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3 hours ago, ditchcrawler said:

If you close off the cylinder the pressure should remain static, if you have a leak in the high or low pressure side it will leak away. A bubble tester will only detect leaks down stream of the bubble tester.  We use to leak test using helium gas mixed with nitrogen as if will pass through smaller holes.

Hadn't thought of shutting off the cylinder! 

That would make the gauge a really good test, testing everything apart from the cylinder valve spindle. Wonder why it's not included as a test method in the BSS, while a bubble tester is deemed acceptable?

 

 

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9 minutes ago, Iain_S said:

Wonder why it's not included as a test method in the BSS

It is, well at least that is how my BSS examiner does it, turn cylinder off, release a small amount of pressure, check manometer reading, wait a while, check manometer reading again. If it's dropped there is a leak. 

IMO Bubble testers are a waste of time.

Wasn't there something about them failing when they first got introduced by the BSS ?

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17 minutes ago, Iain_S said:

Hadn't thought of shutting off the cylinder! 

That would make the gauge a really good test, testing everything apart from the cylinder valve spindle. Wonder why it's not included as a test method in the BSS, while a bubble tester is deemed acceptable?

 

 

 

 

I think that is why it is a requirement of the RCD, it tests the whole system.

 

 

YES, YES, I know that no one on the canals cares a jot about the RCD, but despite some individuals 'feelings', some legislation is beneficial, and whilst the BSS pays lip-service to safety we all know it does nothing (very little) for boater safety.

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38 minutes ago, Iain_S said:

Hadn't thought of shutting off the cylinder! 

That would make the gauge a really good test, testing everything apart from the cylinder valve spindle. Wonder why it's not included as a test method in the BSS, while a bubble tester is deemed acceptable?

 

 

 

Because a leak on the high pressure side of the system within the gas locker shouldn't be a major issue as the gas should just drain overboard. On the other hand a leak on the low pressure side of the system in the cabin will collect in the bilges and is much more hazardous.

 

I'm not saying that you would want to have a leak in your gas locker, but it happens all the time. Lots of people don't tighten the brass fitting to the bottle properly or the fitting is worn and gas leaks out. If it was a choice between the two I know where I'd rather have the leak.

 

24 minutes ago, Loddon said:

 

IMO Bubble testers are a waste of time.

Wasn't there something about them failing when they first got introduced by the BSS ?

 

I have to disagree with you there. For those of us without a manometer bubble testers are a great but of kit. I've picked up a couple of leaks now that I definitely wouldn't have done otherwise.

Edited by blackrose
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49 minutes ago, blackrose said:

 

I have to disagree with you there. For those of us without a manometer bubble testers are a great but of kit. I've picked up a couple of leaks now that I definitely wouldn't have done otherwise.

Having no bubble tester fitted I rigged up an ad-hoc manometer by buying a length of clear plastic tubing from B&Q, attaching one end to the test nipple on the cooker, then taping the tube to the cabin side in a U shape, with some water in the bottom of the U. Not an accurate calibrated test, but by turning on the gas at the bottle, marking the water level on a bit of masking tape, then shutting off at the bottle and leaving it for a while, I could confirm that the water level difference was not reducing, and so the system was gas-tight.

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1 minute ago, David Mack said:

Having no bubble tester fitted I rigged up an ad-hoc manometer by buying a length of clear plastic tubing from B&Q, attaching one end to the test nipple on the cooker, then taping the tube to the cabin side in a U shape, with some water in the bottom of the U. Not an accurate calibrated test, but by turning on the gas at the bottle, marking the water level on a bit of masking tape, then shutting off at the bottle and leaving it for a while, I could confirm that the water level difference was not reducing, and so the system was gas-tight.

In a mains gas installation and a land LPG situation that is exactly how it is done, no other way is acceptable. I hate bubble testers. I don't trust anything that relies on a teaspoon full of antifreeze, introduces at least 2 more potential leak points, is subject to damage easily and induces the unskilled to think that everything is hunky dory.

They were only introduced because the examiners were not trained or skilled enough to use the test nipple, not being registered as Corgi or now Gas Safe, yet had to certify gas soundness tests.

