FAT and SAT Procedures for Automation Systems
Guide to Factory Acceptance Testing (FAT) and Site Acceptance Testing (SAT) procedures for automation systems including test plan templates.
Published on September 21, 2025
FAT and SAT Procedures for Automation Systems
This guide provides a detailed, practical reference for Factory Acceptance Testing (FAT) and Site Acceptance Testing (SAT) specific to industrial automation systems. It combines industry guidance, regulatory references, and field-proven procedures to help automation engineers, integrators, and plant owners plan, execute, and document FAT and SAT activities that minimize commissioning risk and reduce time-to-production. The procedures emphasize functional verification of control logic, I/O, interlocks, alarms, communications, and mechanical interfaces, and describe the documentation and acceptance criteria required for a formal handover.
Key Concepts
FAT and SAT serve distinct but complementary purposes in the lifecycle of an automation installation. FAT verifies the system at the vendor or integrator premises under controlled, simulated conditions to catch assembly and software defects before shipment. SAT verifies the system after installation on the customer's site, validating integration with site utilities, mechanical systems, and real process conditions. Performing a comprehensive FAT first reduces the frequency and cost of fixes during SAT and commissioning, because correcting defects at the factory typically costs orders of magnitude less than correcting them in the field. This cost-benefit is well-documented across industry sources and integrator best practices [1][3][6].
Key technical checks that appear consistently across published sources include:
- I/O verification and loop checking — confirm every input and output channel functions, matches the I/O list, and is mapped correctly to the control logic and HMI/SCADA screens [4][6].
- Control logic and functional tests — validate interlocks, permissives, alarms, recipe management, and sequence of operations against P&IDs and the functional specification [2][4].
- Hardware and wiring inspection — verify panel dimensions, wiring terminations, wire labeling, earthing/grounding, and component mounting before shipment to avoid installation delays [7].
- Calibration and instrument checks — supply calibration certificates, simulate analogue signals, and confirm transmitter ranges and alarm thresholds [2].
- Communications and protocol compatibility — test PLC-to-SCADA, PLC-to-PLC, and fieldbus or Ethernet communications under expected traffic loads [6].
- Safety device verification — demonstrate that safety interlocks, E-stops, and shutdown sequences operate as designed [4][6].
Distinguishing FAT and SAT
FAT takes place at the vendor’s factory and focuses on assembly, software, and simulated functional verification. SAT takes place on the customer site and evaluates installation integrity, utility dependencies (steam, compressed air, process media), mechanical interfaces, environmental conditions (temperature, humidity), and sustained operation under real process loads. For some SCADA and continuous-process projects, SAT includes an extended run period (commonly 1–2 weeks) to demonstrate stable operation without major errors before final acceptance [1][5].
Standards, Regulations, and Compliance
FAT and SAT activities must align with multiple regulatory and industry standards depending on the sector. Pharmaceutical and life sciences projects often require compliance with EU GMP Annex 15; Annex 15 explicitly recognizes FAT and SAT roles in qualification and requires documented evidence for critical instrumentation, calibration, and process verification [2]. For general industrial equipment, CE marking and applicable ISO standards require demonstration that equipment meets safety, performance, and technical specifications before commissioning [6]. Instrumentation and control best practices recommended by ISA support structured loop checking, interlock validation, and functional safety validation where applicable [4][7].
Typical regulatory expectations include:
- Documented test plans and traceability from requirements through test cases and acceptance criteria [2].
- Calibration certificates traceable to national standards for instruments used in critical measurements [2].
- Signed test records and a formal sign-off matrix that defines responsibility for corrective actions and final acceptance [2][4].
- Preservation of electronic evidence and backups of control system code and configurations before and after tests [6].
Implementation Guide
Effective FAT and SAT require structured planning, well-defined scope, and clear roles. The following step-by-step approach reflects combined guidance from industry sources and field experience:
- Define scope and acceptance criteria. Document the tests to be performed, the expected results, environmental constraints, and pass/fail criteria. Include references to P&IDs, control narratives, I/O lists, and regulatory requirements [2][6].
- Prepare documentation pack. Include drawings, logic diagrams, I/O lists, datasheets, calibration certificates, mechanical drawings, and operator manuals. FAT depends on the completeness of this documentation to validate conformance [4][6].
- Develop test scripts and procedures. Create deterministic test scripts that exercise each control function and I/O point. Each script should record pre-test conditions, test steps, expected results, actual results, deviations, and signatures [2][4].
- Execute FAT in a controlled environment. Simulate field signals, exercise interlocks and alarm handling, and validate operator interfaces and recipe management. Log all results and generate a punch list for identified non-conformances [1][6].
- Resolve factory faults and re-test. Prioritize fixes that reduce field commissioning risk. Re-run affected tests and update documentation and configuration baselines [3][6].
- Plan and perform SAT. Verify mechanical installation, cabling terminations, site utilities, and environmental conditions. Perform loop checks with actual field devices, validate final control elements (valves, drives), and conduct a continuous run test to demonstrate reliability [1][5].
- Commission and handover. Complete operator training, deliver as-built documentation, and obtain final sign-off after all punch-list items close. Archive FAT/SAT records and back up final control system configurations [2][4].
Typical Timeline and Resources
Project timelines vary with system complexity, but typical estimates include 1–5 days for a medium-sized FAT at the vendor site, plus 2–10 days for SAT depending on installation complexity and coordination with other trades. For SCADA or continuous-process SATs, plan for a 7–14 day observation period to demonstrate stable operation without major errors [1][3][5]. Allocate multidisciplinary teams—automation engineers, QA, site commissioning specialists, instrumentation techs, and client representatives—to ensure comprehensive coverage.
