A Complete Guide to FAT SAT 2026 Protocols

Factory acceptance testing is your best strategy for preventing a six-figure rework bill or costly site delays. By catching issues before shipment, FAT verifies that equipment meets design requirements and delivers the results you expect from the very first day of installation.

Site Acceptance Testing confirms the proper functioning of equipment after installation at the client’s process plant.

Together, FAT and SAT form a robust two-stage quality assurance process that identifies control systems faults early — preferably in the factory, where fixes are fastest and least expensive.

The cost difference is significant. According to the IBM Systems Sciences Institute, fixing a defect during implementation costs four to five times more than fixing it during design. Costs rise even further if the problem is only found after the equipment arrives on site.

By 2026, new automation engineering standards and the accelerating move toward digital plant environments have raised expectations for FAT and SAT protocols considerably. To stay ahead, plant managers should prioritize these immediate actions:

1. Identify and gather all current FAT and SAT protocols used at your site for review.
2. Compare your existing protocols with the latest IEC 62381:2024 and ISA standards to spot major gaps.
3. Update or create a checklist of required documentation, making sure everything is audit-ready and up to date.
4. Schedule a review meeting with cross-functional teams — engineering, operations, IT, and quality — to assign responsibilities for updating protocols and documentation.

It is also advisable to consult with an independent expert to evaluate your testing scope and provide an external perspective on compliance and good practice.

Starting with these prioritized steps helps ensure your process plant stays on track with 2026 expectations and lays the foundation for a smooth, compliant commissioning process.

Effective planning is key to meeting these expectations. Start protocol reviews at the project bid or FEED (Front-End Engineering Design) stage, ideally 6 to 9 months before scheduled commissioning. Involve cross-functional teams early — including engineering, operations, IT, quality assurance, and safety — to ensure all requirements are captured from the outset.

Allocate sufficient time for document updates, stakeholder workshops, and test plan development. Typically, this means 4 to 6 weeks for the initial protocol review and 2 to 4 weeks for FAT/SAT planning, depending on project complexity. A clear timeline with defined roles helps avoid last-minute issues and reduces the risk of commissioning delays.

Taking these actions helps ensure compliance, reduces risk, and provides confidence when commissioning new equipment. Sarom Global’s engineering consultants bring practical experience with FAT and SAT across energy, oil and gas, and manufacturing companies — both in Australia and worldwide.

With these foundational steps in place, it helps to clearly define factory acceptance testing and understand its specific role within quality assurance protocols.

Factory acceptance testing is conducted at the manufacturer’s facility and checks that control systems, instrumentation systems, and mechanical components meet the buyer’s requirements — before anything leaves for the process plant.

The scope of FAT is not one-size-fits-all. Testing methods and coverage are determined by equipment type, and applying the same checklist to both a mechanical skid and a DCS panel is a common oversight that experienced consultants are trained to avoid.

For example, a mechanical skid checklist focuses on pressure testing, material certification, and dimensional verification. A DCS panel checklist, by contrast, emphasizes software configuration, wiring integrity, and I/O signal mapping. Tailoring the FAT checklist to each equipment type ensures all relevant risks are properly addressed.

Here is how testing requirements differ by equipment category:

• Mechanical equipment (pumps, heat exchangers, pressure vessels): Structural integrity, NDE (Non-Destructive Examination), pressure testing, PMI, and dimensional compliance
• Control panels and electrical systems: Wiring verification, interlock logic, control panel placement, and I/O point checks
• SCADA, DCS, and PLC systems: Software-level functional testing, HMI configuration, data communications, and cybersecurity validation — for example, IEC 62443-3-3 SR 3.1 on system integrity and SR 4.1 on secure data communication. Referencing these specific clauses positions your FAT checklist as an actionable compliance roadmap for control systems teams
• Instrumentation systems: Calibration certificates, loop checks, transmitter and sensor verification against design datasheets

Factory acceptance testing usually takes place at the end of the engineering and design phase, before commissioning begins. It is standard practice across oil and gas, energy, chemicals, utilities, and manufacturing companies worldwide.

Having established the fundamentals of factory acceptance testing, the next stage — Site Acceptance Testing — complements factory-based efforts and completes the two-stage assurance process.

Site Acceptance Testing takes place at the client’s site after installation. It checks how equipment performs under real conditions — with live utilities, interconnected systems, and site-specific factors that simply cannot be replicated at the factory.

Even after a successful FAT, SAT remains necessary. On-site installation introduces variables and inter-system dependencies that do not exist in a controlled factory environment.

A control system that performs flawlessly in isolation may behave very differently once connected to a site’s DCS, field cabling, or third-party communication interfaces. These integration points are where hidden issues tend to surface.

