Factory Acceptance Test (FAT) vs SAT: Process, Checklist, and Standards Guide

A Factory Acceptance Test (FAT) is a formal inspection and functional test of equipment or machinery at the manufacturer's facility, performed before shipment, to confirm it meets the buyer's specifications and applicable safety standards. It gives buyers documented proof that equipment works before it leaves the factory, and it is distinct from a Site Acceptance Test (SAT), which verifies the same equipment after installation.

Table of Contents

• What Is a Factory Acceptance Test?
• Why FAT Matters for Equipment Buyers
• When to Schedule a FAT
• The FAT Process, Step by Step
• The FAT Protocol: What the Test Document Should Include
• Factory Acceptance Test Checklist
• Who Should Attend a FAT
• Standards That Govern FAT
• Site Acceptance Test (SAT): What It Is and How It Works
• FAT vs SAT: Side-by-Side Comparison
• FAT vs Commissioning
• FAT and SAT vs Other Quality Validation Methods
• What FAT and SAT Cost
• Common FAT Failures and How to Prevent Them
• How to Prepare for a Successful FAT
• Frequently Asked Questions
• Verify Your Equipment Before It Ships

What Is a Factory Acceptance Test?

A FAT verifies that equipment, a machine, or an automated system performs as designed before it leaves the supplier's factory. Unlike a standard product inspection, which checks a sample against a specification sheet, a FAT runs the actual equipment through its full operating sequence: power-up, functional cycles, safety interlocks, and performance under load, with the buyer's team present or reviewing the results directly.

FAT is standard practice for capital equipment: automation lines, CNC machinery, robotic work cells, control panels, test stands, and packaging or assembly equipment. It is less common for simple components or consumer goods, where a pre-shipment inspection is the more typical checkpoint.

A successful FAT results in a signed acceptance document. That signature usually triggers a milestone payment and starts the shipping and installation clock, which is why buyers treat FAT as a contractual gate, not just a quality check.

Why FAT Matters for Equipment Buyers

Equipment defects caught after installation are far more expensive to fix than defects caught at the factory. Once a machine is crated, shipped, and installed on your production floor, correcting a wiring error, a software bug, or an undersized component means downtime, a technician flight, and a delayed production start, on top of the original defect.

FAT shifts that risk back to the factory, where the supplier's engineers, spare parts, and tools are already on hand. It also creates a documented record of what was tested and what passed, which protects the buyer if a dispute over performance comes up later.

For OEMs and industrial buyers sourcing equipment from overseas suppliers, FAT is often the only opportunity to physically verify the machine before it becomes difficult and expensive to inspect again.

When to Schedule a FAT

Schedule a FAT once the equipment is fully assembled, wired, and functionally complete, but still at the factory. In practice, that means:

• After final assembly and internal commissioning by the supplier
• Before the equipment is disassembled, crated, or packed for shipment
• After control software and HMI programming is loaded and stable
• With enough lead time before the shipping date to correct any punch list items found during the test

Scheduling FAT too early, before the equipment is functionally complete, produces a test full of unresolved issues that aren't representative of final performance. Scheduling it too late leaves no time to fix problems without delaying shipment.

The FAT Process, Step by Step

1. Define acceptance criteria. Before the test date, the buyer and supplier agree on what "pass" means: the specifications, tolerances, cycle times, and safety standards the equipment must meet. This is written into the FAT protocol document.

1. Supplier pre-test and dry run. The supplier runs its own internal test before the buyer arrives, to catch and fix obvious issues in advance. A supplier that skips this step wastes the buyer's time on the test date.

1. Documentation review. The inspection team reviews drawings, wiring diagrams, the bill of materials, software version records, and calibration certificates against what's actually installed on the machine.

1. Visual and mechanical inspection. The equipment is checked for build quality, correct components, proper labeling, guarding, and workmanship, comparing the physical machine to the approved design.

1. Functional and performance testing. The equipment is powered up and run through its full operating sequence, including normal cycles, changeovers, and any specified stress or endurance runs, to confirm it performs to the agreed specifications.

