Re-expansion of tubes for Air Fin Cooler.........

[Vinod Jotwani]

Dear Experts,

 

We have one of our fin fan cooler leaking from tube to tubesheet joint. The tube material is Duplex stainless steel.

 

We would like to carry out re-expansion of the tubes, your advise is needed for %age expansion allowed when these tubes are to be re-expanded. The tubes are in operation since last one year in Sour Water Recovery Unit ( H2S service).

 

Also if some body can share their experience in case of leakage even after re-expansion how to repair the tube to tube-sheet joint. For information the header is welded constuction.( Ref attached file )

 

 

Thanking you,

 

Vinod

 

 

[R.Lenin]

Dear Vinod,

1.0 Expansion ratio for Stainless Steel and High alloy steel : 6-8%

2.0 Tubes shall be expanded into the tube sheet for a length at least
the smaller of the following (a) 50mm (b) the tube sheet thickness
less
3 mm.In no case shall the expanded portion extend beyond the air –
side face of the tube sheet.

3.0 verify the essentially uniform expansion throughout the expanded
portion of the tube without a sharp transition to the unexpanded
portion.

4.0 The ends of tubes shall extend at least 1.5mm and not more than 10
mm beyond the tube sheet.

The formula for reduction in wall thickness (K)

( d2-d1) – (H-d0 )
K = ------------------------ x 100
( d0 – d1 )
d 2 – Tube I.D. after expansion.
d1 - Tube I.D before expansion
H – Tube Sheet hole diameter.
d0 - Tube O.D before expansion

Best Regards,
R.Lenin

>  AFC.pptx
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[mustaffi]

Dear Vinod,

 

Recommended for DSS Material Expansion required for 3 – 5 %.

 

The main thing , you need to know whether AFC for Tube Sheet Holes were Design with Groove or not , coz your references said the tubes also welded .

 

In certain procedure were adopted with references from Client Specification. It doesn’t show groove means your tubes was performed with Light Expansion only ( close the clearances between tubes to tube sheet ) then the welding tubes need a degree for bevelling for strength weld.

 

Regards

Mus7.

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[hizad idris]

Dear Vinod,

 

If still leaking after re-expand, my suggestion to plug off the tube, if the performance still within the required coolers performance. Normally , cooler have over design up to 20%. Need to calculate the cooler performance with the remaining tube, after plug off.

-izad-

 

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[Suresh]

Yes ..I agreed with Mr. Izad  ....

Suresh

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Thanks  & Best Regards,

Suresh

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