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hi all
Expansion and contraction due to temperature can it cause flares to leak.
We maintain some variable temperature cold rooms that operate from +1c to +30c. Experience a high number of leaks from TEV suction flares.
Iv heard it said that expansion and contraction can cause things to work loose over time but is this just an excuse for poorly made flares.
Flare joints are one of the main causes of refrigerant leaks. There are many causes as to why they leak from expansion and contraction of the pipe, ice build up ,vibration ,bad flares etc.
Copper tube comes in various conditions from soft ,half hard and hard, and there are several versions of flaring tools .
Flare Tools
1) The flareing tool cone forms the tube into the flare block by a compression motion which can cause "knecking " at the flare kneck which can cause it to fracture due to the kneck thickness being reduced as the flare is squeezed against the block ( Standard flare block system)
2) The flareing tool cone has a ripple on the cone which rolls the flare out of the block so that no knecking takes place and the kneck of the flare is still of a uniform thickness and strength of the original tube, also the ripple cone polishes the flare face to give a perfect seal area.(Roll Air type flare block)
3) the latest version intended more for use with high pressure refrigerants is similar to the Roll air , but the cone turns an eccentric motion and rolls the tube into a flare ( these types are the most expensive )
4) The old fashion style is a cone punch and block where the cone punch is hammered into the block to force the tube end into a flare shape.
All 4 versions work but versions 2 & 3 are far superior as the flare tube strength is not compromised at the flare kneck (weak point) and the flare joint face has a polished finish.
Copper Tube
Copper tube should be soft or annealed prior to being flared,as a good flare will compress slightly as the soft copper is slightly compressed during being tightened up between the cone on the fitting and the flare nut. The gauge of the tube is also important as if a too thin a gauge of tube is used then during the flaring process with the old compression type block the tube thickness around the flare kneck can again be reduced during the flare process.
Copper tube will both work harden and also age harden so it is important that the flare is produced on good quality tube.
Ice forming around the outlet flare nut can sometimes cause the brass flare nuts to crack or split.
There are alternatives to flare connections on Tevs these days i.e. brazed connections are far superior and modern Tevs are much superior in reliability than to the ones in days gone past
Some countries have banned flare connections due to their poor leak record and a fitting called a flare/ solder adaptor now takes its place as the flare is now a machined brass or steel flare face connector with a copper gasket
When tightening a flare nut it was normally nip the flare nut till it tightens onto the tube then a further half turn of the nut is sufficient to produce a gas tight joint. These days you can get a crows foot socket so that the flare nut can be torqued to the manufacturers recommendation
Cut them out and fit soldier versions with the danfoss flat orifice adaptor stubb they don't leak
Yes the solder type are the way forward and considering the price of refrigerant in Europe.
Just as a good flare, so is brazing, if it is not made correctly, it will leak.
I find more leaks on bad brazing then on bad flares.
A good made flare with a proper sealant will be OK for many years.
I was commissioning some 30 cooling units last summer, imported from Italy for cooling electric and control containers of a solar big plant and there was no leak on any flare [7\8 and 1\2] . I did find two leaks on the condenser inlet though.
Its all depends on the skill and knowledge of the installer.
Hi
might lock nuts will help you to fix it .
but .solder is better than flare for leaks
Thanks for the comments
we recently pressure/leak checked three of the VT rooms with trace gas and remade two flares that were found to be leaking out of the eight TEV flares on that same system.
Three months later on routine maintenance found another flare leaking on the same system that we had pressured tested. Also found two more leaks on two other VT rooms that three months ago passed a sniffer test.
It was my recommendation that we replace TEV's for braised or the mechanical flared fittings but managed wouldn't go for it.
The new leaks found have been nipped up which have stopped them from leaking and waiting repair.
Must admit iv heard bad reports about torquing flaring and the number of leaks it seems to cause.
As I said before brazed is the way,if management disagree then they should be made aware of compliance, chiefs and Indians come to mind but hey I don't live in the wild west?
Years ago had many leaks on expansion valve flares, nut would loosen and leak, a dab of Locktite in the threads and pull up tight cured the problem.