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=falseThe 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