Core SAT checks include:

• Visual inspection and installation verification
• PLC/DCS input-output (I/O) point verification
• Control systems and interlock functionality
• Safety device and alarm system testing
• Operator training readiness

Beyond these well-established testing stages, evolving standards have introduced an important new development worth understanding: the Factory Integration Test.

The Factory Integration Test (FIT) is a stage of acceptance testing where multiple systems from different vendors are tested together to verify seamless operation before installation. IEC 62381:2024 — the international standard for automation engineering systems in the process industry — introduces FIT as an optional but increasingly important fourth stage.

FIT directly addresses integration challenges that FAT and SAT alone cannot resolve. It applies specifically when equipment or systems from different manufacturers must function together effectively before leaving the factory.

If a control system from one vendor needs to communicate with a safety system from another, testing each in isolation leaves the integration itself unverified until the site stage — which is the most expensive point to discover an incompatibility.

FIT brings those systems together at the factory while all parties are still co-located. This ensures that interfaces, data exchanges, and combined functional logic behave exactly as designed. For automation engineering projects involving multi-vendor systems, DCS/SCADA integration, or custom communication protocols, FIT is no longer optional in any practical sense — it is prudent risk management, and it is now formally supported within IEC 62381:2024.

Note on ISA standards: IEC 62381:2024 is the current international standard. The ISA-published version — ANSI/ISA-62381-2011 — is a decade-old, separately adopted document that has not been updated to reflect the 2024 IEC edition. Project teams should verify they are working from IEC 62381:2024, not the 2011 iteration.

Tip for transitioning projects: For projects that began under older standards such as ANSI/ISA-62381-2011, conduct a gap analysis to identify key differences between legacy and current requirements. Consider a phased adoption of new practices and update critical documentation and test procedures to meet the latest standard where feasible. This approach helps ensure compliance during transitions and minimizes the risk of missed requirements at commissioning.

Plant digitalisation and Industry 4.0 are fundamentally reshaping how acceptance testing is planned and executed. In 2026, automation engineering practitioners are expected to validate not only mechanical and electrical systems, but also data communications, historian integration, and cybersecurity resilience.

For plant managers, these changes mean incorporating new steps into daily workflows — coordinating with IT teams, reviewing cybersecurity test results, and ensuring that digital plant records and data integrations are checked alongside traditional hardware inspections. Project planning now requires earlier involvement from multidisciplinary teams and a much sharper focus on validating software and interface points.

The following updates are now active in leading-practice FAT/SAT scopes:

Virtual and Remote FAT Virtual and remote FAT now lets stakeholders witness factory acceptance testing from anywhere. Real-time video, digital plant dashboards, and cloud-based test records help reduce travel costs and eliminate scheduling friction. Best practices include careful camera placement for full test visibility, live Q&A sessions for real-time interaction, and secure digital sign-off procedures — ensuring remote FAT maintains the same transparency and accountability as in-person testing.

Digital Twin Pre-Simulation: Digital twin models allow teams to simulate equipment behaviour before physical testing begins. Studies using Siemens PCS7 and the SIMIT simulation framework show that digital twin-based FAT delivers measurable time and cost savings. Broader industry analyses indicate that virtual testing can reduce commissioning timelines by 20–40%.

Cybersecurity Validation: For SCADA, HMI, and control systems, cybersecurity testing is now a standard section within FAT scope documentation. This reflects the growing cyber threat exposure facing connected industrial environments and digital plant infrastructure.

Standards Alignment: IEC 62381:2024 now governs FAT, FIT, SAT, and SIT requirements across automation engineering systems. For alarm management and control systems safety, ISA 18.2/IEC 62682 remains the applicable standard.

Quick rule for standard selection: If your project started in 2023 or earlier, continue referencing the standard active at project kickoff — such as ANSI/ISA-62381-2011 — unless the client or regulatory requirements specify an update. For projects beginning in 2024 or later, apply IEC 62381:2024 and ensure all test plans and documentation reflect the latest requirements.

With the shift to a digital plant model, acceptance testing now focuses as much on software, data integrity, and integration validation as it does on physical hardware.

Sarom Global structures every factory acceptance testing engagement across three phases, following the IEC 62381:2024 methodology. The value they bring is not simply a standard checklist — it is the depth of multi-disciplinary automation engineering expertise applied within each phase.

Failures and non-conformances are not simply noted and moved past. Each Punch List item carries a classification, and items designated as hold-point defects must be resolved and independently re-verified before equipment is approved for dispatch.

Where a non-conformance appears ambiguous, Sarom Global can provide a Technical Deviation Assessment. This evaluates whether the issue reflects a genuine deficiency or an over-specification — enabling the project to move forward without unnecessary delay and without compromising safety or performance.

FAT vs SAT: Core Differences at a Glance

Relying solely on in-house OEM testing introduces a structural conflict of interest — the same party that builds the equipment is also responsible for evaluating it. This typically results in a narrower testing scope, reduced awareness of cross-system interactions, and an elevated risk of overlooking critical interdependencies.