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47 minutes ago, David Mack said:

Having no bubble tester fitted I rigged up an ad-hoc manometer by buying a length of clear plastic tubing from B&Q, attaching one end to the test nipple on the cooker, then taping the tube to the cabin side in a U shape, with some water in the bottom of the U. Not an accurate calibrated test, but by turning on the gas at the bottle, marking the water level on a bit of masking tape, then shutting off at the bottle and leaving it for a while, I could confirm that the water level difference was not reducing, and so the system was gas-tight.

 

Just commenting, aren't you supposed to burn off the high pressure gas in the flexible hoses before letting it stand, otherwise high pressure gas between the bottle and  regulator can top up any slight leaks and hide them?

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1 hour ago, Tony Brooks said:

Just commenting, aren't you supposed to burn off the high pressure gas in the flexible hoses before letting it stand, otherwise high pressure gas between the bottle and  regulator can top up any slight leaks and hide them?

Yes - I just shut off the gas connect up the tube manometer, check the pressure and then shut off the cylinder. Then run the gas out until the pressure just starts to drop and leave it for 5 minutes. I have fitted a bubble tester as well as it allows anyone to check most of the system.

 

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5 hours ago, David Mack said:

Having no bubble tester fitted I rigged up an ad-hoc manometer by buying a length of clear plastic tubing from B&Q, attaching one end to the test nipple on the cooker, then taping the tube to the cabin side in a U shape, with some water in the bottom of the U. Not an accurate calibrated test, but by turning on the gas at the bottle, marking the water level on a bit of masking tape, then shutting off at the bottle and leaving it for a while, I could confirm that the water level difference was not reducing, and so the system was gas-tight.

 

That sounds like a bit of a palava, but then retro-fitting a bubble tester is too I suppose. I fitted mine when I installed the system and find then very useful.

Edited by blackrose
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4 hours ago, Mike Adams said:

Yes - I just shut off the gas connect up the tube manometer, check the pressure and then shut off the cylinder. Then run the gas out until the pressure just starts to drop and leave it for 5 minutes. I have fitted a bubble tester as well as it allows anyone to check most of the system.

 

Obviously this is fine in principle, but there are a couple of pitfalls:

When you run the gas off from the flexi hoses, the expanding gas in those hoses cools. Then after everything is shut off, the gas which is now cooler than ambient, absorbs ambient heat and thus its pressure slowly increases. And those flexi hoses which had taken a bit of a set under constant high pressure, now relax and over some time, the volume in the hose reduces, thus also increasing the pressure. So there needs to be quite a long stabilising time, I’d say 5 mins isn’t really enough. The risk is that the leak matches the increasing pressure for the 2 reasons above, and thus the leak is masked.

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2 hours ago, Mike Adams said:

I don't have any high pressure hoses, maybe a bit old school but just a regulator on to the bottle in use. I don't think those hoses should expand under normal pressure anyway- a bit like brake  or hydraulic hoses.

Fair enough on your setup, but yes flexi hoses do expand slightly under pressure. Not visibly of course, but it makes a difference to the pressure when they relax. I’ve seen it in action. We are after all talking about checking for very small changes in pressure.

 

As to brake hoses, the reason why you can buy bog standard flexible brake hoses, OR much more expensive fancy ones for racing and performance cars and motorbikes, is that the former do expand a bit under pressure, giving a slightly spongy feel.

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21 hours ago, David Mack said:

Having no bubble tester fitted I rigged up an ad-hoc manometer by buying a length of clear plastic tubing from B&Q, attaching one end to the test nipple on the cooker, then taping the tube to the cabin side in a U shape, with some water in the bottom of the U. Not an accurate calibrated test, but by turning on the gas at the bottle, marking the water level on a bit of masking tape, then shutting off at the bottle and leaving it for a while, I could confirm that the water level difference was not reducing, and so the system was gas-tight.

I recall seeing a BSS examiner turn up to do a test with a piece of  skirting board holding a loop of clear pvc tube attached with cable/pipe clips. A few measured marks for reference of levels and it is a lot cheaper than a purchased 24" (18" at a pinch) manometer which is what you need for lpg.

