VENTILATION FOR SINKING VERTICAL, SUB-VERTICAL AND DECLINE SHAFTS

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VENTILATION FOR SINKING VERTICAL,SUB-VERTICAL
AND DECLINE SHAFTS
Derek Walters Turgis Consulting
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Virtually every shaft or decline sunk is
unique in some way
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Major differences being

• Location
• Size and Depth
• Capacity
• Infrastructure
• Amount of development required from shaft or
  decline

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Regulatory requirements

• No longer prescribed
• (formerly 0.15 m³/s/m² face area).
• Based on risk assessment and occupational
  exposure limits.

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Occupational Exposure Limits (OEL)

• OEL Time weighted average 8 hour day 40 hours
  a week.
• OEL C Instantaneous value which must never
  be exceeded.
• OEL-STEL Maximum exposure for 15 minute TWA
  and not more than 4 times per day.

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OEL AND STEL AFTER BLASTING OEL AND STEL AFTER BLASTING OEL AND STEL AFTER BLASTING OEL AND STEL AFTER BLASTING OEL AND STEL AFTER BLASTING
Substance OEL OEL OEL-C / STEL OEL-C / STEL
ppm mg/m³ ppm mg/m³
Carbon Monoxide (CO) 30 35 100 115
Carbon Dioxide (CO2) 5000 9000 30000 54000
Nitric Oxide 25 30 35 45
Nitrous Oxide 50 90 - -
Nitrogen Monoxide 25 30 35 45
Nitrogen Dioxide 3 5 5 9
Silica dust (respirable) - 0.1 - -
Coal dust (respirable) - 2 - -
Particles not otherwise classified
Inhalable particulates - 10 - -
Respirable particulates - 3 - -
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Operating outside South Africa

• Comply with local regulations.
• Or
• In the absence of local regulations use South
  African regulations.
• These comply with internationally accepted norms
  and are thus defensible.

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The purpose of ventilation is to dilute and
remove pollutants.

• Always assume that flammable gas may occur.
• SA Limit 1.4 flammable gas in atmosphere.
• Define Atmosphere as 150 mm away from the
  source in any direction.
• Design must be robust enough to cater for
  abnormal but reasonably anticipated events.

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Vertical shafts

• Determine requirement for ventilating the
• shaft barrel.
• Determine work that is to be done
• concurrently or in conjunction with sinking.
• Including
• Station and other development
• Raise Boring
• Holing with other excavations

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Determining basic air requirements

• Ordinary sinking
• Air volume providing minimum of 0.5 m/s in shaft
  is good practice.
• Example
• An 8.0 m shaft would require 50.3 m² x 0.5 25.2
  m³/s

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Determining re-entry times

• Shaft diameter 8 m diameter (50.3 m²)
• Required re-entry time 15 minutes
• Number of air changes 8 between face stage
• Distance from the face to the stage when raised
  for blasting 50 m
• Air quantity (Q) (Air changes x Volume) /
  Time
• Q ( 8 x 50.3 x 50) / 15 x 60 22.3 m³/s
• In this case the minimum air quantity required is
  22.3 m³/s

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Force system
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Exhaust overlap system
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Force exhaust system
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Airflow reversal
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Ventilation of development from the shaft

• Unique design for each shaft.
• Designed as an integral part of the sinking shaft

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Common problems

• Inadequate air for development activities.
• Column leakage due to improper installation and
  damage.

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Recommended

• 2 or 3 mm thick Corten columns
• They are
• Robust
• Can easily be refurbished and re-used

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Decline development

• Single decline using conventional force system
  with flexible ducting (world norm).
• Twin declines.

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Occupational exposure limits - Diesel Equipment Occupational exposure limits - Diesel Equipment Occupational exposure limits - Diesel Equipment
Carbon dioxide CO2 5000 ppm
Carbon monoxide CO 30 ppm
Nitric oxide NO 25 ppm
Nitrogen dioxide NO2 3 ppm
Sulphur dioxide SO2 2 ppm
Diesel particulate matter DPM Not specified Suggested 400 µg/m³
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Determining air requirements

• Currently no legislated minimum air quantity in
  SA
• Many other countries have regulations in place.
• These minimum air quantities vary considerably
  from country to country.
• Suggested volume is 0.075m³/s/kW rated power
• A 150 kW LHD would require (150 x 0.075)
• 11.3 m³/s

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Multiple vehicles used in series
Equipment kW m³/s/kW Factor m³/s
20 t Truck 240 0.075 1 18.0
LHD 185 0.075 0.75 10.4
Utility vehicle 80 0.075 0.5 3.0
Drill rig 40 0.075 0.5 1.5
Total air required Total air required Total air required Total air required 32.9
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Sizing of ventilation columns

• Identical 1.0 m Ø columns, 1500 m long, 15
  leakage.

Air quantity 15 m³/s 20 m³/s
Fan Pressure 4147 Pa 7295 Pa
Face quantity 12.9 m³/s 17.2 m³/s
Fan input kW _at_ 75 efficiency 82.9 kW 194.5 kW
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Heat loads

• These are site specific and are affected by
• Ambient conditions
• Depth
• Rock geothermal gradient
• Rock thermal characteristics
• Area of rock exposed
• Diesel equipment
• Other mechanical and electrical heat loads
• Ground water inflow rate

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• To determine the need for cooling a heat
• balance must be done.
• There are a number of computer
• programs to calculate this and to predict
• The working conditions in the decline
• being sunk.

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Conclusions

• The ventilation system should be uniquely
• designed to cater for sinking and any
• additional development that may be
• required.
• Avoid the one size fits all approach.