2025 Coal Mining Face Methane Sensor Layout Standards and System Integration Application Guide

In coal mining faces, the effectiveness of gas monitoring systems directly determines ventilation safety, the timeliness of personnel evacuation, and the reliability of power-off interlocking for equipment. Statistics released in recent years by the National Mine Safety Administration show that a considerable proportion of gas over-limit incidents and accidents are closely related to improper sensor placement, airflow blind zones, delayed calibration, or unreasonable system integration.

As a supplier specializing in industrial-grade gas sensors, Nexisense provides system integrators, coal mine safety IoT solution providers, and EPC contractors with high-reliability laser methane sensors and complete integration solutions. From a system integration perspective, this article systematically reviews the methane sensor layout requirements under current 2025 standards, key technical parameters, common integration pitfalls, and real-world project implementation experience, helping B2B customers achieve higher compliance and system stability during solution design, construction acceptance, and long-term operation and maintenance.

Core Principles and Regulatory Basis for Methane Sensor Layout in Coal Mining Faces

The main current regulatory and technical references include:

• Coal Mine Safety Regulations (2022 revised edition)

• Specifications for the Construction of the “Six Major Systems” for Underground Coal Mine Safety and Emergency Avoidance

• MT/T 1134-2019 Laser Methane Sensors for Coal Mines

• AQ 6203-2020 Laser Methane Sensors for Coal Mines

• Special gas monitoring rectification requirements issued by local mine safety supervision authorities for 2024–2025

The core layout principles can be summarized as “three-point coverage, key area monitoring, and reliable interlocking”:

• Three-point coverage: intake side (T1), return air side (T2), and upper corner (T0)

• Key area monitoring: coal cutting points of the shearer, gas emission zones in goaf areas, and accumulation zones in return air corners

• Reliable interlocking: cutting off power to the mining face and triggering audible and visual alarms when concentration exceeds limits

  
  

Standard Layout Positions and Functional Roles

T1 Sensor (Intake Side / Near the Shearer)

Typically installed in the intake roadway of the mining face or near the coal wall on the return side, within ≤10 meters of the shearer coal cutting point (≤7 meters is recommended for high-gas mines).

Main monitoring objective: methane concentration peak values released instantaneously during coal cutting and coal falling, providing a basis for implementing “power-off upon cutting”.

Installation height: ≤300 mm from the roof, with the gas inlet facing downward to avoid direct impact of coal dust on the optical window.

T2 Sensor (Return Air Side)

Installed in the return air roadway of the mining face, within a straight section 10–15 meters from the coal wall.

Monitoring objective: the average methane concentration after airflow mixing across the entire mining face, serving as the main basis for judging ventilation effectiveness and gas control performance.

Installation requirements: avoid areas with severe airflow disturbance such as roadway bends, air doors, and local ventilation facilities. Height is generally 1.5–1.8 meters from the floor or ≤300 mm from the roof (determined by airflow direction).

T0 Sensor (Upper Corner Dedicated)

Installed at the upper corner of the mining face (the intersection of the roof and coal wall on the return side), serving as the last line of defense against methane from goaf areas flowing into the mining face.

Installation position: on the support column side or an independent hanging bracket, ≤200 mm from the roof, with the sensor axis inclined approximately 10–15° from the horizontal plane to better capture rising methane.

Mandatory for high-gas and outburst mines; strongly recommended for low-gas mines.

Configuration Strategies for Different Gas Grade Mines

High-Gas Mines and Coal and Gas Outburst Mines

Minimum configuration: T1 + T2 + T0

Recommended configuration: T1 + T2 + T0 + mid-face backup point (T3)

Example of power-off interlocking logic (adjustable according to actual mine conditions):

• T1 ≥ 1.0%–1.5% CH₄ → audible and visual alarm

• T1 ≥ 1.5% CH₄ → cut off all non-intrinsically safe power supplies on the mining face except local ventilation fans

• T2 ≥ 1.0% CH₄ → alarm + enhanced ventilation

• T0 ≥ 1.0% CH₄ → alarm + activation of outburst prevention emergency measures

  
  

Low-Gas Mines

Minimum statutory configuration: T1 + T2

Upgrade recommendation: for mines with obvious seasonal gas emissions or high risk of large-area goaf collapse, add a T0 sensor to form complete three-point protection.

Key Points for System Integration and Compatibility

The Nexisense laser methane sensor series is designed for coal mine safety monitoring systems and supports the following mainstream integration methods:

• Wired communication: RS-485 Modbus RTU protocol (most common), baud rates of 9600/19200 supported, clear 16-bit register mapping, up to 32 devices on the same bus

• Analog output: 4–20 mA current loop (two-wire/three-wire optional), corresponding to 0–4% CH₄ or 0–100% LEL

• Wireless expansion: optional LoRa, 4G/5G mine-grade wireless modules, compatible with existing KJ series monitoring systems or IoT platforms

• Power supply: 9–24 V DC wide voltage input, intrinsically safe power supply, compatible with mine flameproof and intrinsically safe power boxes

• Data content: real-time concentration, percentage of range, alarm status 1/2, fault codes, optical intensity, internal temperature, zero drift values, etc.

