What is SAT (Site Acceptance Test)?
The SAT, or Site Acceptance Test, is a test procedure performed on site (at the end user’s location) to verify that a system, installation, or machine works correctly in its final operational environment. It is the last formal step before commissioning.
The SAT follows the FAT (Factory Acceptance Test) and confirms that everything works as agreed under real-world process conditions.
🧠 How does an SAT work?
- Preparation
- Drawing up a test plan and checklist (often based on FAT documentation)
- Coordination between client, system integrator, installer, and IT/OT department
- Installation check
- Physical inspection of connections, components, labels, power supply
- Verification of network connections (OPC UA, Modbus, ProfiNET)
- Validation of cabling, earthing, EMC
- Functional tests
- Live testing with actual inputs/outputs
- PLC logic, HMI, SCADA, Historian connectivity
- Emergency stop, fault handling, safeguards
- Acceptance and handover
- Results are documented in an SAT report
- On approval: formal handover to the operations organisation
🏭 Application in industrial projects
- Commissioning of new installations, lines, or systems
- Upgrades/migrations of automation platforms
- Validation of Safety PLC, safety relays, Drives, Remote IO
- Network integration with Firewall, Router, Switch, Historian
Examples:
- Water treatment, manufacturing, food, chemicals, pharma, power plants
- OEM machines and turnkey projects
🔍 Difference between FAT and SAT
| Aspect | FAT | SAT |
|---|---|---|
| Location | At the supplier (factory/test environment) | On site at the customer (end user) |
| Environment | Simulated or partial | Real process, full integration |
| Goal | Verify technical operation | Validate the system in its operational setting |
| Test type | Modular, component-oriented | System-oriented, including interfaces |
| Impact | No risk to the process | May impact business operations |
The SAT is often required for formal project acceptance or release for production.
🔐 Security aspects
- Verification of user access control, password policy, and RBAC
- Testing of secure network communication (e.g. TLS, VPN)
- Validation of Firewall settings, network segmentation, and logging
- Testing of recovery and Backup procedures
- Documentation of security aspects in the handover dossier or Audit trail
The SAT provides the moment to test cybersecurity and Security by Design principles before going live.
📌 In summary
The SAT is a crucial step to confirm that an installation works as intended in the actual production environment. It is the final piece of engineering, installation, and security before handover to operations.