Tightness test lpg system?

[Illuminate]

can somebody explain to me the reason why you have to do a tightness test then purge and then complete another tightness test on a lpg system rather than purging and then just doing one tightness test. How help will be much appreciated and so I get a better understanding. Thanks

 

[ShaunCorbs]

I’m guessing new install with no gas in the pipework?

 

[Illuminate]

I believe it has to be done everytime a purge would be needed so yes on a new installation or when adjusting gas pipework or changing gas appliance (if I'm right but I'm not entirely sure) plus what would be the reason for doing it before and after?

 

[ShaunCorbs]

It’s because air is lighter than lpg so if only testing with air it could mask a leak

 

[Illuminate]

It’s because air is lighter than lpg so if only testing with air it could mask a leak

Hi Shaun, thanks for the good and quick response. I kind of though that but I still don't understand why you can't just purge then tightness test as then there will be no air present at all?

 

[ShaunCorbs]

You don’t know if the pipework is sound so could be leaking into a void eg open end etc and wouldn’t disperse as it’s heavier than air

 

[Illuminate]

You don’t know if the pipework is sound so could be leaking into a void eg open end etc and wouldn’t disperse as it’s heavier than air

Shaun, your a legend and you have just help to make it click in my head. You are always on point. Thanks again from a trainee gas engineer

 

[ShaunCorbs]

Where all here to learn and help it’s one of them once explained it clicks

 

[Illuminate]

Online there is such a lack of information on lpg systems. Have a good evening

 

[DRAGONEXPRESS]

Methane propane butane molecules smaller than air, tightness pass for air maybe fail for fuel.