Gas leak

[springy]

The possibility of the bubble tester being faulty has been mentioned a couple of times, I've been considering the potential "failure modes" - did you check the fittings on the bubble tester itself with leak detector ? Could it be a genuinely faulty bubble tester which only leaks (up the button stem ?) when the button is held down ?

 

springy

[blackrose]

2 minutes ago, springy said:

The possibility of the bubble tester being faulty has been mentioned a couple of times, I've been considering the potential "failure modes" - did you check the fittings on the bubble tester itself with leak detector ? Could it be a genuinely faulty bubble tester which only leaks (up the button stem ?) when the button is held down ?

 

springy

 

Yes I checked the bubble tester fittings with leak detector spray and with the sniffer.

 

 

[ditchcrawler]

45 minutes ago, blackrose said:

I'm sending the gas sniffer back to Amazon to pay for the manometer. If there is a small leak I don't think the cheap sniffer is very useful. 

 

What about a digital manometer? Can I use one of these? It's not much more expensive and much easier to store.

 

https://www.amazon.co.uk/dp/B078YDFX4R/ref=cm_sw_r_cp_apa_glc_fabc_BXJC2SQC3REA1CG8Z9YG?_encoding=UTF8&psc=1

 

Why not keep it simple with 4 foot of clear plastic pipe and a bit of water. You are only looking for a change, ie. the pressure falling, not an accurate measurement

 

[blackrose]

1 hour ago, ditchcrawler said:

Why not keep it simple with 4 foot of clear plastic pipe and a bit of water. You are only looking for a change, ie. the pressure falling, not an accurate measurement

 

 

Ok but which tube? Some say not suitable for LPG?

4 hours ago, ditchcrawler said:

I thought you found a leak with your sniffer where it went through the bulkhead 

 

Yes I thought I did too but as I said, the sniffer if giving false readings

[blackrose]

4 hours ago, Tracy D'arth said:

 

Or make one.

Its only 4ft of clear plastic tube, clipped to a bit of wood and a bit of 8mm rubber tube to connect to the nipple. 

 

So how do you make one and how do you use it exactly? I'll need a bit more info.

Edited April 16, 2021 by blackrose

[David Mack]

https://www.komar.org/faq/manometer/

[Tony Brooks]

7 hours ago, blackrose said:

 

Ok but which tube? Some say not suitable for LPG?

 

 

That will be for permanent use and bottom covering. I would use any clear tube.

 

You get a plank of wood about 30 inches long and 4 inches wide.  Clip clear plastic tube (round type nail in plastic cable clips will do) in a long U shape with one end of the tube close to the top of the board. (30 inches or longer to allow for a high regulator adjustment)

 

Fit the rubber tube to the free end of the plastic tube. Rubber tube mentioned above.

 

Half fill the U with clean water and connect to the gas test nipple taking care to avoid any gas leak.

 

The exact procedure is not 100% clear to me but I think its turn the bottle on and then turn it off. Burn some gas off while watching the water in the tube and as soon as the higher side of the water column drops a little turn the burner off. Mark the water level on the board and wait for a fair time. Note the advice about changing temperature affecting the reading.

[Tacet]

Tony's explanation is fuller, but essentially it is a U shaped tube with some water within.

 

When both end are open to the atmosphere, the water is the same height in both legs of the U.  Connect one end to the gas nipple, and the pressure will force the water further along the U such that the difference in height is proportional to the pressure.  Once you have turned off the supply and used up any high-pressure gas before the regulator (by lighting a burner) a leak in the system will be show by a creeping reduction in the difference in height in the columns of water.

 

Any reasonable, clear pipe will do.  I am sure Tony is correct that not-suitable for LPG relates to prolonged use.  If you want to measure the pressure, it needs to have a uniform bore although it is probably difficult to find pipe that doesn't.  The tricky bit will be in making a good seal with the gas end..

 

[David Mack]

13 minutes ago, Tacet said:

If you want to measure the pressure, it needs to have a uniform bore although it is probably difficult to find pipe that doesn't. 

No it doesn't. The pressure will be the difference in level on the two sides of the U times the density of the liquid times the gravitational constant g, regardless of whether the tube diameter is constant or widely varying.

The boat's regulator should be set to a nominal 37mbar. That equates to a 377mm level difference (with water in the manometer).

[blackrose]

2 hours ago, Tony Brooks said:

 

 

Fit the rubber tube to the free end of the plastic tube. Rubber tube mentioned above.

 

 

 

Thanks, but I don't understand this bit. Why wouldn't you just use a single length of tube? 

 

I've seen 8mm diameter tube mentioned. Is this ID or OD?

 

 

 

 

Edited April 17, 2021 by blackrose

[Flyboy]

18 minutes ago, blackrose said:

 

Thanks, but I don't understand this bit. Why wouldn't you just use a single length of tube? 

 

I've seen 8mm diameter tube mentioned. Is this ID or OD?

 

 

 

 

You could use a single length of tube. The use of a bit of rubber tube is to ensure you get a good seal on the nipple.  The diameter of the tube makes no difference so use what you can obtain.  