After filling the system with gas and stabilising for the requisite time in the gas regs, reducing the pressure will show a fall much more clearly, A manometer will also test for the correct operating pressure, and regulator let by. A bubble tester does none of this.

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I would agree the manometer is a long standing almost fail safe drop tester carried by all gas engineers and in my experience is better for long duration drop tests than an electronic one, as they tend to wander off after a time. The home made one is no different to a purchased one. The only thing is the water must be changed before use if not used for a time as any algal growth will affect the mass density of the water and alter the pressure reading.

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22 minutes ago, plumbob said:

The only thing is the water must be changed before use if not used for a time as any algal growth will affect the mass density of the water and alter the pressure reading.

Yes, if you are using it to measure the regulated pressure, but not important if you are only checking for leaks.

Anyway, my bit of B&Q tubing has been coiled up and put away, so it will have fresh water in it anyway when I next come to check for leaks.

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Ok, I've just got back home and collected the new handheld gas sensor and I've located the leak. (Great bit of kit by the way, even though it looks cheaply made).

 

The leak seems to be coming from the fitting on the bulkhead at the bow where the main 1/2" run enters the cabin. I've also sprayed it with leak detector spray but it's not registering as far as I can see.

 

The thing is there isn't a joint at this point (marked in red in the diagram below). Instead, the pipe just comes through a brass sleeve fitted to the bulkhead which was intended to prevent chafing by the bulkhead. However, the brass gland must be chafing the pipe. I'm quite surprised as there's no movement between the two. 

 

Do I need to replace the entire run? It's about 12m long. Or could I fit a new section of pipe and have one "unnecessary joint"? 

 

 

InkedIMG_20210409_094811.jpg.da29c9c99311fd62f00fe8b0a16c285f_LI.jpg

Edited by blackrose
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2 minutes ago, blackrose said:

Ok, I've just got back home and collected the new handheld gas sensor and I've located the leak. 

 

It seems to be coming from the fitting on the bulkhead at the bow where the main 1/2" run enters the cabin. The thing is there isn't a joint there, the pipe just comes through a brass sleeve fitted to the bulkhead which was intended to prevent chafing. However, the brass gland must be chafing the pipe. I'm quite surprised as there's no movement between the two. 

 

Do I need to replace the entire run? It's about 12m long. Or could I fit a new section of pipe and have one "unnecessary joint"? 

 

 

InkedIMG_20210409_094811.jpg.da29c9c99311fd62f00fe8b0a16c285f_LI.jpg

Is the pipe clamped to the bulkhead fitting, or can it slide within it? If it can move then it may be moving with daily temperature change and may have worn through.

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1 minute ago, David Mack said:

Is the pipe clamped to the bulkhead fitting, or can it slide within it? If it can move then it may be moving with daily temperature change and may have worn through.

 

Yes, it's not clamped. That's a good point.

I guess I could have a gas fitting at the bulkhead instead of the gland.

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22 minutes ago, blackrose said:

 

Yes, it's not clamped. That's a good point.

I guess I could have a gas fitting at the bulkhead instead of the gland.

I have always used proper gas bulkhead fittings drilled out so the pipe can pass straight through but tightened up as normal with olives etc. Possible overkill but not had one fail.

 

If you can cut the pipe at the bulkhead then you could just fit a proper gas bulkhead fitting, provided the hole in the pipe is in the correct place.

 

A snotty bss inspector could get arsey about the "unnecessary joint"

Edited by Loddon
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3 minutes ago, Loddon said:

I have always used proper bulkhead fittings drilled out so the pipe can pass straight through but tightened up as normal with olives etc. Possible overkill but not had one fail.

 

If the pipe is not cut, there is nothing to fail, best way.

 

I don't understand the brass sleeve bit, especially if the pipe is loose in the sleeve. Its a BSS fail and I have never seen it done this way.

Edited by Tracy D'arth
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So the answer to Blackrose's problem is to replace his existing sleeve with such a fitting, and with a bit of luck he will not need an intermediate joint or to replace the whole 12m length. As the fitting is designed to have separate pipes attached, no BSS inspector can claim this is an unnecessary joint.

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