Contentsmvssa.co.za/wp-content/uploads/2017/11/MVS_Q3_2017-1.pdfIt is that time of the year that we...

Volume 70 • Number 3 • July/September 2017

Published quarterly by the Mine Ventilation Society of South AfricaCSIR Property Cnr Rustenburg and Carlow RoadEmmarentiaP O Box 291521 Melville 2109Tel: +27 11 482-7957 Fax: +27 11 482-7959 / 086 660 7171E-mail: [email protected]

[email protected]: http://www.mvssa.co.za

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Copyright © 2017 of the Mine VentilationSociety of South Africa

Contents

Cover Picture:

Journal of theMine Ventilation Society

of South Africa

Photographer: Marthinus van der Bank. 15MW Bulk air Cooler that was constructed and commissioned at Beatrix 3# Operation

Editorial: Hello again! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

73rd Annual General Meeting of the Mine Ventilation Societyof South Africa Friday 23rd June 2017 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Presidential address: The MVSSA, A working society . . . . . . . . . . . . . . . . . . .8

A theoretical comparison of ventilation on demand strategiesfor auxiliary mine ventilation systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

A new approach to extinguish coal fires by using water misttechnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Application of computational fluid dynamic modelling in thedesign of shaft systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Journal of the Mine Ventilation Society of South Africa, July/September 2017 1

It is that time of the year that we say goodbye andhello - again.

The new Council for the 2017 / 2018 terms ofoffice has already finalised its work programme andis weaving away in meeting this term’s lofty objectives.

On your behalf, let me congratulate and thank Mr.Neil Roman and his Council who have steered theMVSSA through what proved to be, once more,difficult waters with professional aplomb and efficiency and setting-up what is looking to be moreand more a new era for the Society as it approaches its diamond jubilee. Neil and crew,know that your efforts are sincerely appreciated.

It is "hello" to Mr. Kobus Dekker and the incoming2017 / 2018 Council who have set themselves anarduous task, planned and developed during thelast term of office. May you be successful in yourendeavours.

A large section of this journal is devoted to the73rd Annual General Meeting including the presidential address, in which these objectives areoutlined.

If I may wet the reader's appetite, you will noticefrom the Presidential Address, that several plans arebeing proposed to renew the Society in manyaspects. Kobus and his team have their workplanned and cut-out. Interestingly enough, the planhas been laid out for execution over a number ofyears - probably a first in the history of theMVSSA.

Re-inventing the MVSSA is needed to strengthenthe Society as it and the Mining Industry faceincreasing challenges that require quick, tacticaltransformations based on flexible and resilientstrategies.

Ventilation Engineering is rightly deemed to beliable - to some extent, rightly or wrongly - for theincreasing costs of operating underground mines atdepth. This has several implications on the professional preparation of the individuals taskedwith such work, the long-term planning of newmining projects and the impact of many of novel

Marco BiffiHonorary Editor

Please send your comments and

opinions to [email protected]

mining methods and technologies introduced toimprove safety and profitability.

The technical papers in this issue reflect that imperative by showcasing fire-fighting techniques incoal mines, the design of shaft systems, indicatingways in which this age-old technique may still beharnessed to optimize aerodynamic losses, and athird paper evaluating different ventilation-on-demand strategies, another tactic at the disposal ofthe Ventilation Engineer to reduce operational costs.

Lastly a big word of thanks to Professor Jan duPlessis who has had to relinquish the position ofHonorary Editor due to work commitments fol-lowing a change in career. Please join me in thanking him for the contributions to the Journalover the last three years and in wishing him well inhis future ventures.

That leaves me to say hello - again. From our part,the Editorial Committee, as part of the winds ofchange sweeping though the MVSSA, has undertaken also to bring about changes that willmake this publication and the MVSSA more accessible and aligned with modern communicationtechnologies.

I look forward to interacting with readers and inhearing suggestions on how we can improve theJournal.

Hello again!

2 Journal of the Mine Ventilation Society of South Africa, July/September 2017

THE MINE VENTILATIONSOCIETY OF SOUTH AFRICAOFFICER BEARERS

President:Mr Kobus Dekker

Senior Vice President:Mr Marthinus van der Bank

Junior Vice President:Mr Ronald Motlhamme

Honorary Editor:Mr Marco Biffi

Honorary Treasurer:Mr André van der Linde

Honorary Chairman of Education:Mr Morné Beukes

Immediate Past President:Mr Neil Roman

COUNCIL MEMBERSMr Frans Cloete, Mr Johan Maass, MrWynand Marx, Mr Barry Nel, Mrs CeciliaPretorius , Mr Selvin Subban, Ms Julize vanNiekerk

EDITORIAL COMMITTEE MEMBERSMr Marco Biffi (Hon. Editor), Mr Bruce Doyle,Mr Frank von Glehn, Mrs Cecelia Pretorius,Mrs Debbie Myer

SECRETARIALCSIR Property, Cnr Rustenburg and CarlowRoad, EmmarentiaP O Box 291521 Melville 2109Tel: +27 11 482-7957 Fax: +27 11 482-7959 / 086 660 7171E-mail: [email protected]

[email protected]: http://www.mvssa.co.za

PAST PRESIDENTSMr Marco Biffi, Mr Mike de Koker, Mr Len deVilliers, Mr Bruce Doyle, Mr James J vanRensburg, Mr Dries Labuschagne, Mr HenryMoorcroft, Mr Vijay Nundlall, Mr AndrewThomson, Mr Frank Von Glehn

BRANCH REPRESENTATIVES

The Collieries BranchMr Neil McPherson

The Free State BranchMr Johan Pienaar

The Northern BranchMr Billy Letlape

The Western BranchMr Brian Yates

The Eastern BranchMr Tsietsi Letanta

The International BranchMr Frank von Glehn


73rd Annual General Meeting of the Mine Ventilation Society of South Africa

Friday 23rd June 2017 at 10h00, EnGedi Guesthouse & Conference Venue, Kromdraai

The 73rd Annual GeneralMeeting opened with the welcome from the President MrNeil Roman to the executive, council, members,guests, DMR representatives andsuppliers / supporters of the society.

The president confirmed the minutes of the 72nd AnnualGeneral Meeting held at EnGeniconference venue, Plot 22, ProteaRidge Road / Honingklip Road,Kromdraai on Friday 24th June2016 which were published in the

Journal, Volume 67 Number 3 of 2016.

OBITUARIESIt is with regret that the MVSSA Council records the deaths ofthe following members of the Society. Our condolences to theirfamilies, friends, and colleagues. They will be fondly rememberedand greatly missed. Let us stand in a minute of silence.

Mr Oscar Benjamin Colliery Branch

Mr GP Jass Northern Branch

Mr M Moroa Western Branch

Mr Nick van Rensburg Western Branch

Mr Maurice Simmons Western Branch

Mr DE Wrigley Western Branch (Past President ofthe MVSSA)

PRESENTATION OF PRIZES AND AWARDS 2016/2017In order to recognise special achievements and to encourage thesubmission of papers for publication in the Journal to enhance itsquality, the society awards annual prizes.

The Prizes and Awards Committee recommended the followingawards:

Gold Medal - No prize awarded.

Society Prize - For the best paper of the year excluding a GoldMedal Paper.

Pressure Piling and the Impacts of Blast Relief to Protect PrimaryFans in a Highwall Longwall Operation. Mr R Brake, Q1 2016.

AMM Award - (Associate of Mine Managers of SA Prize). Bestpaper published in Q4 of volume 69.

An evaluation of fuels and retrofit diesel particulate filters to reduce dieselparticulate matter emissions in an underground mine. Mr MC Wattrus,Mr M Biffi, Mrs CJ Pretorius and Mr D Jacobs.

SACMA Award - (South African Colliery Managers Association).

Using Computational Fluid Dynamics (CFD) to Evaluate the Factorsthat Contribute to Effective Methane Dilution in a Continuous MinerHeading. C.F. Meyer, Q2 2016.

Associate Prize - No prize awarded

Best Technical Note - No prize awarded


JP Rees Award - For the best paper describing a mine ventilationsystem. To be awarded every second year and selected from thejournals of the past two calendar years.

XLP/ULP On-ReefMechanised Mining Methodby Ventilation on Demand asa Concept. J. Venter andM.B. Diedericks, Q4 2016.

The award was collected byMr J. Venter.

Best Student Awards

Best student award - University of Pretoria)2016 Mr Gabriel Gomes-Sebastiao

Best student award (University of Witwatersrand) MissMmathapelo Thale

AFROX Trophy -Awarded to the best MECstudent

This award was presented by Mr PeterRowland from Afrox to MrThabiso Jerry Maimela.

Certificate in Mine Environmental Control (MEC)

Sixty four (64) candidates obtained their Intermediate Certificatein Mine Environmental Control. Only six were members.

Certificates of Achievement are awarded to those who havereceived their Certificate in MEC for the last two examinations.

Candidates who achieved the highest marks for each paper (papers1 to 6) received the Presidential Award which included the newtextbook and a cash prize of R3,000.00.

Intermediate Papers 1 - Mr Lewellin V Bennette (achieved90% for Paper 1)

Intermediate Papers 2 - Ms Crisca Cronje (achieved 73% forPaper 2)

Advanced Paper 1 and 6 - Mr Thabiso Jerry Maimela -Bokoni Platinum

Advanced Paper 2 - Ms Susan S Swanepoel - Lonmin

Advanced Paper 3 - Mr Johannes Jacobus Ferreira - Sasol

Advanced Paper 4 - Mr Mapula Jepi - Sibanyegold

Advanced Paper 5 - Mr Michael Maluleke - South Deep

The President’s trophy

This trophy is awarded to a branch of the President’s choice. Thisyear the President’s Trophy was awarded to the Free State Branch.Barry Nel (Past Chairman) and current chairman Johan Pienaar),accepted the trophy on behalf of the Branch.

Honorary fellows

Henry Moorcroft and Dirk van Greuning were awarded honorary fellowship.

Mr Lewellin V Bennette Ms Crisca Cronje

Mr Thabiso Jerry Maimela Ms Mapula Jepi

Mr Johannes Jacobus Ferreira Mr Michael Maluleke

Mr Henry Moorcroft Mr Dirk van Greuning


ANNUAL REPORT OF COUNCIL FOR THE YEARENDING 31/03/2017Copies of the report containing information on the highlights ofthe Society for the 2016/2017 year were distributed:

1. National Mine Ventilation Congress

2. Presidential Banquet

3. New MVSSA website

4. Success of committees

5. Good financial performance

6. Increase in membership

7. Office activities.

FINANCIAL STATEMENTS AND BALANCE SHEET FOR2016/2017 Mr André van der Linde presentedthe Financial Statements. The financial feedback is based on theaudited statements by GenesisChartered accountants.

The auditor's opinion is unqualified,meaning they found no fault and thatfinancial management of the Societyis in line with the “Generally AcceptedAccounting Practice”. They complimented the Society on:

• A budget that was well considered and accurate

• Good financial discipline

• Good financial administration - the secretary had kept accuraterecords of all transactions of the MVSSA office.

Details of the income statement were presented to the members.

APPOINTMENT OF AUDITORS FOR THE YEAR The President announced that, in terms of Section 18.8 of theConstitution, the Council agreed to re-engage Genesis CharteredAccountants to audit the 2017/2018 accounts.

BRANCHESThe full annual reports of the branches are included in the 2017Annual Report.

DECLARATION OF ELECTION OF OFFICE BEARERS AND COUNCIL MEMBERS FOR 2017/2018In terms of the Constitution, the outgoing Council has elected thefollowng Office Bearers for the year 2017/2018:

President - Mr Kobus Dekker

Senior Vice President - Mr Marthinus van der Bank

Junior Vice President - Mr Ronald Motlhamme

Honorary Editor - Prof Jan du Plessis

Honorary Treasurer - Mr André van der Linde

Honorary Chairperson Education - Mr Morné Beukes

Members of Council elected by ballot are:Mr Frans Cloete

Mr Johan Maass

Mr Wynand Marx

Mr Barry Nel

Mrs Cecilia Pretorius

Mr Selvin Subban

Ms Julize van Niekerk

These newly elected Council Members were congratulated andwelcomed in the customary manner with sincere wishes for anenjoyable and fruitful year on Council.

