing tea!
VicS
Well-Known Member
If SWMBO is standing there with the gas top open they'll not have to wait for a whole minute before seeing bubbles .............. and concluding that there is a massive gas leak
rotrax
Well-Known Member
On our boat I religously ask First Mate to hit the gas solenoid switch, as soon as the main batteries are on. When she calls " on " I turn the gas on at the bottle and depress the tester button and watch closely. No bubbles I call " OK " and she switches it off. Never seen a bubble yet unless the cooker is on, or on the occaision I cracked a joint at my " belt and braces "tap.
Simples.........................
Simples.........................
pvb
Well-Known Member
rotrax
Well-Known Member
I dont have a gas alarm period.
I use primary safety.
Gas alarm is secondary.
The gas is turned off at the cylinder when we leave the boat.
The bubble leak tester is used as soon as we get back to the boat and the batteries switched on-the electric solenoid will not work untill then. As I stated earlier, this tests the lines right up to the appliance. I am happy-no bubbles= no leaks. Our cooker is a high quality American one more often used in the posh motorhomes from that country.
I was crew on a boat with a gas alarm.
It kept going off when there were no leaks and was disconnected by the skipper.
As another poster said, gas accidents are very rare on boats compared to the number of boats fitted with gas.
pvb
Well-Known Member
OK, so if there had been a leak, and there was gas in the boat, sparks from switching on the batteries or the solenoid could conceivably cause an explosion. I'm not saying this is likely, just that fitting something such as a bubble tester doesn't necessarily improve the basic safety level.
And it was me that suggested that the number of gas-related accidents is incredibly low. Unless one is very careless, LPG in a boat is very safe. I don't have a bubble tester, a solenoid valve or a gas alarm.