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AL fin severe distortion

AL fin severe distortion

AL fin severe distortion

(OP)
Now, we found severe distortion at AL fin of finned tube of the air cooler heat exchanger. (In my experienced, i'm never found this problem before)

Is this cause by heat that exceed AL temperature limit?

Anyone experience this issue, please advise.

Thanks for any help

http://files.engineering.com/getfile.aspx?folder=d...

http://files.engineering.com/getfile.aspx?folder=7...

http://files.engineering.com/getfile.aspx?folder=d...

Normal condition of AL fin in the others unit

http://files.engineering.com/getfile.aspx?folder=a...

RE: AL fin severe distortion

My guess is that they were physically damaged by accidental contact.

RE: AL fin severe distortion

Agree with chicopee...no reason for temperature to cause that type of effect.

RE: AL fin severe distortion

For that to happen just from temperature you have to in the range where the Al softens, If you had gotten that hot then you would have lots of other problems.

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P.E. Metallurgy, Plymouth Tube

RE: AL fin severe distortion

(OP)
Thank you for all advice.

Chicopee and Ron; We can confirmed that this is not caused from accident. from the day one of operation it look very good condition and then 9 years of operation it look like in the picture.

Edstainless: Now, we try to verify the type/ grade of AL fin to find the temperature limit.


RE: AL fin severe distortion

Could it be from thermal distortion? Depending on the manufacture type of the fin or the sheets from that were manufactured they might already be under stress. After having additional thermal stresses the fins may get distorted. I guess you need to contact to the manufacture to source the reason.

RE: AL fin severe distortion

The thermal stress might be caused by the the fan (if the air forced by fan for the operation) which might not be working during the operation. Check all the connections with motor for the operability of the motor-fan combination for the cooling action.

RE: AL fin severe distortion

The waviness of the fins indicates that the center of the discs has shrunk relative to the OD of the discs. This could have occurred due to many thermal cycles where the tubes got hot enough so that the aluminum at the center of the fin expanded while cooler aluminum at the outside of the disc (fin) restrained this expansion. The thermal stresses then went past the yield point and the center of the disc compressed slightly, so when it cooled again it had permanently shrunk slightly. Each thermal cycle past a certain temperature would add to the shrinkage. This then resulted in circumferential buckling of the aluminum at the outside of the disc.

RE: AL fin severe distortion

They are remarkably clean for having been in service for 9 years.

Pressure washer?

RE: AL fin severe distortion

How quickly can this unit be heat/cooled?
If the unit were running very hot (over design) and then cooled fast you could start buckling the fins.

But I am with MJ, has this unit ever been washed?

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P.E. Metallurgy, Plymouth Tube

RE: AL fin severe distortion

(OP)

Quote (MintJulep (Mechanical)8 May 17 19:22

They are remarkably clean for having been in service for 9 years. Pressure washer?)


This exchanger is placed on the Platform, Offshore installation and cleaned by HP water in some shutdown period. (Very rare)



Quote (EdStainless (Materials)8 May 17 19:27
How quickly can this unit be heat/cooled?)


I will check with production team for the exact cycle of thermal cyclic.

RE: AL fin severe distortion

Quote:

and cleaned by HP water

There is your answer.

RE: AL fin severe distortion

High pressure water or other physical damage will cause bending and fold-over of the discs in very localized areas. Eventually this could add-up to the whole area but the pattern will not be uniform. These fins are wavy and not folded, and the pattern is very uniform. Water on hot fins could be the cause damaging temperature gradients.

RE: AL fin severe distortion

Could they have been damaged during the cleaning process?

RE: AL fin severe distortion

Spraying even low pressure water on them while hot can lead to extensive distortion.
I have never seen it look exactly like the posted photos, but it is a possibility.

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P.E. Metallurgy, Plymouth Tube

RE: AL fin severe distortion

(OP)
We clean it during plant Shutdown, so exchanger temperature will be at ATM around 29 - 33 C.

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