A factory acceptance test, or FAT, checks agreed requirements at the supplier’s premises before equipment is dispatched. A site acceptance test, or SAT, checks agreed requirements after installation at the customer’s site. They serve different purposes. A successful factory test does not automatically establish that the installed system is ready for production.
For a plant team buying a process skid, vessel package or heat-transfer system, the most useful question is not “Will there be an FAT?” It is “What exactly will be demonstrated, under which conditions, and what evidence will support acceptance?”
This guide is for engineering, procurement, quality and operations teams. It explains how to prepare an acceptance plan and manage the conversation with a supplier. It is not a pressure-testing procedure or an instruction to operate unfamiliar equipment.
Why acceptance planning belongs near the start
Late disagreement often begins with an early assumption. The buyer expects a performance demonstration using representative process conditions. The supplier has planned dimensional checks and a limited functional demonstration using available utilities. Both parties arrive at the test believing the other understood.
Resolve that difference while defining the purchase scope. Identify which requirements can be verified at the factory, which need site conditions and which require another agreed method. Put those decisions into the acceptance documentation rather than leaving them in a meeting conversation.
The goal is not to test everything twice. It is to know what each stage proves, what it does not prove and who is responsible for closing the remaining questions.
Separate requirements, methods and evidence
A requirement describes the expected outcome. A test method explains how it will be checked. Evidence records what happened. Keeping those three elements separate makes the plan easier to review.
For example, “the package must communicate with the site control system” is a requirement. A defined interface check is a method. Recorded signal results and signed observations are evidence. A photograph of the control panel alone would not prove the communication requirement.
Create a simple acceptance matrix. Give each requirement an identifier, a verification method, an acceptance criterion, a responsible person and an evidence reference. Add the intended stage: factory, site or document review.
Use measurable criteria where appropriate. “Good finish” and “satisfactory operation” invite interpretation. Define the relevant drawing, specification, tolerances or approved performance conditions instead.
Conceptual factory-review scene. It does not depict an actual GI equipments test or a certified installation.
Decide what can realistically happen at the factory
Factory facilities may differ from the final installation. Utilities, process fluids, surrounding equipment and control-system connections may not be available in their final form. Those limitations should be documented before the test date.
A demonstration using a substitute medium can answer some questions while leaving others unresolved. A simulated control input can show logic response without proving that the actual field instrument and site wiring work correctly. State the limitation beside the result.
Discuss the configuration being tested. Is the equipment fully assembled? Are temporary connections in use? Are software settings final? Are guards, instruments and accessories included? A test on an incomplete configuration should not quietly become evidence for a different final configuration.
Any pressure, electrical or functional testing must follow approved procedures, applicable requirements and competent supervision. The acceptance plan should identify those procedures, not invent test pressures or bypass protective controls to save time.
Build a practical FAT agenda
An agenda helps the visiting team prepare and prevents the day becoming a sequence of improvised requests. Begin with a review of the scope, configuration, safety arrangements and outstanding prerequisites. Then follow the approved verification sequence.
Document reviews may cover approved drawings, material records, inspection results and relevant certificates. Physical checks may address dimensions, identification, accessibility and supplied components. Functional demonstrations should be tied to the agreed requirements.
Identify witness and hold points in advance. A witness point gives a party an opportunity to observe. A hold point usually requires the specified release before work proceeds, according to the agreed inspection plan. The exact obligations must come from the contract and approved plan.
Allow time to discuss deviations and compile the record. If the team schedules only the demonstration, the most important decisions may be rushed at the end of the day.
Use instruments and records you can trace
A result is more useful when its measurement basis is clear. Record the instrument identifier, relevant calibration status, measurement location and test conditions. Avoid copying a number into a report without preserving the context needed to interpret it.
Where measurements are time-dependent, agree how long data will be collected and how a stable condition will be recognised. Do not select a single favourable moment from a fluctuating run and present it as representative performance.
Photographs and video can support the record, but they do not replace measurement data or signed observations. Give files names that connect them to the equipment identifier and test step.
Keep raw data as well as the summary. If a question arises later, the team should be able to review the original record rather than reconstructing it from memory.
Illustrative measurement and documentation scene. Any displayed instruments or paperwork are conceptual.
What changes at site acceptance?
At site, the installed system meets its actual environment: foundations, utility supplies, connecting pipework, electrical feeds, controls and operating interfaces. SAT planning should address the requirements that depend on those conditions.
