Gas Test Pressure

mikewilkes

mikewilkes

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Does anyone know what pressure to test a butane gas system to?
Answers in psi would be more useful as I dont understand the other stuff.
Cant get a "corgi" type man here so have to resort to self test.
 
I would at all cost get a gas fitter to check it...maybe bad luck but in the last 4 years i have been moored close to two yachts that exploded due to gas.One of them had been told by several people not to diy his system but the worst happened.
 
With domestic gas systems the normal procedure that I have observed is not to pressurise them above normal working pressure but to do a leakage test at normal operating pressure.

A water filled U tube manometer is connected to a test point the gas is turned on and then off again. The manometer must show no perceptible drop in pressure for a new installation but I forget over what period of time. For old installations some slow loss of pressure was allowed but again I forget the maximum rate of drop that was accepted.

That's not very helpful but it may give you some idea about how to test. I can't imagine that the procedure will be any different for an lpg system. Its some time since I watched a gas fitter doing this and the requirements may now be stricter of course.
 
I have a "Gaslow" pressure guage permanently attached to my system. If you have a leak it will show you as soon as you turn off the system. - worked perfectly the one time I did have a leak. That means I test my system every time I use it!
 
Vic,
I am at the moment helping a gas fitter connect up some mobile holiday homes with propane.

The test pressure is held at between 38 to 40 for 5 minutes to allow for temperature settlement, and then another two minutes to ensure there is no leakage (drop in the manometer) in the system. Being an electrician, I think I have the times correct. (If not, someone will put me right!)

This is all in 22 and 15 mm copper piping.

I am in the midst of having my gas installation altered with a new gas locker that will take two bottles. The piping will have the same test when I have finished - using his manometer - even though I have a bubble leak detector in the line.
 
Thanks Mark.
That "gaslow" thing rings a bell now. Must get one sorted when I return to Lionel Blair land just before easter.
The reason for the query was a wake up call the other morning, 0235, when the bl**dy gas alarm went off. The bottles were turned off as they usually are so thought it was just whatever was in the pipe. Anyway the pipework has pressure tested ok so I guess it was an electronic blip.
Could cause a problem though if you are one of these people who dont believe in turning the bottles off when not in use!!!
 
Hi Philip.

Thanks for confirming that the basics of my post are correct but [ QUOTE ]
The test pressure is held at between 38 to 40 for 5 minutes to allow for temperature settlement, and then another two minutes to ensure there is no leakage

[/ QUOTE ] You say 38 to 40 but what are the units? I assume that they are cm but am I correct? I am very surprised that the test is only for 2 minutes I would have thought that was way too short but I cant remember. If I was testing my own system I would make it longer than that! So much depends on the size of the system (volume of the pipe work) though. A very large system would lose quite a lot of gas before a pressure drop was readable on the manometer, whereas a small system would lose very little before the manometer showed a change.

How was your fitter pressurising the system was that from the gas supply, did he have a small pump or did he do as I have seen them do simply blow into it using Mk1 lungs.

Easy enough to make a manometer. All you need is a length of clear plastic tubing taped to a piece of wood.
 
As I have a gas fridge and gas water heater as well as the cooker, I prefer to be safe not sorry. I can isolate each element of the system in turn to discover where a possible leak is located. The only leak I have had was last summer, , and was quickly traced to the area of the regulator itself. Had to replace the whole gaslow guage, regulator and manifold to be certain I had problem solved, as the system I had was overage and no spares were available!
 
The units are millibars as marked on the u gauge.The pipe work on its own should NOT show any drop regardless of age.

Suppose I should say dont DIY etc etc ,all very correct but not much help to you. Testing for long periods is no good as the temperature can change giving false readings possibly masking a small leak /forums/images/graemlins/crazy.gif
 
Vic, as Graham has said, millibars of pressure (which I think is also centimetres of height)[anyone confirm?]. The system was pressed up with the bottle of Propane, and then dropped by gently releasing the pressure to 38 to 40mB and holding to settle for 5 minutes

As you suggest, a small pipework system should, and probably will, show a fast drop if there is a leak.

Again, as Graham has said - there should be no leak and no drop on the manometer.

As I remember - perhaps my times may be slightly out, but that is as how I recall it.

I am seeing him on Monday, so will verify his times. If there is any change, I'll add to this thread.
 
From what I was taught on my gas course many years ago;
"The maximum allowed gas leak is zero as the maximum allowed explosion is zero"...

I gas tested hundreds of mobile homes around Europe using a device that looks like a cycle pump with a pressure guage on it - cannot remember the name at the moment and cannot find one on the web - but remember that it was sub £40 8 years ago, so is probably £400 now...

Could use a U gauge like Manometer to test it as Corgi doesn't count here - may invalidate insurance etc

Usual disclaimers about don't blame me if you blow yourself up etc, etc,...
 