Past Presidents who have agreed to serve on Council are:Mr Marco Biffi

Mr Mike de Koker

Mr Len de Villiers

Mr Bruce Doyle

Mr James J van Rensburg

Mr Dries Labuschagne

Mr Henry Moorcroft

Mr Vijay Nundlall

Mr Andrew Thomson

Mr Frank Von Glehn

The Branch Representatives who will serve on Council are:The Collieries Branch - Mr Neil McPherson

The Eastern Branch - Mr Tsietsi Letanta

The Free State Branch - Mr Johan Pienaar

The Northern Branch - Mr Billy Letlape

The Western Branch - Mr Brian Yates

INDUCTION OF THE NEW PRESIDENT Outgoing President Mr Neil Roman introduced incomingPresident Mr Kobus Dekker and called him to the podium to present the pledge of honour on behalf of all Council Members.

“I Jacobus Johan Dekker accept and undertake to faithfully execute theduties of the Mine Ventilation Society of South Africa, to the best of myability, preserve, protect and defend the Constitution of the MineVentilation Society of South Africa.”


Presidential Certificate and gift. He also presented flowers to thewife of the outgoing President as well as to the secretary MarieAckerman and office assistant Madelein Terre’Blanche.

GENERAL The new President asked if there were any matters for general discussion.

CLOSURE The meeting was closed andeveryone was invited for lunchand refreshments.

The chain of office was then handed over to the new President.

Mr Neil Roman invited the Senior Vice President,Marthinus van der Bank to take the podium. The Senior VicePresident presented a pledge of honor on behalf of all membersof Council:

"I Jacobus Marthinus van der Bank as the Vice President undertake onbehalf of all members of Council and accept to faithfully execute theduties of the Mine Ventilation Society of South Africa, to the best of ourabilities, to preserve, protect and defend the Constitution of the MineVentilation Society of South Africa."

Mr Marthinus van der Bank then invited the newly electedCouncil members to move to the reserved seats in the front.

PRESIDENTIAL ADDRESS Mr Jacobus Johan Dekker delivered his Presidential Addressentitled “The MVSSA. A workingsociety” which is published in thisJournal.

VOTE OF THANKS Mr Neil Roman called on Mr Marthinus van der Bank to proposea vote of thanks to the President on his Presidential address.

Mr Marthinus van der Bank called upon Mr Kobus Dekker whothanked the outgoing President and presented him with the

Council 2017/2018


INTRODUCTIONIt is my opinion that the Mine Ventilation Society of South Africa(MVSSA) consist of members that are extremely proud of bothour profession and our heritage.

However, the MVSSA faces some real challenges arising mainlyfrom the current economic and South African climate. This iscomplicated further by non-members' (and even current members)poor familiarity with the objectives and work practices of theMVSSA.

In this Presidential Address a number of issues will be coveredwhich need to be analysed with the aim of highlighting areas thatneed improvement together with the actions necessary to addressthese shortcomings:

• Objectives of the MVSSA;

• Membership benefits;

• Management structure;

• Current committees;

• Proposed new committees; and

• New challenges.

OBJECTIVES OF THE MVSSAThe objectives of the MVSSA are entrenched into its Constitutionand, amongst others, include:

• Promoting personal professional contact both in South Africaand internationally, to serve both the mine ventilation and mineoccupational hygiene professions;

• Disseminating knowledge to assist members in their professionaldevelopment;

• Arranging technical meetings, conferences and symposia onissues related to mine ventilation and mine occupationalhygiene; and

• Publishing information relating to the latest advances in researchand development, to system design, system management andperformance and to show-case practical achievements in theengineering of systems and equipment.

MEMBERSHIP BENEFITSThe Executive and Council believe that MVVSA members benefit from the collective sharing of the science, art and expertisein this profession, that include:

• Access to specialised publications and study workbooks atreduced rates;

• Participation in conferences and symposia at reduced rates;

• Participation in specialised technical development courses;

• Receiving the quarterly journal;

• Access to the members' section of the website;

• Sharing skills, expertise and knowledge with other members;

• Being part of a group of dedicated and specialised professionals.

Despite these apparent benefits, the need has been perceived toimprove the quality of services that the MVSSA should provide toits members. It is also apparent that the prestige and self-esteem inbelonging to the MVSSA needs to be refocussed.

Finally, many of our members who have many years of expertise,must be encouraged to join the growing group of mentors willingto share their experience and collective expertise for the benefit ofyounger members and to instil in them the importance ofbelonging to a professional grouping which is the MVSSA.

MANAGEMENT STRUCTURE OF THE SOCIETYThe MVSSA is administered by a council consisting ofprofessionals who are elected annually and who volunteer theirservices. The only requirement is that council members be fellowsof the MVSSA, who are in good standing at the time of the elections.

The Council consists of:

• Office bearers, elected by the previous Council and forming theMVSSA's executive, consisting of the:

- President;

- Senior Vice President;

- Junior Vice President;

- Honorary Treasurer;

- Honorary Editor;

- Education Committee Chairperson; and

- Immediate Past President.

THE MINE VENTILATION SOCIETY OF SOUTH AFRICA

73rd ANNUAL GENERAL MEETING PRESIDENTIAL ADDRESS

The MVSSA, A working society…

By Kobus Dekker


while growing existing ones, is becoming more apparent if allchanges envisaged in enhancing the professional status of theSociety and in expanding its influence, strength and membership,are to be addressed. The following is a list of potential areas ofinterest and changes that should be considered.

Communication

It is proposed that the current website committee be replaced by acommunications committee with broader mandates. This committee should investigate ways to keep up with modern technology, ways in which social media can be used to bring theMVSSA's services closer to its members (e.g. through Facebook,Twitter, customised apps, etc.). In addition, there is a need toestablish more effective two-way communication beyond thelimited current, traditional domains.

Corporate Governance

A corporate governance committee is required to advise Councilon various facets of the changing business environment. Councilmust be informed and, where necessary, educated on current andexpanding legal compliance requirements and changes.

Awards and prizes

This committee requires the formation of a subordinate taskgroup to manage the awarding of annual prizes presented at theAnnual General Meeting (AGM). This group needs to encourageSociety's members to submit more papers for publication.

Currently the following prizes are awarded at the AGM:

• Gold Medal Award

• Society Award.

• Association of Mine Managers (AMA) Award.

• South African Colliery Managers Association (SACMA) Award.

• Associates Prize (for junior members)

• J.P. Rees Memorial Award.

• Prize for Best Technical Note.

Papers are peer reviewed and adjudicated based on the followingcriteria:

• Content originality;

• Author's contribution to the work;

• Application of the paper to the mining industry; and

• Contribution to the advancement of mine ventilation.

The submissions of papers should be encouraged by increasingmembers' awareness to the importance of continuing professionaldevelopment through research and optimisation work as part ofroutine activities. Junior members should be encouraged to submitpapers for publication as part of their formal professional development. The establishment of a formal structure wherepapers are evaluated and members assisted in this task will facilitate the process.

SAQA Registration

The professional status of our society needs to be enhanced.During some extensive soul-searching conducted in 2006 it

• Seven Fellows elected by the members;

• Five branch chairpersons, one from each branch as elected bythe branch; and

• A maximum of two (2) co-opted fellow members.

COMMITTEESSeveral committees are operational under the direction of theCouncil to complete the annual programme of work devised bythe Council. Essentially the role of Council is to ensure that thatthe work programme is delivered appropriately and effectively.These committees report to Council at the bi-monthly Councilmeetings.

Current committees include:

• The executive and strategy committee consider both operationaland strategic issues regarding the operations of the society;

• The finance committee manages the Society's finances to ensurethat planned activities may be undertaken and that the MVSSAremains financially stable and sustainable;

• The education committee is currently charged with establishingstructures and resources to introduce the new qualifications inline with National Qualification Framework (NQF) requirements;

• The membership committee aims to increase member numbers,manage the membership database and evaluates requests membership grades;

• The conference committee is responsible for the organisation ofthe annual conference;

• The branch committee represents all five local branches as wellas the international branch;

• The editorial committee controls not only the publishing of thequarterly journal, but also all other publications such as thestudy notes and technical books;

• The sponsorship committee aims to find new and innovativemethods to continue the current valuable relationship with current sponsors and broaden the base of these benefactorswhose input and participation is essential in helping fund theMVSSA's activities.

• The website committee is the youngest in terms of its maturityand objectives. It aims to provide a modern and alternative centre of communication. Anyone who visits the MVSSA's website regularly will notice how much more user-friendly thishas become thanks to continual efforts aimed at facilitating navigation through the site to find information on membershipstatus, conferences and workshops, copies of the journal andmuch more.

In addition, several Council members are also assigned the task ofrepresenting the MVSSA in other committees and institutionssuch as the GEEs, SAIMM, SAIOH, SABS, etc. to ensure that theMVSSA and its members are supported and represented in various industry initiatives.

PROPOSED NEW COMMITTEESLooking ahead, the potential need for forming new committees


became apparent that this ambition would be best satisfied by registering as a Professional Association.

Three scenarios were investigated and considered by Council,namely:

• The MVSSA should remain an independent (and unregistered)voluntary association;

• The MVSSA should become a voluntary association in partnership with an existing professional body; and

• The MVSSA should register as an independent professionalbody with the South African Qualification Authority (SAQA).

During the Council meeting held on 30 September 2016 it wasdecided that the option of registering the MVSSA as an independent professional body should be explored further.

To pursue this resolution, the SAQA Registration committee mustbe established to investigate the due process to be undertaken andprovide council with findings, suggestions, and options for registration, considering:

• The overall registration plan (including potential costs to theMVSSA);

• Formulation and establishment of a formal continuous development programme;

• Establishment of a code of conduct and ethics committee toenforce this; and

• Formulation of a transformation plan.

Constitution

As times change, the rules and guidelines that are entrenched inthe Constitution of the MVSSA need to be reassessed and reevaluated. A constitution committee would fulfil this purpose.The committee will be tasked to evaluate if the constitution needsto be streamlined, or if new bylaws need to be added or othersrepealed, and if so, for what purpose. Also, given all the changesenvisaged and described in this address, alignment must beensured between these new plans, the Constitution and its by-laws.

It is important for members to be in touch with the MVSSA'sConstitution, an instrument vital in providing the necessary guidance for their professional development and growth.

IMVS

Having accepted the challenge of growing in order to remainviable and develop, the need has been recognised to look beyondSouth African borders to enhance the skills of members and thoseof professionals in other countries and also to provide additionalopportunities for our members. Council has approved to hold anexploratory workshop with the MVS Australia to form an opinionas to whether the establishment of an International MineVentilation Society (IMVS) would be both feasible and beneficialto both Societies and other similarly-minded associations acrossthe world. This workshop is scheduled for 26 July 2017.

CHALLENGES TO EXISTING COMMITTEESThe MVSSA is currently facing several challenges, and the existing committees will continue to confront these issues.

Membership fees

One of the biggest challenges on an annual basis is the review ofmembership fees. The difficulty is in aligning the need to increasebadly needed income in view of the increasingly demandingfinancial squeeze to which this part of the world has been subjected for almost a decade that has affected not just the Societybut also individual members and the South African mining industry. This income is essential to provide the funds in support ofexisting and new projects and ultimately to balance the books atthe end of each year.

As indicated in the graph below, membership fees were onlyincreased twice in the last twelve years.

Publication sponsorships

Income from the industry in the form of sponsorships from advertisements in the journal and in support of conferences andworkshops, is another major contributor to the financial incomestream.