Test Plan Templates and Sample Checklists
Standardized templates accelerate FAT/SAT preparation and ensure repeatable coverage. Below are the essential elements of FAT and SAT test plans and an example checklist table that programs can adapt to project needs.
| Test Area | FAT (Factory) | SAT (Site) |
|---|---|---|
| I/O Verification | Simulate signals to confirm mapping and logic; bench test analogue ranges and digital toggles [4] | Loop check with field devices, verify cable terminations, and confirm signal conditioning under process conditions [4][5] |
| Control Logic & Interlocks | Execute sequences, alarms, and interlocks using simulated inputs; validate recipes and setpoints [2][6] | Validate logic against actual equipment; confirm safe shutdown, E-stop and safety interlocks functioning in situ [2][4] |
| Communications | Test protocol compatibility and data exchange under load in a controlled network [6] | Confirm integration with site SCADA/DCS, historian, and remote I/O; test network resilience [6] |
| Mechanical & Wiring | Inspect panel wiring, labels, terminal block continuity; dimensional checks [7] | Verify cable routing, gland seals, earthing, and environmental protection on-site [7] |
| Sustained Operation | Run system through extended simulated cycles where feasible | Continuous operation test for 1–14 days depending on project; observe for intermittent failures [1][5] |
Sample FAT Plan Sections
- Objective and scope, including exclusions.
- Reference documents (P&IDs, functional spec, I/O list, CAD drawings).
- Test equipment and signal simulation requirements.
- Detailed test scripts with expected outcomes and pass/fail criteria.
- Punch list process and retest protocol.
- Acceptance sign-off matrix listing vendor, client, and QA approvers [2].
Best Practices
Industry sources and field experience converge on a set of best practices that materially reduce commissioning risk and accelerate acceptance:
- Plan FAT as a project milestone, not an afterthought. Pre-FAT planning clarifies scope, prevents scope creep, and ensures required instruments and simulation rigs are available [6].
- Use FAT as a baseline for SAT. Record configuration baselines and use FAT results to compare SAT behavior and detect transportation or installation-induced anomalies [3][6].
- Resolve high-risk issues at the factory. Addressing mechanical and wiring defects pre-shipment is less costly and minimizes schedule risk on site [3][7].
- Maintain traceability. Trace each test case to requirements and P&IDs; record deviations, corrective actions, and retest evidence for regulatory audits [2][4].
- Include client and QA representatives in tests. Early client engagement reduces acceptance disputes and ensures operational requirements are validated [2].
- Conduct operator training during SAT. Hands-on training concurrent with SAT shortens the post-handover learning curve and improves initial operating discipline [1][4].
- Use a clear punch list and closure process. Track issues with owners, target dates, and verification steps; do not accept open critical items [2][5].
Common Pitfalls and Mitigation
Awareness of common failure modes helps teams focus limited FAT/SAT time on high-risk areas:
- Insufficient test coverage. Avoid generic "smoke tests." Instead, use deterministic scripts that exercise all safety and control paths [4].
- Poor documentation quality. Incomplete I/O lists or missing calibration certs delay acceptance; maintain a complete documentation pack before FAT [2].
- Over-reliance on simulations in FAT. Simulations cannot recreate site process media and utilities; include SAT tests that validate the system with actual steam, compressed air, or process fluids [5].
- Network and timing issues. Communications and latency problems often surface only when integrated on site—include realistic load tests during FAT and retest in SAT [6].
- Undefined acceptance criteria. Avoid subjective approvals by defining clear pass/fail metrics and acceptance thresholds in advance [2].
Roles and Responsibilities
Successful FAT/SAT execution depends on a clear division of roles and responsibilities. Typical participants include:
- Vendor/Integrator — leads FAT, provides test equipment, corrects defects, and delivers documentation and trained personnel to support SAT [6][7].
- Customer/Owner — reviews and approves FAT scope, participates in FAT witness sessions, performs SAT inspections, and provides site utilities and permits for SAT [2][3].
- Quality Assurance (QA) — verifies compliance with regulatory requirements, ensures traceability of test evidence, and signs final acceptance documents [2].
- Commissioning Engineer — coordinates on-site installation checks, performs loop checks, coordinates with other trades, and manages the punch-list closure [4].
- Safety Officer — ensures tests, especially SAT live tests, execute under approved safe work procedures and lockout/tagout where required [4].
Test Documentation and Deliverables
Deliverables for FAT and SAT typically include the following, each of which must be complete and signed to satisfy acceptance and regulatory audit requirements:
- FAT and SAT test plans and scripts with pass/fail criteria [2][4].
- Executed test logs with actual results, timestamps, and signatures.
- I/O lists, wiring termination lists, and updated as-built drawings [4].
- Calibration certificates for instruments and sensors, traceable to recognized standards [2].
- Control system configuration backups and software/firmware version records.
- Punch lists and closure evidence, including retest logs for corrected items [2].
- Operator manuals, maintenance procedures, and training records [6].
Example Specification Table: FAT vs SAT Responsibilities and Success Criteria
| Specification | Responsible Party | Success Criteria | Reference |
|---|---|---|---|
| I/O Mapping and Loop Checks | Vendor completes at FAT; Commissioning Engineer verifies at SAT | All I/O mapped correctly; 100% loop continuity and expected signal levels | [4][6] |
| Control Logic Functional Tests | Vendor executes functional scripts; Customer witnesses | All interlocks and sequences perform per functional spec; no critical failures | [2][4] |
| Safety Device Verification | Vendor and Safety Officer | E-stop and safety shutdowns trigger properly; documented test evidence | [4][6] |
| Communications Integration | Vendor configures; IT/Customer validates | SCADA, historian, and PLC exchange required data under expected load | [6] |
| Sustained Operation Test | Vendor supports; Customer runs process | No major errors during 1–14 day run depending on project class | [1][5] |