DGMS Circular 02/2025: Minimum Air Quantity Guidelines for Continuous Miner & Longwall Panels

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  🔹 1. Legal Basis

• CMR 2017, Regulation 153(1):
  Mine management must provide adequate ventilation to:
• Clear smoke, steam & dust
• Dilute inflammable/noxious gases
• Supply sufficient oxygen
• Control temperature & humidity for health and safety
• Existing Norms (Reg. 153(2)(a), CMR 2017):
  Ventilation district must have:
• ≥ 6 m³/min air per person employed in largest shift OR
• ≥ 2.5 m³/min air per tonne of daily output
• Whichever is higher, measured at Last Ventilation Connection (LVC)

⚠️ Problem:
In Mass Production Panels (MPP), high daily output requires very large air quantity → causes:

• Excessive dust
• High ventilator water gauge (pressure)
• Risk of spontaneous heating

🔹 2. R&D Study (CMPDIL Ranchi)

• Project: Requirement of Air in Mass Production Technology
• Data from:
• 1 development & 2 depillaring Continuous Miner (CM) panels
• 2 Longwall (PSLW) panels
• Parameters analyzed: humidity, dust, gases, temperature rise
• Recommended new ventilation criteria

🔹 3. Recommendations A. Continuous Miner (CM) Panels

1. Minimum Air Quantity at LVC (Qmin):
• Degree I & II gassy coal mines:
  Qmin = 3 × Amax × 0.5 m/s
• Degree III gassy coal mines:
  Qmin = 3 × Amax × 0.75 m/s
• Where Amax = cross-sectional area (m²) of largest gallery in panel
2. Humidity & Temperature Control:
• Relative Humidity ≤ 80%
• Maintain ≥ 2°C difference between DBT & WBT
• To limit temperature rise by machines:
  ➝ At least 25 m³/s air at LVC

B. Powered Support Longwall (PSLW) Panels

1. Minimum Air Quantity at Face (Qmin):
• Qmin = Area of max span (m²) × 3 m/s air velocity
2. Temperature Control:
• Maintain ≥ 2°C difference between DBT & WBT
• To limit machine heat:
  ➝ At least 60 m³/s air

C. General Rule for MPP (Mass Production Panel)

• Calculate air requirement using all above criteria
• Deliver the highest value in LVC of CM or PSLW panel

🔹 4. Implementation

• While planning ventilation for CM & PSLW panels, use above formulae.
• After panel starts, prepare ventilation scheme based on factual mine conditions as per Reg. 153(2), CMR 2017.

📝 Key Points for Competitive Exams

• Circular No.: DGMS (Tech.)(S&T) 02/2025
• Issued to: Owners, Agents, Managers of Coal Mines
• Focus: Minimum air quantity in CM & Longwall panels
• Formula (CM panels):
• Degree I & II → Qmin = 3 × Amax × 0.5 m/s
• Degree III → Qmin = 3 × Amax × 0.75 m/s
• Formula (PSLW panels):
• Qmin = Area × 3 m/s velocity
• Min. delivery:
• CM panels → 25 m³/s
• PSLW panels → 60 m³/s
• Humidity Control: RH ≤ 80%, DBT–WBT ≥ 2°C
• Final Rule: Highest of all criteria must be provided