1. Safety systems testing. Emergency stops, interlocks, guarding, and other safety devices are tested to confirm they function as designed, including deliberately triggering fault conditions rather than only observing normal operation. This step is non-negotiable regardless of how well the equipment performs functionally.

1. Software and controls verification. Test HMI screens, alarms, fault handling, and control logic against the functional specification.

1. Punch list and sign-off. Any deficiencies are logged as a punch list with an owner and a deadline. Once critical items are resolved, or a written agreement covers how remaining items will be closed before or after shipment, both parties sign the FAT acceptance document.

The FAT Protocol: What the Test Document Should Include

The FAT protocol is the written test plan both parties agree to before testing begins. Without it, "pass" and "fail" become a negotiation on the test floor instead of a documented outcome. A complete protocol includes:

• Test case list. Each functional requirement written as an individual, numbered test case, not a general description of what the machine should do.
• Pass/fail criteria per test case. A specific, measurable threshold for each test (a cycle time, a tolerance, a fault-response time), not a subjective "runs correctly."
• Test sequence and duration. The order tests are run in, and how long any load or endurance runs last.
• Roles and sign-off authority. Who from each side is authorized to accept or reject a test result on the spot.
• Punch list and deviation procedure. How a failed test case is logged, who owns the fix, and the process for re-testing that item without repeating the full protocol.
• Acceptance signature block. A dated signature section tied to the shipping and payment milestone in the purchase order.

Buyers who skip a written protocol and rely on a verbal walkthrough are the ones most likely to end up in a dispute over whether the equipment "actually" passed.

Factory Acceptance Test Checklist

Who Should Attend a FAT

A FAT is more effective with the right people in the room, whether in person or reviewing remotely.

• Buyer's process or manufacturing engineer: confirms the equipment meets the functional and performance requirements it was designed against.
• Buyer's quality representative or third-party inspector: verifies build quality, documentation, and safety compliance independently of the supplier's own sign-off.
• Supplier's project engineer: runs the test sequence and addresses issues in real time.
• Controls or automation engineer: needed on both sides if the equipment includes custom software, PLC programming, or a networked control system.
• Procurement or project manager: manages the punch list, sign-off, and payment milestone tied to acceptance.

When travel isn't practical, a live video FAT with a local third-party inspector on-site is a common alternative. The inspector operates as the buyer's eyes and hands at the factory, running the physical checks while the buyer's team observes and directs remotely.

Standards That Govern FAT

FAT protocols are typically built around a mix of the buyer's own specifications and recognized industry standards, which give both parties an objective reference instead of subjective judgment calls.

• ISO 9001 sets the quality management framework that a supplier's own testing and documentation practices should follow. It doesn't dictate FAT procedures directly, but a supplier operating under a certified quality management system is far more likely to run a disciplined, well-documented test.
• IEC 61508, the international functional safety standard for electrical, electronic, and programmable electronic safety systems, is the reference point for testing safety-related control functions like emergency stops and interlocks on automated equipment.
• NFPA 79, the Electrical Standard for Industrial Machinery, governs the electrical design, wiring, and control panel construction of industrial machines operating at 600 volts or less and is a common FAT reference point for equipment destined for U.S. facilities.
• UL 2011 and other relevant UL or IEC product safety standards may apply depending on the equipment type, particularly for robotics and automated material-handling systems.

Which standards apply depends on the equipment and its destination market. Building the relevant standard into the FAT protocol upfront, rather than discovering a gap during the test, avoids last-minute disputes over what "compliant" actually means.

Site Acceptance Test (SAT): What It Is and How It Works

A Site Acceptance Test verifies that equipment which already passed FAT performs correctly after it's shipped, installed, and connected to the buyer's actual facility: real power and air supply, real upstream and downstream equipment, and real production materials. SAT answers a different question than FAT. FAT asks whether the equipment works as built. SAT asks whether it works here.

