Spontaneous gas leak.

[Eeyore]

I have a typical Vanette oven and hob installation as the only gas appliances on my 1996 boat. The gas locker was relocated about six years ago and all new pipework and fittings installed. Tested at install and on two subsequent Boat Safety examinations. The boat was dropped off at the brokerage mooring and, for the first time since the installation, the valve on the gas bottle was turned to the off position. There was certainly no smell of gas on the boat when I lifted the cabin bilge hatch as part of the pre sale tidy up. A month latter the surveyor opened the bottle valve, performed the leakage test, and pronounced that the oven was leaking.
I guess I really am a lucky B*****d, but what could have failed simply as a result of isolating and then de isolating the supply?

[Alan de Enfield]

2 minutes ago, Eeyore said:

I have a typical Vanette oven and hob installation as the only gas appliances on my 1996 boat. The gas locker was relocated about six years ago and all new pipework and fittings installed. Tested at install and on two subsequent Boat Safety examinations. The boat was dropped off at the brokerage mooring and, for the first time since the installation, the valve on the gas bottle was turned to the off position. There was certainly no smell of gas on the boat when I lifted the cabin bilge hatch as part of the pre sale tidy up. A month latter the surveyor opened the bottle valve, performed the leakage test, and pronounced that the oven was leaking.
I guess I really am a lucky B*****d, but what could have failed simply as a result of isolating and then de isolating the supply?

 

1) Boat hit mooring hard and dislodged cooker fitting.

2) Surveyor pulled out the oven to check for correct installation and dislodged fitting

3) Surveyor finding imaginary faults to 'beat the price down'

4) Broker has been on board and disconnected the cooker pipe

5) You have had C19 and lost your sense of smell

[Eeyore]

22 minutes ago, Alan de Enfield said:

 

1) Boat hit mooring hard and dislodged cooker fitting.

2) Surveyor pulled out the oven to check for correct installation and dislodged fitting

3) Surveyor finding imaginary faults to 'beat the price down'

4) Broker has been on board and disconnected the cooker pipe

5) You have had C19 and lost your sense of smell

Ahh, the joys of leaving your boat in the care of others.

I'm strangely drawn to number 3 😏

[Tracy D'arth]

The grease in the cooker taps dried out and the cold weather causes contraction of metals to break the seal?

[ditchcrawler]

1 hour ago, Tracy D'arth said:

The grease in the cooker taps dried out and the cold weather causes contraction of metals to break the seal?

 

And no pressure behind them to hold them up tight.

[Arthur Marshall]

Mine failed a gas test when I had a new regulator installed, though it had passed Safety Test a month before. It seems testers are allowed a margin of error in their readings, but GasSafe registered bods aren't, and so he refused to sign it off.

We found the leak was in the isolator tap adjacent to the cooker. It seems that over time the whatever it is makes them gasproof dries out, so they leak. I have certainly never smelt anything, and it was a tiny, very slow leak. The tap must be over twenty years old, but presumably wasn't leaking when the new oven was installed five years ago.

[Tracy D'arth]

There is no allowable leak on a boat LPG system.

 

Taper plug gas valves depend on the grease to make a seal.

[system 4-50]

26 minutes ago, Tracy D'arth said:

Taper plug gas valves depend on the grease to make a seal.

I had the idea that the BSS did not allow taper plug gas valves, can somebody tell me if I'm wrong to save me looking it up?

[MtB]

1 hour ago, Tracy D'arth said:

There is no allowable leak on a boat LPG system.

 

Taper plug gas valves depend on the grease to make a seal.

 

What if there is a manometer drop with appliances connected and "no smell of gas"? 

 

Just curious because in a house this is not classed as a leak, and we get a chart of allowable drops "with appliances connected and NO SMELL OF GAS". I can't remember if there is an equivalent chart for boats. 

 

With appliance isolator valves closed though, no drop is allowable on domestic (house) systems of 0.01 cubic metres and smaller IIRC.

Edited November 3, 2021 by MtB
Add a detail.

[Ex Brummie]

1 hour ago, system 4-50 said:

I had the idea that the BSS did not allow taper plug gas valves, can somebody tell me if I'm wrong to save me looking it up?

The cooker control taps are taper plugs. I found out earlier this year when after being laid up for the winter, my Vanettte was leaking on all four hobs. Removal of the rail and greasing all the taps did not improve them much, so new cooker was installed. The old one had done 27 years.

Edited November 3, 2021 by Ex Brummie

[blackrose]

30 minutes ago, MtB said:

 

What if there is a manometer drop with appliances connected and "no smell of gas"? 

 

Just curious because in a house this is not classed as a leak, and we get a chart of allowable drops "with appliances connected and NO SMELL OF GAS". I can't remember if there is an equivalent chart for boats. 

 

With appliance isolator valves closed though, no drop is allowable on domestic (house) systems of 0.01 cubic metres and smaller IIRC.

 

I would wager that the no smell of gas is irrelevant if a manometer drop is found on a boat. The difference of course being that even a small lpg leak will gradually collect in the bilges of a boat whereas it's more likely to escape from a house.

