FAT and SAT Explained
Two terms appear constantly on engineering and commissioning projects:
- FAT — Factory Acceptance Test
- SAT — Site Acceptance Test
They Are Related, but They Are Not the Same
A FAT normally confirms that equipment or a system performs as required before it leaves the manufacturer or vendor facility.
A SAT confirms that the equipment still performs correctly after it has been delivered, installed and integrated at site.
ABB describes FAT as verifying equipment and configuration against requirements, while SAT checks the installed system and its site connections.
What Happens During a FAT?
The FAT takes place before shipment.
The exact test depends on the equipment, but typical activities may include:
- Visual inspection
- Dimensional checks
- Verification against drawings and specifications
- Electrical testing
- Control-system checks
- Alarms and trip testing
- Simulated inputs and outputs
- Functional testing
- Software and logic verification
- Documentation review
- Demonstration of operating sequences
Why Identify Problems Before Shipment?
On larger equipment packages, representatives from the client, vendor, engineering contractor and third-party inspection body may attend.
The objective is to identify problems before the equipment reaches site.
Fixing a problem in the vendor workshop is usually far easier than discovering it during final commissioning offshore or on a live plant.
Does Passing FAT Mean the Equipment Is Ready to Operate?
Not necessarily.
An equipment package can pass FAT and still experience problems during transport, installation or integration.
Cables are disconnected. Equipment is lifted and transported. Pipework is connected. Software interfaces may change. Site power supplies, field devices and control systems are introduced.
That is where SAT becomes important.
What Happens During a SAT?
SAT is performed after the equipment has been installed at the actual project location.
It confirms that the delivered system has been correctly:
- Installed
- Connected
- Configured
- Integrated
- Powered
- Communicated with
- Functionally proven
Typical SAT Activities
Typical SAT activities could include:
- Verifying installation against drawings
- Checking electrical connections
- Confirming communication links
- Checking instrumentation signals
- Verifying alarms and trips
- Functional testing
- Interlock testing
- Control-system interfaces
- Testing equipment under site conditions
SAT Can Repeat Selected FAT Functions
ABB notes that SAT verifies the installed equipment is correctly set and connected and may repeat selected functions already demonstrated during FAT.
FAT Finds One Type of Problem. SAT Finds Another.
Think of it this way:
FAT asks: “Did the vendor build and configure this correctly?”
SAT asks: “Does it still work correctly now that we have installed it here?”
Both are essential because many problems only become visible once several systems are connected together.
What Documents Are Normally Involved?
Depending on the project:
- Approved FAT procedure
- Approved SAT procedure
- Datasheets
- Drawings
- Cause-and-effect diagrams
- Control narratives
- Vendor documentation
- Inspection records
- Calibration certificates
- Test sheets
- Punch lists
- Signed acceptance records
Record Deviations and Carry Them Forward
Any deviations identified during FAT should be recorded and either resolved before shipment or formally carried forward.
The same principle applies to SAT.
Who Signs FAT and SAT?
This depends on the contract and project structure.
Typical signatories may include:
- Vendor representative
- Client representative
- Commissioning engineer
- QA/QC
- Package engineer
- Third-party inspector
Signing Confirms Acceptance Criteria
Signing does not simply mean “the test happened.”
It should confirm that the agreed acceptance criteria have been met, or clearly record any outstanding items.
Where Commissioning Fits In
FAT and SAT are parts of the wider equipment acceptance and commissioning process.
A typical sequence may look like: Engineering → Manufacture → FAT → Shipment → Installation → Mechanical Completion → SAT → Pre-Commissioning → Functional Testing → Commissioning → Start-Up → Handover.
The exact order can change depending on the equipment and project.
Final Thought
FAT protects the project before equipment leaves the factory.
SAT protects the project after that equipment reaches site.
Understanding both is essential for commissioning engineers, QA/QC personnel, package engineers, vendors and client representatives.
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