SAT typically follows this sequence:

1. Installation verification. Confirm the equipment was installed per the layout drawings, with correct utility connections, anchoring, and clearances.
2. Utility and connectivity checks. Verify actual site power, air, network, and data connections match what the equipment requires, since factory test conditions rarely match site conditions exactly.
3. Integration testing. Run the equipment connected to upstream and downstream stations or systems it wasn't tested with at FAT, to confirm handoffs, timing, and material flow work as intended.
4. Functional re-verification. Repeat the core functional and safety tests from FAT to confirm nothing was damaged or misaligned in transit and reassembly.
5. Operator and maintenance sign-off. The buyer's operations and maintenance staff, who will run the equipment day to day, confirm they can operate and service it, since a FAT often involves engineers rather than the floor operators who take over afterward.

SAT is usually run by the buyer's operations and maintenance team, with the supplier's commissioning engineer present, and it typically takes one to several days depending on integration scope. It's the milestone that starts the warranty period. Because it happens in a live production environment, SAT surfaces problems FAT can't: utility mismatches, layout conflicts, software integration issues with existing plant systems, and gaps in operator training.

FAT vs SAT: Side-by-Side Comparison

FAT and SAT are sequential, not interchangeable. FAT proves the equipment works at the factory; SAT proves it still works, and works correctly, once it's installed in your actual production environment.

Skipping FAT and relying only on SAT means the first time you learn about a defect, the equipment is already installed and the supplier's engineers are no longer on-site. Skipping SAT and relying only on FAT means you never confirm the equipment behaves correctly once it's connected to your real production line, which is where integration problems typically surface.

FAT vs Commissioning

FAT and commissioning are frequently confused, but they happen at different stages and cover different scopes. FAT is a discrete, time-boxed test event, typically hours to a few days, that either passes, fails, or passes with a punch list. Commissioning is the broader, ongoing process of bringing equipment into full operational readiness: fine-tuning process parameters, running production trial batches, calibrating to actual materials, and training operators over days or weeks after installation.

In practice, FAT happens once, at the factory, before shipment. SAT is the acceptance checkpoint after installation. Commissioning is the surrounding process that includes SAT but extends beyond it, continuing until the equipment is reliably running production at target rates. A machine can pass both FAT and SAT and still take additional weeks of commissioning to reach stable, full-rate production.

FAT and SAT vs Other Quality Validation Methods

Buyers sourcing both capital equipment and manufactured parts sometimes use FAT interchangeably with other validation methods that sound similar but serve a different purpose.

FAT vs Pre-Shipment Inspection

A pre-shipment inspection checks a statistical sample of finished, packaged product against a specification, using sampling standards like AQL, shortly before the goods ship. It's built for repeatable, produced-in-volume goods. FAT tests a single piece of equipment, or a small number of identical units, through its full functional sequence rather than sampling a batch. It's built for capital equipment where every unit needs to be individually proven, not statistically sampled.

FAT vs First Article Inspection.

First Article Inspection validates that the first part or subassembly off a new or modified production process conforms to the engineering drawing, before that process runs at volume. It's a check on the part and the process that makes it. FAT validates a piece of equipment or machinery itself, before it ships, not the parts that equipment will eventually produce.

FAT vs PPAP.

The Production Part Approval Process (PPAP) is a documentation-heavy approval process, common in automotive and aerospace, that proves a supplier's production process can consistently produce conforming parts over time. It's a process capability approval for parts. FAT is a one-time functional test of the equipment itself, run before that equipment ever produces a part.

What FAT and SAT Cost

FAT and SAT costs are driven primarily by engineer time and travel, not the test itself. A single FAT typically runs from one inspector or engineer man-day for a simple, single-station machine to several man-days for a multi-station automation line with extensive load and endurance testing. Using a local third-party inspector at the supplier's factory is usually less expensive than flying an internal engineer overseas, since it removes airfare, lodging, and multi-day travel time from the cost.

SAT costs follow a similar pattern but tend to run longer, since integration testing and operator training add time that a standalone FAT doesn't require. Buyers should also budget for the supplier's commissioning engineer time if the contract requires the supplier's presence during SAT, which is common for complex or first-of-type equipment.

