Catalytic Combustion Gas Sensor Technical Manual

In the context of accelerated industrialization and urbanization, combustible gas leaks cause frequent accidents, posing serious threats to life and property. As a key technology to prevent such risks, catalytic combustion gas sensors are reliable guardians of industrial safety. This manual, based on Nexisense’s expertise, explains the sensor’s principle, features, applications, and maintenance, helping users monitor gas concentrations effectively and ensure safety in both industrial and residential environments.

Overview

The catalytic combustion gas sensor is a specialized device for measuring combustible gas concentration, primarily in percentage of the Lower Explosive Limit (LEL). This technology has evolved over many years and is widely applied due to its low cost, stable output, and fast response. It is a preferred tool for industrial safety monitoring and also plays an important role in residential applications, such as home gas alarms.

Nexisense, a renowned sensor brand, uses advanced materials and precision manufacturing to ensure stable performance even in complex environments. Its core function is real-time combustible gas monitoring, triggering alarms when concentrations approach dangerous levels. Compared to electrochemical or infrared sensors, catalytic combustion sensors excel in detecting multiple gases (methane, propane, hydrogen), making them ideal for high explosion-risk areas.

Main Applications

Applications include industrial safety monitoring, residential gas alarms, and coal mine gas detection. In industry, they are placed near chemical plants, gas pipelines, and storage tanks; in homes, integrated into alarms; in mines, essential for monitoring gas concentration. Concentration is expressed in %LEL: for example, 20% LEL triggers a low alarm, 50% LEL a high alarm.

Working Principle

The sensor combines catalytic combustion with a Wheatstone bridge for sensitivity and accuracy. It has two main elements: the detector and the compensator, both platinum coils on alumina supports. The detector is coated with catalysts like platinum or palladium to facilitate gas oxidation; the compensator is passivated and serves only to compensate for environmental conditions.

These elements form a Wheatstone bridge with precision resistors. In clean air, the bridge is balanced and output is zero. When a combustible gas enters, it diffuses to the detector, undergoes flameless catalytic combustion, releasing heat, increasing platinum resistance, unbalancing the bridge, and generating a voltage signal proportional to concentration. Response is within seconds, with compensation for temperature, humidity, and pressure. Nexisense optimizes the catalyst for anti-poisoning performance and minimizes interference from silicates or sulfides.

Key Components and Technical Features

The detector is the core, using high-purity platinum and nano-scale catalyst coating. The compensator uses the same material without catalyst for reference.

• High sensitivity: detection limit down to 0.1% LEL

• Wide range: 0–100% LEL

• Strong interference resistance: internal filters reduce environmental effects

• Long life: 3–5 years under normal conditions

• Standard 4–20 mA output; compatible with PLC/SCADA and Modbus RTU protocol

Advantages and Limitations

Advantages: cost-effective, fast response, detects multiple combustible gases. Limitations: requires oxygen for reaction; performance decreases in low-oxygen environments; prolonged exposure to high concentrations may poison the catalyst. Nexisense mitigates these with optimized design and protective layers.

Application Fields

Widely deployed in high-risk industries. In petrochemical plants, monitors tank and pipeline leaks to prevent explosions. In coal mines, detects gas concentrations for worker safety. In residential alarms, integrated for timely alerts in kitchens and boiler rooms. Nexisense has demonstrated a 30% accident reduction in large chemical plants and is used in emerging areas like hydrogen energy storage for safety monitoring.

Installation and Maintenance

Select explosion-proof enclosures per ATEX or IECEx standards. Install near potential leak points, avoiding direct sunlight or strong airflow. Calibrate every six months using standard gas, clean with soft cloth, check power and wiring if output is abnormal. Replace detector element if catalyst ages.

Frequently Asked Questions (FAQ)

1. What is %LEL? Percentage of the Lower Explosive Limit; 100% LEL means the minimum explosive concentration.

2. Which gases does it detect? Methane, ethane, propane, hydrogen; not inert gases.

3. How to calibrate? Introduce known concentration gas and adjust output; typically every six months.

4. What is the lifespan? 3–5 years depending on environment.

5. Can it be used in low-oxygen environments? Not recommended.

6. How to prevent catalyst poisoning? Avoid exposure to silicates, lead, or sulfides; use models with filters.

7. Output types? 4–20 mA, voltage, or digital (Modbus).

8. Installation height? Light gases up, heavy gases down according to density.

9. Difference from infrared sensors? Catalytic is cheaper, faster, requires oxygen; infrared no oxygen required, higher cost.

10. Is Nexisense customizable? Yes, for range, explosion-proof rating, and interface.

Summary

Catalytic combustion gas sensors are core industrial safety technology, protecting countless workplaces. Nexisense provides reliable high-performance solutions. Understanding principles, applications, and maintenance ensures safe use. Choosing the appropriate model maximizes value and safeguards production and homes.