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Thread: Strange phenomena
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03-04-2007, 09:27 PM #1
Strange phenomena
http://www.coolandcomfortforum.be/viewtopic.php?t=53 hope this links works.
What can be the reason of this.
The holes you see is in the aluminum that is and expand fin over the copper tube.
It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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03-04-2007, 09:40 PM #2
Re: Strange phenomena
Internal helically grooved pipe. Too much grooved and later bursted.
Last edited by NoNickName; 21-03-2008 at 03:22 PM.
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03-04-2007, 09:59 PM #3
Re: Strange phenomena
.
He might be right.....
.
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03-04-2007, 10:11 PM #4
Re: Strange phenomena
I have seen this loads of times, its only moisture getting under the coating , freezing and then bursting the coating (which is very thin anyway).
Copper pipes underneath remain intact.
ChillinIF AT FIRST YOU DON`T SUCCEED.
DESTROY ALL EVIDENCE THAT YOU TRIED!
and go get a cuppa
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04-04-2007, 10:14 AM #5
Re: Strange phenomena
I did not find anything in the link above. Just saw the picture by NoNickName.
I am in coil business but I have not seen anything like this before
Are the fins aluminum? or they are steel and dip galvanized.
If they are aluminum then after tube expansion there is no way that the moisture can get between fin collars and the tubes.
As Chilling Out said, if it is the coating then it is possible.
CheersEven Einstein Asked Questions
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04-04-2007, 10:51 AM #6
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04-04-2007, 10:55 AM #7
Re: Strange phenomena
Here are the pictures for those wgo can't open the link
It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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04-04-2007, 10:56 AM #8
Re: Strange phenomena
Chillin, also the copper is leaking
Fins are aluminum
They hang there for several years
Brand Friga Bohn France (=Heatcraft)It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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04-04-2007, 11:11 AM #9
Re: Strange phenomena
Dear Peter-1,
You are completely right to call it "Strange phenomena".
I have not seen anything like this. If moisture gets there and freezes then the rupture will not be like this.
What comes to my mind is :
1- This is like corrosion or something at certain points.
2- The alloy of the aluminum is not good.
3- The coating problem.
CheersEven Einstein Asked Questions
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04-04-2007, 05:07 PM #10
Re: Strange phenomena
Al the pinholes came at once, that's what's so strange.
This is of course the first time that this happens.It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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04-04-2007, 05:22 PM #11
Re: Strange phenomena
You wrote it's also in the copper pipes? Is it possible that the copper is not strong enough to withstand the pressure/temperature combination?
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04-04-2007, 05:30 PM #12
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04-04-2007, 07:40 PM #13
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04-04-2007, 08:24 PM #14
Re: Strange phenomena
Hi Sanderth,
Copper tubes used in coil industry (Fin-tube) is usually 3/8" , 1/2 " , 5/8 " OD. The thinesst tube I have seen is 0.45mm thickness. You can see that they can stand a lot of pressure.
These tubes are used to make condenser coils which usually operate in the range of 16 to 22 bar (or more).
If you had a tube which ruptured under 1bar then, I think there was another problem which caused it NOT the pressure.
CheersEven Einstein Asked Questions
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04-04-2007, 11:52 PM #15
Re: Strange phenomena
Was the evaporator (?) treated with inappropriate chemicals that by capillary action flowed under the aluminium to copper joint, then salt formation, water absorbtion, freeze and pop, pop, pop... even if cleaned off with water afterwards.
I think you mentioned the copper leaked and simultaneity of the occurance. I'm not a chemist but the first to go will be the aluminium (locally we suffer salty dust/spray a lot, but that usually first rots away the Al - even Daikin coatings suffer particle impact damage!)
A similarity could be: steel car rust, once the oxidisation action starts it spreads ramifications like a cancer under the paint (later sunlight holes appear in you van's roof! ) here it went radially between the materials then causing pin points AL-Cu weakening the pressure resistance.
Looking at the geometry the holes: the gentleman from Merate could also be right as to weaker points in the structure.
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05-04-2007, 10:27 PM #16
Re: Strange phenomena
I seen this tons of times it isn't strange or seldom. Stuff forming under the Alu, wether salt or moisture or Alu oxide the result is the same. With the coastal air I see it more on evaps but I do at times see it on condencers.
