— A Practical Guide for Engineers, EPCs, and Project Teams
Factory Acceptance Testing (FAT) proves that an instrument works at the manufacturer's facility. Site Acceptance Testing (SAT) proves that the same instrument works after it has been shipped, stored, installed, wired, and connected to the actual control system. Between FAT and SAT, many things can go wrong: transport damage, incorrect installation, reversed polarity, loose terminals, wrong I/O configuration, damaged cable insulation, moisture ingress, or configuration errors.
SAT is the formal verification step that catches these problems before commissioning begins. It is the bridge between construction completion and plant start-up. A well-executed SAT confirms that the instrumentation system is ready for live process operation. A rushed or incomplete SAT leaves hidden faults that will appear during start-up—when every minute of delay is expensive and every undetected fault can become a safety incident.
This guide explains the purpose, scope, preparation, execution, documentation, and common pitfalls of Site Acceptance Testing for instrumentation systems.
1. What Is SAT?
Site Acceptance Testing (SAT) is the documented inspection and testing of instrumentation and control systems at the project site after installation is complete. It verifies that:
Instruments are correctly installed and accessible
Cables are correctly routed, terminated, and protected
Junction boxes, marshalling panels, and cabinets are correctly wired
Loop continuity, insulation resistance, and polarity are correct
Instruments power up and respond correctly
Calibration is verified at site conditions
Signals reach the control system accurately
Alarms, trips, and interlocks function correctly
Control system I/O is configured correctly
Documentation reflects the as-installed configuration
SAT is not the same as loop checking, but loop checking is usually a major part of SAT. SAT is broader: it covers mechanical, electrical, functional, documentation, and system integration aspects.
2. SAT vs FAT: What Changes at Site?
| Aspect | FAT | SAT |
|---|---|---|
| Location | Manufacturer's facility | Project site |
| Equipment state | New, uninstalled | Installed, wired, connected |
| Environment | Controlled factory conditions | Actual plant conditions |
| Primary purpose | Verify product before shipment | Verify installed system before commissioning |
| Scope | Instrument calibration, function, documentation | Installation integrity, loop checks, system integration, functional tests |
| Responsibility | Supplier-led, EPC/client witnessed | EPC/contractor-led, client witnessed |
| Documentation | Manufacturing and calibration records | As-built records, loop check sheets, SAT reports |
| Typical timing | Before shipment | After installation, before commissioning |
Key principle: FAT verifies the product. SAT verifies the installation and system integration.
3. When Does SAT Occur?
SAT occurs after construction is complete and before commissioning begins. The typical project sequence is:
| Phase | Activity |
|---|---|
| 1. Construction completion | Instruments installed, cables pulled, terminations made |
| 2. Pre-SAT documentation review | As-built drawings, loop diagrams, cable schedules reviewed |
| 3. SAT preparation | Test equipment calibrated, personnel coordinated, work permits obtained |
| 4. SAT execution | Inspection, testing, loop checks, functional tests |
| 5. Punch list resolution | Non-conformances corrected and re-verified |
| 6. SAT sign-off | Formal acceptance to proceed to commissioning |
| 7. Commissioning | Loops energised, process introduced, control loops tuned |
Critical rule: SAT must be completed before the process is introduced. Once the process is live, SAT becomes difficult, dangerous, and in some cases impossible.
4. Objectives of SAT
| Objective | What It Confirms |
|---|---|
| Installation integrity | Instruments are mounted correctly, accessible, and protected |
| Wiring correctness | Cables are continuous, correctly terminated, and polarity is correct |
| Insulation integrity | Cable insulation is not damaged during installation |
| Power supply | Loop power and instrument power are correct |
| Calibration | Instruments are calibrated and accurate at site conditions |
| Signal integrity | Signals reach the control system without distortion or noise |
| Control system configuration | I/O cards, channels, and databases are correctly configured |
| Alarm and trip functions | Alarms and trips activate at the correct setpoints |
| Documentation accuracy | As-built documentation matches the installed system |
| Readiness for commissioning | The system is safe and ready for live process operation |
5. SAT Scope by System and Component
SAT scope depends on the system and the project requirements. The following table summarises typical SAT activities by component.
