FAT (Factory Acceptance Test) for PLC, DCS & SIS — Before It Reaches the Plant
Imagine discovering a critical logic error after installation… 
That’s exactly why FAT is performed before equipment leaves the factory 
What is FAT?
Factory Acceptance Test (FAT)
Formal testing performed at the vendor’s facility
Verifies that the PLC, DCS, or SIS meets project requirements
Catch problems before site installation.
Main objective
Verify hardware configuration
Verify software & logic
Verify graphics & alarms
Verify communication interfaces
Verify cause & effect implementation
What is tested during FAT?
PLC Systems
I/O logic verification
Motor start/stop sequences
Interlocks & permissives
Communication testing
DCS Systems
Control loops
Graphics & HMI screens
Alarm management
Trends & historian functions
SIS Systems
Safety Instrumented Functions (SIFs)
Cause & Effect Matrix
Trip logic verification
Bypass logic
SOE (Sequence of Events)
Typical FAT Activities
Document review
Logic testing
I/O simulation
Alarm testing
Trip testing
Communication checks
Common FAT Findings
Wrong alarm limits
Incorrect interlocks
Missing tags
Logic errors
Communication issues
Better to find them in the factory than in the plant.
FAT vs SAT
FAT → Vendor facility
SAT → Actual site after installation
Simple understanding
FAT answers one question:
“Did the vendor build the system correctly before shipment?”
Because fixing a problem in the factory is much cheaper than fixing it during commissioning.
#FAT #PLC dcs #SIS #FactoryAcceptanceTest #Instrumentation Automation #ControlSystems #Engineering #ProcessAutomation