[Tracy D'arth]

50 minutes ago, MtB said:

 

What if there is a manometer drop with appliances connected and "no smell of gas"? 

 

Just curious because in a house this is not classed as a leak, and we get a chart of allowable drops "with appliances connected and NO SMELL OF GAS". I can't remember if there is an equivalent chart for boats. 

 

With appliance isolator valves closed though, no drop is allowable on domestic (house) systems of 0.01 cubic metres and smaller IIRC.

Domestic allowance on nat gas is dependant on the meter size and the system volume. On LPG in a boat, no allowance for any leaks as I understand the regs, as there is no meter and the system volume is small this is a very tight requirement.

 

Appliance gas taps are practically always greased taper plug.

[Ronaldo47]

I still have a jar of gas graphite grease of dad's ( he was a pipe fitter for the North Thames Gas). It still works, I used it a few years ago to re-grease a stiff tap on our gas cooker.   In the 1970's, at my my previous house I found that the main stop cock had been leaking slightly when in the OFF position when I went to turn it on again after returning from holiday (at that time, insurance companies used to require you to  turn off gas and electricity when  houses were unoccupied) . Fun and games reporting it when I  explained  to the customer services person that, no, I didn't actually have a leak at present, I only had a leak when I turned it off, and it was definitely the stop cock that was leaking (checked with soapy water) , and that I was certainly not  going to turn my stopcock to the OFF position as per her obvious gas leak script because  that was what would cause a leak: I ended up talking to the supervisor, and when the gas man came, he simply tightened the stopcock plug nut  with a large spanner as a temporary fix so you couldn't turn it off, and arranged for a crew to come and fit me a new one.

 

A couple of months later, a friend's newly-bought old house was found to have the same problem. I assured her that it was almost certainly not a case of the previous owner not hiding a problem, just a consequence of disturbing the stop cock that hadn't been turned for years.  

Edited November 3, 2021 by Ronaldo47
typos

[MtB]

3 hours ago, Tracy D'arth said:

Domestic allowance on nat gas is dependant on the meter size and the system volume. On LPG in a boat, no allowance for any leaks as I understand the regs, as there is no meter and the system volume is small this is a very tight requirement.

 

Appliance gas taps are practically always greased taper plug.

 

True, but with the vastly bigger system volume of a domestic system, the sensitivity of the manometer to a given size of leak is much reduced. I'd have expected a bigger drop to be permissible on a tiny system volume with no meter. But there we are. One day I might find a training skool where I can renew my expired boat ticket. 

[Tracy D'arth]

9 hours ago, MtB said:

 

True, but with the vastly bigger system volume of a domestic system, the sensitivity of the manometer to a given size of leak is much reduced. I'd have expected a bigger drop to be permissible on a tiny system volume with no meter. But there we are. One day I might find a training skool where I can renew my expired boat ticket. 

Correct, that's why I said its a very tight requirement to get zero drop on a very small volume.  Training on boat and caravan/mobile home LPG is scarcer now than it was 15 years ago! Colleges make more money teaching baking, nail  and hair dressing. Sad state we are in as far as engineering education.

[Machpoint005]

Far more bakers, hairdressers and nailer are needed* than caravan or boat gas fitters.

 

I agree about the parlous state of engineering education, but the lack of gas fitters is a tiny part of the problem.

 

 

*ie there is aconsumer market to be serviced

[Ex Brummie]

10 hours ago, MtB said:

 

True, but with the vastly bigger system volume of a domestic system, the sensitivity of the manometer to a given size of leak is much reduced. I'd have expected a bigger drop to be permissible on a tiny system volume with no meter. But there we are. One day I might find a training skool where I can renew my expired boat ticket. 

My examiner always lowers the pressure in the system before drop testing as it shows leaks sooner.

[MtB]

38 minutes ago, Tracy D'arth said:

Training on boat and caravan/mobile home LPG is scarcer now than it was 15 years ago!

 

Well I renewed all my LPG tickets last summer and got mobile homes/LAVs added on to my 'park homes' for just answering a handful of trivial questions. When I asked why I can't do the same for boats (like when I first qualifed for boats - it was just two extra questions and a short practical) they said the skool elected not to offer boats as the test rigs they'd need to set up were too onerous nowadays!

 

They suggested I try some training skools on the coast, reasoning that big marine conurbations like Portsmouth and Southampton must need skools that do boat LPG. 

[Tony Brooks]

49 minutes ago, Ex Brummie said:

My examiner always lowers the pressure in the system before drop testing as it shows leaks sooner.

 

That is, as I understand it, what he is supposed to do. If this is not done any high pressure gas trapped in the regulator and pigtails will flow into the system and hide any small leaks.

[Tracy D'arth]

20 minutes ago, Tony Brooks said:

 

That is, as I understand it, what he is supposed to do. If this is not done any high pressure gas trapped in the regulator and pigtails will flow into the system and hide any small leaks.

Exactly.  You get regulator lockup when you turn on. This has to be stopped before drop testing. Also if the reg is locked, you do not test the connection to the bottle.

[Eeyore]

Thanks for all your replies, some interesting technical stuff for me to absorb.