Understanding FAT and SAT in Gas Detector Commissioning
Factory Acceptance Testing (FAT) and Site Acceptance Testing (SAT) are critical phases in the deployment of gas detectors. These procedures ensure that equipment meets design specifications, operates reliably, and complies with safety standards before being put into service. Skipping or poorly executing either test can lead to undetected failures, false alarms, or even hazardous conditions in industrial environments.
The Role of FAT: Ensuring Design Integrity
FAT is conducted at the manufacturer’s facility and focuses on verifying that each gas detector functions as designed. During this phase, every unit—whether from the GDE, GDC, or GDA series—is tested for electrical performance, signal output, display functionality, and alarm triggering. For example, the GDE820 infrared gas detector is subjected to simulated gas exposure using certified test gas to validate its T90 response time, which must be within 20–25 seconds for most combustible gases.
Critical FAT checks include:
- Verification of 4-20mA output linearity across the full measurement range
- Confirmation of relay activation thresholds (low and high alarm)
- Validation of RS485 bus communication integrity
- Check of auto-zeroing and temperature compensation algorithms
- Inspection of mechanical fit, finish, and labeling
FAT also confirms compliance with standards such as GB15322-2003 and GB3836-2010. At Shanghai Gewe Electronics Safety Equipment Co., Ltd., all detectors undergo FAT using automated test rigs that simulate real-world conditions, including power fluctuations and electromagnetic interference, to ensure EMC compliance per GB16838.
SAT: Validating Real-World Performance
SAT takes place at the installation site and evaluates how the system performs in its actual operating environment. Unlike FAT, SAT accounts for field-specific variables: ambient temperature, humidity, vibration, electrical noise, and gas dispersion patterns. A detector that passed FAT may fail SAT if installed in a high-vibration area or near a source of electromagnetic interference.
Key SAT procedures include:
- Gas challenge testing using certified span gas at each detector location
- Verification of alarm annunciation at the central GM810/GM820 gas alarm controller
- Testing of remote display and status LEDs from a distance of 25 meters (critical for GDE series with color LED display)
- Validation of communication with the cloud platform or SCADA system
- Check of grounding, cable shielding, and loop resistance
For systems using the GDC811 with catalytic sensors, SAT must confirm that the zero drift remains below 2% over six months under site conditions. Infrared models like the GTYQ-GDA100VIR are tested for long-term stability and resistance to condensation, especially in outdoor or humid environments.
Common Pitfalls and How to Avoid Them
Inadequate Gas Exposure Testing
Many SAT failures stem from improper gas testing. Using expired or uncertified calibration gas, applying gas at the wrong flow rate, or failing to account for gas density (e.g., methane vs. propane) can lead to inaccurate results. Always use certified test gas with a flow rate between 0.5–1 L/min and allow sufficient time for gas to reach the sensor.
Ignoring Environmental Interference
Detectors placed near HVAC vents, exhaust fans, or chemical storage areas may experience false readings due to air currents or cross-contamination. The GDC series, with its high-performance catalytic and infrared sensors, is designed to minimize such effects, but proper placement is still essential. Perform airflow mapping and avoid locations with direct gas washout or stagnation.
Poor Integration with Control Systems
Even if individual detectors pass SAT, system-level integration can fail. The GM820 controller supports modular expansion and auto-addressing, but incorrect dip switch settings, mismatched baud rates, or unshielded RS485 cables can disrupt communication. Use twisted-pair shielded cables with proper termination and verify signal integrity with an oscilloscope if needed.
Leveraging Advanced Features for Reliable Commissioning
Modern gas detectors like those from Gewe offer features that simplify FAT/SAT. The pre-calibrated smart plug-in sensors in GDE and GDC series allow field replacement without recalibration, reducing downtime. The remote operation via infrared remote enables configuration and testing without opening the housing—critical for explosive environments.
The 4G/WiFi modules and cloud-based monitoring software enable real-time data logging during SAT, allowing engineers to analyze trends, detect anomalies, and generate compliance reports. This integration supports predictive maintenance and remote diagnostics, reducing lifecycle costs.
Conclusion
FAT and SAT are not optional checklists but essential quality gates in gas detection system deployment. By following structured procedures, using certified equipment, and leveraging advanced features such as auto-zeroing, temperature compensation, and cloud connectivity, operators can ensure reliable performance. Shanghai Gewe Electronics Safety Equipment Co., Ltd. supports clients through full-cycle commissioning, providing FAT/SAT protocols, technical training, and on-site validation for all GT-GDE820, GT-GDC811, GTYQ-GDA100V, and GM820 systems.