Factory Acceptance Testing

Factory acceptance testing is a formal verification process conducted at a manufacturer's facility to confirm that equipment or a system meets contractual specifications before it is shipped to the customer's site.

FAT takes place after manufacturing is complete but before delivery, giving the purchasing organization a structured opportunity to witness equipment performance under controlled conditions. Inspectors verify mechanical integrity, electrical safety, interlock functions, and system performance against the agreed design specification, typically following a pre-approved FAT test plan document that defines scope, acceptance criteria, and required evidence.

The process usually begins with pre-FAT readiness checks — confirming that the vendor has completed internal testing and that all documentation is available — before the formal witnessed runs begin. Deviations found during FAT are logged, classified by severity, and resolved or formally accepted as concessions before the equipment leaves the facility. A FAT test report captures all results, punch-list items, and sign-off signatures, forming part of the project's quality record.

FAT sits upstream of site acceptance testing (SAT), which re-verifies the same system after installation in its operational environment. Together they form a two-stage acceptance chain common in industries such as pharmaceuticals, oil and gas, and industrial automation, where relocating or modifying equipment post-delivery is costly and regulated.

Also known as: FAT, factory acceptance test

• en.wikipedia.org — Acceptance testing