Factory Acceptance Test vs Site Acceptance Test: What Each Test Proves
The factory acceptance test and site acceptance test process verifies that new machinery meets its agreed specification before shipment and performs correctly after installation.
A Factory Acceptance Test (FAT) proves that the machine works under controlled conditions at the manufacturer’s facility. A Site Acceptance Test (SAT), meanwhile, confirms that the equipment performs correctly once installed in its final production environment.
Understanding the difference between factory acceptance test and site acceptance test procedures is important when commissioning special purpose machinery. Although the two tests are closely connected, they prove different things and take place at different stages of the project.
How does the FAT and SAT process work?
The handover process for special purpose machinery is structured around two formal acceptance stages.
The Factory Acceptance Test is carried out at TQC’s facility once the machine build is complete but before the equipment is shipped. The Site Acceptance Test is carried out at the customer’s premises following delivery, installation and commissioning.
Each test has a distinct purpose.
FAT confirms that the machine has been built correctly and operates in accordance with the agreed specification under controlled conditions, with the customer able to witness its performance.
SAT confirms that the same machine operates correctly in its permanent production environment, including its interaction with surrounding equipment, utilities and plant infrastructure. It also provides an opportunity to verify that outstanding issues identified during FAT have been resolved.
Together, the factory acceptance test vs site acceptance test provide structured evidence that the equipment is ready for production use.
Neither test should be considered a replacement for the other.
A machine that passes FAT has demonstrated that it works at the machine builder’s facility. However, the customer’s site may have different temperature, humidity, power or cleanliness conditions. The machine may also need to interact with upstream and downstream equipment that could not be fully replicated during factory testing.
Equally, proceeding directly to SAT means problems that could have been identified and resolved at the machine builder’s facility may instead have to be addressed on the customer’s production floor, potentially making them more disruptive and expensive to rectify.
What is a Factory Acceptance Test?
A Factory Acceptance Test (FAT) is a formal inspection and performance test conducted at the manufacturer’s facility before equipment is shipped to the customer. The customer’s engineering team attends to verify that the machine operates according to agreed technical specifications, often using real product samples and tolerance extremes to ensure consistent processing.
Key Objectives:
- Verify the machine is built to specification and functions correctly.
- Confirm it can handle required product variants and tolerances.
- Resolve identified issues prior to shipment.
- Provide performance evidence to secure customer approval for delivery.
A successful FAT normally results in customer agreement for the machine to be shipped, either with all items closed or with agreed outstanding points to be completed before SAT.
Site acceptance testing definition: What is a Site Acceptance Test?
A useful site acceptance testing definition is: a formal test conducted at the customer’s production facility after the machine has been delivered, installed and commissioned.
Unlike FAT, SAT assesses the machine in the environment where it will operate permanently.
That means testing can take account of real production conditions, including local utilities, factory temperature and humidity, upstream product feeds, downstream processes and connections with surrounding plant equipment.
SAT also verifies that outstanding FAT snag-list items have been closed and identifies any additional issues that arise specifically because of installation, site conditions or system integration.
Once the agreed SAT requirements have been achieved, the acceptance certificate can be signed and the equipment formally handed over for production use.
Factory acceptance test vs site acceptance test: what is the difference?
The main difference between factory acceptance test and site acceptance test procedures is where they take place and what they are intended to prove.
FAT asks: Has the machine been built correctly and does it meet the agreed specification before shipment?
SAT asks: Does that machine operate correctly once installed within the customer’s real production environment?
| Factor | Factory Acceptance Test (FAT) | Site Acceptance Test (SAT) |
| Location | Machine builder’s facility, such as TQC’s site | Customer’s production site |
| Timing | After the machine build is complete and before shipping | After delivery, installation and commissioning |
| Environment | Controlled factory environment | Actual production environment |
| System integration | Machine typically tested largely in isolation | Machine tested with relevant upstream, downstream and plant systems |
| Product | Customer-supplied product covering required variants | Production product in the condition it reaches the machine on site |
| Primary purpose | Confirm the machine meets the agreed specification before leaving the factory | Confirm the machine operates correctly in its permanent environment |
| Issues identified | Logged, agreed and resolved before shipment where possible | Outstanding FAT items verified and site-specific issues addressed |
| Outcome | Customer agreement for shipment | Signed acceptance and handover for production use |
| What it cannot confirm | Full performance within the customer’s actual production environment | Whether the machine originally met its specification in isolation before shipment |
This is why a factory acceptance test vs site acceptance test comparison should not be viewed as choosing between the two. They are complementary stages of the same machine validation and handover process.
Why are both FAT and SAT necessary?
Skipping FAT may shorten commissioning, but it can shift problems to the customer’s production site, where they may be more disruptive and costly to resolve. FAT provides a documented record of machine performance before shipment, while SAT confirms the equipment works correctly after installation and integration.
The factory acceptance test and site acceptance test therefore serve different purposes: FAT verifies performance before shipment, while SAT confirms performance in the final production environment.
TQC’s approach to Factory and Site Acceptance Testing
At TQC, FAT and SAT procedures are agreed with the customer as part of the project documentation before testing begins. This establishes what will be tested, the relevant pass/fail criteria and the process for recording and resolving issues.
Our engineering team runs the machine through the FAT procedure internally before the customer arrives. This means the formal FAT acts as a witnessed demonstration of a machine that has already been verified to perform rather than being the first occasion on which the complete system is tested.
Following FAT, TQC’s project engineer manages the snag list through to closure. The same engineer attends the customer’s site for commissioning and SAT, helping maintain continuity between factory testing, installation and final acceptance.
The handover process is complete once outstanding actions have been resolved and the SAT acceptance certificate has been signed by both parties.
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