Gas Detection Instruments | Indian Minerology

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Part 2: Gas Detection Instruments

Key Learning Objective: Master the types, specifications, statutory requirements, and maintenance of gas detection instruments as per DGMS Circulars and CMR 2017.

2.1 Types of Gas Detection Instruments

📱 Hand-held Detectors

Handheld Gas Detector

Usage: Spot checks, personal monitoring

🏭 Fixed Systems

Fixed Gas Monitoring

Usage: Continuous monitoring at critical points

⚡ Multi-gas Detectors

Multi-gas Detector

Usage: 4-in-1 (CH₄, CO, O₂, H₂S)

2.2 Popular DGMS Approved Instruments

Instrument Brand/Model Gases Detected Range DGMS No.
Methane Detector Dräger Pac 7000 CH₄ 0-5% DGMS/Tech.Appr/...
Explosimeter Siebe Gorman CH₄ (CAT - 35) 0-5% Classic Model
Multi-gas BW Clip4 CH₄/CO/O₂/H₂S 4-gas DGMS Approved
CO Detector MSA Altair CO 0-2000ppm DGMS/Tech.Appr/...

2.3 Calibration and Maintenance Procedures

🔧 Daily Pre-use Checks (Mandatory)

  1. Battery check (>80% charge)
  2. Zero calibration in fresh air
  3. Span calibration with standard gas
  4. Alarm test (audible + visual)
  5. Sensor response time test

Statutory Calibration Requirements:

  • CMR 121: Gas detectors tested before each use
  • Frequency: Daily zero + Monthly full calibration
  • Gas Standards: NIST traceable 1.5% CH₄, 50ppm CO
  • Records: Calibration register (Form V-25)

2.4 Fixed Gas Monitoring Systems

Installed at critical locations as per DGMS guidelines:

  • Return airways
  • Ventilation splits
  • Goaf edges
  • Stone dust barriers
  • Substation areas

⚠️ Exam Checklist:

  • Explosimeter CAT-35: Wheatstone bridge principle
  • Methane LEL: 5% vol = 100% LEL
  • CO Alarm: 50ppm (low), 100ppm (high)
  • Bump test: 30 seconds response
  • Maintenance tag: Color coding (Green=OK, Yellow=Cal due, Red=Failed)

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