If this is in petrochemical service, follow API 510.
How the patches are welded will depend on the base material and service.
This work should be done by a qualified repair company. If this is a stamped vessel the repairs will need to be done by a contractor with a ASME "R" stamp. The datum will need to be updated with a repair datum added to the original vessel datum.

vignesh5585

API 510 is an inspection code applies to all refining and chemical process vessels that have
been placed in service (in-Service Inspection, Rating, Repair, and Alteration).

You may engage an API 510 Authorized Inspector, get those inspector from Inspection Firm who had been seasoned in API 510 requirements.

What API 510 says on repair organization? i.e.: Any one of the following who makes repairs in accordance with the inspection code:

a. The holder of a valid ASME Certificate of Authorization that authorizes the use of an appropriate ASME Code symbol stamp
(e.g. U-stamp).
b. The holder of a valid R-stamp issued by the National Board.
c. An owner or user of pressure vessels who repairs his or her own equipment.
d. A contractor whose qualifications are acceptable to the pressure-vessel owner or user.
e. An individual or organization that is authorized by the legal jurisdiction.

~Joey~

Basically an 8" x 16" x 3/16" thk overlapping patch was discovered in a 1-1/2" thk shell pressure vessel???

May I ask what the stamped plate on the outside of the pv states?  And what country/jurisidiction does it reside?  Service, MAWP, temp?

QCRobert

Vignesh,
I would recommend you read the replys from the last time you posted about "R-Stamp"work. There are some great questions and info you can review.

Thanks
Jim

This is from an older version of API 510

"8.1.5.1.3 Lap Band Repairs

A full encirclement lap band repair may be considered if the following requirements are met:

a. The design is approved and documented by the engineer and inspector.

b. The repair is not covering a crack in the vessel shell.

c. The band is designed to contain the full vessel design pressure.

d. All longitudinal seams in the repair band are full penetration butt welds with the design joint efficiency and inspection consistent with the appropriate code.

e. The circumferential fillet welds attaching the band to the vessel shell are designed to transfer the full longitudinal load in the vessel shell, using a joint efficiency of 0.45. Where significant, the eccentricity effects of the band relative to the original shell shall be considered in sizing the band attachment welds.

f. Appropriate surface NDE shall be conducted on all attachment welds.

g. Fatigue of the attachment welds, such as fatigue resulting from differential expansion of the band relative to the vessel shell, should be considered, if applicable.

h. The band material and weld metal are suitable for contact with the contained fluid at the design conditions and an appropriate corrosion allowance is provided in the band.

i. The damage mechanism leading to the need for repair shall be considered in determining the need for any additional monitoring and future inspection of the repair.

*See ASME PCC-2 Article 2.6 on full encirclement sleeves for vessel nozzles."

Look for Chapter 5, Page 69, Figure 5.6 in this book linked below which covers to API 510 Section 8, under the heading "Alterations Re-rating and Repairs":

http://books.google.com/books?id=a3dwAgAAQBAJ&pg=PA72&lpg=PA72&dq=pressure+vessel+%22Lap+Band+Repair%22&source=bl&ots=AbKBwKvuHm&sig=9AEdi3riYPpPPDkoD7mSF2s9HGc&hl=en&sa=X&ei=sAq1U_DAJYW_8gHAmYDICQ&ved=0CFYQ6AEwBQ#v=onepage&q=pressure%20vessel%20%22Lap%20Band%20Repair%22&f=false

The difference between that picture in Figure 5.6 is the temporary lap patch is localized like a "band aid" whereby a full encirclement lap band would cover the entire circumference of the pressure vessel like a belt covering your entire "waist."

If I can locate some pictures to post I'll do so and then again, somebody else might do so before I do.

Respectfully,
Henry