Damaged Fins of Heat exchanger-Acceptance criteria

[athilatt]

The Fins of Tube bundle of a Heat exchanger got badly damaged. Bundle is U1 stamped and API 661 requirements to conform.(New construction)

what would be the acceptance limit/criteria in damage of Fins ?

 

[metengr]

athilatt
First off, you have double posted in the ASME Code forum. So, to conform with site rules here is the cross post link.

thread292-251346

Now in response to your question, this is a contractual matter between the manufacturer and the client, and not a code of construction matter. If it was me, and I had a detailed engineering specification when I sent out my request for proposals, it would probably have language that mentions no physical or mechanical damage during handling or shipping.

This means - no fin damage period.

 

[GenB]

sometimes we smash them on purpose and its acceptable, depending on your HX rate and temp., and material yiou may be okay with smashet fins but the tube has to be intact. if the fins aren't there your tube may get hotter and fail. be careful
genb

 

[SnTMan]

GenB, curious why you smash them on purpose. Care to elaborate?

Regards,

Mike

 

[jmiles]

Well fin damage will only affect your heat transfer rates, BUT depending on how the fins got damasged and how they are attached there might be tube damage which could affect the integrity of the pressure retaining side.

At the very least id do a visual inspection and hydro of the tubes again, and possibly some NDE. as for the fins, you just ahve to make the call on if you think those fins are damaged enough to adversely affect the heat transfer.

 

[vesselguy]

GenB,
Very interesting! Do your customers actually know that they will get a product is deliberatly "deformed"? I know the first thing that comes to mind for the reason is "enhanced HT". It must be me, but I get this uneasy feeling about seeing deformed tube fins.

 

[GenB]

is not that you want to do it, sometimes space is critical and instead of cutting you smash them as I said: depends on the material and system temp, you run tests and if it works,
you mass produce.

 

[boilerone]

I would not worry too much about the fins if no tube damage is found. It is just like the radiator of your car or your AC outdoor unit, the fins on them always get deformed some sort by careless persons but they still work without problems. I'd say if the damaged area is just a few percentage of the total then go ahead and install it without delaying your project. Commercially you can always ask for some money back from whoever caused the damage.

 

[rmw]

If there is no damage detrimental to tube or fin to tube integrity, your concern should be for performance. If your supplier has enough over capacity in his design to allow a lot of tubes to be smashed, he is selling more material than he needs to. Most don't do that any more, so my concern would be how much performance degradation will be caused by the section(s) where the fins are damaged and impeding flow through them.

You need to get him to justify with something like HTRI that the unit will still make its duty with a safety margin.

rmw

 

[AllHandlesTaken]

You could also look into straightening the fins with a fin comb/straightener.