Mine Planning

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Ventilation & Working Environment: Content

• Mine Ventilation Basics

• Ventilation (Airflow)

• Fans

• Psychrometry & Heat Stress

• Hazards in the Underground Environment

• Mine Ventilation Planning

Mine Ventilation Planning: References

• McPherson Chapter 9

• “Le Roux’s” Notes Chapter 18

• “MV for beginners” Notes No 65

Other Resources on ELE• Papers on ELE

• Hard Rock Miners Handbook Chapter 18

• Anglo Coal Mine Planning Guide

Mine Ventilation System Objectives The Coal and Other Mines (Ventilation) Regulations, 1956

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Traditional Method of Ventilation Planning

1. Determine air volume flows required in working areas to dilute and remove all pollutants.

2. Assess the airflow requirements for development areas, mechanical or electrical plant and workshops, and estimate the volume flows that pass through abandoned workings, stoppings and other leakage paths.

3. Indicate the estimated airflows on a mine plan and compound them to show air flow rates, through each major airway.

4. Using the given airflows and proposed size of airways, determine the corresponding air velocities. If these exceed limiting values, the need for larger or additional airways is required.

5. Assess the resistance, R, of each branch along the main ventilation routes, either from estimated friction factors and airway geometries or on the basis of local empirical data.

6. Using the square law, p = RQ2, or charts, determine the frictional pressure drop, p, for each main branch and indicate these on the mine plan.


7. Commencing from the top of a down flowing surface connection, trace a path along intake airways to the most distant workings, and back to the surface via return airways.

8. Sum the frictional pressure drops around the complete traverse. This exercise is repeated for a number of such traverses to incorporate various working areas. The loop showing the greatest summation of frictional pressure drops then gives an approximation of the main fan pressure to ventilate the mine.

9. Subsidiary circuits may be controlled by regulators or upgraded by booster fans. Pressure gradient diagrams may be employed to give a visual indication of the cumulative pressure drops.


Ventilation Rate = A x production + B

A – varies with mining method and complexity

B – about 50 m3/s for single hoist systems – increases with size of

mine and number of hoisting systems

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Establishment of the Basic Network

A mine ventilation system simply consists of a

network of airways, fans and regulators. In general, the correct quantity and quality fresh air

distributions to all working places may be achieved by;

– the optimal sizing of surface openings;

– the use of the proper shape, size and number of trunk

airways;

– the correct location and sizing of control devices, and

– the optimal duties and locations of main and booster

fan units.

Establishment of the Basic Network (New Mines)

• For a new underground mine, the ventilation system should be flexible in order to service mining operation needs from the period of its initial sinking, through to its various projected development and production phases and to its final closure.

• The mining planning process may be conveniently scheduled across three time intervals, namely the short, medium and long term (typically 1, 5 and 10 years) periods.

• The objective of the mine ventilation design is to provide safe and comfortable working environment for each period in order to provide a safe environment and maintain the productivity levels.

Establishment of the Basic Network

(existing mines)

• For existing mines, ventilation planning should entail a regular revision process to mirror any changes in development and production plans.

• The modification and improvement of the ventilation systems are inevitable to maintain the quality and quantity of fresh airflow delivered to all working areas.

• Those effects may include the adjustment of the locations and duties of the fan units, an increase or reduction of regulation devices, and the construction of alternative surface openings and/or trunk airways.

Ventilation Design Methodology

(Outline of Principle Stages)

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Determine Method & Rate of Production

• Diesel Equipment– Number of units, individual & fleet power

• Auxiliary and Booster Fans– Number of units & capacity

• Development Rate & Schedule– Number of faces & planned lengths

• Stope Production– Number of & peak requirements

• Depth of workings & climate– Consider annual temperature profile

• Workshop & Fuel Bays– Additional capacity for nominal velocity

Define Acceptable Environmental Standards

• Dust/Gases’s

– Legal limits defined in TLVs/OELs

– Specific pollutant OEL’s

– Dust OEL’s given in SIMRAC document on

ELE

• Heat & Humidity

– Air cooling power

– Ideally 0.5 m/s and

27ºC wet bulb

Define Acceptable Environmental Standards (ii)Calculate Heat Increases, Gas emissions &