| Component | Typical SAT Activities |
|---|---|
| Field instruments | Visual inspection, mounting check, tag verification, calibration verification, functional test |
| Junction boxes | Visual inspection, terminal tightness, labelling, shield termination, ingress protection |
| Marshalling panels | Visual inspection, terminal tightness, labelling, shield grounding, ferrules |
| Instrument cables | Continuity, insulation resistance, polarity, shield continuity, routing inspection |
| Control system I/O | Channel configuration, signal type verification, scaling, alarm configuration |
| Control valves | Stroke test, positioner calibration, fail-safe action, limit switches |
| SIS/F&G loops | Functional test, trip verification, proof test, SIL documentation |
| Analysers | Sample system check, calibration, validation |
| Power supplies | Voltage verification, redundancy check, UPS operation |
| Earthing systems | Earth resistance, bonding continuity, shield grounding |
| Panels and cabinets | Visual inspection, labelling, termination check, cooling, sealing |
| Instrument air | Pressure, dew point, filtration, point-of-use FRL check |
For bulk items such as cables, junction boxes, and gauges, SAT may use sampling as defined in the Inspection and Test Plan (ITP).
6. Preparation for SAT
Proper preparation is essential. SAT is not an activity to be improvised in the field.
6.1 Documentation Review
Before SAT begins, review:
| Document | Purpose |
|---|---|
| Instrument Index | Tag numbers, service, location |
| I/O List | Control system channels and signal types |
| Loop Diagrams | Wiring details, terminal numbers, shield grounding |
| Cable Schedule | Cable numbers, types, routing |
| Junction Box Schedule | JB locations, terminal assignments |
| Marshalling Panel Schedule | Panel terminations, shield grounding |
| Instrument Datasheets | Calibration range, signal type, connection details |
| Installation Drawings | Mounting, impulse lines, hook-up details |
| P&IDs | Instrument function and control strategy |
| ITP | SAT scope, witness points, acceptance criteria |
| FAT Reports | Baseline calibration and test results |
Key action: Verify that as-built documentation reflects field changes before SAT.
6.2 Test Equipment
| Equipment | Purpose | Calibration |
|---|---|---|
| Multimeter | Continuity, voltage, current | Required |
| Loop calibrator | 4–20 mA simulation | Required |
| HART communicator | Configuration and diagnostics | Firmware current |
| Pressure calibrator | Pressure instrument testing | Required |
| Temperature calibrator | RTD/TC testing | Required |
| Megohmmeter | Insulation resistance | Required |
| Earth resistance tester | Earthing verification | Required |
| Two-way radios | Field-control room communication | Battery check |
All test equipment must have current calibration certificates traceable to national standards.
6.3 Personnel and Coordination
| Role | Responsibility |
|---|---|
| Instrument technician (field) | Applies test signals, verifies field response |
| Instrument technician (control room) | Verifies control system response |
| Control system engineer | Configures I/O, verifies DCS/PLC response |
| Commissioning engineer | Supervises SAT, resolves issues |
| Construction contractor | Corrects installation errors |
| Client witness | Witnesses SAT if required |
6.4 Safety Preparation
| Requirement | Purpose |
|---|---|
| Work permits | Authorisation to work |
| LOTO | Process isolation and de-energisation |
| Gas testing | Safe atmosphere in hazardous areas |
| PPE | Hard hat, glasses, gloves, FR clothing |
| Barricades and signage | Warning of testing activities |
| Emergency procedures | Evacuation routes and contacts |
Critical: SAT must be performed with the process isolated and de-energised unless otherwise specified.