[ QUOTE ]
Quite accept what you are saying but CORGI dont exiat here.

[/ QUOTE ]

Maybe not, but the Spanish have strict regulations for bottled gas so there will be an equivalent.

I too have seen a couple of blown up boats - one a Prout cat where the whole deck moulding had been lifted off the hull. So gas is one of the very few things I wont "chance it" with.
 
[ QUOTE ]
From what I was taught on my gas course many years ago;
"The maximum allowed gas leak is zero as the maximum allowed explosion is zero"...

I gas tested hundreds of mobile homes around Europe using a device that looks like a cycle pump with a pressure guage on it - cannot remember the name at the moment and cannot find one on the web - but remember that it was sub £40 8 years ago, so is probably £400 now...

Could use a U gauge like Manometer to test it as Corgi doesn't count here - may invalidate insurance etc

Usual disclaimers about don't blame me if you blow yourself up etc, etc,...

[/ QUOTE ]

I worked in QC in caravan manufacture and used the same "bike pump" type tester, would love to get hold of one now. Been a few years since then, so memory may be slightly out, but the test time was about 5 mins.
 
[ QUOTE ]
cycle pump with a pressure guage on it

[/ QUOTE ] The beauty of a manomter compared with the pressure gauge is the length of the scale and the lack of "sticktion" I have not yet worked out what 38mb is in cm water gauge about 36cm I think very roughly (and that agrees with what someone else says.) Thats several times the length of the pressure guage scale.
I'm not sure what pressure you could get to by blowing, a bit more than that I think, so I reckon unless you are checking gas installations daily a home made manometer (It doesn't have to be calibrated in any particular units) and the mk 1 lungs is they way to go.
 
when the bl**dy gas alarm went off.
_______________________________

can happen because of low battery.

kept on happening on a charter boat. Crew thought it was my am alarm - 0430 hrs.
 
the correct working pressure for butaine is 28mbrs the correct working temperature for propaine is 36mbrs if you use a water guage to check you system then you must not check it at working pressure you should always check it undersay 25 and 33 resectively. The reason for this is that you must allow and high pressure gas in the sustem to pass though the regulator before testing, otherwise you will get faulse readings. once you have allowed the pressure to drop (light a hob burner for a few seconds) you must wait for a a few minutes to allow the temperature of the gas in the pipes to stabalise. then read the water guage, wait 5 mins and read again. As well as doing this you will also need to check the connections on the high prseeure side if you have any! DO NOT USE SOAPY WATER use a proper test solution as the chemicals in soapy water can degrade gas type sealent. If you find a leak on a connection do not use red hermatite or (belive it or not) calor tite as bottled gas degrades these too! (Dont ask about the calor tight its a long story) also if you use ptfe tape use one suitable for gas. There are other tests you should do concerning regulator function etc.
 
I'm with Talbot on this one. We too have a 'Gaslow' as it's a good check of your installation everytime you turn the gas on and off.

Re the testing pressure etc, a good friend of mine is a Corgi registered installer. I completely renewed the 21 year old gas system on my boat last year as part of a major refit, and when I came to test it, the pressure fell very slowly.

Worried (and annoyed!!) about this I consulted my friend. I told him it had held the pressure for just over one and half hours, and then only JUST dropped into the yellow sector on the Gaslow for a few hours - at which point he fell about laughing!!

He pointed that, as far as he was concerned, that was 100% good! He said that when installing gas systems, the test used requires that the pressure to be mantained for around 5 minutes with no loss of pressure at all.

He also pointed out that as the total volume of gas in the very short runs we have is tiny and it only requires a VERY small degree of absorption, swelling of the final rubberised connection to the cooker etc to produce what looks like a dramatic leak!

I still wasn't totally convinced, but as I'd tested the damned system with leak detection fluid several times and could find absolutely no sign of an escape, and as the gas sensor has remained completely silent, I've gradually relaxed and accepted that it's fine!

However, just in case, no smoking below .............!! /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
 
I think I understand that. If I am right you are saying that gas on the hp side of the regulator (ie between that and the bottle shut off valve) will continue to maintain the pressure in the lp side for a time even if there is a small leak.

That is a good reason to pressurise the system from an indepenent source rather than the bottle. In fact it would it be better not to have the botle connected at all because a small leak past the bottle valve would mask a small leak from the system? The trouble then would be if the regulator allowed a little leak backwards as that would then give the appearance of a leak from the lp system. At least that would be a "safe" situation that you could investigate compared with having a genuine leak masked by gas from the bottle maintaining the pressure during the leak test.

BTW I have now worked out the relationship between millibars and cm water gauge.
1 mb = 1.02 cm water gauge so 25 mb = 25.5 cm and 33 mb = 33.7 cm
Whoever said 1mb = 1cm was right for all practical purposes.
 
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