FAT and SAT: Factory and Site Acceptance Testing Guide

Acceptance Testing Overview

Factory Acceptance Testing (FAT) and Site Acceptance Testing (SAT) are critical quality gates that verify automation system functionality before shipment and after installation. FAT validates that equipment and control systems meet contractual technical specifications under controlled factory conditions. SAT confirms that the same equipment performs reliably within the buyer’s site environment, with site utilities, process materials, and full integration into existing systems. Both phases produce formal acceptance documentation — test records, deviation lists, corrective action items, and final acceptance certificates — signed by supplier and buyer representatives. Effective FAT/SAT planning reduces start-up risk, shortens commissioning time, and protects capital project schedules and budgets (see Control.com, S3 Process, KAIZEN) [2][3][4][5].

Purpose and High-Level Objectives

• Verify conformance to specification: Confirm mechanical, electrical, software, safety and documentation requirements as defined in the contract and technical data sheets (e.g., PLC program features, panel wiring diagrams).
• Reduce site risk: Detect and resolve defects in the factory to reduce SAT time and avoid costly on-site rework [4][6].
• Validate integration: At SAT, demonstrate compatibility with site power, communications, process inputs/outputs and third-party systems under real production parameters [1][5].
• Provide formal acceptance evidence: Produce signed test protocols and certificates to transfer responsibility for performance and warranty activation.

Standards, Regulations and Industry Expectations

FAT and SAT protocols do not have a single universal standard, but they must adhere to contractual technical specifications and applicable industry standards such as IEC electrical installation rules, IEC 61511 / ISA-84 for safety instrumented systems, and any project-specific regulatory requirements. Project teams should reference the contract, vendor datasheets and relevant functional safety or electrical standards when defining acceptance criteria. Standardized test methods, documented deviation handling and change control practices are generally expected by project stakeholders to ensure traceability and repeatability of test results [2][3][4].

Factory Acceptance Test (FAT)

The Factory Acceptance Test occurs at the manufacturer’s facility. FAT confirms that equipment, subsystem or packaged systems function per design before shipment. The FAT scope typically includes mechanical checks, electrical tests, functional software testing, safety verification, performance metrics, and documentation review. FAT is the buyer’s first opportunity to witness full-system functionality under controlled conditions and to require corrective action before the system leaves the factory [3][4][6].

Typical FAT Objectives and Acceptance Criteria

• Functionality: Demonstrate all control logic sequences, operator interfaces and alarms work as required (e.g., PLC interlocks, HMI screens, recipe handling). Acceptance: no critical alarms unresolved and all critical interlocks operate within spec.)
• Mechanical integrity: Verify alignment, tolerances and movement under load (example: conveyor tension and tracking under 500 kg continuous load without slippage or misalignment) [4].
• Electrical performance: Verify wiring, short-circuit protection, grounding, and voltage drop limits (example: voltage drop <5% at 80% nominal load across key feeders) [4].
• Software and response times: Test response to emergency stop and critical operator actions (example: control panel response <0.5 s to E-Stop) and confirm program versions documented and backed up.)
• Safety compliance: Validate guards, interlocks and any safety instrumented functions meet safety requirements and any applicable SIL/PHA outcomes per IEC 61511 / ISA-84 when relevant.)
• Documentation: Confirm delivery of as-built drawings, wiring lists, PLC/HMI code listings, spare parts lists, calibration certificates and FAT protocol filled and signed.)

FAT Execution: Roles, Activities and Deliverables

• Pre-FAT preparation: Manufacturer compiles test procedures, pre-checks, and sets up a FAT environment that mirrors contract conditions. Buyer confirms attendance, test scope and acceptance criteria in advance [2][4].
• Witnessing and participation: Buyer personnel (engineer, operations, maintenance) and supplier test engineers jointly execute tests and record results. Independent third-party inspectors may attend when required by contract.
• Deviation handling: Record any non-conformances in a “Deviation and Action List” with root cause, corrective actions, owner and target close-out dates. Minor deviations may be accepted conditionally; critical deviations typically block shipment until resolved [4][6].
• FAT acceptance certificate: After successful tests or agreed closure actions, parties sign the Factory Acceptance Test Certificate transferring responsibility to the buyer for shipment and insurance.

Sample FAT Test Items and Typical Acceptance Values

Site Acceptance Test (SAT)

The Site Acceptance Test occurs after shipment, installation and commissioning on-site. SAT demonstrates that equipment performs under real operating conditions, with site utilities, process materials, environmental conditions and integration into host systems. SAT repeats many FAT tests but under site-specific constraints, and includes additional checks such as installation integrity, transport damage, grounding, and end-to-end process validation with product or representative materials [1][5].

SAT Objectives and Typical Activities

• Confirm installation quality: Verify correct mounting, anchoring, guarding and that no components were damaged in transport [3][9].
• Verify site utilities: Confirm compatibility with site power quality, compressed air, cooling water and other utilities (e.g., cable sizing, transformers, earthing resistance measurements) [2][4].
• Integration tests: Validate communications and data exchange with host systems (MES, SCADA, batch systems) under live network conditions.)
• Process performance: Run production trials using actual product (e.g., filling machine trials with production fluid) to confirm yield, cycle times, and product quality parameters.)
• Operator acceptance and training: Confirm operator procedures, maintenance tasks and provide training; include runbooks and emergency procedures in handover documentation.)

