ventilation for sinking vertical, sub-vertical and decline shafts derek walters turgis consulting
TRANSCRIPT
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VENTILATION FOR SINKING VERTICAL,SUB-VERTICAL AND
DECLINE SHAFTS
Derek WaltersTurgis 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 BLASTINGSubstance OEL 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 theshaft barrel.Determine work that is to be doneconcurrently 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 developmentSingle decline using conventional force
system with flexible ducting (world norm).
Twin declines.
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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 specifiedSuggested 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 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 @
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.