Quoting API 510 Tenth Edition: 7.7 Evaluation of Existing Equipment with Minimal Documentation
For pressure vessels that have no nameplate and minimal or no design and construction documentation, the
following steps may be used to verify operating integrity.
1) Perform inspection to determine condition of the vessel including a complete dimensional checking of all
components necessary to determine the minimum required thickness and adequacy of the design of the vessel
[i.e. heads, shell(s), transitions, openings, reinforcement pads, saddle supports, etc.].
2) Define design parameters and prepare drawings.
3) Perform design calculations based on applicable codes and standards. Do not use allowable stress values of
the current ASME Code (based on design factor of 3.5) for vessels designed to an edition or addendum of the
ASME Code earlier than the 1999 addendum and was not designed to ASME Code Case 2290 or ASME Code
Case 2278. For vessels designed to an edition or addendum of the ASME Code earlier than the 1999
addendum and were not designed to ASME Code Case 2290 or ASME Code Case 2278, use allowable stress
values of the pre-1999 ASME Code (based on design factor of 4.0 or 5.0). See ASME Code, Section VIII,
Division 1, Paragraph UG-10(c) for guidance on evaluation of unidentified materials. If UG-10(c) is not followed,
then for carbon steels,[highlight #FCE94F] use allowable stresses for SA-283 Grade C and for alloy and nonferrous materials, use
X-ray fluorescence analysis to determine material type on which to base allowable stress values.[/highlight] When the
extent of radiography originally performed is not known, use joint efficiency of 0.7 for Type No. (1) and 0.65 for
Type No. (2) butt welds and 0.85 for seamless shells, heads, and nozzles or consider performing radiography if
a higher joint efficiency is needed. (Recognize that performing radiography on welds in a vessel with minimal or
no design and construction documentation may result in the need for a FFS evaluation and significant repairs.)
4) Attach a nameplate or stamping showing the MAWP and temperature, MAT, and date.
5) Perform pressure test as soon as practical, as required by code of construction used for design calculations.
I hope this helps.
Larry