Dust production

Gases

• MAC = Max Allowable Concentration (ppm)

• N = “Normal” amount of that gas in air (ppm)

• Qgas = Rate of emission of gas

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Calculate Heat Increases, Gas emissions & Dust

production (ii)

• Dusts

Calculate Air Requirements (Metal)

(i) Design Rules of Thumb for Quantity

Air Quantity for Stope Production m3/s per ‘000tpy

Block Cave 0.05 to 0.1

Large mines, long hole stopes 0.2 to 0.4

Smaller mines 0.4 to 0.5

Larger pillar recovery mines 0.6 to 0.9

Air Quantity for Diesel Equipment (per kW)

“Over the engine” minimum > 0.035m3/s

Design Ventilation for gross fleet requirements 0.06 to 0.08 m3/s

Local regulations

Quantities elsewhere required to provide:

Ventilation of mine services (crushers, workshops etc)

Clearence times for blasting fumes/Dilution of Strata Gas


(ii) Design Rules of Thumb for Velocity

Intake Airways

Intake Shaft velocities < 10 m/s for typical haulage guide methods

Intake drift & decline velocities < 5 m/s to minimise dust pick up

General airways between 2 and 4 m/s

Working Places

Working places >>0.5 m/s for dust clearance and gas layer prevention

Hot working areas > 0.5 m/s for cooling effect

Large workshops > 0.25 m/s

Return Airways

Return airway velocity < 12m/s for pedestrian access

Main return shaft velocity < 7 m/s or > 12 m/s to avoid droplet suspension

Ventilation shaft velocity typically 16 to 22 m/s for optimum cost


(iii) Design Rules of Thumb for Temperature

Air Temperatures ºC WB

Design 26-28

Possible short shift conditions 28-29

Significant Lost Time likely 29-31

Unacceptable for continuous loss 31-32

Absoluatly no work 32 +

Actual design limiting temperatures will be determines by heat stress index employed;

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(iv) Design Rules of Thumb for Pressure

Surface Fans

Surface fans typically operate between 1 to 2.5 kPa

Some fans operate 3 to 4 kPa

Higher pressures required when shaft or development costs are high

Economic & leakage issues associated with higher pressures

Underground Pressure Differentials

Frictional air losses in mine workings usually very much less than primary ventilation shafts

Calculate Air Requirements (Coal)

Design Rules of Thumb

Velocities

Intake shaft velocities < 10 m/s for typical haulage guide methodsIntake shaft & decline velocities < 5 m/s to minimise dust pick upWork places >> 0.5 m/s for dust clearance & gas layer protection

Return air velocity < 12 m/s for pedestrian accessMain return shaft velocity < 7 m/s or > 12 m/s to avoid droplet suspension

Ventilation shaft velocity typically 16 to 22 m/s for optimum cost

Quantity (Regs – Oz – NSW)Continuous Miner -> 0.3 m3/s per m2 airway areaLongwall – 4 m3/s for each metre of extraction height

Diesel – 0.06 m3/s per rated KW or > 3.5 m/s

PressureSurface fans typically operate between 1 to 2.5 kPa

Some fans operate 3 to 4 kPaHigher pressures required when shaft or development costs are highEconomic & leakage issues associated with higher pressures

Gate roadways run typically at 200 Pa to 400 Pa

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Optimise Alternatives

• There are a number of viable alternative ventilation system configurations a design engineer may employ to maintain the safety, integrity and efficiency of a main ventilation system.

• These may include, – the upgrade of existing main fan(s);

– the installation of new main surface fan(s);

– the maintenance and/or sealing of major leakage paths to reduce air leakage;

– the installation (or removal) of booster fans or regulating doors;

– the provision of additional surface connections and the development of new trunk airways.

Computer Software

• There are many computer-based tools available

today to assist mine ventilation engineers in design and planning of mine ventilation system,

– VNETPC (MVS Inc. USA),

– Ventsim(Ventsim, Australia)

– VUMA (COMRO/BBE, South Africa).

• These tools may be used in conjunction with theoretical design and/or ventilation survey data

to achieve safe and economic ventilation

solutions.

VUMA: Data Entry

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VUMA: Analysis Vuma: Visual Analysis

Mine Planning

Documents