Iana, Rule one nothing is perect or 100% sealed, rule two see rule one. No matter what they decay and die, this is fact, so the name of the game is getting it to live as long as possible, so no shame in seing it happen to a coil no matter who made them.
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06-04-2007, 01:04 AM #17
Re: Strange phenomena
I have been trying to look at these pictures Peter and have some problems trying to see what may have happened.
NoNickName has an interesting reason as the failure seems to have occurred over most of the tubes. Is this a DX evaporator?
I looked for a picture to describe what I think NoNickName was describing. (see below)
If the holes popped up in the tubing grooves, the holes would have followed the helix angle of the grooves. This is also the thinnest part of the tube.
I have seen coating failure before and it did not look like the pictures. This looks like some type of failure mechanism due to a sudden high pressure such as a hydrostatic pressure. Although I'm not sure what would have caused it.
Has anyone cut the tube apart to see where the small holes formed?If all else fails, ask for help.
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06-04-2007, 09:34 PM #18
Re: Strange phenomena
Hi Folks, I see you have been busy here.
If it was a pressure burst, there would be tears from the hoop stress.
If there was corrosion inside the copper tube and this caused a weakening, then the pressure would cause rupture at the stress point. But, once the pipe bursts, the pressure is gone and it cannot burst in so many sites at once.
Freeze damage can cause multiple breaks but the holes don't look like a freeze burst. These would look more like tears.
Frozen moisture under the coating would not cause the copper tubes to rupture.
I think that the damage is caused by surface corrosion on the outside. The only problem with this is the outward splayed out shape of the hole. Could be caused by escaping fluid under pressure.
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06-04-2007, 10:03 PM #19
Re: Strange phenomena
Originally Posted by nh3simman
If the coil were liquid locked with cold refrigerant and isolated, then a very slight rise in temperature would generate a lot of pressure/stress extremely quickly and UNIFORMLY across the tube internal surfaces.
That would cause the miniature holes to splay outwards. The distribution of the holes around the helix may be due to manufacturing imperfections.If all else fails, ask for help.
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06-04-2007, 10:19 PM #20
Re: Strange phenomena
It's a colleague of mine who gave me this pictures.
It's indeed a DX evaporator
This is the one
http://www.friga-bohn.com/literature/gb/MR.pdf
It's also very strange for me. Al the ruptures seems to happen at once.
I notice that they have indeed an internal grooved structure.
So this can point us in the right direction.
PeterIt's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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07-04-2007, 05:05 AM #21
Re: Strange phenomena
But if it was isolated and the temperature rise caused an increase in pressure, then the pressure would have been relieved as soon as the first hole ruptured. Also, a pressure burst would be a slit in the same direction as the tube since this is the maximum stress line.
These are a lot of outward holes that must have happened at the same time. It must have been pressure because of the outward splays.
If there was a chemical treatment that was left on the coils and this corroded the tubes. The splinters from the copper could have been like bullets perforating the fin in an outward direction.
Indeed a tricky one.
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07-04-2007, 09:53 PM #22
Re: Strange phenomena
Could this be electrolosis between the aluminium, copper and salt from seawater air offering perfect conditions for pitting on the copper surface and when one hole blew they all blew (clutching at straws here)?
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07-04-2007, 10:53 PM #23
Re: Strange phenomena
The coils are still perfectly good with no leaks, I vote electrolisys as this makes perfect sense. Like I said I see it all to often on the coast.
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07-04-2007, 11:05 PM #24
Re: Strange phenomena
Originally Posted by nh3simman
I still think the culprit is pressure and the helix angle and surface enhancements have something to do with it. What, I don't know now.
Those holes in a pattern are trying to tell us something...If all else fails, ask for help.
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08-04-2007, 08:43 PM #25
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08-04-2007, 09:13 PM #26
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09-04-2007, 12:36 AM #27
Re: Strange phenomena
If the root thickness is very thin and any possible manufacturing imperfections exist that coul dbe the cause. The holes seem to occur in somewhat of a regular spacing which leads me to believe problems with tooling when the grooves are formed.
If all else fails, ask for help.