advise required on countering oxidisation

[frosty74]

when brazing pipework and you trickle nitro through is it just as good to blow nitro through pipe work straight after braze is complete rather than trickling the nitro through whilst brazing.is it still good practice to do this or would you advise against doing it this way.

[DVaider]

I rnow it is good practice. Daikin advise this way in case of VRV installing.

[HallsEngineer]

The aim is to stop oxygen getting into the pipe whilst brazing to stop the black flakes on the inside of the pipe. Try it and you will see. There is absolutely no point in doing it after.

[frosty74]

after each braze done whilst going along doing the pipework if nitro was to be blown through the pipe you have just brazed wouldnt the nitro blow the black flake straight out of the pipe and keep the pipe clear just as well.
for instance if you was swage connecting 2 x 6 metre lengths together and once you have brazed the pipe you then blew nitro through the full 12 metres wouldnt this clear the pipe of any build up of flake.

on my previous post i dont mean complete the install and then blow nitro through the pipe work this would be done after each brazed connection.

[airconadam]

also dont cool it by a wet rag let it cool naturally, u can blow nitro though and then cool it by a wet rag and u will still get the flakes, i purge it through all the time especially on big systems thanks alot

adam

[expat]

Adam, I can't think of why you would still get oxidization while brazing and cooling with a wet rag, if you are running nitrogen through the system, as oxgen shouldn't be present?

[taz24]

on my previous post i dont mean complete the install and then blow nitro through the pipe work this would be done after each brazed connection.

Venting OFN at low pressure through the pipes while brazing is the only way to do it.
Blowing the crud out afteryou have brazed will use a lot of OFN, certainly a lot more than just slow purgeing.
Also most of the oxide will remain on the inside of the pipe even after you flush with OFN so some crud will remain in your system.

Cheers taz.

[HallsEngineer]

Here, Here. no point in doing it after at all

[airconadam]

hey expat iknow what you mean and agree but it still does it and got told that from college give it ago you will see what i mean thanks alot

adam

[norfolkboy]

hi all has anyone tried using a solonoid switched with a remote controller to control nitrogen when working away from cylinder, i have thought of using a model plane remote for this but never got around to trying it. although i saw some one installing a vrv on an adjacent roof a few weeks ago no ofn in sight, yet another quality install.

[expat]

Cool#9 spoke of this idea in this thread.
http://www.refrigeration-engineer.com/forums/showthread.php?t=8300

[norfolkboy]

thanks expat, i was thinking more of a radio type remote probably as used in model aircraft, no wires to run. probably a lot of use in shopping centers avoiding lots of stairs. i may borrow a radio control to see if signal will penentrate.

[ozairman]

I have not seen it myself but have heard of using a system the same as Cool#9's post mentioned above. In Australia you can buy some 1 or 2 channel remote control receivers that can be retrofitted to motorised garage doors or home alarm system that would be suitable with a bubble flowmeter and solenoid.

Lack of OFN is a big killer on systems and most failures on VRV, VRF systems I have seen have come down to poor install practices. It is amazing how good a solvent POE oil is in combination with R410A or R407C