Before scheduling the test, check installation readiness. Are required services available? Have relevant inspections been completed? Are access and work permits arranged? Are the necessary operators, engineers and supplier representatives available?
Transport and installation can introduce issues that were not present at the factory. Receiving inspection and installation checks therefore have their own purpose. Record damage or missing items promptly and follow the agreed resolution process.
Do not assume SAT is identical to commissioning or full performance qualification. These terms can have different contractual and sector-specific meanings. Define the boundaries for your project and identify the separate approvals needed before routine operation.
Hypothetical case study: a successful FAT, an incomplete site
This scenario is illustrative, not a reported GI equipments project.
A plant orders a skid and agrees a factory demonstration of its control sequence. The test uses simulated signals because the final field instruments belong to the customer’s site scope. The factory result is satisfactory within that stated limitation.
At site, the team discovers that one interface uses a different signal configuration from the approved schedule. Instead of declaring the equipment defective or accepting the system prematurely, the parties compare the requirement, factory evidence and site wiring record.
The discrepancy is assigned to an owner, corrected under the project’s controls and retested at the appropriate stage. The lesson is that acceptance evidence must be read within its scope. A simulated factory result did not promise that every later site connection would be correct.
A clear interface schedule would have made the remaining responsibility visible earlier. That is why the acceptance plan should connect to the project’s division of supply and installation duties.
Manage deviations without losing the decision trail
A deviation should describe the requirement, the observation and the proposed response. Record who will act, the target date and the evidence needed for closure. Avoid entries such as “to be attended” without an owner or acceptance basis.
Distinguish issues that prevent release from those that can be managed under an agreed conditional acceptance. The classification should be made by authorised project representatives using the contract, technical requirements and safety implications.
A punch list is useful only if it is controlled. Keep one current version, retain the history and link each closure to evidence. A verbal assurance that an item is complete should lead to the required verification, not replace it.
If a change affects a previously tested function, consider whether retesting is needed. Closing one defect can alter another part of the system.
A signed test report is valuable when it makes the limits of acceptance visible.
An editorial principle for project review, not an attributed customer quotation.
Conceptual site-readiness review. Final acceptance depends on the project’s approved requirements and evidence.
Prepare the people who will inherit the equipment
Operations and maintenance teams should have an opportunity to review relevant aspects before handover. They may identify access difficulties, unclear labels or missing instructions that a procurement-only review overlooks.
Agree what training and operating information are included. Record attendance and remaining questions. Familiarity with a demonstration does not automatically establish competence to perform maintenance or hazardous testing.
Make the final handover package easy to navigate. Include the accepted configuration, approved drawings, test records, operating manuals, maintenance information and the status of outstanding items. Identify the contact route for technical questions.
Questions to ask before booking the test
What is being accepted? Name the package, revision and scope.
What are the conditions? Identify real, simulated and unavailable conditions.
What counts as a pass? Link each decision to an agreed criterion.
Who can approve release? Confirm authority before the meeting.
What happens if a step fails? Agree correction, retest and schedule responsibilities.
What remains for site? Carry unresolved verification into the SAT plan visibly.
These questions are simple enough to fit on one page and specific enough to prevent many avoidable misunderstandings.
Frequently asked questions
Is FAT compulsory for every equipment purchase?
The required inspections and acceptance activities depend on the equipment, contract, applicable rules and project requirements. Do not assume that one universal FAT checklist satisfies every purchase.
Can a remote FAT replace a visit?
It may be suitable for some agreed checks if visibility, data access, witnessing and evidence requirements are met. Discuss limitations in advance. A camera view does not make an unobserved measurement verified.
Does passing FAT mean production can start immediately after delivery?
No. Installation, site verification, commissioning, training and other applicable approvals may remain. Follow the project’s defined release process.
Make acceptance a shared plan
A well-prepared FAT and SAT process gives engineering, procurement and operations a common basis for decisions. It helps the supplier understand what evidence the customer needs and helps the customer understand what each stage can demonstrate.
When discussing an industrial equipment package with GI equipments, bring the intended duty, interfaces and acceptance expectations together. Agreeing the test early is often easier than resolving different expectations beside a finished machine.
Further reading
Siemens’ validation guidance illustrates how acceptance specifications and reports distinguish factory and site activities in a particular system context. Use your project’s current contract, applicable standards and approved procedures as the governing documents; this article provides a planning framework.