One of the big challenges is to motivate financial support throughthese trying times.

In terms of publications, sales need to be extended beyond thecurrent membership to attract an audience extending beyond theSociety. Funds generated from sales to non-members could be utilised to discount rates to members.

Conference

The annual conference is still a major event in the MVSSA's calendar. A vexing question is whether members, particularly themore junior ones, see this as a valuable opportunity to acquireknowledge, network and be exposed to novel technologies in thisarea of expertise. Once more, cross-subsidisation may allow levelsof affordability that will encourage greater member participation -particularly where employers do not afford the requisite financialassistance.

Communication

There is a need to improve levels, regularity and effectiveness ofcommunication with members. Although this should be easierusing existing modern technologies such as the website and socialmedia combined with the use of computers, laptops and smart-phones, communication with members still has some way to go torealise the fullest potential.


Journal

To reach a higher level of professionalism, the journal must attainaccreditation from the Department of Higher Education andTechnology (DHET). This requires the publication of originalresearch and technical work.

Education

As education of ALL members is a continuous process, theMVSSA must continue to support all members and, particularly"up-and-coming" young talent, to grow and develop. The holdingof an annual junior members' symposium is deemed to be onesuch vehicle to motivate such development at grass-roots.

In parallel with this, the current drive for the development andregistration of the profession's qualification must be completed andmust enjoy the support of the Group Environmental Engineers.

Constitution

Members must be able look up to the various aspects of the

constitution and its bylaws to guide their professional journey. It istherefore important that the Constitution and by-laws of theMVSSA become flexible enough and reshaped if necessary tokeep pace with the changes within this profession, the industry itserves and civil society.

CONCLUSIONIn the opening of this address I stated that in my opinion theMVSSA consists of members that are extremely proud of bothour profession and our heritage. I hope that I have demonstratedthis to be true despite the numerous challenges it faces.

The MVSSA is a living, working society dedicated to a broad professional audience. Hopefully members realise that they are anintegral part of this wonderful and prestigious association, that theMVSSA is alive and can provide meaningful support and guidance to attain higher levels of personal and professionalachievement.


E.I. Acuña1, R.A. Álvarez1, S.G. Hardcastle2

1New Level Mine Project (NLMP), El Teniente, Codelco, Chile.2CANMET-MMSL, Natural Resources Canada, Sudbury, Ontario,Canada

ABSTRACTVentilation for underground mines is undergoing important developments to improve system effectiveness and performance.Ventilation systems can be divided into two categories: the mainsystem, responsible for bringing fresh air from surface to the vicinity of the working faces, and then the auxiliary system,responsible for delivering that air to the working faces. Each system employs a fan, or fans, to provide the required pressure topromote the flow through their respective areas. The two systemstogether are responsible for diluting and removing the contaminants generated in the mine to secure an environment thatis healthy for the workforce and suitable for the operation ofequipment, and thereby guarantee that production happens asscheduled. In particular, the task is critical at the auxiliary level, asit is at the working faces that the generation of contaminants isusually concentrated. Ventilation On Demand (VOD) is becomingpopular, as some of its applications have demonstrated that bothmore effective and efficient ventilation for working faces can beachieved. This paper presents a study developed to simulate threedifferent strategies for keeping concentration levels within requiredlimits, in order to compare the effectiveness and efficiency of theauxiliary systems. Applying the first strategy, the base case, theauxiliary fan is used continuously; for the second strategy, the auxiliary fan is used only when the equipment is in the workingarea and for the third strategy, the auxiliary fan is used only whenneeded to keep contaminant concentrations under a certain predefined limit value. The effectiveness and efficiency of the threestrategies are then compared to demonstrate the benefits of thesecond and the third strategy against the base case.

INTRODUCTIONAn underground mine ventilation system is typically composed oftwo elements, each with a specific purpose, namely a main systemand auxiliary systems. The main system's function is to bring thefresh air from surface to the vicinity of where mining activity istaking place, i.e., the work faces, and then take that air once usedback to surface. The auxiliary systems are responsible for creatinga circuit whereby the air is taken from the primary air routes to theactual working areas to dilute and remove contaminants and thento rejoin the primary circuit. Fans, a component of both systems,generate the necessary pressure that is needed to overcome thefriction and shock losses occurring throughout the airflow paths of

A theoretical comparison of ventilation on demandstrategies for auxiliary mine ventilation systems

the mine. Fans also help achieve the desired airflow distributionaccording to the mine's activity schedule. However, mines aren'tnecessarily active twenty-four hours a day, seven days a week, norare they performing the same activities at the same place everyday. In a week, a mine could have anywhere between ten andtwenty-one work shifts, depending on whether they work on week-ends, of anywhere from 8 to 12 hours duration (i.e., 2 or 3 perday). During a shift, the mine is not always performing the scheduled activities continuously, as the workforce has to travel toand from surface to the underground working areas, mobilise theequipment, perform safety and maintenance functions, be briefedand provide debriefing. Also, during the different shifts there canbe several breaks such as lunch-time, when the workers retreatfrom the active areas or faces. Furthermore, there can be significant periods of time when the mine is inactive and no personnel are underground, such as for an explosive blast to liberate the rock. Given that the spatial and temporal distributionand intensities of activities are constantly changing, accordinglythe mine's airflow requirements are ever changing and need frequent redistribution. However historically, due to a lack ofcontrols, the mining industry has tended to over-ventilate a working area, the number of such areas, and the mine as a wholeso as not to hinder production. The degree of this oversupply is afunction of the resources, manpower and infra-structure a minehas for timely redistribution of the airflow. Consequently, the mining industry has identified a potentially significant opportunityto save energy while delivering the airflow requirements and main-taining an effective operation (Hardcastle, 2006).

This approach, now commonly referred to as Ventilation OnDemand (VOD), is not a new consideration for both auxiliary andmain mine ventilation systems as shown in the following exampleearly references taken from previous congresses. Rustan (1979) discussed the regulation of fresh air quantities by diesel vehicle situation control amongst other developments for Swedish mines.Pickering and Robinson (1984) described methane monitoring asan integral part of controlled air recirculation in auxiliary and district ventilation circuits for coal mines in the United Kingdom.McPherson (1988) in a keynote address looking to the future ofsubsurface ventilation states that control was achievable at thattime and the idea of coupling continuous environmental monitorwith planning functions dated back to the 1960s. Hatakeyama(1992) presented a paper describing realtime network analysisbased upon the input of multiple anemometers with the expansionto include carbon monoxide and methane gas monitoring,concentration prediction and control for coal mines in Japan.

The particularly case studied here is for auxiliary systems delivering air to dead-end active areas in the mine, for either production or development, via a fan and ducting arrangement.Here, VOD has focused on delivering a certain volume of air tomeet a specific airflow requirement, for example 0.06m3/s perkW(100 cfm/bhp; cubic feet per minute per engine brake horse-

Peer reviewed for Journal publication

Original paper presented at the the 10th International Mine VentilationCongress 2014


power) for diesel powered equipment in Ontario mines (Ontario,2013 and Chile, 2004). However, the main interest from a workersafety perspective and historically is to limit exposure to a contaminant to within safe levels, as set out in health and safetyregulations. This suggests the focus should be on the quality of theairflow and not just the volume delivered to the face. The questionthat arises nowadays is whether an air quantity rule as opposed toquality, is more than sufficient to guarantee air quality for theworkforce, or should it be changed to a quality-based approach?

The theoretical approach presented in this paper was developed toprovide a mechanism to help evaluate three different ventilationoperational strategies for auxiliary fan systems. The first strategy,the base case, is to ventilate according to a common practice ofrunning an auxiliary fan without stoppage across multiple shifts oreven indefinitely; the second strategy is to provide an airflowrequirement (such as100cfm/bhp) only when the diesel equipmententers the working face, i.e., responding to monitored activity; andfinally, the third strategy is to ventilate the working face accordingto the contaminant concentration, ensuring a given limiting valueis never exceeded. The upcoming sections present the mathematical model used to develop the simulation of the contaminant concentrations for the auxiliary system, describe theventilation strategies and how they affect the simulation ofcontaminants, present the results obtained, conclusions and the lessons inferred from this study.

2. MATHEMATICAL MODEL FOR CONTAMINANT DILUTIONAuxiliary systems are usually referred to as forcing, exhausting, oreither of these with an additional overlap element (McPherson,1993), depending on their physical configuration. Figure 1 presents a forcing auxiliary system. Independent of the type ofauxiliary system used, the main objective of the auxiliary system isto dilute and remove the contaminants produced within the working face to guarantee a safe and healthy environment for theworkforce, and suitable conditions for the operation of dieselequipment. For this purpose, the auxiliary system provides a flowof fresh air to the working area which mixes with the contaminants generated by mining activities within the area. Thiscontaminated air then leaves the working area as more fresh air isintroduced by the auxiliary system.

Although auxiliary fan systems have been utilised for a considerable time in underground mines, most of the researchrelated to their usage has been concerned with the correct modelling of the system's characteristics and not the method ofoperation. For example, Duckworth and Lowndes (2003) studiedthe variables that define the system such as leakage and resistance,in order to accurately predict the volumetric delivery of air thatwill be achieved at the face for a specific auxiliary system configuration. Some work has focused on how to design an auxiliary system for a regular heading (Mirakovski and Krstev,2002) and long excavations with multiple headings (Calizaya andMousset-Jones, 1994). Particular attention has been given to theplacement of fans and minimising the leakage within the system(Calizaya and Mousset-Jones, 1997). Leakage from a ventilationsystem not only represents a loss of energy, but it is also a loss ofcontaminant dilution capacity. Some recent work has applied linear optimisation techniques to select auxiliary fans and their

operational settings for a working period, but only considering thepossibility of changing the blade angle settings (Acuña et al, 2010).

Figure 1. Example of auxiliary forcing system

Additionally, considerable work has been dedicated to justifyingand developing VOD systems (Hardcastle et al, 2006, Allen andKeen, 2008 and O'Connor, 2008). The observation-based study ofHardcastle et al (2006) showed one mine to be devoid of activitysignificant 44% of the time and that auxiliary fans for the activitiestaking place at specific locations only needed to operate on average 20% of the time. O'Connor (2008) went on to show thatvariable frequency drives controlling the speed of the fans andthereby the quantity they deliver could also be justified considering the variable requirements and duct length through thelife of the system. Such work has concentrated on showing that, incomparison to the conventional practice of running fans continuously, it is cost effective to install such VOD systems.

However, it is unclear as yet what operational method is preferable: to remain with an event-driven quantity-basedapproach, or to move towards a quality-based control process. Inorder to understand the implications of both, the concentration ofcontaminants needs to be determined in the working area. Thisstudy presents the initial results of a simulation used to model theconcentration within the working area.

The dilution process as described by Hartman et al (1997) byEquation (1) was used to calculate the time that it will take to reachthe expected concentration of a contaminant in a working area.

(1)

where Y is the volume of the working area, Q is the volume of theincoming airflow, Qg is the gas in-flow, Bg is the concentration ofthe contaminant in the incoming airflow, xo is the initial concentration of contaminants in the working area and x is theconcentration at time τ. Based on Equation (1), the concentrationof contaminants in the working area can be calculated for anypoint in time.

Occupational health and safety regulations typically contain a legalrequirement to limit exposure to harmful contaminants in the airto under a prescribed level. These are often referred to as


3. VENTILATION STRATEGIES AND CASE STUDYThree ventilation strategies were defined and assessed. The firstone is still the conventional practice of auxiliary fan operation formany underground mines where the fan is turned on at the beginning of a shift or simply left on all the time. In the secondstrategy, event based, the auxiliary fan is turned on only when theLHD enters the working area, and then turned off after it exits.Finally, the third strategy is to turn the auxiliary fan on only whenthe concentration of a contaminant reaches a certain thresholdwarning value (TWV) to prevent it exceeding a safe level duringthe shift. Table 1 summarises the three strategies and the conditions that differentiate them.