This risk is especially pronounced in complex process plant configurations where equipment from multiple vendors must work together seamlessly.

Independent consultants with process engineering services expertise help close this gap. Sarom Global’s team applies a multi-disciplinary lens spanning process engineering services, automation engineering, instrumentation systems, and control systems — ensuring the full scope of acceptance testing reflects the client’s requirements, not the manufacturer’s routine procedure.

Consider a practical example: a control skid destined for an upstream oil and gas facility. An OEM team focused on its own deliverables may not have full visibility into how that skid must interface with the site DCS. An independent FAT witness with process engineering services experience will assess both the skid’s standalone performance and its interface specifications — catching mismatches before the skid ever leaves the factory.

Sarom Global’s consultants also ensure that all compliance documentation — calibration certificates, test records, as-built drawings, and Certificates of Compliance — is audit-ready. This significantly reduces post-commissioning rework costs for manufacturing companies and process plant operators alike.

Good planning begins at the bid stage — not the week before testing. Here is a practical planning framework to guide your approach:

1. Define what is being tested — mechanical equipment, control systems, software systems, and instrumentation systems each require a distinct test regime
2. Agree on acceptance criteria early — tie each test case to a specific customer specification, P&ID reference, or applicable standard
3. Determine witness requirements — identify who must be present and which tests are hold-points requiring formal sign-off. Typical roles include the plant manager, quality assurance representatives, the OEM or manufacturer’s representative, independent consultants, and — for complex projects — IT or automation engineering specialists. Listing these roles early ensures clear accountability at every stage
4. Prepare essential documentation templates before testing begins. Key documents include the Inspection Test Plan (ITP), punch list template, witness sign-off sheets, calibration certificate templates, as-built drawings, compliance certificate templates, and equipment-specific checklists. Having these ready streamlines the process and ensures compliance requirements are met from day one
5. Develop the ITP (Inspection Test Plan) — this becomes the master reference document governing all testing activities
6. Assess FIT applicability — if multi-vendor integration is in scope, determine whether a Factory Integration Test is warranted before site dispatch
7. Establish the Punch List process — define how non-conformances are classified, assigned, and cleared before approval for shipment

Sarom Global’s process engineering services team supports scope development from the bid stage through to final sign-off. At the planning stage, they help define testing requirements, acceptance criteria, and witness roles. During FAT and SAT execution, their consultants oversee and witness testing to ensure protocols are followed and all findings are accurately documented. After testing, Sarom Global provides comprehensive documentation support — helping clients assemble audit-ready test records, punch lists, and compliance files.

This end-to-end support gives plant managers clarity and confidence throughout every phase of acceptance testing.

What is the difference between FAT and SAT?

FAT is conducted at the manufacturer’s facility before shipping to verify design compliance. SAT is conducted at the client’s process plant after installation to assess real-world operational performance. The two tests work together — SAT validates what factory acceptance testing cannot replicate in isolation, particularly inter-system integration and site-specific environmental variables.

Who conducts factory acceptance testing?

Factory acceptance testing is typically led by the OEM or manufacturer, with the client or an independent consultant acting as witness. For complex projects, an independent consultant with automation engineering expertise provides objective oversight — ensuring the testing scope fully reflects the client’s requirements, not just the manufacturer’s standard checklist.

What is the difference between FAT and commissioning?

Factory acceptance testing verifies equipment at the factory before dispatch. Commissioning is the process of activating and integrating equipment at the process plant in its final operational configuration. FAT and SAT are the validation gates that precede and follow installation — commissioning is what comes after both gates have been cleared.

What is FIT, and when is it needed?

The Factory Integration Test (FIT) is an optional stage introduced in IEC 62381:2024. It applies when systems from different manufacturers need to be tested together before shipping — most commonly in multi-vendor projects involving DCS/SCADA interfaces or custom communication protocols.

While FIT requires additional time and coordination upfront, it typically costs far less than resolving integration failures after equipment arrives on site. Skipping FIT may appear to save money initially, but it increases the likelihood of costly rework, delayed commissioning, and unplanned downtime. For most complex modern projects, the cost of FIT is fully justified by the reduction in integration risk and overall project savings.

Sarom Global’s team of expert engineers are skilled FAT consultants with deep experience in skid testing, process plant design, automation engineering, and plant digitalisation. Whether you are starting a new greenfield project or upgrading an existing facility, Sarom Global delivers structured, compliant, and thoroughly documented factory acceptance testing — from the first scope review through to the final Punch List sign-off.

Services include: FAT/SAT planning, FIT coordination, independent witnessing, documentation packages, ITP review, and commissioning support — all aligned to IEC 62381:2024 and current process engineering services standards.

Planning your next factory acceptance testing project? Contact Sarom Global’s engineering consultants for independent, expert support.