7. SAT Procedure: Step by Step
Step 1: Visual Inspection
Verify that instruments, cables, junction boxes, and panels are installed correctly.
| Check | What to Verify |
|---|---|
| Tag numbers | Match the Instrument Index and loop diagram |
| Mounting | Secure, accessible, correct orientation |
| Process connection | Correct type, size, rating, and tightness |
| Cable connection | Correct gland, tight, sealed |
| Terminals | Tight, correctly labelled, ferrules installed |
| Polarity | Positive and negative correct |
| Shield | Terminated correctly; grounded at one end only |
| Enclosure | Cover installed, gasket intact, IP rating maintained |
| Labelling | Cable tags, terminal labels, instrument tags |
| Damage | No transport or installation damage |
Step 2: Cable Continuity and Insulation Testing
| Test | Method | Acceptance |
|---|---|---|
| Continuity | Measure between field and control room terminals | <1 Ω |
| Insulation resistance | 500V DC megohmmeter | >100 MΩ |
| Polarity | Verify + and - | Correct |
| Shield continuity | Verify shield is continuous | Continuous |
| Shield grounding | Verify grounded at one end only | Single-point grounding |
Caution: Disconnect instruments and I/O cards before insulation testing.
Step 3: Power Supply Verification
| Check | Acceptance |
|---|---|
| Loop voltage | Within instrument specification (e.g., 24V DC ±10%) |
| Instrument power | Correct voltage and polarity |
| Redundant supply | Both supplies operational |
| UPS operation | Transfer test if applicable |
| Fuse and breaker | Correct rating and operational |
Step 4: Instrument Calibration Verification
| Test | Method | Acceptance |
|---|---|---|
| Zero check | Apply 0% input | Within tolerance |
| Span check | Apply 100% input | Within tolerance |
| Mid-point | Apply 25%, 50%, 75% | Within tolerance |
| Repeatability | Apply same input multiple times | Within specification |
| Hysteresis | Increase and decrease input | Within specification |
| Local display | Compare with applied input | Within tolerance |
| HART communication | Read device parameters | Device responds |
For temperature instruments: Verify cold junction compensation and lead resistance compensation.
Step 5: Loop Check
| Test | Method | Acceptance |
|---|---|---|
| 4 mA | Simulate at field | Control room reads 0% |
| 12 mA | Simulate at field | Control room reads 50% |
| 20 mA | Simulate at field | Control room reads 100% |
| HART signal | Verify digital communication | Device communicates |
| Signal noise | Observe stability | Stable reading; no noise |
Step 6: Alarm and Trip Verification
| Test | Method | Acceptance |
|---|---|---|
| Alarm setpoint | Apply input at setpoint | Alarm activates at correct value |
| Trip setpoint | Apply input at trip point | Trip activates at correct value |
| Trip output | Verify final element | Correct valve, pump, or device operates |
| Reset | Reset alarm/trip | Returns to normal |
| First-out indication | Verify sequence of events | Correct first-out recorded |
Step 7: Control System Integration
| Test | Method | Acceptance |
|---|---|---|
| I/O channel | Verify channel assignment | Correct channel |
| Signal type | Verify AI/AO/DI/DO configuration | Correct type |
| Scaling | Verify engineering units | Correct scaling |
| Control loop | Verify controller response | Correct action |
| Graphics | Verify HMI display | Correct tag and value |
| Historian | Verify data logging | Data recorded |
| Alarm management | Verify alarm display and priority | Correct priority |
Step 8: Functional Tests
| System | Test | Acceptance |
|---|---|---|
| Control valve | Stroke test 0–100% | Full stroke; correct position feedback |
| Control valve | Fail-safe test | Correct fail action (FC/FO/FL) |
| On/off valve | Open/close test | Correct operation; limit switches |
| Pump | Start/stop test | Correct operation; status feedback |
| SIS loop | Proof test | Trip operates correctly |
| F&G loop | Detector test | Alarm and trip operate correctly |
| Analyser | Validation test | Reading within specification |
Step 9: Documentation and Sign-Off
| Activity | Output |
|---|---|
| Complete SAT sheets | Record all test results |
| Record discrepancies | Note any non-conformances |
| Create punch list | Items requiring correction |
| Update as-built documentation | Reflect field changes |
| Obtain signatures | Field, control room, commissioning engineer, client |
| File documentation | Submit to project documentation system |
8. SAT Documentation
Documentation is a critical output of SAT. It proves that the system has been tested and is ready for commissioning.