All of these strategies share the goal of diluting and removing thecontaminant, guaranteeing a safe and healthy work environment.The intent of this study is to compare both the level ofcontaminants reached and the energy consumption under eachstrategy in order to evaluate potential energy savings. The contaminant level will be used as the effectiveness index and theenergy consumption as the efficiency index. The first strategy willbe used as the baseline to evaluate the two VOD strategies: eventand quality driven.

The hypothetical case study considers a ~300 kW (400 bhp, brakehorsepower) LHD operating alone in a working area as per theone shown in Figure 1. The LHD was the only expected source ofdiesel engine contaminants in the working area. Under these conditions, the concentration of the contaminants is a function ofthe level of contaminants in the exhaust of the LHD, which wasassumed to be ~10, 7.5 & 5 x 10-5 m3/s (0.2, 0.15 and 0.1 cfm), torespectively simulate high, medium and low contamination scenarios that the LHD could produce. These values were generated to simulate, and not surpass, the expected concentrationin the heading according to the TWA. Additional field work is required to validate this numbers. The auxiliary fan was able todeliver ~20 m3/s (40,000 cfm) to the working face when turned onand zero flow otherwise. The initial concentration in the workingarea was assumed to be 0 ppm, and the exposure or action limitwas set at 5 ppm. The volume of the working area considered was~3400 m3 (120,000 ft3). In every 10 minute cycle, the LHD wasconsidered to be 3 minutes in the working area and 7 minutes out-side travelling to the ore pass, dumping the ore and then returning.

4. RESULTS OF STRATEGIES SIMULATIONThe three strategies were simulated with the three scenarios for thecontaminant gas and the input data detailed in the previous section. The results are presented in Table 2. Figures 2, 3 and 4present the simulation of the different strategies for the first scenario. The horizontal axis displays the time in hours, and thevertical axis the concentration of the contaminant in ppm. The

Permissible or Occupational Exposure Limits, or threshold limitvalues (TLVs), and those normally cited within North Americanand Chilean regulations, as published by the ACGIH, are 8-hrtime weighted average (TWA) limits assuming exposure five days aweek. In the workplace, these limits may have to be adjusteddownwards to accommodate extended work-shifts or different altitudes in the particular case of Chile. Furthermore, dependingon the accuracy of the contaminant measurement method an action limit for the mine to take corrective action or withdraw theworker may be at an even lower value. These values will differdepending on the contaminant and the regional legislation applying to the mine. Depending on the contaminant there mayalso be short-term exposure limits, acceptable for 15 minute periods possibly with a limited number of excursions per shift, andceiling exposure values representing the maximum exposure concentration regardless of duration.

A load haul dump (LHD) machine is the primary mover of bro-ken rock from the working faces of a mine. These machines are powered by diesel engines, and produce a variety of combustionproducts that need to be rendered harmless; their dilution oftenbecomes the primary ventilation design consideration due to thesize of their engines. Among the contaminants generated by theLHD, the main ones are DPM (diesel particulate matter), NitricOxide (NO), Nitrogen Dioxide (NO2), Carbon Monoxide (CO)and Carbon Dioxide (CO2), but depending on their generationrate in relation to its exposure limit, only one of them may dictatethe air volume and its duration time needed for dilution.

Within the context of highly mechanised Canadian base metalmining industry, which was the focus of this study, diesel emissiondilution is the prime ventilation driver when the system is operating, dust is typically minor. Heat is a secondary concern,and although relevant, it would need to be subject of a moredetailed analysis and modelling considering dilution and heattransfer. The case for considering the development of block cavemines in Chile such as the New Level Mine, is similar to theCanadian context.

In this hypothetical study, only one LHD is considered to be operating and generating contaminants in the working area.Furthermore, the analysis will only consider a single contaminant,namely that with the highest demand to represent the worst casescenario. Other contaminants would have been diluted both earlier and below their respective limits. The other gases do notneed to be considered in Equation 1 because of their negligible contribution to the overall flow within the modelled volume. Thishypothetical study also considers the contaminant to be stable andnot being lost through a chemical reaction.

An expected schedule of the entrance and exit times of the LHDfor the working face was compiled to simulate the operationunderground. This schedule is deterministic, being used as a firstapproach, and would need to be adjusted according to each particular case. Additionally, an expected generation ofcontaminants was assigned to the LHD, and finally, Equation (1)was used to simulate the expected concentration of contaminantsin the working area. The resultant contaminant levels were thenused to decide how to operate the auxiliary ventilation system, notonly within assigned limits but also to do so in the most efficientway.

Strategy Rule

Conventional Fan always on

Event Fan on when LHD is in the working area; off otherwise

Quality Fan on when warning value is reached or exceeded; off otherwise

Table 1. Strategies and conditions


bottom line set at a value of zero or one represents the operationof the fan. In the case of the conventional strategy, the fan is on during the full shift. In the case of the quantity strategy, the fan isturned on, and the value set to one, when the LHD is in the working area and then turned off, and value set to zero, when theLHD is out of the working area. Finally, for the quality strategy,the fan is turned on only when the concentration goes over thethreshold warning value (TWV), a trigger value set manually toactivate the fan and avoid having the contaminant concentrationexceed the limit concentration value (LCV) of 5 ppm defined forthis analysis.

As can be observed in Figure 2, the difference between the LCVline and the concentration line is an indicator of how much energy can be saved. Clearly, the first strategy has plenty of roomfor improvement and strategies 2 and 3 are able to gain most of it.In the second and third scenario, the observed behaviour of the concentration curve is similar, but with reduced concentrationvalue according to lower levels of contamination for both the conventional and the quantity strategy. For the quality strategy, theresults observed in terms of the concentration curve are similar,but the use of the fan is further reduced to achieve larger energysavings.

The first strategy, the conventional approach, proved to be aneffective approach, not letting the contaminant concentrationexceed the target of 5 ppm in any of the three scenarios. The maximum concentration recorded for the first scenario was 3.28 ppm however the time weighted average was only 1.19 ppm,indicating that airflow to the working area was more than sufficient. Therefore the solution is effective but may not be efficient whereas it is expected that the other two strategies canimprove it further in terms cost while staying under the thresholdof 5 ppm.

Figure 2. Simulation of conventional strategy

Figure 3. Simulation of quantity strategy

Figure 4. Simulation of quality strategy

The event based quantity approach, the first VOD strategy, wasable to reduce the energy consumption by 76% compared to theconventional approach. While being equally effective in keepingthe maximum concentration at or below the 5 ppm limit value, asrequired, the time weighted average for the worst case increasedfrom 1.19 to 4.61 ppm. The event-quantity approach providedexactly the same percentage energy improvement for every scenario as the benefits are just a function of the time of the LHDin the working area. The shorter the amount of time that theLHD is in the working area, the larger will be the improvementthat this type of operation for the fans can generate, compared tothe conventional operation. In all instances, both the maximumand TWA concentrations increased.

The quality approach to operating the auxiliary ventilation systemwas able to further improve the energy performance over theevent-quantity strategy. The improvements, as summarised inTable 3, ranged from a modest 0.61% in the first high pollutantrate generation scenario through to significantly out performing

Table 2. Scenario resultsContaminant flow ~10 x 10-5 m3/s(0.2 cfm)

Strategy Energy Max Conc. (kWh) (PPM) Improvement TWA Conc.

Conventional 534 3.28 0.00% 1.19

Event 127 5.00 76.25% 4.61

Quality 124 5.00 76.86% 4.58

Contaminant flow ~7,5 x 10-5 m3/s(0.15 cfm)


Conventional 534 2.46 0.00% 0.89

Event 127 3.75 76.25% 3.46

Quality 93 5.00 82.57% 4.52

Contaminant flow ~5 x 10-5 m3/s(0.1 cfm)


Conventional 534 1.64 0.00% 0.59

Event 127 2.50 76.25% 2.31

Quality 61 4.97 88.51% 4.49


the conventional approach by 12% for the low pollutant generation scenario. As can be seen in Table 2, the qualityapproach maintains the maximum concentration of contaminantsacross all scenarios much closer to or just below the action limit of5 ppm. Correspondingly, the TWA concentrations also increasedcoming closer to the action limit.

It is clear that the quality approach improvements in terms ofenergy use come from the increase in the time weighted average(TWA) concentration in the heading throughout the shift. As canbe observed in Table 2, the TWA of the quality strategy as expected is the highest, and the greater the difference with theTWA of the other two strategies, the larger the improvement.

This overall exercise shows the potential to quantify, in terms ofenergy, the benefits of VOD systems while maintaining the concentration of pollutant within a set limit to ensure the healthand safety of the workers in an auxiliary ventilated area.Consequently, it has been shown that while both event based andquality based control are effective, quality based control could bemore efficient. However this analysis does not consider the logistics to implement the higher complexity control system or itsactual operational logistics. Furthermore, it does not addresswhether the volume supplied under the continuous deliveryoption, which might be prescribed by regulation, is appropriate.

It is important to state that the analysis is based in an idealisedoperation and generic pollutant generation values. However thesimplification still provides an example of how the VOD strategycan improve the efficiency of an auxiliary ventilation system.Nevertheless there are a number of paths for further research thatwould help bridge the gap between the current model as used inthis study, and mining reality. Some of them are listed here:

• The schedule of the equipment (LHD in this case) should beadjusted to each operation and would benefit from including astochastic component.

• The inclusion of other pieces of diesel equipment.

• Considering the significance of the equipment spending most ofits heading occupancy time at the working face and a short transit time, and variations thereof.

• For regular and long headings, how does the "plug" ofcontaminant produced near the working face gradually dispersethrough the heading?

• How the leakage in the ducting affects the dilution process forboth forcing and exhausting auxiliary systems?

• Where is the best position to place the sensors?

5. CONCLUSIONSA theoretical approach has been developed to simulate the concentration of contaminants that could occur when using threedifferent strategies to ventilate a working area under different

contaminant generation levels and operating scenarios. The resultsof the simulation approach used demonstrated that it was possibleto save energy while maintaining a prescribed condition, such asthat which are based upon assuming continuous activity at a work-place. All strategies tested were able to limit the concentration of apollutant within a prescribed limit. This would be representative ofensuring a safe and healthy environment for the operator of theLHD or any other worker that would enter into the working area,but only within the limitations of the analysis performed in thisstudy. As expected, both of the ventilation on demand strategiesout-performed the conventional approach by virtue of them beingactivated by the diesel LHD or its by-product.

Using this approach, it was possible to identify a significant advantage of the event based air quantity and quality dictated fanoperation approaches using the energy consumption index for thesecond and third scenario. Depending on the situation the incremental benefit of a quality approach over event driven (i.e.the vehicle) may not be significant. For the system and processdefining data used, under the first scenario the benefits were notsignificant because the contaminant concentration levels beinggenerated did not leave much room for improvement between thequantity and the quality strategies, given the available incomingairflow of the auxiliary system. As contaminant generationdecreased, the improvement of a quality strategy over quantity increased.

The ability to theoretically predict the savings for this type ofoperation is important, and depending on the data available thisshould be more evident with the development of a more detailedmodel, using more realistic data and possibly including temporaland spatial variability. As indicated, numerous gaps have beenidentified as potential paths for improving the simplified modelpresented in this study.

In terms of cost, it is still unclear what the effect of turning a fanon and off so often could be on its failure rate, or the expectedadditional maintenance that would be needed to guarantee that afan will always be available to work as required during the shift.Another consideration would be to reduce the fan to a lower speedwhen not required, significantly saving power but reducing thelikelihood of fan or motor failure, and other operational problemssuch as duct rupture on starting the fan.

Another consideration would be to try and convert the qualitydriven strategy into a more predictable event-quantity drivenapproach. Here, relating pollutant generation of a specific activityor specific vehicle to a limited number of airflow delivery rateswould be considerably easier than a reactive approach.

