Sigma checks that the most current revisions of As-Built drawings are in use on the shop floor. Inspectors verify As-Built Drawings with Engineering Drawings, P&IDs, and Wiring Diagrams for compliance. Sigma will mark up As-Built Drawings with all findings, inspection notes, and dimensional measurements of the equipment as follows:

1. Check Head / Baffle Fit-up
2. Complete Internal inspection / Open end inspection
3. Check Head / Baffle clean before Post Weld Heat Treatment (PWHT) if applicable, visual & dimensional
4. Check installation of all nozzles and coupling, with the correct orientation, and liner location
5. Check all nozzles and couplings for proper corrosion allowance and pressure ratings
6. Check for the presence of nozzle baffles
7. Check Head coupling(s) and nozzle(s) positioning
8. Check Head(s) for proper welding to shell
9. Check the dimensional spacing of tray shelves
10. Check the shell and the skirt (identify if insulation rings or hangers are present)
11. Check the diameter of apertures, vents, and couplings (manway openings, T-connections, Elbow connections, valves, nipples, & nozzles) on equipment
12. Check point-to-point length between Center-point of apertures, vents, and couplings (manway openings, T-connections, Elbow connections, valves, nipples, & nozzles) on equipment
13. Check point-to-point length between structure supports (legs, cradles, and saddles) on equipment
14. Check point-to-point length between weld seams on equipment
15. Verify tolerance as ≤ max on all measurements and mark up As-Built Drawings
16. Mark on equipment any anomalies for repair/remediation, such as weld quality or appearance, and/or quantitative physical measurements > max tolerance of engineering specifications
17. QA/QC “Sign-off” signature on As-Built Drawings

Sigma provides As-Built Drawing verification as part of the company's core competency in Third-Party Verification (Vendor Surveillance) and QA/QC review/oversight.