% wall thinning in expanded tube to tube sheet joint

abc123 · **Joined:** Fri Nov 06, 2009 7:02 am **Posts:** 40

Dear All

What is the criteria / reference for expanded tube to tube sheet joint
for full expanded joint?
i.e. how we make it sure that the joint is adequate
I think the designer should either mention % thinning in tube wall or should mention a tube pull out load?
Kindly advise what is the responsibilty of designer when he recomends
an "expanded" tube to tube sheet joint as per ASME code.
or
it is the responsibility of fabrication engineer to sure that "expanded" joint is adequate.?

Thanking in anticipation

Javed Nasir · **Posted:** Thu Jun 09, 2011 2:16 pm

We normally use 7% expansion in CS tubes and 9-10% in SS tubes, for LAS 4%.
Code does not specify the amount of expansion. Expansion shall not be excersised beyond the tubesheet face, see Figure UHX-11.1(b).
% expansion is calculated as;

% Expansion= {(D-d)-c}/2t

D= inside diameter of tube after expansion.
d= inside diameter of tube before expansion.
t= nominal wall thickness of the tube.
c = clearance between tube outside diameter and tube hole diameter in the tubesheet.

Javed Nasir · **Posted:** Thu Jun 09, 2011 3:08 pm

Sorry for SS tubes it is 3-5%.
Also note the reference please.

Heat Exchanger Design Handbook by Marcel Dekker

abc123 · **Joined:** Fri Nov 06, 2009 7:02 am **Posts:** 40

Javed Nasir wrote:

We normally use 7% expansion in CS tubes and 9-10% in SS tubes, for LAS 4%.
Code does not specify the amount of expansion. Expansion shall not be excersised beyond the tubesheet face, see Figure UHX-11.1(b).
% expansion is calculated as;

% Expansion= {(D-d)-c}/2t

D= inside diameter of tube after expansion.
d= inside diameter of tube before expansion.
t= nominal wall thickness of the tube.
c = clearance between tube outside diameter and tube hole diameter in the tubesheet.

Dear Nasir Bhai
AOA WRWB
JAZAKALLAH KHAIR for your kind help.Have you any idea about "qualification of expanded tube to tube sheet joints by the criteria of tube pull out load"
Whats your practice to qualify such joints?

Many thanks once again !

Faisal
Heavy Mechanical Complex, Taxila

niraj_kuwait · **Posted:** Mon Jun 13, 2011 10:46 am

Go To ASME SEC- 8 Div-1 Non mandatory Appendix- A.
Describe fully for Basis For Allowable loads in T-TS Joint

Javed Nasir · **Posted:** Mon Jun 13, 2011 4:06 pm

I agree with Niraj, You can use Appendix A of Section VIII-1 for Tube-to-Tubesheet joints. Keep remember the following points.

1- Full strength welds calculated as per UW-20.4 do not require shear testing.
2- Partial strength welds calculated as per UW-20.5 do not require shear testing.
3- The welds calculated as per UW-18(d) do not require shear testing.
4- You cannot apply rules of Appendix A to U-Tube construction.

abc123 · **Joined:** Fri Nov 06, 2009 7:02 am **Posts:** 40

Thanks to friends for their valuable guidance

I m confused about just one thing now.
How to qualify a fully expanded joint (without welding) in case of U tube heat exchanger?

Regards

Faisal

niraj_kuwait · **Posted:** Tue Jun 14, 2011 10:16 am

Make a Mockup
Expand as per job requirement
take hydro, Establish leak tightness.
You can't follow Appendix A Since it is U tube Exchanger
Reason to not follow App -A is There is no axial Load on tube to tube sheet joint.
Hope it is clear

abc123 · **Joined:** Fri Nov 06, 2009 7:02 am **Posts:** 40

niraj_kuwait wrote:

Make a Mockup
Expand as per job requirement
take hydro, Establish leak tightness.
You can't follow Appendix A Since it is U tube Exchanger
Reason to not follow App -A is There is no axial Load on tube to tube sheet joint.
Hope it is clear

Thanks niraj

Can we qualify as per ASME code as follows:

Either
designer should mention % expansion of tubes
or
designer should mention "tube pull out load"

Another question is "To mention a qulifying criteria in this case is the responsibility of designer or its solely a respeonsibility of fabrication engineer?"

Thanks once again

niraj_kuwait · **Posted:** Sat Jun 18, 2011 1:49 pm

Yes you can qualify but Pull out is not applicable in your case.
regarding your 2nd Question
mentioning and maintain Qualifying criteria is purely in your case falling under fabrication.

BUT

As a designer you should know what exactly they are doing and if they are wrong at certain point you should be in position to guide them to meet your designed equipment.

Javed Nasir · **Posted:** Sat Jun 18, 2011 2:07 pm

We did never follow Appendix A for the qualification for tube-to-tubesheet joint that falls under under its scope, we simply adopt the practice of controlled expansion up to the amount as I mentioned in my first reply to abc123 question. We did never have any problem both in hydro and in operating conditions.
Once we faced the leakage problem of a water tube boiler during hydro, the tube-to-tubesheet joint was made by expansion and enhanced by two grooves, the reason we found latter was the improper amount of expansion.

% wall thinning in expanded tube to tube sheet joint

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