REFERENCESAcuña, E., Hall, S., Hardcastle, S. and Fava, L., (2010). The application of a MIP model to select the optimum auxiliary fan and operational settings for multiple period duties. INFOR, Vol. 48, No. 2,May 2010, pp. 89-96.

Allen, C. and Keen, B., (2008).Ventilation on demand (VOD) project - Vale Inco Limited, Coleman Mine. Proceedings of the 12th USMine Ventilation Symposium, Reno, Nevada, pp. 45-50.

Calizaya, F. and Mousset-Jones, P., (1994). Computer program for solving complex auxiliary ventilation systems. SME Transactions, Vol.296, pp. 1887-1893.

Table 3. Improvements of quality strategies over quantity strategies

Contaminant Generation Scenario Improvement

First (Qg = 0.2 cfm) 0.61%

Second (Qg= 0.15 cfm) 6.32%

Third (Qg= 0.1 cfm) 12.26%


Calizaya, F., and Mousset-Jones, P., (1997). Estimation of leakagequantity for long auxiliary ventilation systems. Proceedings of the 6thinternational Mine Ventilation Congress, pp. 475-478.

Chile, DecretoSupremo N°132, Reglamento de Seguridad Minera, Ministerio de Minería. Capítulo Tercero y CapítuloCuarto, 2004, pp.46-51. http://www.sernageomin.cl/pdf/mineria/seguridad/reglamentos_seguridad_minera/DS132_Reglamento_SEGMIN.pdf

Duckworth, I.J., and Lowndes, I.S., (2003). Modelling of auxiliary ventilation systems. Mining Technology, Vol. 112, No. 2, pp. 105-113.

Hardcastle, S.G., Kocsis, C., and O'Connor, D., (2006). Justifyingventilation on demand in a Canadian mine and the need of process based simulations. Proceedings of the 11th US Mine VentilationSymposium, The Pennsylvania State University, University Park,Pennsylvania, pp. 15-27.

Hartman, H.L., Mutmansky, J.M., Ramani, R.V., and Wang, Y.J.,(1997). Mine ventilation and air conditioning. John Wiley & Sons, Inc.New York.

Hatakeyama, Y., Sakai, T., Kimura, Y., and Inoue, M., (1992). Realtime ventilation network analysis based on anemometers in an underground coalmine. Proceedings of the 5th Interna-tional Mine VentilationCongress, pp. 345-350.

McPherson, M.J., (1993), Subsurface Ventilation and EnvironmentalEngineering, London: Chapman & Hall.

McPherson, M.J., (1988). Subsurface environmental engineering - A lookinto the future. Proceedings of the 4th International Mine VentilationCongress, 1988, pp. 19-27.

Mirakovski, D.G., and Krstev, B., (2002). Design process and equipmentselection for auxiliary fan ventilation systems. Application of Computerand Operational Research in the Mineral Industr, pp. 383-390.

O'Connor, D.F., (2008). Ventilation on demand (VOD) auxiliary fan project - Vale Inco Limited, Creighton Mine. Proceedings of the 12th USMine Ventilation Symposium, Reno, Nevada, pp. 41-44.

Ontario (2013), R.R.O. Regulation 854, Section 183.1 (3), Minesand Mining Plants, R.S.O. 1990 Occupational Health and SafetyAct, http://www.e-laws.gov.on.ca/html/regs/english/elaws_regs_900854_e.htm

Pickering, A.J., and Robinson, R., (1984). Application of controlled airrecirculation to auxilaiary systems and mine district ventilation circuits.Proceedings of the 3rd International Mine Ventilation Congress,pp. 315-322.

Rustan, A., (1979). Review of developments in monitoring and control ofmine ventilation systems. Proceedings of the 2nd International MineVentilation Congress, pp. 223-229.


together with soil backfill. Moreover, inorganically cured foam, gel,liquid nitrogen and carbon dioxide are also used in controllingsome local coal fires. However, these technologies have limitations, for instance, excavation is costly, environmentally disruptive and dangerous, and the fire may spread more quicklyafter the excavation due to the abundant oxygen penetration.Water and grout injection together with soil backfill cannot extinguish fires in high places which are common in coal fire areas.

Inorganically cured foam and gel, which are characterised by smallflow, high cost and limited diffusion range, have difficulties in controlling coal fires with large areas and high temperature. Thestorage and gasification equipment of liquid nitrogen and carbondioxide are complex and costly, so it is difficult for these two technologies to control coal fires where fissures always widely distributed.

Three-phase foam technology has been used to fight coal fires andachieved good results in recent years (Cao, et al., 2012), but thehigh cost limited its wide application.

Quick displacement of the large amount of heat contained in thefire area is the key to effectively control coal fires. Water has a largespecific heat capacity and vapourisation heat, and is easy to obtainwith low cost, which make it the best material to effectively displace the abundant heat contained in fire area. Therefore, thecore principle to efficiently extinguish coal fires with the lowest costis to improve the utilisation of water.

In recent years, water mist technology, characterised by non-pollution, low water consumption, low cost and good fire fightingeffects has been used in fighting library fires, civil architectures,transportation, storage of fuel and other places. However, watermist technology has not been applied in the prevention and control of coal fires. Fires frequently occur in abandoned roadwaywith large space, high temperature and cover a large area.

There are always fires existing near mine roofs and walls of the abandoned roadways. Traditional fire fighting methods cannotefficiently extinguish such fires with low cost. However, the good performance in diffusion and extinguishment makes water misttechnology a new choice to solve this problem.

In this paper, the characteristics and extinguishing mechanisms ofwater mist are first analysed, the water mist coal fire suppressionsystem is then developed according to the characteristics of fires inthe abandoned roadway.

Finally, this system is applied to extinguish a fire in the abandonedroadway in the Anjialing Open Pit Mine. The results showed thatwater mist technology extinguished coal fires efficiently at minimum cost, and the fire did not burn back anymore. Theresearch provides an important example for the efficient and economical control of coal fires with large area.

A new approach to extinguish coal fires by using watermist technology


D. Wang, Z.Shao, F. Han, X. Zhu& Y. ZhangSchool of Safety Engineering, China University of Mining &Technology, Xuzhou, Jiangsu,China

ABSTRACTCoal fires are serious health and safety hazards throughout theworld. In this paper, the characteristics and extinguishing mechanisms of water mist are first analysed, which then form thebasis for a water mist coal fire suppression system in abandonedroadways. Finally this system has been applied to extinguish a firein an abandoned roadway in Anjialing Open Pit Mine. The resultsshow that the temperature and the concentration of CO declinedrapidly within a short time, and the fire was extinguished quicklyand efficiently at minimum cost. Moreover the fire did not burnback based on monitoring. We concluded that the water mist technology, characterised by small amount of water consumption,low cost, non-pollution, showed favourable prospect in extinguishing coal fires. The research provides an important reference for the governance of coal fires in the future.

1. INTRODUCTIONCoal fires result in the burning (mostly smouldering) of largeamounts of coal underground. They occur in many coal-producing countries such as China, India, Indonesia, the UnitedStates and South Africa. (Stracher, 2004; Stracher and Taylor,2004; Zhang et al., 2004; Kuenzer, 2005; Kuenzer et al., 2008;Kuenzer and Stracher, 2012). This hazard has become worse sincethe beginning of the industrial revolution (Stracher and Taylor,2004). Coal fires will not only burn away non-renewable coalreserves, release toxic gases and substances, but also lead to thedeath of vegetation (Finkelman, 2004; Yang et al., 2005;Finkelman and Stracher, 2011; Rathore and Wright, 1993). Chinasuffers the most serious coal fires in the world. An estimated 20million tons of coal are burned each year in China, which is equalto Germany's annual hard coal production (Kuenzer, 2007).

Coal fires also lead to the release of large amounts of greenhousegases, such as CO2 and CH4 (Dai et al., 2002). Kuenzer et al.(2007) calculated that coal fires in China alone account for ~0.1%of all global human-induced CO2-equivalent green-house gasemissions. Therefore, it is urgent to extinguish existing coal firesefficiently, which will ensure the security of national energy,improve the ecological environment around fire areas and protectthe health of residents.

To prevent and mitigate the hazard, various traditional techniqueshave been developed and applied all over the world over the past50 years. Currently, the main technologies are excavating theburning coal and its overburden, or injecting water and grout



2. CHARACTERISTICS AND EXTINGUISHING MECHANISMS OF WATER MISTThe term "water mist" refers to fine water sprays in which 99% ofthe volume of the spray is in drops with diameters less than 1000microns (NFPA750, 2010). NFPA 750 has divided the dropletsproduced by a water mist system into three classes to distinguishbetween "coarser" and "finer" droplet sizes within the 1000microns window. The classifications are: Class 1 mist has 90% ofthe volume of the spray (Dv0.9) within droplet sizes of 200 micronsor less; Class 2 mist has a Dv0.9 of 400 microns or less; and Class 3mist has a Dv0.9 value larger than 400 microns.

There are varieties of methods to generate water mist, such asimpingement atomisation, ultrasonic atomisation, high pressureatomisation, centrifugal atomisation, twin-fluid atomisation, and soon. Centrifugal atomisation and twin-fluid atomisation are especially practicable for extinguishing coal fires covering largeareas, for both methods can provide Class 1 mist with large volume flux and droplet momentum under relatively low waterpressure.

The mechanisms of water mist in extinguishing fires are essentially different from traditional water injection. Besides thecooling effect on the hot surface of combustible material, watermist also extinguishes coal fires by smoke cooling, oxygen diluting, radiant heat attenuation and kinetic effect on the flame(Liu, et al., 2003).When droplets impinge on the solid surface, theheat flux released from the high-temperature surface (higher than150°C) could be as high as 106 W/m2 (Wendelstorf, et al., 2008).The cooling efficiency of the water mist is tens of times higherthan traditional water injection due to the small droplet sizes. Andfor the same reason, these fine droplets could suspend for a longtime and disperse widely in the limited space, which enables watermist to reduce smoke temperature quickly and attenuate radiantheat. Both mechanisms above would result in the reduction of theheat migrating back to the burning zones. In the process of heatexchange, large quantity of water evaporates into water vapourwith 1600 times of volume expansion. The large volume of steamcould decrease the oxygen concentration in the limited space,which would reduce the fire extinguishing time dramatically.Moreover, the impact effect of the droplets with large momentumwould stretch and tear apart the flames, which would turn theflames into unstable state and result in the extinguishment of fires.

From the above analysis, we could find that water mist is a promising method for extinguishing the widely distributed coalfires burning in abandoned roadways, which are characterised by,high temperature covering a wide area. Water droplets could dis-perse over the whole limited space and reach the burning surfaces (especially the roof), so the contact area between waterand high temperature materials as well as the utilisation of waterare improved, which enables water mist a full play to the advantage of surface and smoke cooling, oxygen diluting, radiant

heat attenuation and kinetic effect on the flame. Consequently,coal fires burning in abandoned roadways could be extinguishedefficiently at minimum cost.

3. COAL FIRE SUPPRESSION SYSTEM USING WATERMISTA fire in an abandoned roadway can be uncovered by twoapproaches: drilling and excavation, which will form a boreholeand cavity that penetrate into the fire area. The coal fire suppression system using water mist was developed aiming at thesetwo kinds of extinguishing approaches, which contained a twin-fluid water mist coal fire suppression device that atomised by atwin-fluid nozzle, and a single-fluid water mist coal fire suppressiondevice that atomised by a centrifugal nozzle. The water mist generated by the twin-fluid water mist coal fire suppression devicecovers larger space because it takes not only high pressure waterbut also high pressure nitrogen as the power source. So it wasapplied at the borehole with large space, while the single-fluidwater mist coal fire suppression device was applied at the cavitywhich was relatively open (Figure 1).

