Ventilation Principles | Indian Minerology

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Part 6: Ventilation Principles

Key Learning Objective: Master ventilation planning, quantity surveys, fan performance, and statutory air velocity requirements (CMR 2017 Chapter VI Reg 104-111).

6.1 Natural vs Mechanical Ventilation

🌤️ Natural Ventilation

  • Temperature/pressure difference
  • Shallow mines only (<100m)
  • No control over direction
  • Supplementary only
  • Monsoon dependent

⚙️ Mechanical Ventilation

  • Main fans (75k-5L CMH)
  • Auxiliary fans (30k CMH)
  • Booster fans (deep mines)
  • Directional control
  • 24×7 operation

6.2 Statutory Airflow Requirements

Roadway Type Min Velocity (m/s) Quantity (m³/s per 100m) CMR Reference
Intake Airway 0.5 3.0 CMR 106
Return Airway 1.0 6.0 CMR 107
Face Roadway 1.5 9.0 CMR 108
Aux Vent Duct 3.0 30,000 CMH DGMS Circular

6.3 Airflow Measurement Techniques

🎯 Quantity Survey Methods

MethodInstrumentAccuracyApplication
Traversing Anemometer + planimeter ±5% Main airways
Tube Bundle Manometer array ±3% Aux ventilation
Vane Anemometer Digital vane type ±2 m/s Spot readings
Smoke Test Smoke tube Qualitative Direction check

6.4 Fan Laws and Performance

📈 Fan Performance Formulas

Main Fan Capacity:
[ Q = A \times V ]
Q=Quantity (m³/s), A=Area(m²), V=Velocity(m/s)
Aux Fan Pressure:
[ P = \frac{L \times f \times V^2}{2g} ]
P=Pressure(Pa), L=Duct length(m), f=friction factor
Fan Law #1:
[ Q propto N ]
Quantity proportional to RPM
Fan Law #2:
[ P propto N^2 ]
Pressure proportional to RPM²

6.5 Ventilation Planning & Leakage Control

🗺️ Ventilation Survey Components:

  • Air door conditions
  • Stoppings integrity
  • Regulators position
  • Fan water-gauge
  • Duct leakage check
  • Leakage <20% total quantity

📋 Daily Ventilation Report (Form V-20):

  • Main fan on/off time
  • Aux fan pressure
  • Face velocity readings
  • Total quantity survey
  • Gas concentrations
  • Leakage percentage

⚠️ Exam Formulae & Limits:

  • Leakage limit: 25% max
  • Aux duct velocity: 10-15 m/s
  • Fan efficiency: 65-75%
  • Water-gauge units: 1mmWG=9.81Pa
  • Form V-20: Daily ventilation return
  • Air door gap: <75mm

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