Our supplier had a heat treated car 2

[qualitypro]

Our supplier had a heat treated carbon steel heat exchanger that was in a storage yard and something caused a dent in the shell there. The supplier is not able to tell us how or what happened, but it looks like maybe a trailer was backed into it. Anyway, there is now a dent in the shell about 9” from the head seam and is located past the last baffle so the bundle should pull easily. The dent is approximately 5/16” deep and the affected area is about 18” in diameter. The heat exchanger has been transported back to supplier shop for repair. We asked for a CA plan from the supplier to correct the dent. The supplier gave us the below,

Jack out the dent with a 250 ton hydraulic jack by placing a curved plate that matches the inside shell radius between the jack and the shell.
Some heat may be applied, but will be controlled to under 500 deg. F.
Dress the area on the outside of the shell by grinding smooth.
Ultrasonic thickness check the shell and record the readings.
Reassemble the exchanger with new gaskets and hydrotest.
Blast and repaint and ship prep.

Is the above acceptable?
My concern is given the fact that the exchanger was heat treated already shouldn't it be heat treated once again after restoring the contour. Is there a ASME Code requirement that governs when a re- heat treatment is required? Please give me your feedback with respect to ASME inspection and heat treating requirements.

 

[TGS4]

Was the U-stamp already applied?

 

[chicopee]

Get a copy of the NBIC for repair guidelines to determine acceptability . Also consult with you boiler and machinery insurance inspector and with jurisdiction. I remember during my days as N.B. inspector, between the late 70's and early 90's, anecdotes of old timers using heat to soften areas of distress and manually hammer to restore boilers to operating condition; I wish I had been around to see the procedures. It appears the scope of the proposed work is acceptable but nonetheless do the research with the stated reference.

 

[r6155]

Please, can you tell us shell diam. and thickness?

Regards
r6155

 

[chicopee]

My 1987 NBIC, section I-501.4, DENTS, "...In some cases a dent can be repaired by mechanically pushing out the deformation" NBIC also indicate that the shop should be qualified by the jurisdiction as indicated in I-504. All proposed works should be submitted to the jurisdiction. Obviously the NBIC has been modified over the years therefore an updated one needs to be used.

 

[NBrink]

Regardless of acceptability to code, you need to consider the service impacts as well.

For instance, if this was in amine or caustic service, not a chance I'd allow it without heat treatment.

Nathan Brink

 

[Ehzin]

As mentioned by NBrink, take extra consideration regarding the fact that the vessel was originally heat treated. Essentially that area has been cold worked and a few hundred degrees to assist with reshaping it isn't doing anything to regain the benefit of the original heat treatment. First find out if it's service related or possibly related to low temperature requirements.

Thanks,
Ehzin

 

[TGS4]

Sometimes doing nothing - leaving it alone - might be the best solution.

 

[r6155]

My proposal:
1) 100% UT on affected area
2) 100% PT or MT inside and outside on affected area

If 1) and 2) are OK, continue with hydrotest.

Regards
r6155

 

[metengr]

I agree with TGS4 except I would perform surface NDT and shear wave UT to ensure no indications (cracks or tears).