In the twin-fluid water mist coal fire suppression device, waterwould be pumped through the high pressure hose No. 1 and themetal pipe in sequence, and finally arrives at the atomising nozzle.Meanwhile, nitrogen is driven through a high pressure hose No. 2and meet the water at the atomising nozzle. Under the impact ofthe high speed nitrogen, the water would be forming into finedroplets and be sprayed out of the nozzle

The working parameters of the twin-fluid nozzle are shown inTable 1. The metal pipe is connected by short pipes with screwthreads. The number of short pipes depends on the depth of thefire, which could be as deep as dozens of meters. The positionadjusting knob on the bracket is designed for adjusting the nozzleto reach different depth. Pressure gauges are installed on both themetal pipe and the high pressure hose No. 2 in order to monitorand regulate the water pressure and nitrogen pressure, and consequently ensuring the best atomisation of the device.

Table 1. Working parameters of the nozzles

Nozzle type Water flow rate Gas consumption Droplet diameter Water pressure Spray cone angle(m3/h) (m3/h) (µm) (MPa) (°)

Twin-fluid 4 120 <200 0.4~0.5 90

Centrifugal 8 0 <320 1.2~1.3 80

Figure 1. Schematic diagram of water mist coal fire suppression system


The relatively low water pressure is one of the most obviousadvantages of the twin-fluid atomisation, which ensures the goodatomisation effect after the water pumped through a long flowpath.

Moreover, the bore diameter of the twin-fluid nozzle is relativelylarge, so nozzle blockage is well avoided. In addition, the highpressure nitrogen is not only effective in atomising, but alsodecreases the oxygen concentration in the limited space,improves the diffusion effect of the fine droplets, and in turnenlarges the extinguishing range.

High pressure water is the only power source of the single-fluidwater mist coal fire suppression device. The working parameters ofthe centrifugal nozzle are shown in Table 1. Water is pumpedthrough high pressure hose No. 3. It is in a rotational motion inthe nozzle and breaks up into fine droplets under the centrifugalforce. The centrifugal nozzle is installed on the bracket through thedirection-adjusting knob, through which the azimuth, angle andheight of water spraying can be adjusted.

The single-fluid water mist coal fire suppression device is onlyatomised by water instead of both water and nitrogen, whichmakes it much lighter and more flexible. The space at the cavity isrelatively open, so the oxygen diluting effect of the nitrogenbecomes weak. The advantages above make the single fluid watermist coal fire suppression device suitable for the fire in the cavity ofthe abandoned roadway.

4. THE EXTINGUISHMENT OF COAL FIRES IN THEANJIALING OPEN PIT MINE4.1 Overview of coal fires in the Anjialing Open PitMine

The Anjialing Open Pit Mine, located in Shuozhou City ofShanxi Province, is one of the three open pit mines of China CoalPingshuo Group Co., Ltd. Coal seams are thick with shallow over-burden in this area, which results in the over-exploitation by manysmall coal mines for a long time. Currently, the 1330 and 1345platforms have entered the goaf of the abandoned Houdong CoalMine, where the spontaneous combustion of coal is quite serious.Many fires in roadways were uncovered with high temperature(Figure 2). The boreholes for blasting could not be blasted sincethe explosive could not be charged due to high temperature, whichseriously affected the normal production of the mine. Moreover,

high temperature and large amounts of toxic gases threatened thehealth of workers. The water mist coal fire suppression system wasapplied in borehole and cavity above burning roadway to extinguish the fire effectively, and thus ensure the safe productionof the mine.

4.2 Scheme for the extinguishment of coal fires in theroadway with water mist technology

The scheme consists of four stages, which are temperature and gasanalysis before spraying water mist, installation and adjustment ofthe water mist coal fire suppression system, temperature and gasmeasurement during spraying water mist, and temperature monitoring after spraying water mist..

(1) Before spraying water mist, infrared thermal imager was usedto measure the temperature of borehole and cavity. Meanwhile,gases in the borehole were collected and the concentration of COwas also analysed. While gases in the cavity were not collectedsince the cavity was semi-open, and gases were easily influenced byatmosphere.

(2) The water mist coal fire suppression system was installedaccording to Figure 1. After the installation, the air pressure andwater pressure were adjusted to ensure the system was at the bestworking condition. Then the two devices were placed in the borehole and cavity, respectively. The spray orientation, angle andheight were adjusted according to the actual situation of the fire.

(3) During the extinguishment, the infrared thermal imager wasused to measure the temperature distribution in the borehole andcavity every three hours. Moreover, gases in the borehole were collected every three hours to obtain the concentrations of CO.Charts showing temperature variation in the borehole and cavitytogether with the concentration of CO in the borehole during andafter spraying water mist were plotted to fully monitor fire conditions. Temperature measurement and gas sample collectionmust be conducted half an hour after stopping spraying.

(4) The spraying was halted when the temperature was below70°C and showed a steady decline, and the concentration of COwas also below 0.1%. The temperature and concentration of CO measurements were continued every six hours in the following twodays to monitor whether the fire rekindled. If the temperaturerises, the spraying will carry on; otherwise, withdraw the watermist coal fire suppression system and terminate the firefightingprocess.

5. RESULTS AND DISCUSSIONS5.1 Extinguishment of fire in borehole

The temperature in the borehole was very high (221.22°C) beforespraying water mist. A lot of smoke with pungent odour emittedfrom the borehole, whose pressure is very strong (Fig. 3). CO concentration of the smoke was as high as 12.87%.

The spraying water mist was started from 15:00 pm on August 2,2013 using the nitrogen-water twin-fluid water mist coal fire suppression device. During the process, the smoke of the boreholewas significantly suppressed, and a large amount of water vapouremitted from the borehole nearby (Fig. 4). The measured temperature of water vapour was up to 99°C, which indicatedthat the water mist evaporated after impacting on coal and rocks

Figure 2. Photograph of the burning roadway in the AnjialingOpen Pit Mine


with high temperature. Consequently, a lot of heat in the fire areawas removed by the water vapour, and the temperature reduced quickly.

The maximum temperature in the borehole has dropped to 65°Cat 15:00 pm on August 3, and met the temperature requirementper "Regulation of Coal Fire Extinction of China" (70°C).However, there was still a lot of smoke emitting. The concentra-tion of CO was still as high as 1.13%, which was much higherthan the extinction standards (0.1%) per Regulation. The

maximum temperature dropped to 40.85°C at 9:00 am on August4, after 42 hours of operation (Fig. 5). The highest temperaturewas close to the surface temperature, and showed a steady decline(Fig. 6). Smoke didn't emit from the borehole anymore. The concentration of CO declined to 0.08‰ (Fig. 7). Both temperatureand concentration of CO met the requirement of "Regulation, sothe spraying of water mist was on hold temporarily.

The temperature and concentration of CO monitoring wasconducted in the following two days after the suspension. Themonitoring results were shown in Figures 6 and 7. Temperatureand the concentration of CO decreased slowly, which indicatesthat the fire was extinguished successfully and did not rekindleanymore.

5.2 Extinguishment of fire in cavity

A lot of smoke with pungent odour emitted from the cavity beforespraying water mist. Temperature up to 210°C was measured inthe cavity. A charcoal smell was obvious when getting close to it(Fig. 8).

The spray restarted at 17:00 pm on August 2. Plenty of watervapour emitted from the cavity during the spraying (Fig. 4). Thisindicated that the water mist has impacted on coal and rocks withhigh temperature. Consequently, a lot of heat in the fire area wastaken away by the water vapour, and the temperature in the cavityreduced quickly.

The maximum temperature in the cavity dropped to 65.9°C at11:00 am on August 3, only after 18 hours of spraying (Fig. 5).There were only a few water vapours emitting from the cavity.The temperature met the requirement of the Regulation, so thewater mist spraying was on hold temporarily. In the following twodays, monitoring of temperature showed a declining trend,indicating that the fire was extinguished successfully.

Figure 6. Variation of temperature in the borehole during andafter spraying water mist

Figure 7. Variation of CO in the borehole during and after spraying water mist

Figure 3. Thermal infrared figure of borehole before sprayingwater mist

Figure 4. Figure of borehole during spraying water mist

Figure 5. Figure of borehole after spraying water mist


6. CONCLUSIONS(1) There are often high fires existing on the roofs and walls of theabandoned roadways in coal fire area that cover a large area withhigh temperatures. A new coal fire fighting method was proposedby using water mist technology based on characteristics of fires inabandoned roadways as well as the characteristics of water mistand extinguishing mechanisms.

(2) The water mist coal fire suppression system was developed,which contained the twin-fluid water mist coal fire suppressiondevice that was atomised by a twin-fluid nozzle, and the single-fluid water mist coal fire suppression device that atomised by acentrifugal nozzle. The system is simple in structure, easy to operate, which makes it especially suitable for coal fire areas wherethe terrains are complex and water resources are scarce.

(3) The nitrogen-water twin-fluid and single-fluid water mist coalfire suppression devices were applied in a borehole and a cavity toextinguish a fire in the abandoned roadway in the Anjialing OpenPit Mine. The results show that water mist technology can extinguish the fire quickly and efficiently with low cost. Moreover,the fire didn't rekindle. This technology ensured the safe production of the Anjialing Open Pit Mine. What is more important is that this study provides a new valuable method for thecontrol and extinguishment of coalfires.

7. ACKNOWLEDGEMENTSThis research was sponsored by the Joint Funds of The NationalNatural Science Foundation of China and Shenhua GroupCorporation Limited (No. 51134020).

REFERENCESCao, K., Zhong, X., Wang, D., Shi, G., Wang, Y., Shao, Z., (2012).Prevention and control of coalfield fire technology: A case study in the AntaibaoOpen Pit Mine goaf burning area, China. International Journal ofMining Science and Technology, 22(5), 657-663.

Dai, S., Ren, D., Tang, Y., Shao, L.Y., Li, S.S., (2002). Distribution,isotopic variation and origin of sulfur in coals in the Wuda coalfield, InnerMongolia, China. International Journal of Coal Geology, 51(4):237-250.

Finkelman, R.B., (2004). Potential health impacts of burning coal beds andwaste banks. International Journal of Coal Geology, 59(1): 19-24.

Finkelman, R.B., Stracher, G.B., (2011). Environmental and healthimpacts of coal fires. In: Stracher, G.B., Prakash, A., Sokol, E.V.(Eds.), Coal and Peat Fires: A Global Perspective: Coal-Geologyand Combustion, Volume 1, pp: 115-125.

Künzer, C., (2005). Demarcating coal fire risk areas based on spectral testsequences and partial unmixing using multi sensor remote sensing data.Austria, Technical University Vienna.

Kuenzer, C., (2007). Coal mining in China. Business Focus China: Energy,A Comprehensive Overview of the Chinese Energy Sector. gic DeutschlandVerlag, Frankfurt, Ger-many: 62-66.

Kuenzer, C., Hecker, C., Zhang, J., Wessling, S., Wagner, W.,(2008). The potential of multi-diurnal MODIS thermal bands data for coalfire detection. International Journal of Remote Sensing, 29(3):923-944.

Kuenzer, C., Stracher, G.B., (2012). Geomorphology of coal seamfires.Geomorphology, 138(1): 209-222.

Kuenzer, C., Zhang, J., Tetzlaff, A., Voigt, S., Van, DijkP., Wagner,W., Mehl, H., (2007). Uncontrolled coal fires and their environmental impacts: Investigating two arid mining regions in north-centralChina. Applied Geography, 27(1): 42-62.

Figure 8. Visible and thermal infrared figures of cavity beforespraying water mist

Figure 9. Visible and thermal infrared figures of cavity duringspraying water mist

Figure 10. Thermal infrared figure of cavity after spraying watermist

Figure 11. Variation of temperature in the borehole during andafter spraying water mist


Liu, J.H., Liao, G.X., Li, P.D., Fan, W.C., Lu, Q., (2003). Researchand progress into water mist fire suppression technology. Chinese ScienceBulletin, 48 (8):761~766.

