VENTILATION FOR SINKING VERTICAL,SUB-VERTICAL AND
DECLINE SHAFTS
Derek WaltersTurgis Consulting
Virtually every shaft or decline
sunk is unique in some way
Major differences being:
• Location
• Size and Depth
• Capacity
• Infrastructure
• Amount of development required from shaft or decline
Regulatory requirements
• No longer prescribed (formerly 0.15 m³/s/m² face area).
• Based on risk assessment and occupational exposure limits.
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.
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 - -
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.
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.
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
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
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
Force system
Exhaust – overlap system
Force – exhaust system
Airflow reversal
Ventilation of development from the shaft
• Unique design for each shaft.
• Designed as an integral part of the sinking shaft
Common problems
• Inadequate air for development activities.
• Column leakage due to improper installation and damage.
Recommended
2 or 3 mm thick “Corten” columns
They are:
• Robust
• Can easily be refurbished and re-used
Decline developmentSingle decline using conventional force
system with flexible ducting (world norm).
Twin declines.
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
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
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
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
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
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.
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.