Abnahmeprozess (FAT/SAT)

What is the FAT/SAT acceptance process?

The acceptance process is structured into two defined test phases: the Factory Acceptance Test (FAT) and the Site Acceptance Test (SAT). Both phases serve to ensure that a system – such as a conveyor, an automated storage system, or a sorting installation – actually meets the requirements specified in the functional specification or supply contract. Acceptance is not merely a technical formality; it carries direct legal and financial consequences: upon signing the acceptance report, liability for defects typically transfers from the manufacturer to the operator.

FAT – Factory acceptance at the manufacturer's site

The FAT takes place at the supplier's production facility before the system is dismantled and transported. The aim is to identify design and manufacturing defects as early as possible, since corrections made at the factory are considerably less costly than those carried out after installation. Typical elements of a FAT include functional and load tests, safety inspections, a review of software logic, and document verification (circuit diagrams, operating manuals, CE documentation). Test conditions are inevitably simulated: real goods, hall conditions, and interfaces to existing systems are usually absent. The FAT is therefore primarily meaningful for assessing basic technical functionality, not for evaluating overall system behavior under operational load.

SAT – Site acceptance under real conditions

The SAT is conducted after installation at the deployment site. Here, the system operates under actual conditions for the first time: with real products, connected IT systems such as WMS or ERP, and within the real hall layout. The SAT verifies whether the system achieves the contractually guaranteed throughput and availability values in integrated operation. The SAT is frequently followed by a trial run, during which key metrics such as error rate and throughput are recorded over a defined period before final acceptance is declared.

What matters when planning the process

A well-prepared acceptance process begins long before the actual test date. The following aspects are critical:

• Define acceptance criteria in the contract: Which throughput values, availability levels, and error rates qualify as acceptance prerequisites? Ambiguous criteria lead to disputes.
• Define defect categories: Distinguish between defects that block acceptance and those that can be accepted under reservation and remedied subsequently.
• Specify test scenarios: Which product types, peak loads, and fault cases will be simulated? The test scenario should reflect real operations as closely as possible.
• Ensure documentation: All test results must be recorded without gaps – both for internal audit purposes and for future warranty discussions.
• Clarify responsibilities: Who from your own organization will participate in the FAT – only the project procurement team, or also operations and IT? A missing perspective at the FAT can come back to haunt you at the SAT.

Whether FAT and SAT are conducted as separate milestones or in a combined procedure depends on system complexity, project volume, and contractual agreement. For simpler systems, some clients forgo a formal FAT and consolidate all testing into the SAT – this saves travel costs but increases the risk of discovering defects only after installation.