Integration recommendations:

• Configure primary and backup sensors at the same monitoring point to achieve hardware redundancy and data comparison

• Install repeaters or opto-isolators when RS-485 bus length exceeds 500 meters

• For critical power-off interlocking points, use hard contact outputs (relay dry contacts) combined with software alarms for double protection

Dynamic Management Requirements During Mobile Production

As the mining face advances, sensor positions must be dynamically adjusted with production progress:

• For every 50 meters of advance, T1 and T0 sensors should be repositioned and on-site zero calibration performed

• Calibration should use fresh air (zero gas) and standard gas samples (typically 2.00% CH₄)

• After calibration, time, concentration values, and environmental parameters must be recorded locally or in the host system to form traceable records

• Laser methane sensors have extremely low zero drift and can support long-term stable operation, but mine-specific mobile calibration制度 must still be followed

Common Layout and Integration Issues and Mitigation Methods

Issue 1: T2 installed in areas with severe airflow disturbance (near air doors or bends)
Consequence: severe concentration fluctuations and high false alarm rates
Solution: select straight roadway sections and stay away from disturbance structures

Issue 2: T0 directly fixed to hydraulic support roof beams
Consequence: support movement vibration causes optical component misalignment or damage
Solution: use independent suspension brackets, ≥0.5 meters away from the main support structure

Issue 3: failure to consider long-term coal dust shielding of optical windows
Solution: regularly (recommended monthly) clean gas chamber windows with 75% medical alcohol; organic solvents are strictly prohibited

Issue 4: power-off interlocking logic relies on a single concentration point
Solution: adopt multi-sensor concentration logic or concentration + rate-of-change composite criteria to improve system reliability

Typical Project Application References

A ten-million-ton-class mining face in northern Shaanxi Province
Layout scheme: T1 (8 m from shearer) + T2 (12 m in return roadway) + T0 (independently suspended in upper corner) + mid-face T3 backup
Integration method: Nexisense sensors connected via RS-485 to a KJ725 coal mine safety monitoring system, enabling real-time interlocking between methane concentration and mining face power supply
Results: 18 consecutive months without production stoppages due to gas monitoring failures; false alarm rate reduced by 68% year-on-year

An intelligent mining face in a high-gas outburst mine in eastern Shanxi Province
Adopted Nexisense laser methane sensors with 5G mine-grade wireless transmission. T1/T0/T2 data uploaded in real time to a surface management platform, supporting remote calibration and diagnostics. After project acceptance, gas over-limit incidents decreased by approximately 81%.

Frequently Asked Questions (FAQ)

1. How many methane sensors are minimally required for a mining face in 2025?
Low-gas mines require a minimum of 2 sensors (T1 + T2). High-gas and outburst mines must have at least 3 sensors (T1 + T2 + T0).

2. What should be the distance between the T1 sensor and the shearer?
Generally ≤10 meters; ≤7 meters is recommended for high-gas mines. Final determination should be based on gas geological reports and actual airflow calculations.

3. Can the upper corner T0 sensor be directly mounted on supports?
Not recommended. Independent mounting brackets are strongly advised to avoid vibration impacts from support movement.

4. How often is recalibration required after mining face advancement?
On-site zero calibration should be performed for every 50 meters of advance or according to production scheduling requirements.

5. What are the layout differences between laser methane sensors and catalytic combustion sensors?
Laser sensors do not rely on oxygen and can be placed closer to high-concentration areas; optical windows require better dust protection; response time is faster, making them suitable for rapidly changing scenarios.

6. Do Nexisense sensors support hard contact outputs for power-off interlocking?
Yes. Dry relay contact outputs are provided and can be directly connected to KJ series substations for power-off interlocking.

7. Are laser methane sensors accepted for mobile calibration in coal mines?
Laser sensors that comply with MT/T 1134-2019 and hold mining product safety certification are fully acceptable for mobile calibration and offer lower drift and better stability than traditional catalytic types.

8. What should be done if communication distance is long during system integration?
RS-485 is recommended within 800–1000 meters. For longer distances, install repeaters or select Nexisense wireless module solutions.

Conclusion

Reasonable layout of methane sensors in coal mining faces is the first technical line of defense in gas control systems and directly affects the timeliness of power-off interlocking and the credibility of the entire monitoring system. In 2025, coal mine safety supervision continues to tighten, and requirements for sensor positioning, calibration cycles, system redundancy, and data transparency will only become more stringent.

The Nexisense laser methane sensor series, with high selectivity, fast response, extremely low drift, and rich interface features, is specifically designed to provide stable and reliable sensing-layer components for system integrators working on high-gas, outburst mines, and intelligent mining face projects. We offer partners complete protocol documentation, integration case references, on-site commissioning support, and customized selection recommendations.

If you are advancing upgrades to coal mining face gas monitoring systems, intelligent transformations, or new mining face designs, you are welcome to contact the Nexisense technical team to obtain the latest layout standard references, sensor selection tables, and project collaboration solutions, ensuring safe, compliant, and efficient project implementation.