A Factory Acceptance Test (FAT) is a formal verification performed at the manufacturer’s facility to confirm that equipment or systems meet the specified functional and performance requirements before shipment. The FAT is witnessed by the buyer’s representative (or a third-party inspector) and must be passed before the equipment is released for delivery.
FATs are standard practice for control systems, packaged equipment, actuated valves, and instrumentation. For bulk piping materials (standard pipes, fittings, flanges), the equivalent verification is the mill inspection per the Inspection and Test Plan (ITP).
What Gets a FAT
Equipment Type FAT Scope Typical Duration Control panels / DCS Software logic, I/O checks, alarm testing, HMI verification 3-10 days Motor control centers (MCC) Wiring checks, functional tests, protection relay settings 2-5 days Actuated valve assemblies Stroke test, torque verification, fail-safe position, signal response 0.5-1 day per valve Metering skids Flow accuracy, calibration, communication protocols 2-3 days Compressor/pump packages Performance test, vibration, noise, control system integration 3-7 days Fire and gas detection panels Detector response, alarm logic, cause-and-effect matrix 2-5 days
FAT Procedure
Step Activity Responsible 1 Vendor prepares FAT procedure based on PO and data sheets Vendor engineering 2 Buyer reviews and approves FAT procedure Buyer engineering 3 Vendor schedules FAT and notifies buyer (minimum 2-4 weeks advance notice) Vendor 4 Buyer or third-party inspector attends FAT at vendor facility Buyer / TPI 5 Tests performed per approved procedure; results recorded Vendor with buyer witness 6 Punch list issued for any deficiencies or non-conformances Buyer 7 Vendor closes punch items Vendor 8 FAT certificate signed by both parties Both 9 Equipment released for shipment Buyer
FAT vs Inspection
Aspect FAT Mill Inspection (ITP-based) Purpose Verify functional performance Verify material and dimensional compliance Applies to Packaged equipment, control systems, assemblies Bulk materials—pipes, fittings, flanges, valves Tests Functional, performance, software logic Chemical, mechanical, NDE, hydrostatic Location Vendor’s assembly/test facility Mill or forge shop Witness Buyer engineer or TPI TPI per ITP hold/witness points Output FAT certificate and punch list Inspection release note (IRN)
Send an engineer who understands the system design, not just an inspector who checks paperwork. The FAT is the last opportunity to verify functionality before equipment leaves the factory. Finding a software logic error during FAT costs hours to fix. Finding it during site commissioning costs weeks.
Common FAT Deficiencies
Deficiency Example Impact Software logic error Emergency shutdown sequence executes in wrong order Safety-critical—must fix before shipment Wiring error I/O terminal miswired; signal reads incorrect channel Re-termination required at factory Calibration drift Instrument reading outside +/-0.5% accuracy Recalibration and retest Missing documentation Test certificates, calibration records not available at FAT Delays FAT sign-off Cosmetic damage Scratched panel, damaged label Minor—punch list item, fix before packing Performance shortfall Pump not reaching specified head at rated flow Major—may require impeller change or redesign
FAT Certificate
The FAT certificate is a signed document confirming that the equipment has passed all tests. It typically includes:
Section Content Equipment tag Tag number per P&ID PO reference Purchase order number Test date Date(s) FAT was conducted Tests performed List referencing FAT procedure clauses Results Pass/fail per test with recorded values Punch list Outstanding items (if any) with closure deadlines Signatures Vendor QA, buyer representative, TPI (if applicable)
The signed FAT certificate authorizes shipment. Without it, the equipment should not be released. For procurement documentation requirements and shipping documents needed after FAT completion, see the detailed guides.
Read the full guide to pipe classes and specifications
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