The cost of either test is small relative to the cost of discovering the same defect after installation, which typically adds technician travel, production downtime, and schedule delay on top of the original repair.

Common FAT Failures and How to Prevent Them

In Vietnam, a buyer's FAT protocol caught a hidden interlock bypass because it required triggering fault conditions, not just watching a normal cycle. In Mexico, a protocol that specified cycle time but not changeover time missed a costly gap that only surfaced after installation.

The pattern in both cases repeats across most FAT failures:

• Testing only normal operation, not fault conditions. Equipment that runs a clean cycle can still have safety or software gaps that only appear when something goes wrong.
• Incomplete acceptance criteria. If every relevant performance metric, not just the obvious ones, isn't written into the protocol in advance, gaps surface after the equipment is already installed.
• Accepting a verbal "it's ready" without a pre-test. A supplier dry run before the buyer arrives catches basic issues that otherwise consume the entire test window.
• No independent verification. Relying solely on the supplier's own test data, with no buyer engineer or third-party inspector physically confirming results, removes the main value of doing a FAT at all.
• Treating the punch list as optional. Deficiencies noted at FAT and left open without a deadline or an owner tend to still be open at installation.

How to Prepare for a Successful FAT

• Vet the equipment supplier itself before the purchase order is signed. The habits that produce a smooth FAT, like transparent communication and a track record of on-time delivery, are the same ones worth checking before signing with a new manufacturer in the first place.
• Put the FAT protocol in writing before the equipment build starts, not the week of the test, and include every performance metric that matters to your operation, not just the obvious ones.
• Request the supplier's internal test data and pre-test results in advance so the FAT isn't the first time anyone runs the machine.
• Send an engineer or a qualified third-party inspector who understands both the equipment and your production process, not just a general QC checklist.
• Build in a schedule buffer for punch list items; assume something will need correction before sign-off.
• Confirm in the purchase order how shipment and payment are tied to FAT sign-off, and how SAT and commissioning responsibilities are divided, so there's no ambiguity if issues are found at either stage.

Frequently Asked Questions

How long does a FAT take?

Anywhere from a few hours for a simple machine to several days for a complex, multi-station automation line. Complexity and the number of test cases drive the timeline, not equipment size alone.

Who pays for FAT travel and inspection costs?

This varies by contract. Some buyers send their own engineers at their own cost; others use a local third-party inspector, which is often cheaper than flying an internal engineer to the supplier's country.

Can a FAT be done remotely?

Yes, through a live video FAT, often with a local third-party inspector performing the physical checks while the buyer's team observes and directs in real time.

What happens if equipment fails FAT?

The supplier corrects the deficiencies and the affected tests are repeated, either in full or for just the failed items, before sign-off and shipment proceeds.

Is a FAT legally required?

No, but it's frequently written into the purchase contract as a condition for shipment and payment release, which makes it contractually binding even though no regulation mandates it.

Does passing FAT guarantee the equipment will pass SAT?

No. FAT confirms the equipment works standalone at the factory. Integration issues tied to your specific utilities, layout, or upstream and downstream equipment can still surface at SAT.

Verify Your Equipment Before It Ships

A Factory Acceptance Test is only as reliable as the people running it. AMREP supplier management service provides on-the-ground engineers and inspectors across China, Vietnam, Malaysia, Thailand, Mexico, and the Philippines who can represent your interests at FAT, verify build quality and safety compliance independently of the supplier, and document the results before the equipment ships. Once your equipment or shipment is on its way, AMREP's third-party inspection services also cover container loading supervision to confirm exactly what was approved is what leaves the factory. Contact AMREP Inspect to schedule a FAT for your next equipment purchase.

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Sources: ISO 9001 Explained, ISO · IEC Functional Safety (IEC 61508), International Electrotechnical Commission · NFPA 79, Electrical Standard for Industrial Machinery, National Fire Protection Association