From FAT to Commissioning: Building Confidence in Go-Live

Executive Summary

The journey from equipment delivery to operational handover is fraught with risk. Systems that functioned flawlessly in the vendor's workshop fail on-site. Integration issues emerge during startup. Undiscovered defects trigger costly rework or, worse, safety incidents during operations.

The root cause is often an inadequate testing strategy. Many projects treat acceptance testing as a series of disconnected checkpoints - Factory Acceptance Test (FAT), Site Acceptance Test (SAT), commissioning - rather than a continuous confidence-building process. Gaps between test stages allow defects to propagate undetected until they become expensive problems.

This guide presents a pragmatic, integrated approach to testing that systematically de-risks start-up and accelerates handover. We examine each test stage (FAT, SAT, pre-commissioning, commissioning, performance testing), define clear objectives and acceptance criteria, and provide actionable checklists. The goal: arrive at go-live with confidence that systems will perform as designed, safely and reliably.

The Testing Continuum

Effective testing is not a series of discrete events but a continuum that builds confidence progressively:

Equipment Design -> FAT -> Shipping -> SAT -> Installation -> Pre-Commissioning -> Commissioning -> Performance Testing -> Handover -> Operations

At each stage, testing verifies specific attributes:

Key Principle: Each stage builds on the previous one. Skipping or rushing a stage does not save time - it pushes defects downstream where they are exponentially more expensive to fix.

The testing continuum aims to discover defects as early as possible, when they are cheapest to resolve.

Stage 1: Factory Acceptance Test (FAT)

Objectives

FAT verifies that equipment meets specification before shipping. It is the last opportunity to identify defects in a controlled environment where the vendor has full resources to rectify issues quickly.

Who Attends FAT?

Critical Success Factor: Owner/PMC representatives must have authority to approve or reject equipment. A FAT where attendees observe but cannot decide wastes everyone's time.

FAT Preparation

Vendor Responsibilities (2-4 weeks before FAT)

1. FAT Procedure: Submit detailed test procedure covering setup, sequence, acceptance criteria, safety precautions, and roles.
2. FAT Schedule: Provide realistic schedule (typical FAT: 1-3 days depending on complexity).
3. Test Equipment: Calibrate instruments and provide certificates.
4. Documentation Package: Prepare drafts of O&M manuals, as-built drawings, material certificates, and quality records.
5. Punch List Resolution: Close all open punch items from internal quality checks.

Owner/PMC Responsibilities (1-2 weeks before FAT)

1. Review FAT Procedure: Approve test procedure or request modifications.
2. Define Witness Points: Identify critical tests requiring Owner/PMC presence (e.g., safety shutdown, performance test).
3. Prepare Inspection Checklist: Customize checklist based on equipment type.
4. Logistics: Arrange travel, accommodation, and site access for the FAT team.

FAT Execution

Day 1: Documentation Review & Visual Inspection

Output: Punch list of documentation and visual defects.

Day 2: Functional Testing

Typical sequence (control panel or SCADA system):

1. Power-Up Test: Apply power, verify no faults, check voltage levels and UPS functionality.
2. I/O Test: Simulate inputs and outputs, verify correct readings and device response, test alarms.
3. Control Logic Test: Execute control sequences, verify interlocks and PID loop behavior.
4. Safety System Test: Trigger shutdowns, verify sequence and fail-safe behavior.
5. Communication Test: Verify device communications and redundancy, simulate failures.
6. HMI/SCADA Test: Validate screens, commands, historian logging, and access control.

• Record all test results in FAT report (pass/fail per test).
• Photograph defects or non-conformances.
• Video-record critical tests for training and traceability.

Output: FAT test report with pass/fail status for each test.

Day 3: Performance Testing & Wrap-Up

• Run equipment at design conditions and verify compliance with performance parameters.
• Review punch items and categorize:
  • Category A (Critical): Must be resolved before shipment
  • Category B (Major): Must be resolved before SAT
  • Category C (Minor): Can be resolved during commissioning
• Vendor commits to punch list resolution schedule; Owner/PMC signs FAT report (conditional approval if Category A items exist).
• Agree on shipping date (typically 2-4 weeks after FAT to allow punch list closure).

Wrap-Up Meeting: Lessons learned, confirm next steps, and align on documentation finalization and logistics.

