Quality control encompasses the operational techniques and activities used to verify products meet specified requirements. In fabrication, QC ensures equipment conforms to drawings, specifications, and applicable codes through systematic inspection, testing, and documentation.

QC processes include incoming material inspection verifying mill test reports and material markings, in-process inspection during fabrication detecting problems early, dimensional verification confirming measurements match drawings, weld examination using visual and NDE methods, pressure testing validating pressure integrity, and final inspection before shipment.

Effective QC requires documented procedures defining inspection points and acceptance criteria, qualified inspectors with appropriate training and certification, calibrated measuring and testing equipment, objective evidence through inspection records and test reports, and corrective action processes addressing nonconformances.

QC differs from quality assurance—QC verifies product conformance through inspection and testing while QA encompasses the management systems ensuring quality throughout operations. Both are essential: QA prevents problems through systematic processes; QC detects problems that escape prevention.

For ASME code fabrication, third-party authorized inspectors verify QC activities and sign fabrication documentation, providing independent verification of code compliance. Inspector involvement typically begins with material verification and continues through final inspection and data report completion.