One Team One Vision With Pride

The Association of Mine The Association of Mine Surveyors of Zimbabwe AGM Surveyors of Zimbabwe AGM KARIBA 201KARIBA 20122

Technical Paper Title:

Mine Ventilation Up-grade Management

Presentation by :Joshua Tigere

Group Occupational Hygienist

PRESENTATION OVERVIEW

Definition of Mine Ventilation Up-grade Implication of Mine Ventilation Up-grade Need determination Role Of the Mine Surveyor Project justification Proposed Projects appraisal Practical example Conclusion

VENTILATION UPGRADE – DEFINITION

This refers to a change in the overall Mine Ventilation capacity

usually resulting in a higher pressure and intake volumes. This

can be achieved through various ways some of which are:

Replacement of current main surface fans with bigger ones.

Installation of additional Main fans and intake shafts

Sinking of more intake airways to reduce overall mine resistance

Upgrade of the mine refrigeration capacity in the case of ultra – deep mines

PROJECT IMPLICATIONS Increased mine ventilation

cost ( Purchasing of fans and ducting, Additional substation, Telemetry, increased electricity usage, security systems)

More airways in most cases presenting heat management challenges in ultra-deep mines.

Improved environmental conditions in the mine.

DETERMINATION OF THE NEED FOR A VENTILATION UPGRADE

The proposal should come from the initial Life of Mine Planning(LOMP) where the ventilation engineer spells out the stage by stage mine ventilation requirements in line with the development and production phases.

In other unusual cases, it may be necessitated by a desire to vary the initial production and development plan either due to unforeseen geological challenges or other initiatives

ROLE OF THE MINE SURVEYOR

The mine surveyor assist in taking the survey from underground and site the proposed vent raise positions on surface

Assisting in siting of communication holes near the proposed raise bore sites

Measurement of distances to proposed sites to assist in budgeting for power lines and roads to sites

Alignment of machine on site prior to drilling

PROJECT JUSTIFICATION A detailed write up should be generated

spelling out the benefits of the up grade and reference must be made to the production and development needs that should be met.

Issues to be considered include : Overall mine Resistance and current Main fan

duties Current mine ventilation requirements Projected mine ventilation requirements State whether current system can/cannot meet

the needs for the future Present options for meeting the future

ventilation requirements

PROJECT APPRAISALS

Appraise the available project proposals to refine

decision making. Options that can be considered

include the following:

Replacement of current main fans with bigger ones( in terms of fan duty)

Fan Selection and duct size selection Raise-boring additional return shafts & Installation

of additional main fans Raise-boring additional intake airways

VENTILATION PROJECTS APPRAISAL

The Total Owning cost (TOC) Approach is used to determine the overall cost of owning a project over its life at today’s value. This includes the capital costs involved in the scheme and the present value of any running costs involved in the scheme. The technique is applied to all proposed projects and the method assists in determining the most economic project to implement.

AN EXAMPLE OF A COMPARISON BETWEEN TWO PROJECTS

Challenge A volume of 45m3/s is

being delivered to a section through a 3m x 3m tunnel which is 800m long. The pressure drop is 320Pa. It has become necessary to increase the quantity from 45m3/s to 65m3/s. The following schemes are being considered:

SCHEME 1

Cost fan installation - $160 000

Fan Efficiency - 72%

Motor Efficiency - 94%

Power cost per kw per year - $1100

Life Expectancy of Section - 16yrs

Present Value of $1 per year over 16yrs is $6.97

at 12%

SCHEME 2

Widening the airway from 3m to 4m, the pressure drop would again be 320pa when the new quantity flows. The cost of increasing the airway size will be approximately $300/m3. assume that none of the above changes will affect the operating point of the main fans

QUESTION

Which is the most economical scheme?

SOLUTION

Parameter Scheme 1 Scheme 2

Present value of Initial Capital Cost

$ 160, 000 (1x3x800)x300

= $ 720, 000

Duty of Booster Fan required

668-320 = 348kpa nil

Present value of Fan running costs

(33.4 x1200x 6.97)

=$279 358

nil

T.O.C $438 358 $ 720, 000

DECISION MAKING From the above

calculations, Scheme 1 is the most economical choice. In making deductions fro T.O.C calculations, the following needs to be taken into consideration prior to settling for an alternative;

CONCLUSION

A feasibility assessment of selected project given the available space, compatibility with existing infrastructure etc must be made prior to settling for an alternative.

In other words the cheaper scheme is not always the best scheme. Practical considerations need to be made prior to making the final decision regards the best scheme to implement.

ROLE OF THE VENTILATION ENGINEER FOR SUCCESSFUL VENT UPGRADE PROJECT REQUIREMENTS

Competency in basic airflow and fan Engineering calculations

Knowledge of the cost of ventilation equipment to facilitate preparation of accurate budget for the upgrade project.

Knowledge of the cost of electricity in the country of operation

Mine ventilation planning knowledge Must be conversant with the mine development and

production budgets. Must be conversant with present value tables and

their application Have ready contacts for companies that supply vent

equipment and the Raise bore drilling companies

THE END

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