FAT vs SAT: factory and site acceptance tests explained
Deskely Completions team Singapore
A factory acceptance test (FAT) proves that equipment works at the supplier's works, before it is shipped. A site acceptance test (SAT) proves that it still works once it is installed and connected at site. Between them sit shipping, installation and hook-up, which is why both are needed.
This guide covers when each test happens, what it covers, who takes part, and how the results carry through to commissioning and handover.
- FAT: at the supplier's works, before shipment, against the purchase order and the approved FAT procedure.
- SAT: at site, after installation and hook-up, with the real utilities, interfaces and often the real process.
- Punch items from the FAT should follow the equipment to site, not stay in a FAT report.
- Many packages add an integration test, an integrated FAT or a site integration test, for systems that only work together.
FAT and SAT side by side
| Factory acceptance test (FAT) | Site acceptance test (SAT) | |
|---|---|---|
| Where | At the supplier's works | At site, or at the yard for offshore units |
| When | Before shipment, after manufacture and internal testing | After installation, hook-up and pre-commissioning checks |
| Purpose | Prove the equipment meets the purchase order and specification before it leaves | Prove it works in place, with the real power, utilities, interfaces and control system |
| Typical tests | Visual and dimensional checks, function tests, simulated I/O, performance tests on test beds | Function tests with real I/O, interfaces to other systems, start-up and performance in service |
| Who | Supplier, buyer or EPC, often the end client and a third-party inspector | Contractor and commissioning team, supplier representative, client |
| Outcome | FAT report, punch list and release for shipment | SAT report, punch list and acceptance at site |
What a FAT covers
- Documentation: approved drawings, certificates, material records and the FAT procedure itself.
- Visual and dimensional checks: build against the drawings, nameplates, tagging, workmanship.
- Function tests: every function in the specification, with field signals simulated where the real ones are not available.
- Performance tests: where the specification calls for them, run on a test bed: capacity, efficiency, noise, vibration.
- Control system and software: logic, alarms, trips and screens, tested against simulated inputs.
A FAT is only as good as its procedure. It should be agreed before the test, list every function to be shown, and state the acceptance criteria.
What a SAT covers
- Installation check: the equipment is installed, aligned and hooked up as designed, and any transport damage is found.
- Real I/O: field signals and commands through the real cables and the plant control system. See the loop check procedure.
- Interfaces: power, utilities and the other systems the package talks to.
- Function and performance in place: start-up, running and shutdown, with the real process where possible.
- Open FAT items: everything left open at FAT is closed or carried forward with a decision.
Integrated tests: IFAT and SIT
Some systems only prove themselves together: a control system with its safety system and its packages, or a set of skids that share one control system. An integrated FAT (IFAT) brings them together at a works or a test site before shipment. A site integration test (SIT) does the same at site, after each part has passed its own SAT.
Where FAT and SAT fit in completions
- 01FAT
At the supplier's works, before shipment. Punch items raised against the package and its tags.
- 02Installation and hook-up
Construction installs and connects the package. Construction (A) ITRs record the installation.
- 03Mechanical completion
The subsystem is built and inspected, with its A punch cleared.
- 04Pre-commissioning and SAT
Loop checks, function tests and the SAT, recorded on pre-commissioning (B) ITRs and the SAT report.
- 05Commissioning and handover
The system is commissioned with the package in service, and the records go into the handover dossier.
See Commissioning 101 and the ITR guide.
FAT and SAT checklist
- Approved test procedure, with every function and acceptance criterion listed.
- Test equipment listed with calibration certificates.
- Simulations and test set-ups agreed in advance (FAT), or the site prerequisites complete (SAT): power, utilities, loop checks.
- Witness points agreed and the right people invited in time.
- Every result recorded against the tag or function, with signatures.
- Punch items raised with a category and an owner, and carried to the next stage.
- Report issued, with release for shipment (FAT) or acceptance at site (SAT).
Keeping FAT punch items alive
The most common gap between FAT and SAT is a FAT punch list that stays in a PDF report. Items marked to be closed at site are forgotten, and found again at the SAT or after handover. Raising FAT punch items against the package tags in the same system as the site punch keeps them visible all the way to handover. In Deskely, punch items are held against every tag and roll up to the subsystem and the certificates they block. See the punch list template.
The Deskely products for this
Frequently asked questions
What is the difference between FAT and SAT?
A FAT tests equipment at the supplier's works before shipment. A SAT tests it at site after installation, with the real utilities, interfaces and control system.
Is SAT part of commissioning?
Usually yes. The SAT is done after installation and pre-commissioning checks, and is often part of the commissioning of the system the package belongs to.
Who witnesses a FAT?
The buyer or EPC contractor, often the end client and sometimes a third-party inspector, as set out in the purchase order and the inspection and test plan.
What is an IFAT?
An integrated factory acceptance test: several systems, such as a control system, safety system and packages, tested together before shipment.
What is a SIT?
A site integration test: systems tested together at site after each has passed its own SAT.
Can a SAT be skipped if the FAT passed?
Rarely. Transport, installation and the real interfaces can all introduce faults that a FAT cannot show.
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