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Discuss Does it need purging? in the Gas Safe Register Forum - Public Forum area at

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  1. fireman -Sam

    fireman -Sam New Member

    First off I'm not a gas engineer but a fire engineer. I've just had a bit of a problem on a job where the main incoming solenoid valve had been left off but the heaters on the site where then turned on or well where tried to be. They called in a Gas company who found the problem.
    But they are now saying that the hole system needs purging with nitrogen as there will be air in the system. Is this correct as I cant understand how air has got into the system? Surely the heaters/burners would just shut of if the pressure was to low and wouldn't let air into the system.

    Any advice would be appreciated thanks.
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    wont need purging with nitrogen unless they need to work on it

    but depending on volume yes it might need to be purged but not with nitrogen

    no they would try and fire till they locked out (eg fault)

    where are you located just for reference?
  3. fireman -Sam

    fireman -Sam New Member

    Thanks for the reply.
    That was my thoughts don't understand the nitrogen bit, I can understand the possible purging with gas bit and also pressure testing after.
    Its a big pipe around 12-18 inch and over 150+ meter long so will be a fair volume.
    Its around the Birmingham area.
  4. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    yep air to gas purging unless there working on it doesnt matter on size they will have to be commercially gas safe to up1 spec

    whats it supplying just air heaters?
  5. fireman -Sam

    fireman -Sam New Member

    Yeah just air heaters all of which have a auto cut off from the fire alarm themselves sadly the main valve relay had a issue and remain closed.
    I will recommend to the customer to ask why the company are saying it needs purging with nitrogen and tell them to possibly get a second opinion. Thanks again.
  6. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    yea best option if you dont mind me asking wheres the cutomer located / site location

    manchester ?
  7. fireman -Sam

    fireman -Sam New Member

    No I am based in the Manchester area but this site is in Coventry we look after a number of there sites most of which are in the north west area.
  8. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Nice little patch

    Any other questions/ updates just post away :)
  9. king of pipes

    king of pipes Trusted Plumber GSR

    The gas pipework will only need purging with nitrogen if work needs doing on the system ie decommissioning like changing the solenoid valve. If its a power failure and the heating was switched on then it will need testing and then air to gas purging and recommissioning. Cheers kop
  10. fireman -Sam

    fireman -Sam New Member

    Just a quick up date, the gas company carried out a air to gas purge although I still don't get how air would as got into the system, I would have though the valves would just shut once the pressure dropped.
    Anyway it took the gas company about 5 hours for 2 men, think there is 8 heaters in total and a few need a cheery picker to get up to them. Although I think the building owners supplied that. The bill came to around £2.5k in total which I thought was crazy.
  11. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    yep sounds about right
  12. Last Plumber

    Last Plumber Plumber GSR Top Contributor!!

    It's more a case of the system having lost pressure.
    Safety !
    In a large Gas installation you need to be certain that there is no Gas air mixture within. The larger the installation the greater the risk.

    If the installation has depressurised for any reason, it should be tested, purged and recommissioned.

    This does not mean that air definitely entered the pipe work. It means it is unknown whether it did or didn't and therefore we should treat it as if it did.

    hope this makes sense!
    • Agree Agree x 1
    Last edited: Oct 9, 2017
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