NFPA 750, (2010). Standard on Water Mist Fire Protection Systems, 2010Edition. National Fire Protection Association, Inc.

Rathore, C.S., Wright, R., (1993). Monitoring environmental impacts ofsurface coal mining. International Journal of Remote Sensing,14 (6): 1021-1042.

Stracher, G.B., (2004). Coal fires burning around the world: a globalcatastrophe. International Journal of Coal Geology, 59 (1-2): 1- 6.

Stracher, G.B., Taylor, T.P., (2004). Coal fires burning out of controlaround the world: thermodynamic recipe for environmental catastrophe.International Journal of Coal Geology, 59(1): 7-17.

Wendelstorf, J., Spitzer, K. H., Wendelstorf, R., (2008). Spray watercooling heat transfer at high temperatures and liquid mass fluxes.International Journal of Heat and Mass Transfer, 51(19),4902-4910.

Yang, B., Chen, Y., Li, J., Gong, A., Kuenzer, C., Zhang, J., (2005).Simple Normalization of Multi-Temporal Thermal IR Data and AppliedResearch, on the Monitoring of Typical Coal Fires in Northern China[R].BEIJING NORMAL UNIV (CHINA).

Zhang, J., Wagner, W., Prakash, A., Mehl, H., Voigt, S., (2004).Detecting coal fires using remote sensing techniques. International Journal ofRemote Sensing, 25(16): 3193-3220.


Mine Ventilation Society of South AfricaTel: +27 11 482-7957 / Email: [email protected]

ABSTRACTThe objective of the work presented in this paper is to describe theanalysis techniques used for the evaluation of a deep level mineshaft to reduce the ventilation pressure losses over the shaft length.

It was recognised that there is an opportunity to achieve an energysavings and therefore a reduction in the total cost of operating ashaft system by reducing the overall resistance of an equippeddowncast shaft to the ventilation air flowing through it. The analysis of this system was undertaken using computational fluiddynamic (CFD) analysis techniques. This CFD model was validated by evaluating five shafts both from the currently availabletheoretical perspective as well as by measuring the real shaft pressure losses. The results of this analysis demonstrate that thecurrent approach to the design of shaft systems is flawed and thatsubstantial savings can be achieved by the application of the correct analysis methodology in conjunction with currently avail-able analysis tools such as CFD.

1. INTRODUCTIONMine or shaft designs tend to move along the same route, solvingage old questions with proven analysis techniques. This lack ofchange does provide a degree of comfort to prospective investors,however, this certainty does come at a price.

The cost for changing the basic design of an installed shaft systemto a more efficient system is almost never worth the capital outlay.This is because, in order to make the change, either the shaft willhave to stop producing (thus incurring significant opportunity cost)or the change will take years to complete as it will be done duringthe weekly and annual shaft maintenance cycles, assuming thatany proposed design change can be accommodated withoutinterrupting the production cycle.

Thus, inefficient design has a significant effect on the longer termprofitably of any shaft system. In today's world, however, toolshave been developed which are available for the detailed evaluation of a system, and to thus prove the efficacy of designchanges before they are installed. These tools can give rise to savings when used in conjunction with a rational analysis

technique requiring both the analysis to be completed and the validation of theoretical models against measured data. An example of one of the tools available to us today is ComputationalFluid Dynamics (CFD). As will be demonstrated in this paper, theappropriate use of this technique allows the end user to evaluatethe cost effectiveness of design changes before physical changes aremade to the system.

One of the more significant advantages of using CFD analysistechniques, is, that once a technique has been validated, it is comparatively cost effective to evaluate different options and optimise solutions with respect to the savings that can be accruedas well as specific installation requirements.

The details of these techniques and their validation have been discussed in other papers (Kempson et al, 2012), (Kempson et al,2013).

In this paper we will summarise the conclusion of the above workfor the sake of completeness, however the emphasis of the workpresented here is to discuss the analysis of the CFD models whichwere used to come to these conclusions.

1.1 Context of this work

It should be noted that this work was undertaken in conjunctionwith an overall programme which was completed to gain a deeperunderstanding of the resistance which shaft systems offer the ventilation air flowing through them and the consequential pressure losses which occur in these shaft systems. As such a number of shafts were evaluated. The actual pressure losses experienced by these shafts were measured, the same shafts weresubjected to standard calculation to determine the theoretical pressure losses, as well as subjected to a detailed CFD analysis. Inthis way it was possible to validate the CFD model and use thismodel to begin to optimise the design of shaft systems, (Kempsonet al, 2012).

This paper will not report on the details of the calculations, butwill rather only consider the data associated with the CFD analysisof a shaft to describe the process and the insights. Suffice to saythat the overall pressure losses in the downcast shaft accounted formore than half the pressure produced by the main ventilation fans.

2. PREVIOUS WORK COMPLETED 2.1 Efficacy of the use of scale models

The use of scale models depends primarily on the use ofdimensional analysis in order to understand the importance ofcertain parameters in the system being considered. A definitionwas supplied by Pankhurst (1964): "The dimensions of physicalquantities can be manipulated algebraically and the results can be

Application of computational fluid dynamic modelling inthe design of shaft systems


W.J. Kempson1, R.C.W. Webber-Youngmann2, J.P. Meyer3

1Hatch, Johannesburg, South Africa2University of Pretoria, Department of Mining Engineering,Pretoria, South Africa3University of Pretoria, Department of Mechanical andAeronautical Engineering, Pretoria, South Africa



interpreted to provide a great deal of information about the physical processes involved in the situation considered."

Unless the geometry of the system has no effect on the physical situation to be evaluated, the first requirement of a scale model isthat it should be geometrically similar to the actual system beingevaluated, i.e. the distance between any two points in the modelledsystem must bear a constant ratio to the distance between the corresponding two points in the original system. This constantratio is called the 'geometrical factor'.

Similarly, we define the kinematic similarity (i.e. when velocities areinvolved) by the condition that the velocity at any point in the onesystem bears a constant ratio to the velocity at the correspondingpoint in the other system. This is called the 'velocity scale factor'.

Various other factors, such as elastic similarity, thermal similarity,etc., are all defined in a similar fashion but are not pertinent to thisdiscussion.

Although this technique is powerful and allows a meaningful comparison of scale models with full-scale systems, it must beemphasised that this is only valid as long as the system does notrequire extrapolation beyond the ranges of the dimensionlessparameters defined in the tests.

Within these ranges, the dimensional analysis provides therequired scale factors, but it provides no information whatsoeverabout the way in which a given non-dimensional coefficient varieswith the dimensionless parameter on which it depends. As a resultthe specific parameters are allowed to vary and those to which thescale factors will apply must be chosen with care.

As will be discussed below, a number of the measurements carriedout and used in the evaluation of shaft resistances were done onscale models (Chasteau, 1962). The two models generally referredto are the 1.981 m (78 inch) model and the 0.305 m (12 inch) scalemodels which were operated by the CSIR. These models wereconstructed in the horizontal plane and were both configured toallow the flow in them to achieve a fully developed profile beforethe typical shaft obstructions interrupted this flow. Care was takento ensure that the mechanical scaling factors for the models andshafts were carefully correlated before tests began. However, as aresult of practical limitations, the maximum airflow achieved inthese models was half of that generally found in a typical shaftconfiguration. This had a direct effect on the Reynolds numberused in the tests and raises some concern as to the extrapolation ofthe results.

In order to try and define the extent to which the data from thisscale model could be used, various shaft configurations were testedby Chasteau (1962) and the results compared. These tests showedlittle correlation. In the 0.305 m (12 inch) model, the test showedlittle agreement even to standard pipe values. The tested valueswere lower than expected and the results showed that the test flowwas potentially not fully developed.

The results also showed that it is perhaps generally better to usedirect drag measurements to determine the effect of the resistanceof buntons than to use the pressure drop. This has the advantageof removing the pipe wall roughness considerations from the overall measurements. When compared with full-scale shafts, thescaling up of the Reynolds number may be an inaccurate procedure even if the effect of wall roughness can be taken into

account. The differences between the two scale models seems tobe primarily a result of the difference in wall friction effects. Thedirect drag measurements do correlate satisfactorily.

In spite of these shortcomings, the tests completed are sufficient todemonstrate the empirical direction that should be taken to reduceshaft resistances.

2.2 Specific conclusions derived from the review ofmeasured shafts

It is not the intent of this paper to describe the various tests whichhave been completed on shaft systems, the detailed evaluation canbe found in the work completed by Kempson et al (2012). It is,however, relevant that we list some of the specific outcomes ofthese tests. The following general items were noted as necessary forthe design of shaft systems:

1. Buntons and guides should be streamlined.

2. Shaft walls should be lined.

3. Buntons should be spaced as far apart as possible.

4. In addition, it is important to ensure that the velocity profile inany test section is as close to that of the shaft as possible.

However, at this stage no definitive data are available on the actualmanner in which the above systems should be designed. This isprimarily a result of the difficulty in measuring the actual resistances of installed shafts and, once measured, of the highrequirements in terms of time and cost to adapt their configuration for additional tests. At the time, this led to the use ofscale models.

2.3 Historical use of computational fluid dynamics

Computational fluid dynamics (CFD) was proposed as a methodto help further the understanding of shaft resistances. Before anywork was done on using this analysis technique however, it is beneficial that we understand how this technique has been used inevaluating ventilation structure in mines.

It is beyond the purview of this paper to provide a detailed historyof the work which has been conducted in mines using CFD analysis. Some of these works are however highlighted below toemphasise certain aspects of CFD analysis which are consideredimportant.

The first instance of the use of this technique in mining was byWala et al. (1993). One of the objectives of this paper was to showhow CFD simulations can be used to study the airflow across themain airways of a mine ventilation system. In particular, the flowthrough the transition zone between the upcast shaft and the mainfan ductwork was investigated.

Although CFD has many advantages, it does not eliminate theneed for experimental results, which are still needed to validatenumerical solutions. The transition piece was developed and theresults collated with tests conducted on site. In this regardfavourable comparisons between simulations and measurementssupported the use of the software package CFD2000 as a tool forthe design and planning of fan ductwork configurations. This isone of the few applications of CFD to design and verify practicalventilation problems. Wala et al.'s (1997) study showed good correlation between the modelled data and that which was


measured. The CFD technique used in this instance was thereforevalidated.

In a similar vein, Meyer and Marx (1993) used CFD to evaluatethe design of a fan drift-mine shaft intersection. In this work,StarCD was used to create a CFD model of this intersection. Thiswork and that described above was found to be some of the earliest work using CFD to resolve engineering issues on mines.

To explore the potential for using CFD modelling in mines, Walaet al. (1997) used CFD techniques to model the flow of airbetween a shaft and the main ventilation fans of a mine. Thesemodelled results were compared with those from work completedin 1995 on measuring the flow characteristics between thesepoints. The model assumed incompressible airflow and specifiedsteady-state, turbulent, single-phase flow. The effects of body forcesand heat transfer were considered to be small and were not takeninto consideration. This exercise showed favourable comparisonsbetween the data and the measured results.

Additional work was done by Craig (2001) on the CFD evaluationof the drag coefficient on buntons of various shapes. A number ofdifference geometries were evaluated using a 2D model generatedusing Fluent v5.5 software and a velocity of 5 m/s. This analysisproduced coefficients of drag that differ significantly from thoseused by McPherson (1987). However, as was noted by the Craig,there are several concerns with the data presented, the first beingthat the Reynolds number used would be significantly lower thanthat experienced in a shaft (Re = 5×104, whereas a typical shaftconfiguration has a Re = 3×106 or above). In addition, the technique used assumed fully turbulent flow and the transitionfrom laminar to turbulent flow was not noted. This problem is notunique to this analysis and has produced results that are less than50% of the overall published figures for the coefficient of drag.This work did highlight the complexities of calculating the specificdrag coefficient for various bunton configurations.

