Process Equipment and Skid Qualification, From FAT to PQ

The URS should specify battery limits (where the skid's piping and controls end and the facility's begin), utility tie-in points, and exactly which interlocks and control logic live on the skid's own PLC versus the plant's DCS or SCADA layer. This boundary definition drives the entire test strategy — anything fully contained within the skid can often be proven at FAT, while anything that spans the boundary can only be proven once both sides are actually connected.

For single-use systems integrated into the skid — bags, tubing, connectors, filter capsules — an extractables and leachables risk assessment should be scoped at this stage too, based on the specific product, contact time and process conditions, not assumed acceptable because the vendor supplied generic compatibility data.

For a bioreactor skid, PQ typically demonstrates consistent control of pH, dissolved oxygen, agitation and temperature across the range the process actually uses, not just at a single nominal setpoint. For a chromatography or TFF skid, PQ demonstrates flow, pressure and detection accuracy hold steady across representative runs. Three representative runs across the defined operating range is a common convention, though the number should be justified by the process risk the skid needs to demonstrate control over.

Where the skid was fabricated and FAT-tested by a vendor, leveraging that FAT data under ASTM E2500 can meaningfully reduce duplicate testing at OQ — but only for functions FAT could actually exercise in isolation. Anything dependent on the final facility connection still needs its own verification, no matter how comprehensive the vendor's FAT was.

Extractables data — what a material could release under aggressive, worst-case lab conditions — is usually available from the vendor and can support an initial risk assessment. Leachables — what the material actually releases into the specific product under real process conditions — often need product-specific verification when contact time, temperature or solvent characteristics differ meaningfully from the vendor's test conditions. Treating vendor extractables data as automatically sufficient leachables evidence is a common, avoidable gap that BPOG's risk-based E&L framework is designed to help scope correctly.

Integrity testing is the other half: single-use bags and tubing can't be inspected or leak-tested the way permanent piping can, so each unit — or a defined sample per lot — needs a non-destructive integrity test, commonly pressure decay, before use. Skipping this because the system is "disposable, so lower risk" removes the one check that confirms the bag or connector wasn't compromised during shipping or setup.