AL fin severe distortion

[MATEGRITY2009]

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/getfil...a1ef-4472-b885-91117b34a477&file=DSC04364.JPG

http://files.engineering.com/getfil...5bbe-4258-8811-eb3f946f47f5&file=DSC04367.JPG

http://files.engineering.com/getfil...8157-44a2-9656-7d8f2c5f2e07&file=DSC04369.JPG

Normal condition of AL fin in the others unit

http://files.engineering.com/getfil...ce02-4bd8-8330-e4740e2a5c8a&file=DSC04361.JPG

 

[chicopee]

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

 

[Ron]

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

 

[EdStainless]

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

 

[MATEGRITY2009]

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.

 

[saplanti]

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.

 

[saplanti]

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.

 

[Compositepro]

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.

 

[MintJulep]

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

Pressure washer?

 

[EdStainless]

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

 

[MATEGRITY2009]

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




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

 

[MintJulep]

and cleaned by HP water

There is your answer.

 

[Compositepro]

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.

 

[IFRs]

Could they have been damaged during the cleaning process?

 

[EdStainless]

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

 

[MATEGRITY2009]

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