FAT vs SAT : Les deux tests d'acceptation qui devraient détecter les problèmes avant que la production n'en paie le prix

Key takeaways

• FAT (Factory Acceptance Test) = test the equipment at vendor's site before shipping.
• SAT (Site Acceptance Test) = test after installation at customer's plant.
• FAT catches design and manufacturing problems before shipping. SAT catches installation and integration problems.
• Skipping either lands problems in production, where they are much more expensive.
• Both should test against documented acceptance criteria, with sign-off and remediation paths.

Short answer: Factory Acceptance Test (FAT) verifies equipment performance at the vendor's site before shipping. Site Acceptance Test (SAT) verifies after installation at the customer's plant. FAT catches design and manufacturing problems; SAT catches installation and integration problems. Both are non-negotiable. Skipping either lands problems in production where they cost 5-10x more to fix. See also Multi-Site OEE Rollup.

What FAT does

FAT happens at the vendor's site, with equipment built but not yet shipped. Tests include:

• Mechanical assembly checks.
• Electrical and control system function.
• Software validation.
• Communication protocol verification.
• Performance against spec (cycle time, capacity).
• Safety circuit verification.
• Documentation review.

FAT catches what the vendor controls. Design errors, manufacturing defects, software bugs.

What SAT does

SAT happens at the customer's plant, after installation. Tests include:

• Installation correctness.
• Utility connections (power, air, water).
• Integration with plant systems (ERP, OEE, network).
• Performance in the customer's environment.
• Operator workflow validation.
• Final acceptance against documented criteria.

SAT catches what installation and environment introduce. Wrong voltage, network mismatch, environmental issues.

Why both matter

Some problems only appear in one or the other:

FAT-only problems: design defects, manufacturing issues, software bugs that appear at vendor's site under controlled conditions.

SAT-only problems: installation errors, integration mismatches, environmental issues, operator workflow problems.

Skipping either creates blind spots that surface in production.

How FAT should be run

1. Documented acceptance criteria. Signed off before testing starts.
2. Customer participation. Customer reps witness key tests.
3. Comprehensive test plan. Mechanical, electrical, control, software, performance.
4. Defect logging and resolution. Issues found and addressed before sign-off.
5. Sign-off documentation. Captures the agreed state of the equipment.

How SAT should be run

1. FAT must be complete and signed. SAT is not a do-over of FAT.
2. Installation complete. All physical connections done.
3. Customer-specific tests. Integration with plant systems.
4. Operator workflow validation. Real operators using the equipment.
5. Performance verification. Cycle time, capacity, quality.
6. Final sign-off. Equipment ready for production use.

What FAT misses if skipped

• Design defects that only appear at vendor site.
• Software bugs.
• Communication protocol issues.
• Performance shortfalls.

Discovering these after shipment costs 5-10x more in shipping and rework.

What SAT misses if skipped

• Installation errors.
• Utility mismatch.
• Network integration issues.
• Environment-specific problems.

These surface during production, often with downtime impact.

Common mistakes

1. Skipping FAT to save time. "Vendor said it works." Equipment arrives, problems appear.

2. Treating SAT as FAT redo. Time wasted re-testing things FAT covered.

3. Acceptance criteria written after testing. Vendor and customer disagree on what counted as success.

4. No customer participation in FAT. Vendor passes their own test; customer disagrees later.

5. SAT compressed to days when it needs weeks. Hidden problems missed.

Acceptance criteria design

• Specific and measurable.
• Aligned with operational requirements, not vendor capabilities.
• Includes safety criteria.
• Includes performance against spec.
• Documented and signed before testing starts.

Vague criteria produce disputes at sign-off.

What changes with proper FAT and SAT

• Production start-up smoother.
• Hidden problems caught before they cost downtime.
• Vendor and customer aligned on equipment state.
• Documented acceptance trail for audit.

How OEE relates

Properly accepted equipment starts production at higher OEE faster. Plants that skip acceptance testing see ragged ramp-up curves and recurring issues for months.

How a modern OEE platform supports acceptance

A modern OEE platform can be used during SAT to verify communication protocols, data quality, and integration before production handover.

Fabrico's OEE module supports SAT-stage verification of PLC integration, data quality, and operator workflow before production handover.

See how Fabrico captures this automatically — explore OEE for manufacturing or book a demo.

Related reading

• Multi-Site OEE Rollup

Frequently asked questions

Can SAT replace FAT?

No. They catch different problems.

Who pays for FAT travel?

Typically customer for participation; vendor for facility hosting. Document in contract.

How long should FAT take?

2-5 days for simple equipment; weeks for complex lines.

What happens if FAT fails?

Issues logged; vendor remediates; re-test. Equipment does not ship until passed.

Should I witness SAT for every machine?

Customer should always participate in SAT. Vendor leads execution.