FAT Acceptance Criteria

Equipment passes FAT if:

• All functional tests pass (100% for critical functions).
• Performance tests meet specification (typically within +/-5%).
• No Category A punch items remain open.
• Documentation is 90% complete or better with a closure plan.

Conditional Approval: Minor defects may be accepted with a documented closure plan and date.

Rejection: Major defects (safety failures or significant performance shortfalls) require vendor rectification and re-test.

Common FAT Pitfalls

Stage 2: Site Acceptance Test (SAT)

Objectives

SAT verifies that equipment survived shipping and functions in the site environment. Shipping subjects equipment to vibration, temperature swings, and humidity that can damage components. SAT catches issues before installation.

SAT Timing

Optimal timing: Conduct SAT immediately upon equipment arrival, before installation. This allows damaged equipment to be returned without disrupting the installation schedule.

Reality check: Many projects skip SAT or perform it after installation due to schedule pressure or lack of a test area. This is risky - if equipment is damaged, you have already invested installation labor and may face costly removal and re-installation.

Compromise: If full SAT is not feasible, conduct at minimum a receiving inspection (visual check plus power-up test) before installation.

SAT Execution

Receiving Inspection (Day 1)

• Check shipping container for damage.
• Verify all items per packing list (equipment, accessories, spare parts, documentation).
• Inspect equipment for physical damage and loose components.
• Check preservation (desiccant, protective coatings).

• Verify all FAT punch items are closed.
• Confirm final documentation is included.

Output: Receiving Inspection Report with photos of any damage.

Functional Re-Test (Day 2)

Output: SAT report comparing results to FAT baseline.

SAT Acceptance Criteria

Equipment passes SAT if:

• No shipping damage that affects functionality.
• All re-tested functions pass and match FAT results.
• Equipment operates in site environmental conditions.
• All FAT punch items are closed.

Conditional Approval: Minor cosmetic damage may be accepted with vendor commitment to repair during installation.

Rejection: Major damage or failed functional tests trigger warranty claims and repair or replacement.

When to Skip SAT?

SAT may be skipped (with Owner approval) if:

• Equipment is low-risk and simple.
• Shipping distance is short with minimal handling.
• Vendor has a strong track record with no shipping damage history.
• Schedule is critical and installation area can serve as a test area.

Risk: Skipping SAT increases the risk of discovering defects during commissioning, when rectification is more expensive and disruptive.

Stage 3: Pre-Commissioning

Objectives

Pre-commissioning verifies installation quality and system readiness for energization. It is the bridge between construction completion and commissioning start.

Primary Objectives:

1. Mechanical Completion: All equipment installed, connections made, systems closed.
2. Cleanliness: Systems flushed, cleaned, free of debris.
3. Integrity: Pressure tests, leak tests, insulation tests pass.
4. Safety: Systems safe to energize (grounding, LOTO, permits in place).

Key Principle: Pre-commissioning is a quality gate. Commissioning does not start until pre-commissioning is complete. Rushing this stage leads to equipment damage, safety incidents, and rework.

Pre-Commissioning Activities

Mechanical Pre-Commissioning

Output: Mechanical Completion Certificate for each system.

Electrical Pre-Commissioning

Output: Electrical Completion Certificate for each system.

Instrumentation & Control Pre-Commissioning

Output: Instrumentation Completion Certificate for each system.

Loop Checking

Loop checking verifies end-to-end signal integrity from field instrument through control system to final control element.

Example loop: Pressure Transmitter -> PLC -> Control Valve

1. Identify Loop: Reference loop diagram (e.g., Loop 101: PT-101 -> PLC AI-101 -> PLC AO-101 -> PCV-101).
2. Isolate Loop: Disconnect instrument and valve from process using isolation methods.
3. Simulate Input: Apply 0%, 25%, 50%, 75%, 100% of range and record transmitter output (4-20 mA).
4. Verify PLC Input: Check HMI values match calibrator readings (typically within +/-0.5%).
5. Verify Control Logic: Command outputs and verify PLC output signal (4-20 mA) to valve.
6. Verify Control Valve: Confirm valve position matches commanded position (typically within +/-2%).
7. Verify Alarms: Simulate high/low conditions and confirm alarm activation and priority.
8. Document Results: Record readings and sign off Pass/Fail.

Loop Check Acceptance Criteria:

• Signal accuracy within +/-0.5% of span (tighter for critical loops)
• Valve linearity within +/-2% of command
• Alarm activation at 100% of defined setpoints

Output: Loop check sheet for each loop (typically 100-500 loops per project).

