Application of Combustible Gas Detectors in Gas Station Leak Monitoring

Gas stations are essential urban transport infrastructure, handling large volumes of fuel transfer and vehicle refueling daily. Whether 92#, 95#, 98# gasoline, diesel, or ethanol gasoline, all are highly volatile. During refueling, unloading, tank breathing vent emissions, and pipeline connections, combustible vapors can easily form and disperse into the air. Once these vapors mix with air to reach the lower explosive limit (LEL) and encounter static sparks, open flames, or electrical sparks, severe fires or explosions may occur.

Past accidents worldwide emphasize that controlling combustible gas leaks is vital for gas station safety. National regulations, including the "Design Specification for Combustible and Toxic Gas Detection and Alarm in Petrochemical Industry" (GB50493-2009) and "Technical Standards for Vehicle Refueling, Gas Filling, and Hydrogen Stations," require installation of combustible gas detectors in key areas to provide real-time concentration monitoring and over-limit alarms, giving critical response time for emergency situations.

Key Risk Points for Combustible Gas Leaks at Gas Stations

Gasoline mainly consists of C4–C12 hydrocarbons with high vapor pressure, low flash point (~-40℃ to -45℃), and wide explosive limits (~1.0%–7.6% vol). Common leak and accumulation scenarios include:

• Hose connections or loading arm interfaces during fuel unloading;
• Fuel nozzle or valve drips, incomplete nozzle reset;
• Breathing valves, measuring holes, or vent pipes of underground storage tanks;
• Malfunction of vapor recovery systems leading to fuel vapor overflow;
• Accumulation of vapors on the ground during peak refueling times.

These areas often have high foot traffic and vehicle movement, making them prone to flash fires or explosions if concentrations exceed limits near ignition sources, causing injuries, equipment damage, and chain accidents.

Working Principles of Combustible Gas Detectors

Mainstream combustible gas detectors are primarily two types:

• Catalytic combustion type: Uses a platinum wire catalytic bead. When combustible gases contact the heated catalyst, flameless combustion occurs, releasing heat that raises the platinum wire temperature and changes its resistance. A Wheatstone bridge measures resistance change to calculate gas concentration. Fast response and moderate cost make it suitable for most hydrocarbon gases.
• Infrared optical type: Measures gas concentration by detecting specific infrared absorption characteristics of hydrocarbons using dual or multi-beam comparisons. Resistant to poisoning, long life, no oxygen needed, ideal for long-term outdoor use or environments with H2S or other interfering gases.

Both types can be combined depending on gas station area characteristics.

Core Features of Nexisense Combustible Gas Detectors

The Nexisense SGA-501 series is designed for high-risk environments like petrochemical plants and gas stations, with industrial-grade aluminum alloy explosion-proof housing, Ex d IIC T6 Gb rating, durable, and resistant to outdoor weather and fuel vapor corrosion.

Key performance highlights:

• Real-time online monitoring, 0–100% LEL, response time ≤10s;
• 2.4-inch HD display showing gas type, real-time concentration, units, alarm status, and indicators;
• Multi-language interface (English/Chinese), easy operation;
• Three adjustable alarm levels; ≥85dB audible-visual alarm on over-limit, one-touch mute;
• Built-in relay output for linking alarms, solenoid valves, exhaust fans, pump cut-offs, etc.;
• 4–20mA analog output and RS485 digital output, compatible with Modbus, PLC, DCS, and most controllers;
• Full-range temperature and humidity compensation, suitable for -40℃ to +70℃ high humidity environments;
• Imported core chip, 32-bit microprocessor + 24-bit ADC, low long-term zero drift, good repeatability;
• Data storage and wired/wireless export for incident traceability and report generation.

Can function independently or integrate into gas station security systems.

Recommended Installation Points at Gas Stations

Key monitoring locations:

• Underground tank areas: top of each tank or near breathing valves;
• Around fuel dispensers: 1–2 detectors per dispenser, 30–50cm above ground (gasoline vapor heavier than air);
• Unloading area: well openings, hose connections;
• Vapor recovery system outlets and vent pipes;
• Transitional areas between convenience stores, offices, and fuel islands.

Installation notes:

• Signal lines in metal conduits or explosion-proof cables; branch connections in explosion-proof junction boxes;
• Avoid high-power motors, variable frequency drives, RF equipment to reduce interference;
• Independent power supply, not shared with high-power devices;
• After installation, perform calibration with standard gas and linkage tests to ensure detector and control host alarms are synchronized.

Practical Value and Safety Benefits

After deploying Nexisense detectors:

• Micro leaks detected during unloading or peak refueling, preventing vapor accumulation;
• Automatic exhaust and pump cutoff triggered during over-limit events;
• Complete historical data for safety audits, insurance claims, and liability verification;
• Reduced shutdowns, fines, and increased station credibility.

Long-term, a reliable leak monitoring system ensures compliance, public safety, and brand protection.

Maintenance and Management Tips

• Calibrate zero and span with standard gas every 3–6 months;
• Regularly clean sensor surfaces to avoid oil or dust affecting sensitivity;
• Check relay outputs and remote transmission signals;
• Perform at least one annual full function test, including alarm linkage verification;
• Use digital platforms for remote monitoring and predictive maintenance.

FAQ

1. Why must gas stations install combustible gas detectors?
Gasoline vapors easily form explosive mixtures. Detectors provide real-time monitoring and alarms to allow emergency response and prevent fires or explosions.

2. Which gases do Nexisense detectors monitor?
Mainly methane, propane, gasoline vapor, diesel vapor, and other hydrocarbon gases, with customizable ranges.

3. Recommended installation height?
Gasoline vapor is heavier than air; 30–60cm above ground recommended, adjusted per gas characteristics and standards.

4. What signal outputs are supported?
Standard 4–20mA analog, RS485 digital, and relay outputs, compatible with most control systems.

5. What actions are automated after alarm triggers?
Relay linkage activates exhaust fans, alarms, pump cut-offs for automatic emergency response.

6. Is outdoor use at fuel islands reliable?
Explosion-proof aluminum housing with full temperature and humidity compensation, suitable for -40℃ to +70℃ outdoors.

7. How often to calibrate?
Every 3–6 months using standard gas; frequency can be shorter depending on contamination levels.

8. Practical benefits of the system?
Enhanced safety, reduced accidents, regulatory compliance, reduced economic loss, improved public trust.

Conclusion

Gas stations are high-risk, densely populated environments where fuel vapor coexists with people. Combustible gas leak prevention is crucial for public safety and social stability. Nexisense detectors, with explosion-proof design, rapid and accurate detection, and reliable linkage, provide a robust technical safeguard. Proper selection, layout, and maintenance ensure compliance with national standards and protect life and property. As gas safety management becomes more intelligent and digital, high-performance detectors will continue to play an irreplaceable role.