The short answer
Site Acceptance Testing
A site acceptance test repeats the essential parts of the factory test on the installed system with the real instruments, the real wiring, the real network, and the real process, and adds what the shop could not test: loop checks from the field device to the screen, equipment running under control, and the behavior of the whole thing when a real cable is pulled. It comes after installation and loop checks and before the plant is handed to operations, and its record, with the punch list closed, is the basis of acceptance.
Key points
- Loop checks come first: every instrument proven from the field device to the HMI value before any sequence is attempted.
- The SAT runs the equipment for real. The simulation is gone and the process responds.
- Communications are tested on the real network with the real partners, including failover and loss.
- Alarms go to the real dialer, the real phones, and the real people, and the response is observed.
- The record closes the FAT punch list, opens the SAT punch list, and is the as-built reference.
Where it sits
Installation puts the panel on the wall and the instruments on the pipe. Loop checks prove each wire and each instrument. The SAT proves the system: that the pieces work together under control, with the process moving. Commissioning and startup follow, when the plant is tuned and run into service, and some projects fold the SAT into them. The distinction worth keeping is that the SAT is a test against the documents with a record, and startup is running the plant.
Prerequisites
- The FAT is complete and its punch list is closed or its open items are known and agreed.
- Installation is complete, inspected, and energized, with the electrical inspection passed.
- Loop checks are complete: every I/O point proven from the field device through the terminals to the controller and the HMI, with calibration records for every instrument.
- Field devices are commissioned: transmitters ranged, valves stroked, drives parameterized and bump tested for rotation.
- The network is installed and proven, with addresses assigned, switches configured, and radio paths surveyed.
- The SAT procedure is issued, derived from the FAT procedure with the shop-only steps removed and the site-only steps added.
- The process can be run. Water is available, the discharge has somewhere to go, and operations agree to the test.
What is tested
- 1
End-to-end I/O.
Each input from the actual field device: lift the float, block the limit switch, apply pressure to the transmitter. Each output to the actual device: the starter pulls in, the valve moves, the drive runs. The loop check proved the wire; this proves the device in the loop.
- 2
Analog calibration in the loop.
The value on the HMI against a reference at the instrument, at two or three points across the range, for every analog loop.
- 3
Equipment under control.
Each pump, valve, and drive in hand from the panel, then in auto from the controller, with the run feedback, the position feedback, and the interlocks observed.
- 4
Sequences on the real process.
Each sequence run with real flow, real level, and real pressure. Timeouts set from the shop are often wrong for the real equipment; this is where they are corrected.
- 5
Control loops.
Each PID loop closed on the real process, with a setpoint step and the response recorded. Initial tuning happens here, final tuning during startup.
- 6
Interlocks and trips on real devices.
The cause and effect matrix again, this time with the real float lifted and the real overload tripped where it can be done safely.
- 7
Alarms to real recipients.
Each alarm raised, seen on the real SCADA client, sent to the real dialer, received on the real phone by the person on the list.
- 8
Communications on the real network.
Every link, every partner, and then every failure: pull the cable, power down the switch, fail the primary server, drop the radio, and confirm the system and the record do what the narrative says.
- 9
Power failure.
Utility power removed, generator transfer if there is one, the controller and the communications riding through on their backup, and the restart behavior on restoration.
- 10
Operator use.
The people who will run the plant using the HMI to do what they will do, with the integrator watching and not helping.
What is different from the FAT
| Aspect | FAT | SAT |
|---|---|---|
| Field devices | Simulated | Real |
| Wiring | Panel only | Panel and field |
| Process | Simulated or absent | Real, and it pushes back |
| Network | A bench switch | The installed network, with its faults |
| Alarms | On the HMI | To the people on the call list |
| Timing | Shop estimates | Real equipment; timeouts get corrected |
| Who is there | The integrator and a witness | The integrator, the owner, the contractor, and operations |
The record
The SAT procedure is marked step by step as the FAT was, with tester and witness initials, and every deviation goes on the punch list. The calibration sheets, the loop check sheets, the tuning parameters, the setpoints as left, the network addresses, and the software backups taken at the end of the test are collected with it. Together they are the as-built record of the control system, and the narrative and the drawings are revised to match before they are issued as-built. The acceptance signature, when the punch list is closed, is the point at which the owner owns the system.
Frequently asked questions
- What is the difference between a FAT and a SAT?
- The FAT tests the panel and the program in the shop against a simulated field. The SAT tests the installed system with real instruments, real wiring, the real network, and the real process. The FAT finds design and build errors cheaply; the SAT finds installation and integration errors.
- Do loop checks count as the SAT?
- No. Loop checks prove each point individually and come before the SAT. The SAT proves the system as a whole: equipment under control, sequences, interlocks, alarms, and failures, with a record.
- Who witnesses the SAT?
- The owner, usually through their engineer, and operations, who will run the plant. Their observation of the operator-use portion is the most valuable review the HMI will get.
- When is the system accepted?
- When the SAT punch list is closed and the acceptance is signed. Some contracts add a performance period after startup before final acceptance, and the SAT record is what that period is measured against.
Related topics
- Factory Acceptance TestingTesting a control system before it leaves the shop: what must exist before the test, how the procedure is built from the narrative and the matrix, how the field is simulated, what is witnessed, and what the punch list and the sign-off mean.
- Commissioning ChecklistFrom energization to handover: the sequence of commissioning activities for a control system, the prerequisites and records for each, who signs what, and the checklist that keeps a project from being declared finished while half of it has never been tested.
- Startup ChecklistThe checklist for bringing a control system and its process into operation after commissioning or an outage: verification of power, I/O, communications, setpoints, forces, and backups; staged energization; manual first, then automatic; and the watch.
- Loop ChecksProving every I/O point end to end before a system goes live: what a loop check is and is not, the three-point analog check, discrete and output checks, the two-person method with the sheet that records it, what to do with a point that fails, and why a loop check is not a calibration.
- Control NarrativesWhat a control narrative is, what it must contain, how to write statements that can be tested, and how it drives programming, FAT, and the owner’s acceptance.
- Design ChecklistA review checklist for a control system design at each stage from concept to issued for construction: documents, architecture, controllers and I/O, panels and power, instruments, networks and security, SCADA and alarms, deliverables, and commissioning.
Direct contact
Have a controls question?
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