8.1 SAT Test Sheet
| Field | Content |
|---|---|
| Loop number | Unique identifier |
| Instrument tag | PT-101, TT-102, etc. |
| Service description | Pressure, temperature, level, flow |
| Loop diagram reference | Drawing number and revision |
| Cable number | Cable identification |
| I/O card and channel | DCS/PLC address |
| Calibration range | 0–100 bar, 0–200°C, etc. |
| Test equipment | Model and calibration date |
| Test results | Record of each step |
| Discrepancies | Issues found |
| Punch list items | Items to correct |
| Signatures | Field, control room, commissioning engineer, client |
| Date | SAT date |
8.2 Punch List
| Punch Item | Description | Responsible Party | Status |
|---|---|---|---|
| 001 | PT-101 polarity reversed at JB-101 | Electrical contractor | Open |
| 002 | TT-102 shield grounded at both ends | Electrical contractor | Open |
| 003 | FT-103 calibration out of tolerance at 75% | Instrument vendor | Closed |
8.3 As-Built Documentation
After SAT, update:
Loop diagrams
Cable schedules
Instrument Index
I/O List
Junction box schedules
Marshalling panel schedules
Installation drawings
Best practice: As-built documentation should be completed before plant start-up.
9. Acceptance Criteria and Punch List
9.1 Acceptance Criteria
SAT acceptance requires:
All inspection items pass
All tests meet specified tolerances
Loop checks pass
Alarms and trips function correctly
Control system integration verified
Documentation complete and accurate
No Category A punch items outstanding
9.2 Punch List Categories
| Category | Definition | Action |
|---|---|---|
| Category A | Critical; prevents commissioning | Must be resolved before commissioning |
| Category B | Major; affects function or compliance | Resolve before commissioning or by agreed date |
| Category C | Minor; cosmetic or documentation | May be resolved during commissioning or by agreed date |
10. Roles and Responsibilities
| Role | Responsibility |
|---|---|
| Supplier | Provide documentation, calibration certificates, and technical support |
| EPC contractor | Plan and execute SAT; manage punch list; update documentation |
| Construction contractor | Correct installation errors identified during SAT |
| End user / client | Witness SAT; approve deviations; accept system |
| Third-party inspector | Witness SAT if required; verify compliance |
| Commissioning team | Use SAT results as the basis for commissioning |
11. Common Problems Found During SAT
| Problem | Likely Cause | Consequence |
|---|---|---|
| Open circuit | Broken wire, loose terminal, incorrect termination | No signal |
| Short circuit | Damaged insulation, incorrect termination | Erratic signal |
| Reversed polarity | + and - swapped | No signal or reversed reading |
| Wrong terminal | Wire terminated incorrectly | Incorrect signal |
| Shield grounded at both ends | Incorrect grounding | Ground loop, noise |
| Shield not grounded | Missing grounding | No noise protection |
| Calibration drift | Transport, storage, or installation effects | Inaccurate reading |
| Wrong I/O configuration | Incorrect channel setup | Incorrect reading or no communication |
| Alarm setpoint incorrect | Wrong configuration | Alarm does not activate |
| Instrument damage | Transport or installation damage | No signal or incorrect reading |
| Moisture ingress | Damaged gland or enclosure seal | Corrosion, short circuit |
| Cable damage | Pulling tension, bending radius, or mechanical damage | Signal loss or intermittent fault |
12. Common Mistakes to Avoid
| Mistake | Consequence | Prevention |
|---|---|---|
| Starting SAT before installation is complete | Rework, repeated testing | Verify construction completion before SAT |
| Using uncalibrated test equipment | Invalid results | Verify calibration certificates |
| Skipping insulation tests | Undetected cable damage | Always perform insulation resistance testing |
| Not verifying shield grounding | Ground loops, noise | Check shield grounding at one end only |
| Ignoring polarity | No signal or reversed reading | Verify + and - at every termination |
| Not testing alarms and trips | Safety functions not verified | Always test alarm and trip setpoints |
| Not updating as-built documentation | Documentation does not match field | Update documentation after SAT |
| Rushing SAT | Missed errors, commissioning delays | Allow adequate time for each loop |
| No punch list tracking | Items forgotten | Track all punch items to closure |
| Poor communication between field and control room | Errors missed | Use radios; maintain constant communication |
| Testing with process live | Safety risk | Verify process is isolated |
| No spare parts | Delays if instrument fails | Stock spare instruments and cables |