✨ MCQs – DGMS Circular 02/2025 (Ventilation at CM & Longwall Panels) 🔴 Q1. As per DGMS Circular 02/2025, which regulation of CMR 2017 primarily governs adequate ventilation in belowground mines?
A) Reg. 142
B) Reg. 153
C) Reg. 160
D) Reg. 170
E) Reg. 183
✅ Answer: B) Reg. 153
👉 Explanation: Circular is based on Reg. 153(1) & 153(2) of CMR 2017 regarding ventilation requirements. 🔴 Q2. Minimum air quantity at LVC of ventilation district must be:
A) 4 m³/min/person or 2.0 m³/min/tonne output
B) 6 m³/min/person or 2.5 m³/min/tonne output
C) 5 m³/min/person or 3.0 m³/min/tonne output
D) 8 m³/min/person or 2.5 m³/min/tonne output
E) 6 m³/min/person only
✅ Answer: B) 6 m³/min/person or 2.5 m³/min/tonne output
👉 Explanation: Regulation 153(2)(a), CMR 2017. 🔴 Q3. Excessive air requirement in Mass Production Panels (MPP) may lead to:
A) Reduced dust concentration
B) Higher ventilation pressure and risk of spontaneous heating
C) Decrease in water gauge
D) Elimination of humidity issues
E) Reduced machine heat generation
✅ Answer: B) Higher ventilation pressure and risk of spontaneous heating 🔴 Q4. Which organization conducted the R&D project “Requirement of Air in Mass Production Technology”?
A) NIRM KGF
B) IIT-ISM Dhanbad
C) CMPDIL Ranchi
D) CIMFR Dhanbad
E) DGMS Dhanbad
✅ Answer: C) CMPDIL Ranchi 🔴 Q5. In Degree I & II gassy mines, Qmin at LVC of CM panel is given by:
A) Qmin = 3 × Amax × 0.25 m/s
B) Qmin = 3 × Amax × 0.5 m/s
C) Qmin = 3 × Amax × 0.75 m/s
D) Qmin = 2 × Amax × 0.5 m/s
E) Qmin = Amax × 1.0 m/s
✅ Answer: B) 3 × Amax × 0.5 m/s 🔴 Q6. In Degree III gassy mines, Qmin at LVC of CM panel is:
A) 3 × Amax × 0.25 m/s
B) 3 × Amax × 0.5 m/s
C) 3 × Amax × 0.75 m/s
D) 2 × Amax × 0.75 m/s
E) 2.5 × Amax × 1.0 m/s
✅ Answer: C) 3 × Amax × 0.75 m/s 🔴 Q7. In formula for air quantity, Amax refers to:
A) Maximum production capacity
B) Gallery cross-sectional area (m²)
C) Longwall face length (m)
D) Height of coal seam
E) Quantity of coal produced per shift
✅ Answer: B) Gallery cross-sectional area (m²) 🔴 Q8. For CM panels, relative humidity should not exceed:
A) 60%
B) 65%
C) 75%
D) 80%
E) 85%
✅ Answer: D) 80% 🔴 Q9. To maintain comfortable working conditions in CM panels, temperature difference between DBT & WBT should be at least:
A) 1°C
B) 1.5°C
C) 2°C
D) 3°C
E) 5°C
✅ Answer: C) 2°C 🔴 Q10. Minimum air required at LVC of CM panels to restrict machine-induced temperature rise:
A) 10 m³/s
B) 15 m³/s
C) 20 m³/s
D) 25 m³/s
E) 30 m³/s
✅ Answer: D) 25 m³/s 🔴 Q11. For Powered Support Longwall (PSLW) panels, minimum velocity required at face:
A) 1.5 m/s
B) 2.0 m/s
C) 2.5 m/s
D) 3.0 m/s
E) 3.5 m/s
✅ Answer: D) 3.0 m/s 🔴 Q12. Formula for minimum air quantity in PSLW face:
A) Qmin = Area × 2.0 m/s
B) Qmin = Area × 2.5 m/s
C) Qmin = Area × 3.0 m/s
D) Qmin = Area × 3.5 m/s
E) Qmin = Area × 4.0 m/s
✅ Answer: C) Area × 3.0 m/s 🔴 Q13. Minimum air required in PSLW panels to control heat rise due to machines:
A) 30 m³/s
B) 40 m³/s
C) 50 m³/s
D) 60 m³/s
E) 70 m³/s
✅ Answer: D) 60 m³/s 🔴 Q14. In MPP, how should the minimum air requirement be determined?
A) By average of CM & PSLW values
B) By considering CM panel only
C) By considering PSLW panel only
D) By selecting the highest among all criteria
E) By DGMS standard fixed value
✅ Answer: D) By selecting the highest among all criteria 🔴 Q15. Ventilation scheme after commencement of MPP must be prepared as per:
A) Reg. 144 of CMR 2017
B) Reg. 153(2) of CMR 2017
C) Reg. 160 of CMR 2017
D) Reg. 170 of CMR 2017
E) Reg. 175 of CMR 2017
✅ Answer: B) Reg. 153(2) of CMR 2017 🔴 Q16. Excessive rise in water gauge at ventilator is a direct result of:
A) Low air delivery
B) High air quantity supply in LVC
C) Short circuiting of air
D) Blower failure
E) Dust suppression system
✅ Answer: B) High air quantity supply in LVC 🔴 Q17. DBT stands for:
A) Dry Bulb Thermometer
B) Dry Base Temperature
C) Dust Bulb Test
D) Dry Barometer Temperature
E) Direct Base Temperature
✅ Answer: A) Dry Bulb Thermometer 🔴 Q18. WBT stands for:
A) Wet Bulb Thermometer
B) Wet Base Temperature
C) Water Base Thermostat
D) Warm Bulb Test
E) Wet Barometer Temperature
✅ Answer: A) Wet Bulb Thermometer 🔴 Q19. The workshop on ventilation requirements was organized at:
A) CMPDIL Ranchi HQ
B) IIT ISM Dhanbad
C) Jhanjra Project, ECL
D) NCL Singrauli
E) SECL Korba
✅ Answer: C) Jhanjra Project, ECL 🔴 Q20. The Circular 02/2025 is applicable to:
A) Only Degree III coal mines
B) Only metalliferous mines
C) All coal mines using CM and PSLW panels
D) Only opencast coal mines
E) Only fire-area blasting panels
✅ Answer: C) All coal mines using CM and PSLW panels