Site acceptance testing (SAT) — verifying the installed plant operates correctly on site with real services, instruments and interfaces before start-up.
Commissioning, FAT & SAT — in depth
SAT proves the plant works where it matters. After installation, the system is tested on site with real power, water, instruments and interfaces — confirming installation quality, I/O, control sequences and safety functions against the SAT protocol — the gate between construction and live operation.
What matters in practice
Power, water and air verified.
Field I/O and DCS links checked.
Automatic sequences proven.
Interlocks and trips tested.
| Element | Checks | Note |
|---|---|---|
| Services | Connected | Verified |
| I/O | Field/DCS | Loop-checked |
| Sequences | Automatic | Proven |
| Safety | Interlocks | Tested |
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Fundamentals, design drivers and practical guidance
Site acceptance testing (SAT) — verifying the installed plant operates correctly on site with real services, instruments and interfaces before start-up.
Commissioning is the disciplined transition from a constructed plant to a proven, operating one, and it is split into clear stages: Factory Acceptance Test (FAT), Site Acceptance Test (SAT), loop checking, and performance testing. Each stage de-risks the next — faults caught at FAT in the supplier's works are an order of magnitude cheaper to fix than the same fault found during live process commissioning on site.
A Factory Acceptance Test verifies the panel, PLC and software against the functional design specification before it leaves the factory: I/O is simulated, interlocks and trips are forced, alarms and sequences are demonstrated, and the client witnesses and signs off. Site Acceptance Test then repeats the critical checks in situ, confirming that field wiring, instruments and final elements behave as the tested logic expects once connected to real plant.
Loop checking is the systematic, point-by-point proof that every instrument signal travels correctly from field to control system and every output drives the right final element, in the right direction, with the right scaling. Only when loops are proven does performance testing begin — running the process against its guaranteed duty (flow, removal efficiency, energy) over a defined period to demonstrate the contract is met before handover.
What our engineers assess on every scope of this type
| Parameter | Typical basis | Why it matters |
|---|---|---|
| Performance test | Against guaranteed duty | Demonstrates the contract is met |
| Documentation | Signed records per stage | Auditable basis for handover |
| FAT | Witnessed at supplier works | Catches logic/panel faults early and cheap |
| SAT | Repeated on site | Proves field wiring and instruments |
| Loop check | Every signal, point by point | Confirms path, direction and scaling |
| Interlocks | Cause-and-effect tested | Safety functions proven before run |
Common questions on installation and commissioning
Because a fault found in the supplier's works during Site Acceptance Testing (SAT)-type checks is far cheaper and faster to correct than the same fault discovered during live commissioning on site. FAT proves the panel, logic and sequences against specification before anything ships.
FAT verifies the control system in the factory with simulated I/O; SAT repeats the critical checks on site once the panel is wired to real instruments and final elements. SAT confirms that the proven logic still behaves correctly with field reality connected.
That each instrument's signal reaches the control system at the correct value, and each output drives the correct final element in the correct direction with the correct scaling. It is the foundation that performance testing relies on.
Through a witnessed performance test running the process against its guaranteed duty — flow, removal efficiency and energy — over an agreed period. Meeting the targets over that run is the basis for acceptance and handover.
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