Qualification (URS, DQ, IQ, OQ, PQ)

The sequence exists because each stage answers a different question, and skipping one pushes its failure into a later, more expensive stage. The user requirements specification (URS) states what you need the system to do. Design qualification (DQ) demonstrates the proposed design satisfies it. Installation qualification (IQ) verifies it was installed as designed. Operational qualification (OQ) shows it functions across the operating ranges. Performance qualification (PQ) shows it performs consistently in its actual use, typically with real materials.

The URS carries more weight than its length suggests, because it is the traceable origin of everything after it. Requirements that are vague ('adequate mixing') cannot be verified. Requirements that are testable ('homogeneity within ±5% across defined sampling points') generate their own acceptance criteria and make the later stages straightforward. Most qualification arguments are really URS arguments arriving late.

Factory and site acceptance testing (FAT and SAT) can reduce duplication: Annex 15 allows testing performed at the supplier to be leveraged where it is justified and documented, rather than repeating it wholesale at IQ. That is a legitimate efficiency, provided the rationale is recorded and the supplier's test evidence is actually reviewed.

The failure that surfaces fastest during an inspection is qualification status that no longer matches the floor. Equipment modified, relocated, or with a changed control system, while the qualification package describes the original installation, is discovered during the facility tour — often within the first hours.