Refinery Gas Detection Solutions

Refineries are the core of the petrochemical industry, involving complex processes such as crude oil distillation, catalytic cracking, hydrogenation, reforming, and aromatics extraction. These processes generate large amounts of flammable, explosive, and toxic gases, including methane, propane, hydrogen, benzene, toluene, xylene, VOCs, and TVOCs. Leaks can cause poisoning, equipment corrosion, fires, explosions, or even chain accidents. Historically, many major refinery accidents have been directly related to uncontrolled combustible or toxic gases.

Under strict supervision from national safety, emergency management, and environmental authorities, refineries must implement reliable and comprehensive gas detection and alarm systems. Nexisense offers a solution centered on SGA-500 online gas detectors with SGA-800 alarm controllers, providing full-chain risk prevention from leak source to control room.

Key Gas Risks and Monitoring Zones in Refineries

Gas risk distribution in refineries shows clear zone characteristics:

• Process Units (atmospheric/vacuum distillation, catalytic cracking, hydrocracking, etc.): high concentrations of hydrogen, combustible hydrocarbons, H₂S; highest explosion risk.

• Tank Farms (crude oil, finished products, aromatics storage): long-term low-level VOC emissions (benzene, toluene, xylene, TVOC) and potential sudden large leaks.

• Pump Rooms and Pipe Racks: flange and valve seals, pump seals prone to combustible gas leaks.

• Loading/Unloading Platforms: rapid increase of volatile gas concentrations during transfer operations.

• Wastewater Treatment Areas: oil-containing wastewater releases VOCs and hydrogen sulfide.

These zones have diverse gases, rapidly changing concentrations, and complex diffusion paths, making single detection insufficient. Nexisense emphasizes “zoning, prioritization, and system interlock” to ensure key risks are effectively monitored.

SGA-500 Series Online Gas Detectors Core Advantages

The Nexisense SGA-500 series is explosion-proof and optimized for petrochemical environments, with key features:

• Full explosion-proof certification, suitable for Zone 1 and Zone 2 hazardous areas

• Specialized sensors for refinery gases: combustible gases (LEL), benzene series, H₂S, CO, VOC/TVOC

• High-precision imported sensors with full-range temperature and humidity compensation; strong cross-interference resistance

• Dual output: 4-20mA + RS485 Modbus RTU for reliable long-distance transmission

• Integrated audible/visual alarm with optional relay output for immediate field response

• Aluminum or stainless steel explosion-proof enclosure, IP65+, suitable for humid, oily refinery environments

Installation options: diffusion type, pump-assisted, or duct-sampling, matching the process scenario.

Refinery Gas Alarm System: SGA-800 Alarm Controller

Refineries usually have existing PLC/DCS systems; Nexisense solutions support seamless integration or independent networking.

Independent Network Mode (for retrofit or partial enhancement):

• Multiple SGA-500 detectors connect via RS485 bus to SGA-800 controller

• Controller installed in control room, fire control room, or main corridor

• Large-screen real-time display of gas concentrations, alarm status, and trends

• Supports tiered alarms, zone interlocks, and historical data storage and queries

  
  

Integration into Existing DCS/PLC:

• SGA-500 connects via 4-20mA or Modbus directly to the existing system

• DCS displays gas concentrations on existing HMI for unified management

• Complex interlocks handled via DCS logic (e.g., automatic feed cut-off, pump stop, purge interlock)

Both modes support automated responses: fan ventilation, emergency valve shut-off, audible/visual alarms, and sprinkler activation.

SMS Alerts and Remote Notifications

Refinery personnel are limited, especially at night or holidays. The SGA-800 controller can be equipped with SMS modules, sending alerts to multiple personnel when any point triggers an alarm, including:

• Alarm location

• Gas type

• Current concentration

• Alarm level

• Timestamp

SMS notifications greatly reduce response time and provide objective records for accountability.

Typical Deployment Recommendations by Zone

• Tank Farm: 3–4 points per tank cluster, monitor TVOC/benzene series, height 0.5–1.5 m

• Process Unit Pump Rooms: detectors near each pump, height near floor (heavier-than-air gases)

• Pipe Racks: spaced along pipe racks, pump-assisted sampling covers dead zones

• High Platforms: pump-assisted or high-mounted for hydrogen and light hydrocarbons

• Wastewater Treatment: monitor H₂S and VOCs above collection pits and aeration tanks

Point placement should consider wind, diffusion modeling, and personnel activity zones.

Practical Benefits and Industry Experience

• Significant reduction in incidents from combustible/toxic gas leaks

• Faster emergency response, minimizing accident escalation

• Comprehensive monitoring records for safety audits and environmental self-inspection

• Interlocks reduce unnecessary downtime

• Enhanced employee safety and compliance awareness

Refinery feedback shows marked decrease in gas-related anomalies; safety management shifts from reactive to proactive.

FAQ

1. Key gases to monitor: combustible gases (H₂, CH₄, C3-C5 hydrocarbons), benzene series, H₂S, VOC/TVOC, CO. Focus varies by unit.

2. Required explosion-proof certification: National Ex d IIC T6 Gb or higher for Zone 1/2; ATEX or IECEx is a bonus.

3. Cross-interference handling: targeted sensor selection + smart algorithm compensation + full-range T/H correction; benzene vs. alkanes differentiation effective.

4. Response time with DCS integration: 4-20mA<2 s; Modbus 0.5–1.5 s; sufficient for interlocks.

5. Tank farm TVOC placement: 3–4 points per cluster: downwind tank wall, breathing valves, bund area, main corridor; height 0.8–1.5 m; optimize with wind rose.

6. Interlock options: relay dry contact (fan/valve), Modbus register write, 4-20mA step control; supports multi-level alarm interlocks.

7. SMS module reliability: industrial GSM/4G, multi-SIM backup, signal monitoring, heartbeat; internal battery buffer for power outage.

8. Retrofit installation: mostly during scheduled maintenance or night shutdown; phased construction minimizes production impact.

Conclusion

Refinery gas detection is a foundational safety measure and key part of intrinsic safety. The SGA-500 series combined with SGA-800 alarm controllers provides explosion-proof reliability, fast response, flexible integration, and intelligent interlocks. Suitable for both new and retrofit installations, customized solutions match process features and risk distribution.

Effective leak prevention requires scientific layout, precise monitoring, and rapid response. Refineries are advised to plan early, considering unit configuration, historical incidents, and regulatory requirements, to implement professional gas detection systems ensuring intrinsic safety and green production.