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.