[David Mack]

57 minutes ago, blackrose said:

 

Thanks, but I don't understand this bit. Why wouldn't you just use a single length of tube? 

 

I've seen 8mm diameter tube mentioned. Is this ID or OD?

 

I used a single length of clear pvc tubing from B&Q. Choose an internal diameter which is a tight fit over your test nipple. I managed to get tube a bit too big, so had to wrap a bit of insulating tape around the nipple to get the tube to seal. Check that seal with your leak detecting fluid too.

[blackrose]

Thanks. I've ordered 2m of 7mm ID silicone tube from eBay and also a more expensive electronic leak detector from screwfix.

 

https://www.screwfix.com/p/tpi-725l-combustible-gas-detector/6050K?tc=DB8&ds_kid=92700055256569569&ds_rl=1244066&gclid=CjwKCAjwjuqDBhAGEiwAdX2cj5KJDuQpjPFq9oZm7FeW_SIZ9X4grfBbK8GN_-vpaOkNHafdeBR0-hoCJ3kQAvD_BwE&gclsrc=aw.ds

 

I tried nipping up all the joints today but no joy.

[Tony Brooks]

1 hour ago, blackrose said:

Thanks. I've ordered 2m of 7mm ID silicone tube from eBay and also a more expensive electronic leak detector from screwfix.

 

https://www.screwfix.com/p/tpi-725l-combustible-gas-detector/6050K?tc=DB8&ds_kid=92700055256569569&ds_rl=1244066&gclid=CjwKCAjwjuqDBhAGEiwAdX2cj5KJDuQpjPFq9oZm7FeW_SIZ9X4grfBbK8GN_-vpaOkNHafdeBR0-hoCJ3kQAvD_BwE&gclsrc=aw.ds

 

I tried nipping up all the joints today but no joy.

2m might be a bit short because at least 28" (24 x 2) will be on the board forming the U tube.

[blackrose]

Well I think I've fixed it. At about 6pm this evening I decided to get into the gas locker and fit the new regulator and manual changeover switch that I bought recently as mine are over 14 years old. After a couple of hours of contortion and lots of swearing the bubble tester is showing no leaks! So I guess I had a leaking regulator or changeover switch.

 

It's not the consensus view but I think bubble testers are excellent because it's an online test. You don't have to fit anything to the system to test it. It's already in the locker waiting for you to push the button. I wonder how many boaters are out there without bubble testers or manometers who don't realise they have a small gas leak? With a bubble tester you can quickly check the system every time you're in the locker to change the bottle or even weekly if you want to. Not many people are going to bother checking that frequently with a manometer.

 

Thanks for everyone's help. Now to cancel those internet orders!

Edited April 17, 2021 by blackrose

[ditchcrawler]

3 hours ago, blackrose said:

Thanks. I've ordered 2m of 7mm ID silicone tube from eBay and also a more expensive electronic leak detector from screwfix.

Can you see through that ?

[Keeping Up]

I have another way of testing, without a bubble tester. Once a month I turn off the gas, at the bottle, overnight - without the boiler being lit, of course - and in the morning I look at the auto-changeover valve. If it has not turned red, I know that I don't have a leak.

[blackrose]

12 minutes ago, Keeping Up said:

I have another way of testing, without a bubble tester. Once a month I turn off the gas, at the bottle, overnight - without the boiler being lit, of course - and in the morning I look at the auto-changeover valve. If it has not turned red, I know that I don't have a leak.

 

And some say a bubble tester isn't accurate enough! ?

15 minutes ago, ditchcrawler said:

Can you see through that ?

 

Yes it's clear, but don't need to see through it now as I've cancelled it.

[Ex Brummie]

On 17/04/2021 at 20:35, blackrose said:

Well I think I've fixed it. At about 6pm this evening I decided to get into the gas locker and fit the new regulator and manual changeover switch that I bought recently as mine are over 14 years old. After a couple of hours of contortion and lots of swearing the bubble tester is showing no leaks! So I guess I had a leaking regulator or changeover switch.

 

 

Surely your bubble tester is downstream from the regulator and changeover valve? Changing them should not affect the bubble tester throughput.

[blackrose]

5 minutes ago, Ex Brummie said:

Surely your bubble tester is downstream from the regulator and changeover valve? Changing them should not affect the bubble tester throughput.

 

Yes I initially thought the same, but does the bubble tester test the low pressure side of the system which includes the changeover switch, isolator switch and connections?

 

Anyway the leak has gone. I tested the bubble tester by putting the kettle on and then tested the system for 2 full minutes several times and there's no leak.

Edited April 20, 2021 by blackrose

[Ex Brummie]

1 minute ago, blackrose said:

 

Yes I initially thought the same, but does the bubble tester test the low pressure side of the system which includes the changeover switch?

I can't envisage your set up then. All the changeover valves I've seen are fed by the HP hoses, and the regulator is fed from the changeover outlet, so the changeover valve is in the high pressure circuit. If your shangeover valve is after the regulator, how does it control 2 bottles?

[blackrose]

Sorry, yes of course you're right. But the isolator is on the low pressure side, so perhaps that was leaking. It was all due to be changed anyway. 15 years old.

Edited April 20, 2021 by blackrose