gas test point size

[jake_crew]

We have a tiny small leak on the gas (it just failed BSS) and suspect its porosity in the flexible tail from cylinder to fixed pipe in the forepeak gas locker. There's never a gas smell in the boat.

 

We can change that hose.

 

But having done that, it would be nice to confirm all is well, by doing the leak down test, before calling the inspector back.

 

Can some one tell me the size of hose required to fit on the test point - assuming there is a std size.

 

I'm away from the boat so can't check myself.

 

Thanks

 

 

[MtB]

We have a tiny small leak on the gas (it just failed BSS) and suspect its porosity in the flexible tail from cylinder to fixed pipe in the forepeak gas locker. There's never a gas smell in the boat.

 

 

 

Firstly, this is only possible if the regulator is the type that screws directly into the gas bottle. If the reg is on the bulkhead then your bottle line(s) will be high pressure and not included in to BSS bod's soundness test.

 

Secondly, the flexible hose has a design life of ten years and the date of manufacture must be marked on it and be less than ten years ago, or that's a fail too! (Or it is if you want to meet BS5482 2005 Pt III too)

 

Thirdly, if a new hose doesn't fix it, fit a bubble tester. These are FAR more forgiving of leaks i.e. they will show no leak on a system with a leak that 'just' fails when tested with a proper manometer.

 

Fourthly to answer your kwestion, a rubber hose of the correct type for LPG must be used, and a bore of 1/4" will stretch to fit over the gas test point nipple, but it isn't crucial. I'd guess they are usually 10mm diameter so any stretchy hose smaller than that can be persueded to fit onto one.

 

MtB

P.S. and fifthly I forgot to mention, to meet BS5482 and GSIUR the system may be tested with appliances isolated. This is because cooker gas taps and other appliances often leak gas ever so slightly. God knows why such leaks don't 'count' but they don't apparently. Try isolating all your appliances and testing again. You may get a good result and be able to convince the BSS bod this is ok!

 

MtB

[jake_crew]

Thanks Mike.

 

IIRC the regulator does screw straight onto the cylinder.

 

The flexy has been changed before and is around 10 years old, but my brother didn't mention owt about dates.

 

The BBS inspector used a digital manometer I beleive - but would us fitting of a bubble tester over-rule his instruments readings ?

 

Thanks for the size info, I was hoping to use a length of clear hose as a temporary manometer on the test point just for this occasion.

[Pete & Helen]

We have a tiny small leak on the gas (it just failed BSS) and suspect its porosity in the flexible tail from cylinder to fixed pipe in the forepeak gas locker. There's never a gas smell in the boat.

 

We can change that hose.

 

But having done that, it would be nice to confirm all is well, by doing the leak down test, before calling the inspector back.

 

Can some one tell me the size of hose required to fit on the test point - assuming there is a std size.

 

I'm away from the boat so can't check myself.

 

Thanks

 

 

 

I wouldn't assume that the leak is not inside the boat. I failed the BSS for a small leak which was found to be inside the boat but was so small I couldn't smell any gas. It turned out to be a stop end that had been fitted when a gas boiler was taken out by a previous owner.

[MtB]

Thanks Mike.

 

IIRC the regulator does screw straight onto the cylinder.

 

The flexy has been changed before and is around 10 years old, but my brother didn't mention owt about dates.

 

The BBS inspector used a digital manometer I beleive - but would us fitting of a bubble tester over-rule his instruments readings ?

 

Thanks for the size info, I was hoping to use a length of clear hose as a temporary manometer on the test point just for this occasion.

 

That clear plasticky hose is FAR less stretchy than the rubber or neoprene normally used by gas bods to connect to test nipples. In fact I doubt you'll get it to go on unless you measure the size of your nipple <schnerk> and buy hose to match it. Far better to buy a proper manometer and connection hose. You are looking for one MICROSCOPIC leak and a leak on your test gear will wreck your results.

 

The bubble test result doesn't override his digital manometer reading but he is allowed to rely on it instead, should he so wish....

 

 

MtB

[BEngo]

I have always found a good way to find tiny leaks is to increase the pressure a bit. Take the test point out of its tee fitting and fit a Schrader valve then pump up to about 5 psi with either a foot pump or a bike pump. Don't overdo it - normal working pressure is only 37 mbar. Check the joints with leak detecting stuff (not washing up liquid and water). Fix leak(s).

 

Replace gas test point and do a soundness test.

 

 

If there are any appliances on flexible tails it is worth looking at those. All flexibles are to some extent permeable and this gets worse with time. MtB's suggestion of testing with the appliances isolated should eliminate this though.

 

 

N

[MtB]

I have always found a good way to find tiny leaks is to increase the pressure a bit. Take the test point out of its tee fitting and fit a Schrader valve then pump up to about 5 psi with either a foot pump or a bike pump. Don't overdo it - normal working pressure is only 37 mbar. Check the joints with leak detecting stuff (not washing up liquid and water). Fix leak(s).

 

That'a a Good Idea althougn frowned upon by the powers that be, as like you say the seals inside appliances are only designed to hold 37mb or so. 5 PSI is 350mBar roughly!

 

Bear in mind LPG molecules are far smaller too and can still leak out of a system that is airtight.

 

MtB

[BEngo]

Agree both points.

 

It is best to pressure-test the pipework with the appliances isolated. It will stand a lot of pressure then.

 

The extra pressure does offset the smaller size molecules though. In a former life I was responsible for an emergency system which relied on stored Helium at high pressure. If you can keep that stuff gas tight LPG is easy!

 

N

Edited April 4, 2014 by BEngo

[jake_crew]

Many thanks folks,

 

Your suggestions are gratefully received and noted.