just a quick purging question

[beesley121]

Just reading through one of my gas books which explains how to calculate a purge on pipework over 28mm.

now a standard purge can be just vented to a ventillated room (0.01m3) but a purge of over 0.02m3 need to be continually ignited and burnt off until a stable flame is achieved

what i cant understand is say a propety needed a single piperun to a combi that had to be done in say 35mm. Once calculated, the purge volume is over 0.02m3. now there is no gas hob, oven or fire to purge from. The book states that a volume of over 0.02ms has to be burnt off so just cracking the union is not an option.

Can anyone tell me what they expect you to do if this scenario arises?? it mentions a temporary open burner. any idea what it means

also, before a purge is carried out, it says that a tightness test must be done. Fair enough, but it does not say a tightness test has to be done after either!! so by opening up a union say on a boiler again, is a further tightness test not required as it just mentions LDF. I myself would just rely on LDF

 

[Pssst]

Do you want real world or theory..?

Real world,ensure room at vent point is well ventilated and remove sources of ignition. Slacken union or undo valve outlet and let it blow. You will usually hear the change as gas comes through due to differing densities between air and gas. In a typical house,at full bore,if 5 seconds have passed,it;ll be done. Secure connection,test for soundness. Light appliance,check for safe and correct operation. Ensure any residulal gas has been vented.

 

[beesley121]

Do you want real world or theory..?

Real world,ensure room at vent point is well ventilated and remove sources of ignition. Slacken union or undo valve outlet and let it blow. You will usually hear the change as gas comes through due to differing densities between air and gas. In a typical house,at full bore,if 5 seconds have passed,it;ll be done. Secure connection,test for soundness. Light appliance,check for safe and correct operation. Ensure any residulal gas has been vented.

yep, understand how gas fitters do it in the real world as ive worked along side them for long enough but now its time for me to sit the acs myself and if i get asked the very same question, what should my answer be??

 

[dancinplumba]

with your boiler example, why not run boiler till it lights ?

 

[Barry98]

Do you want real world or theory..?

brilliant

 

[beesley121]

with your boiler example, why not run boiler till it lights ?

ever heard of explosive ignition??

heard lots of stories about brand new boilers supplied via copper thats 35mm and has not been purged correctly, thus voiding manufacturers warrantee. just wanted to know what they expect me to say in my acs even though i know and others know to just ventilate the room and extinguish all possible sources of ignition and let it **** out lol till we smell proper gas

 

[AWheating]

bunsen burner??

cheaper than a purging unit, tho i have never need to use one.

 

[sparra1100]

think the book says you should have an outlet like you have on the meter to do tightness test and purge from there and has to be soldered on the pipework next to the boiler i could be wrong or thinking of something else but am sure that was how you done it, personally i wouldnt be comforable letting that much gas into a room and would use my sniffer till it goes to high and then tighten the nut back up