SAT Execution and Handover

• Site preparation: Buyer provides access, utilities and certified environmental conditions per SAT plan. Site team ensures any pre-requisites (bulk materials, process pre-fill) are available [2][3].
• Repeat FAT tests as required: Execute the FAT functional tests in the real environment and confirm results match FAT outcomes; log any new deviations [5].
• Acceptance report and certificate: Produce the SAT report consolidating test results, open items and final sign-off. Successful SAT triggers formal production start-up or warranty commencement [3][5].
• Deferred items and punch lists: Minor items may be placed on a punch list with agreed resolution timelines; critical items usually prevent acceptance until fixed.

Comparison: FAT vs SAT

Documentation, Protocols and Test Records

Robust documentation underpins successful FAT/SAT. Typical deliverables include:

• FAT and SAT protocols: Test objectives, scope, detailed step-by-step test procedures, pass/fail criteria, measured values and accept/reject limits. Templates are commonly used to ensure consistent capture of results [4][10].
• Deviation and Change Control Records: Formal records for any non-conformances, proposed engineering changes and approvals to preserve traceability [4].
• Certificates and As-built Documentation: Wiring diagrams, bill of materials, calibration certificates, software backups and final acceptance certificates signed by buyer and supplier [3][4].
• Maintenance and Operation Handover: Maintenance checklists, spare parts lists, operator manuals and training records to enable safe transfer to operations [3][5].

Roles and Responsibilities

• Supplier / Manufacturer: Prepare and execute FAT, correct defects found during FAT, provide test equipment, produce FAT protocol and ship only after agreed acceptance or conditional release. Facilitate SAT activities and respond to punch-list items [4][6].
• Buyer / Owner: Define acceptance criteria, attend FAT as witness, review and sign FAT protocol, provide site access and utilities for SAT, lead the final acceptance and provide operator/maintenance staff for training [1][2][3].
• Third-party Inspectors / Integrators: When required by contract, independent inspectors may perform audits or witness tests and certify compliance to specific regulations or standards.

Best Practices and Common Pitfalls

Planning and Preparation

• Define acceptance criteria early in the procurement and design phase and include them in the purchase order and contract to avoid scope disputes later [2][4].
• Use FAT templates to standardize test content: include objectives, equipment lists, pre-conditions, expected results and post-test actions [4].
• Allocate production-representative materials and consumables for SAT to ensure realistic process validation [6].

Execution and Communication

• Invite the right stakeholders: engineering, operations, maintenance, quality assurance and safety — each has distinct acceptance responsibilities [3][5].
• Witness tests jointly and record results contemporaneously to avoid ambiguity in later dispute resolution [4].
• Log deviations immediately with owners and due dates, using a controlled change mechanism for any design changes [4][10].

Risk Mitigation

• Perform a comprehensive FAT to catch design and workmanship defects before shipment; well-executed FAT reduces SAT time significantly and mitigates project delays [1][6].
• Keep critical spares and test equipment available during SAT to expedite corrective actions on-site [3].
• Document software versions, backups and configuration snapshots during FAT so SAT can verify identical code and settings on site [4].

Practical Examples and Checklists

Common FAT checklist items include mechanical alignment, lubrication and torque checks; electrical continuity, insulation resistance and phase rotation; PLC program execution and HMI navigation; safety interlock tests; and performance runs. SAT checklists extend FAT items to include cable routing integrity, earthing/ground resistance tests, site power quality (harmonics, voltage dips), and product-specific trials (filling, weighing, packaging) [3][5][9].

Representative FAT/SAT Checklist (Condensed)

• Verify documentation: drawings, BOM, certificates, software backups.
• Mechanical: alignment, torque, load tests, guarding.
• Electrical: insulation resistance, continuity, correct fusing, voltage drop tests.
• Control systems: PLC logic, HMI pages, alarm lists, response times.
• Safety: E-Stop function, interlock sequencing, emergency procedures (include SIL tests if applicable).
• Communications: network topology, IP addressing, latency tests.
• Process: production trials with representative product, sampling & QA checks.
• Punch list: assign owners, target dates and retest schedule.

Handling Failures, Deviations and Change Controls

When tests fail, document the failure immediately with measured data, cause analysis and proposed corrective actions. Categorize deviations as critical, major or minor, and apply contractual rules: critical deviations typically block acceptance and shipment; major deviations may permit conditional acceptance with clearly defined corrective action milestones; minor deviations can be tracked on a punch list to be closed during commissioning or warranty period [4].

Implement formal change control for any engineering changes arising from FAT or SAT. Record version control for software and electrical drawings and require sign-off by both supplier and buyer prior to changes being enacted in production code or hardware that affects functionality [4][10].

Tools, Equipment and Technical Preparation

Ensure calibrated test equipment (multimeters, insulation testers, torque wrenches, load banks, network analyzers) is available and traceable to calibration certificates. During FAT, the vendor should provide instrumentation to verify electrical and mechanical metrics; during SAT, the buyer should provide site-specific test resources (utility meters, process materials) and ensure the availability of any heavy lifting equipment and safety permits required for on-site work [4][9].

Timelines, Costs and Scheduling Considerations

Include FAT and SAT windows in project schedules with explicit durations and contingency time. FAT typically lasts from one day for small skids to multiple weeks for large packaged systems; SAT durations vary with complexity but usually include installation, commissioning and ramp-up time. Budget for travel, accommodation, and logistics for vendor and buyer personnel to attend FAT and SAT, and for spare parts and rework in the event of failed tests. Early FAT completion with minimal deviations reduces SAT costs and production ramp-up time [2][6].

Summary and Takeaways

FAT and SAT are complementary acceptance activities: FAT confirms the equipment meets contract and design intent in a controlled environment; SAT demonstrates the equipment performs reliably