Out of Roundness of Exchanger Shell

[LanceM]

Good day!

Our company purchased a new exchanger shell as replacement for an old one. During the installation of the spare tube bundle we have noticed that the shell is not round on different locations, especially on the shell's vapor belts. We have told the manufacturer about this and we had measured the shell's roundness. The manufacturer would not accept that the shell was poorly fabricated since roundness of the shell is acceptable based on ASME VIII Division 1 UG-80 of 1% tolerance.

UG-80(a)(1) The difference between the maximum and minimum inside diameters at any cross section shall not exceed 1% of the nominal diameter at the cross section under consideration.

Still, the tube bundle won't fit since the length of the shell is wavy (but the manufacturer would still argue that the tolerance is below the acceptance of ASME). Would someone enlighten me on the logic of ASME VIII Div 1 UG-80? The section seemed to only take that out-of-roundness only happened to one cross-section only. The case with the shell is that out-of-roundness happened in different locations for the whole length of the shell. can I use the measured max diameter on one cross section and the minimum diameter on another cross section for the calculation of tolerance?

Are there any other standards that address this problem? I've tried TEMA but it doesn't say anything on out-of-roundness. Basically, we were searching for standard that would definitely back our claim that the shell is rejected.

Also, what repair procedures would you recommend? the manufacturer suggested grinding of the shell internal so that the tube bundle will fit.

 

[TGS4]

The ASME Code represents minimum standards. If your purchase specification didn't include something like "our bundle has to fit in the new shell", or provide additional criteria, you might be stuck with fixing it on your dime.

Don't grind. You will likely go below t_min. Hopefully they can heat and/or beat the shell into shape for you. Do you need a PWHT?

 

[r6155]

See TEMA G.5-5 REPLACEMENT AND SPARE PARTS
When replacement or spare tube bundles, shells, or other parts are purchased, the manufacturer is
to guarantee satisfactory fit of such parts only if he was the original manufacturer. Parts fabricated
to drawings furnished by the purchaser shall be guaranteed to meet the dimensions and tolerances
specified.

Regards
r6155

 

[r6155]

Go / no GO gauge must be used during fabrication. Consult with fabricator if was done.

Regards
r6155

 

That is the purpose of technical specifications prepared by the Owner and attached to purchase orders, which incorporate detailed requirements, inspections and sanctions for non-conformance.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[SnTMan]

LanceM, sorry for your troubles. As r6155 refers to, a couple of discs the OD of the baffles and fastened a foot or so apart should be able to pass thru the shell. This should be done by the fabricator, and as i_m says, should be specified by the buyer. Unfortunately, too late for all that now.

Vapor belt construction is difficult, and as TGS4 says you may be able to improve things by heating and jacking out of round areas. You may also help things by grinding the baffles.

Regards,

Mike



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

 

[r6155]

Not only out of roundness shall be measured, also the inside diameter.
TEMA RCB-3.122 PLATE SHELLS
The inside diameter of any plate shell shall not exceed the design inside diameter by
more than 1/18" (3.2 mm) as determined by circumferential measurement.

Regards
r6155