Evaluation of fiber optic methane sensor using a smoke chamber

Area of Science:

• Mining Engineering
• Sensor Technology
• Environmental Monitoring

Background:

• Underground coal mines face risks from fires and explosions, producing hazardous gases like methane.
• Reliable methane monitoring is crucial for worker safety and operational integrity in these environments.
• Fiber optic sensors offer potential advantages for gas detection due to their immunity to electromagnetic interference.

Purpose of the Study:

• To evaluate a prototype fiber optic methane monitor's performance under simulated post-fire/explosion conditions in an underground coal mine.
• To assess the impact of smoke from various combustible sources on sensor accuracy and response time.
• To determine the effectiveness of the sensor's protective screen against smoke and soot accumulation.

Main Methods:

• Experiments were conducted in a smoke chamber simulating underground mine atmospheres after fires.
• Test fires utilized common mine combustibles: Douglas-fir wood, SBR belt, and Pittsburgh seam coal.
• The fiber optic methane monitor's optical power at 1650 nm and methane response times were measured under varying smoke concentrations and durations.

Main Results:

• The sensor's protective screen effectively prevented direct smoke obscuration of the optical beam.
• Minimal impact on the system's optical power budget was observed.
• Methane response times showed a notable increase with extended smoke exposure, linked to soot accumulation on the screen.

Conclusions:

• The fiber optic methane monitor prototype demonstrates resilience against smoke interference in simulated mine fire conditions.
• Soot accumulation on the protective screen is the primary factor affecting sensor response times.
• Further development may be needed to mitigate the impact of soot loading on sensor performance for prolonged exposures.