reduction in tube thickness due to over expansion

[mandarkardekar]

It was happened the over expanding for shell and tube exchanger during the expanding work.

(Tube min. required Th’k : 2.77mm, Tube Th’k after expanding : 2.70mm)

IS this acceptable?

 

[EdStainless]

Is it too thin because it was overrolled or was the hole too large?
And then how do you know what the wall is after rolling? I would like to see that method.
In general, yes people accept this situation since this is fully backed by the tubesheet.
If they did this though I would be double checking the depth of roll and other details.
Were these rolled using a torque limit?
Did any of the tubes in the mock-up show this condition?

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P.E. Metallurgy, Plymouth Tube

 

[mandarkardekar]

Thank you EdStainless for your quick reply.

Please let me correct my question above. Actually my vendor has come with excuse that he has over expanded the tubes lengthwise. Which means it is expanded beyond the inner face of tubesheet.
Even though thinning of tube is not much in this area (just 0.07mm), where required tube thickness is just 0.5mm for pressure and temp, TEMA do not allow this.

What could be solution in such case.

 

[racookpe1978]

If too long, why is he not trimming the excess? Thinness is a flaw if the tube walls no longer meet your specification. If you have no minimum wall thickness in your contract, it might be difficult to get a payback/replacement.

 

[metengr]

The confusion lies in the terminology. From what I have read and interpreted, the tubes have been rolled beyond the distance of the inner face of the TS. Further explanation is necessary.

 

[EdStainless]

Make him remove them and replace them. The stresses in the area rolled too deep are very bad, and tube failures from this are common.
This is clearly a fabrication error.

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P.E. Metallurgy, Plymouth Tube

 

[Sengland]

I'd agree with getting them replaced. The stresses in the tube at the back of the tubesheet can be quite high without a stress raiser.

 

[SnTMan]

Agreed, replace them if possible, plug them if not.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[r6155]

See API 660
9.10.3 The minimum length of expansion shall be in accordance with TEMA Section 5, Paragraph RCB-7.1.
However, in no case shall the expansion extend within 3 mm (1/8 in.) of the shell side face of the tubesheet.

Regards
r6155

 

[metengr]

This is a nonconformance which requires replacement of incorrectly rolled tubes.

 

[r6155]

1) See API 660.
A.4.4.1 If there is potential for crevice corrosion on the shell side, tubes should be expanded to within 3 mm (1/8 in.)
from the shell side face of the tubesheet.
2)Which is the proposal of the vendor?

Regards
r6155