What is FAT (Factory Acceptance Test)?
A FAT, or Factory Acceptance Test, is a structured test procedure carried out at the supplier’s premises before delivery of an installation, machine or system. The aim is to verify that the solution technically meets the specifications, drawings and functional requirements set out in the design.
A FAT is a crucial step in project-based delivery and reduces failure costs during installation on site. It complements the SAT (Site Acceptance Test).
🧠 How does a FAT work?
- Preparation
- Drawing up a FAT protocol (test plan, specifications, requirements)
- Alignment between client, supplier and system integrator
- Execution at the supplier’s site
- Testing of hardware (wiring, components, PLC, Drives, sensors)
- Simulation of I/O, SCADA, HMI, communications (e.g. OPC UA, Modbus)
- Functional testing in line with the FDS (Functional Design Specification)
- Documentation and sign-off
- Recording results in a FAT report
- Documenting and rectifying any deviations before delivery
A FAT can be carried out either physically (with real hardware) or virtually (emulation or simulation).
🏭 Application in industrial projects
- New installations: production lines, skid construction, packaging machines
- DCS and SCADA systems
- PLC programs, Safety PLC applications
- Migration or upgrade projects in existing factory environments
- OT network components such as switches, firewalls or Historian
The FAT provides an opportunity to detect faults early, before transport or installation takes place.
🔍 Benefits of a FAT
| Benefit | Explanation |
|---|---|
| Risk reduction | Faults are identified before installation |
| Cost savings | Less rework on site |
| Increased reliability | The client can accept the system with confidence |
| Better collaboration | Promotes alignment between client and supplier |
| Traceable test results | The FAT report serves as formal evidence of testing |
A FAT is often a contractual prerequisite for acceptance and delivery.
🔐 Security aspects
- Verification of user access control, passwords, Audit Logging
- Verification of Fail-safe behaviour during emergency stops, faults or communication loss
- Cybersecurity testing of network interfaces and Firewall rules
- Verification of Backups, Restore procedures and system documentation
- Optional integration with Security by Design principles
A preliminary security assessment can also be carried out during the FAT (recommended for OT systems).
📌 In summary
A FAT is a testing phase prior to delivery, in which machines or systems are evaluated for functionality, safety and conformity. It improves the quality of deliveries and prevents issues on site.