Pre-Commissioning Checklist

A comprehensive pre-commissioning checklist ensures nothing is missed. Below is a simplified example; real checklists are system-specific and can span 50-200 pages.

System: Cooling Water System

• Mechanical Engineer: ________________ Date: _____
• Electrical Engineer: ________________ Date: _____
• Instrumentation Engineer: ________________ Date: _____
• Commissioning Manager: ________________ Date: _____

Stage 4: Commissioning

Objectives

Commissioning verifies that integrated systems function under no-load and load conditions. It is the first time systems operate with real process fluids rather than test signals.

Primary Objectives:

1. Functional Verification: Systems start, stop, control, and protect per design.
2. Integration Verification: Systems interact correctly (SCADA commands DCS, DCS controls field devices).
3. Safety Verification: All safety systems function correctly (ESD, fire and gas, relief valves).
4. Operability Verification: Operators can safely control systems using HMI/SCADA.

Key Principle: Commissioning proceeds system-by-system and step-by-step. Never energize all systems simultaneously - isolate, test, prove, then integrate.

Commissioning Phases

Phase 1: No-Load Commissioning (Dry Run)

Objective: Verify systems function without process load (no flow, no production).

• Commission utilities first (power, air, cooling water).
• Power up PLCs, SCADA, DCS and verify no faults.
• Dry run pumps and compressors with no flow.
• Test permissives and interlocks.
• Walk operators through startup and shutdown sequences.

1. Verify pre-commissioning complete and checklist signed.
2. Energize pump motor with discharge valve closed.
3. Verify pump starts with no unusual vibration or noise.
4. Open discharge valve slowly and establish bypass flow.
5. Verify flow transmitter reading.
6. Verify pressure control valve response.
7. Test high pressure alarm.
8. Test emergency shutdown (ESD) and verify pump trip.
9. Shut down system and confirm controlled sequence.

Output: No-load commissioning report for each system.

Phase 2: Load Commissioning (Wet Run)

Objective: Verify systems function under design load.

• Introduce process fluid gradually.
• Ramp load in steps (10% to 25% to 50% to 75% to 100%).
• Monitor pressures, temperatures, flows, vibrations.
• Tune PID loops and adjust setpoints.
• Simulate upsets and verify system response.

1. Open cooling water supply to process heat exchangers.
2. Start pump and establish flow at 25% design rate.
3. Monitor outlet temperature and verify cooling effectiveness.
4. Increase flow to 50%, 75%, and 100% design rate.
5. Verify pressure control maintains setpoint.
6. Simulate pump trip and verify backup pump auto-starts.
7. Verify system sustains 100% load for 24 hours.

Output: Load commissioning report for each system.

Phase 3: Integrated Systems Commissioning

Objective: Verify multiple systems interact correctly when operating simultaneously.

• Test cascaded control loops and dependencies.
• Verify inter-system sequencing and startup logic.
• Validate alarm prioritization and flood suppression.

1. Start utilities (cooling water, instrument air, power).
2. Start feed pumps and establish feed flow.
3. Start process unit equipment.
4. Verify SCADA monitoring and DCS control of all loops.
5. Simulate a process upset and verify shutdown sequence.
6. Verify operators can restart using documented procedures.

Output: Integrated systems commissioning report.

Commissioning Safety

Commissioning is the highest-risk project phase. Systems are energized, process fluids are present, and procedures are executed for the first time. Safety is paramount.

• Detailed procedures reviewed and approved before execution.
• Permit to work for all activities (hot work, confined space, energized).
• Only trained, authorized personnel execute tasks.
• Senior commissioning engineer supervises critical activities.
• Continuous communication between field, control room, and manager.
• Emergency response plan and equipment in place.
• Stop work authority for any unsafe conditions.

Commissioning Acceptance Criteria

A system is commissioned when:

• No-load commissioning complete, all tests pass.
• Load commissioning complete at 100% design capacity.
• All safety systems tested and functional.
• Operators trained and able to operate the system safely.
• All punch items resolved or documented for operations.

Stage 5: Performance Testing

Objectives

Performance testing verifies that systems meet contractual performance guarantees. This is the basis for final acceptance and payment.

Primary Objectives:

1. Capacity Verification: System achieves design throughput.
2. Efficiency Verification: System operates within design efficiency targets.
3. Reliability Verification: System sustains performance over the test duration (typically 72-168 hours).
4. Emissions Verification: System meets environmental limits.