13. Applicable Standards
| Standard | Scope |
|---|---|
| ISA-5.1 | Instrumentation symbols and identification |
| ISA-5.4 | Instrument loop diagrams |
| IEC 61511 | Functional safety—process industry |
| IEC 60079 | Explosive atmospheres—equipment certification |
| IEC 60529 | Ingress protection (IP code) |
| EN 10204 | Metallic products—inspection documents |
| ISO/IEC 17025 | Testing and calibration laboratory competence |
| API RP 551 | Process measurement instrumentation |
| BS 6739 | Instrumentation in process control systems |
14. Why Choose Anhui Tiankang for SAT Support?
Anhui Tiankang (Group) Co., Ltd. has nearly five decades of experience in industrial instrumentation. We support SAT with documentation, instruments, and engineering expertise.
SAT support capabilities:
| Capability | Details |
|---|---|
| Documentation | Instrument datasheets, wiring diagrams, loop diagrams, calibration certificates |
| Calibration certificates | Traceable to national standards |
| Ex certificates | CCC Ex, ATEX, IECEx |
| SIL documentation | SIL2/SIL3 verification |
| Engineering support | Loop check procedure, troubleshooting, commissioning assistance |
| Spare parts | Recommended spares for commissioning and start-up |
| Training | Operator and maintenance training |
Product portfolio for SAT:
| Product | SAT Scope |
|---|---|
| Pressure transmitters | Calibration, loop check, Ex verification |
| Temperature transmitters | Calibration, loop check, Ex verification |
| Level instruments | Calibration, loop check, Ex verification |
| Flow meters | Calibration, loop check, Ex verification |
| Control valves | Stroke test, fail-safe test, positioner calibration |
| Instrumentation cables | Continuity, insulation, shield verification |
| Junction boxes | Termination, labelling, ingress protection |
| Signal isolators | Functional test, isolation verification |
Core advantages:
Complete certifications: CCC Ex, ATEX, IECEx, SIL
CNAS-accredited laboratory: full performance testing
Long-term supplier to CNPC, Sinopec, CNOOC, and international EPC projects
One-stop supply: from instruments to cables to Ex accessories
15. Conclusion
Site Acceptance Testing is the critical gate between construction and commissioning. It verifies that the instrumentation system is correctly installed, properly wired, accurately calibrated, and fully integrated with the control system. A thorough SAT prevents commissioning delays, reduces start-up risk, and provides the documentation required for long-term maintenance.
Key takeaways:
| SAT Phase | Key Activity |
|---|---|
| Preparation | Review documentation, calibrate test equipment, coordinate personnel |
| Visual Inspection | Verify installation, tag numbers, mounting, cable connections |
| Cable Testing | Continuity, insulation resistance, polarity, shield grounding |
| Power Verification | Loop voltage, instrument power, redundancy |
| Calibration Verification | Zero, span, mid-point, repeatability, hysteresis |
| Loop Check | 4 mA, 12 mA, 20 mA, HART communication |
| Alarm and Trip Verification | Setpoints, outputs, reset, first-out |
| Control System Integration | I/O channel, scaling, HMI, historian |
| Functional Tests | Valves, pumps, SIS, F&G, analysers |
| Documentation | SAT sheets, punch list, as-built records |
The most important rule: Complete SAT before commissioning begins. A loop that is skipped will fail when the process is live—when every minute of delay costs money and every undetected fault risks safety.
Remember: SAT is not just about finding wiring errors. It is about proving that the measurement and control system will work when the plant is started—and every day thereafter.
Contact Us
For SAT support, instrument documentation, or project quotations, please contact:
Yin Shuangjie
International Sales Manager
📧 Email: [email protected]
📱 WhatsApp / Zalo: +86 17856068126
🌐 Website: http://www.tiankang-global.com/
Anhui Tiankang – Your partner for reliable instrumentation and commissioning support.