Key Principle: Use independent third-party measurement to avoid disputes. Owner, Contractor, and test agency agree on methodology before testing begins.

Performance Test Procedure

Step 1: Test Preparation (1-2 weeks before test)

• Agree on test duration (72 hours typical, 168 hours for critical).
• Define ambient conditions and feed quality.
• Define acceptance criteria (example: at least 95% of design capacity at no more than 105% of design energy consumption).

• Install calibrated flow meters, power meters, gas analyzers.
• Verify instrumentation accuracy (typically +/-0.5%).
• Seal instruments to prevent tampering.

• Operate at design conditions for 24-48 hours before test.
• Verify steady-state operation (no transients).

Step 2: Test Execution

• Record parameters every 15 minutes (flow, pressure, power, emissions).
• Monitor for upsets or deviations from test conditions.
• Pause and restart test if major upsets occur.

• Real-time data review by Owner, Contractor, and test agency.
• Flag anomalies immediately.

Step 3: Test Analysis

• Average all readings over the test duration.
• Calculate capacity, efficiency, and emissions.
• Compare results to guaranteed values.

• Correct for deviations from ambient conditions.
• Use agreed correction factors (e.g., ASME PTC).

• Performance at or above guaranteed value: Pass.
• Performance slightly below guarantee but within tolerance (95-98%): Conditional Pass with adjustments.
• Performance well below guarantee: Fail, rectify and re-test.

Performance Test Acceptance Criteria

Example: Gas Compressor Performance Test

Overall Result: PASS - All parameters meet or exceed guaranteed values.

Stage 6: Handover to Operations

Objectives

Handover transfers responsibility from the project team to the operations team. The goal is to ensure operations can safely and effectively run the facility.

Primary Objectives:

1. Knowledge Transfer: Operations team understands systems, procedures, and troubleshooting.
2. Documentation Transfer: Manuals, drawings, and records are complete and accessible.
3. Spare Parts Transfer: Critical spares are on-site and cataloged.
4. Warranty Activation: Warranties are activated and documented.

Handover Activities

Training

Documentation Handover

• As-built drawings (P&IDs, electrical schematics, loop diagrams)
• Operation and maintenance manuals
• Commissioning reports (FAT, SAT, pre-commissioning, commissioning)
• Calibration certificates for all instruments
• Material certificates and quality records
• Spare parts lists and vendor contact information
• Warranty certificates

• Hard copy: bound manuals in control room and maintenance office
• Digital copy: searchable PDFs in document management system

Spare Parts Handover

• Identify critical spares (long lead time, high failure risk).
• Verify spares on-site, properly stored, and cataloged.
• Provide spare parts list with part numbers and storage locations.

Warranty Activation

• Register equipment warranties with vendors.
• Document warranty terms (duration, coverage, exclusions).
• Establish warranty claim procedures.

Handover Acceptance Criteria

Handover is complete when:

• Operators and maintenance personnel are trained and competent.
• All documentation is delivered and accessible.
• Critical spare parts are on-site.
• Warranties are activated.
• Operations team signs the handover certificate.

Building Confidence: The Integrated Approach

The testing continuum from FAT to handover is not a series of isolated checkpoints but an integrated confidence-building process. Each stage builds on the previous, progressively reducing uncertainty and risk.

Key Success Factors

The Payoff

• Faster Startup: 20-30% reduction in commissioning duration.
• Higher Reliability: 50% reduction in post-startup failures.
• Lower Cost: 15-25% reduction in commissioning cost.
• Safer Operations: Zero safety incidents during commissioning.

Conclusion

The journey from FAT to handover is complex, but it does not have to be chaotic. A pragmatic, integrated testing approach - where each stage builds confidence progressively - transforms commissioning from a high risk gamble into a controlled, predictable process.

The key is to treat testing not as a series of compliance checkpoints but as a confidence-building continuum. Start early (FAT), verify often (SAT, pre-commissioning, commissioning), measure rigorously (performance testing), and transfer knowledge thoroughly (handover). By the time you reach go-live, confidence should be near 100%. Systems have been tested at every stage, defects have been caught and resolved, operators are trained, and documentation is complete. Go-live becomes a non-event - a smooth transition from commissioning to operations, not a leap into the unknown.

Appendix A: FAT Inspection Checklists

Control Panel FAT Checklist