In 2007 a validation study was carried out by Wala et al. (2007). Inthis work a comparison was made between a scale model test anda CFD model of this test. The area modelled was the flow ofventilation air in a heading created by a continuous miner. Thework consisted of the following:

1. Design and build a scale ventilation model of the area underconsideration.

2. Measure the response of the model to the flow of air through it.

3. Develop a CFD model of the same area.

4. Compare the experimental results with those of the CFDmodel.

The results showed significant correlation between the measuredand the modelled airflow, with sufficient accuracy to allow the prediction of the airflow. This analysis, however, only consideredan empty heading and did not include the equipment and otherobstructions that would typically be found in such a heading. Thisis thought to be one of the first attempts to validate actual measurements with those of a CFD model.

A typical CFD simulation begins with a CAD rendering of thegeometry, adds physical and fluid properties, and then specifiesnatural system boundary conditions. By changing these

parameters appropriately, countless 'what-if' questions can beanswered quickly. One of the most important uses of CFD is tocompare alternatives and to view the effects of upset conditions. Itis therefore best used as a design tool and is particularly usefulwhen it is important to know how the variables temperature,pressure, concentration /composition, and velocity changethroughout the computational domain, in space and time.

Although little information is available on the use of CFD in theevaluation of shaft systems, the evaluations that have been completed indicate that this tool is worth investigating for the evaluation of shaft resistances.

3. COMPUTATIONAL FLUID DYNAMICSThe package used for this CFD analysis was the STAR-CCM+from CD ADAPCO, supplied by Aerotherm in South Africa. Thispackage allowed the 3D modelling of the shaft section under consideration by solving the continuity and momentum equationsinside discrete cells. The various shaft geometries were modelled inthe software using the 3D-CAD module supplied. This moduleallows the complete model to be developed in readiness for themesh generation.

The initial analysis considered the use of scaled down version ofthe shaft systems under consideration. These analyses yieldedresults which highlighted the concerns from the engineers whopreviously used scaled models. Particularly the generation of aReynolds' number which accurately reflected the ventilation conditions in the shaft. As this is directly related to the velocity ofthe ventilation in the shaft, this was an important parameter.

3.1 Mesh generation

The various shaft sections used in this analysis were modelled inthe package using the 3D CAD modelling features and the modelwas created on a 1-to-1 basis with no scaling required. This decision was based on difficulties that previous investigations hadwith regards to reconciling the Reynolds number as well as theconcerns based on the necessity to have fully developed flow. Thismodel was then meshed using a combination of the built-in polyhedral mesher for volumes and the surface remesher. Thenature of the problem being examined also required that theeffects of the solid interfaces and the air be modelled as accuratelyas possible. In this regard the Prism Layer option available as partof the meshing model was selected. This model applies additionalelements at the solid interface to facilitate the accurate modellingof the turbulence around these points.

The length of the primary model section was chosen to be 20 m.However, to ensure that the flow regime within the shaft was fullydeveloped before the pressure losses over the section were measured, the initial length of shaft to be simulated such that thisflow regime could develop was 10 x the diameter of the shaft, inthis instance approximately 80 m. This required that the model beiterated four times (i.e. the output of the simulation becomes theinput of the next simulation).

To ensure accurate results, a mesh refinement analysis was performed until a mesh size was found with small changes in thepressure losses. The results of this exercise are shown in Table 1.


The convergence requirement was set to 1 x 10-4 for continuityand momentum. This was achieved in most cases, although insome cases a convergence of 1 x 10-1 was accepted. In all instancesthe simulation was run until the data showed repeatability. Thisrequired that the respective curves were constant before the analysis was stopped and the results recorded.

4. BOUNDARY CONDITIONS4.1 The following boundary conditions were used:

Inlet: The inlet was defined as a constant-velocity inlet for the firstsection simulated. Subsequent to this, the velocity profile used forthe input was taken from the output of the previous simulation.

It is worth noting that using the mass flow of the fluid as the inputwould have been ideal. However this was not possible, suffice tosay the variation of the mass flow over the test section neverexceeded 2.5% of the total mass flow. This is sufficiently small tonot be a concern.

4.2 Simulation runs

Each of the simulations was run on a personal computer runningWindows XP. The computer had a hard drive with a 500 GBcapacity and 4 GB of RAM in a 64 bit environment. All the simulations were run using STAR-CCM+ version 6.02.007. Eachsimulation took between six and eight hours to complete, includingall the required iterations.

5. BUILDING AND EXECUTING THE MODEL5.1 Shaft model evaluated

The shaft depicted below in Figure 2 was modelled using the CFDsoftware and subjected to the analysis as described above.

Figure 2. Cross section of No. 14 Shaft

To ensure a thorough understanding of the interaction betweenthe various items contained in a shaft, it was decided to build theCFD model systematically and to include the various pieces ofequipment progressively. This would allow the effect of the individual items to be evaluated. In this regard the following series

As can be seen from Table 1, there is very little difference betweenthe pressure drops measured for the mesh sizes of 0.15, 0.20 and0.25 m.

As a result of this analysis, it was decided to use a base size of0.25 m. This base size is sufficiently small to allow the shaft configurations to be accurately sized, but was also sufficiently largeto allow the simulations to be run efficiently.

The next requirement was to determine the effect that using theprism layers would have. These layers provide additional cell dataclose to the skin of the cell and were thought to have an effect onthe overall pressure losses over the shaft length. This setting causesthe software to generate additional layers at each boundary surface, thus improving the accuracy of calculation for the surfaceinteractions. There was, however, a negligible difference betweenthe results from the simulations run with and without these prismlayers. It was decided nonetheless to include a prism layer with asetting of 5 (i.e. five additional layers adjacent to the boundary surface) for the simulations. A schematic of the mesh arrangementis shown in Figure 1.

Figure 1. Example of mesh

3.2 Fluid model selection

Once the geometry had been modelled and meshed, the appropriate fluid models were selected. In this instance, thethermodynamic and body forces were assumed to be small andthe fluid used for the analysis was an ideal gas. The system wasmodelled in three dimensions and the K-Omega turbulencemodel was also used. The SIMPLE algorithm was used to solvethe continuity and momentum equations in every cell.

Table 1. Mesh Refinement Evaluation

Base No. of Ref. PDrop % diff. % of size (m) cells in Pressure (over (against ref.Press.

model (kPa) section) next value)(× 1000)

0.15 1 110 88.0 11.42 -5% 0.01%0.20 470 88.0 11.74 3% 0.01%0.25 350 88.0 11.19 15% 0.01%0.30 210 88.0 12.87 NA 0.01%


of tests were completed.

• T01 - Shaft barrel pressure losses

• T02 - Shaft barrel and one bunton across the shaft

• T03 - Shaft barrel and two vertically spaced buntons across the shaft

• T04 - Shaft barrel and full buntons set at6m

• T05 - Shaft barrel and pipes at pipe diameter

• T06 - Shaft barrel and pipes at flange diameter

• T07 - Shaft barrel and pipe including flanges

• T08 - Shaft barrel and buntons and pipes at pipe diameter

• T09 - Shaft barrel and buntons and pipes at flange diameter

• T10 - Shaft barrel and buntons and pipe including flanges

• T11 - Shaft barrel and buntons and pipe including flanges and skip 1

• T12 - Shaft barrel and buntons and pipe including flanges and skip 2

• T13 - Shaft barrel and buntons and pipe including flanges and man cage 1

• T14 - Shaft barrel and buntons and pipe including flanges and man cage 2

• T15 - Shaft barrel and buntons and pipe including flanges and service cage

The bunton sets were spaced at 5 m.

Table 2. Summary of results (cross sections)


5.2 Results of CFD analysis

It should be noted in the presentation of these results that theoverall pressure differences are not given for the shafts being considered. These pressure differences are calculated for the particular shaft length and are, therefore, difficult to compare witheach other. Thus a value of pressure loss per m of shaft is used toallow for this comparison.

The results here are presented in two tables. The first table (Table2) shows the results of the selected cross section areas associatedwith each of the tests. The second table (Table 3) shows the resultsof the longitudinal section of the shaft.

In order to compare the results of the measured data against thatwhich was calculated, and subsequently against the results fromCFD model, there are two factors which must be quantified.These are the accuracy of the calculation itself as well as the accuracy of the instrumentation and measurement methodology.

The accuracy of calculation made in accordance with the Chezy-Darcy formula is (+15% to -15%) (White, 1986).

The accuracy of the testing methodology and the instrumentationwas calculated to have an accuracy of (+12% to -29%) (Kempsonet al, 2012).

As can be seen from Table 4, there is good correlation between thetheoretical calculation and the CFD analysis. However, there isconsistently poor correlation between the measured results andboth the theoretical and CFD results, although the results are within the accuracy limits defined above.

It is interesting to note that this does not apply to the 1 shaft tests.This is the only shaft that did not use the airflow buntons. Thisbring into doubt the accuracy of the drag coefficient data used forthe theoretical calculations.

Note:

1. The "Calculated Pressure Loss" described above was the anticipated pressure loss for the shaft system calculated in accordance with the methodology laid down by McPherson(McPherson 1987). This process requires the evaluation of thepressure losses associated with each of the individual items in theshaft (ie buntons, pipes, guides etc) and the calculation of theChezy-Darcy pressure loss coefficient associated with these. Thesecoefficients are then summed arithmetically and applied to thestandard Chezy-Darcy equation for the flow of fluid through pipesto calculate the final pressure loss.

2. The T10 Shaft configuration is representative of the ImpalaNo.14 Shaft configuration. All of the five shaft evaluated werecompared and validated against the CFD model, this is discussedin details in referenced papers (Kempson et al, 2012), (Kempson et al, 2013).

Table 3 : Summary of Results (Longitudinal Sections)


The differences noted between the other shafts and the data abovedo, however, highlight the potential differences that arise whenevaluating complex systems from the theoretical perspective. It isnot possible to include the effects of various items such as imperfections between the lining rings, the inclusion of slingingpoints in the shaft, large cable pocket installations, intermediatepump stations and other shaft openings. The differences notedabove are attributed to these as well as the other inaccuraciesnoted above.

This also highlights the importance of ensuring that there is sufficient capacity in any designed system to accommodate futurerequirements, which it is not possible to anticipate in the designphase. In this instance the data indicates that the allowance shouldbe of the order of a 30% increase.

One of the variables that was not measured against time for theduration of the test was the velocity of the ventilation air withinthe shaft. This can make a significant contribution to the overallpressure losses calculated and should be measured in future tests.

5.3 Discussion of CFD results

Overall, the results of the individual sections of the CFD simulations showed little agreement with those of the theoreticalcalculations for the initial simulations.

The initial simulations (T01 to T10) were completed in such a wayas to allow the evaluation of the individual contributors to theoverall shaft pressure drops, as well as to evaluate the effect ofthese being combined.

It is interesting to note that the initial simulations (T01 to T07)showed very little correlation between the theoretical calculationsand those derived from the CFD analysis.

The evaluation of the contribution that the buntons make to theoverall friction losses also showed little correlation with the calculated data. It can be seen, however, that the correlationbetween the theory and the CFD results improves as the complexity of the bunton arrangement increases.

It is also significant that the Coefficient of Drag (CD) calculatedfrom the CFD data is closest to the assumed value with the singlebunton in the shaft. This accuracy decreases in simulation T03and again increases with simulation T04. This is attributed primarily to the interference factor which is included for the calculation of the theoretical pressure loss. The need for this can

be seen from the various representations on the longitudinal sections in Table 3. The CDs for the CFD results calculated without this factor are significantly lower than those assumed forthe theoretical evaluation.

This does show the importance of including the effect from adjacent buntons when calculating the overall drag coefficient.However, as the differences in the drag coefficient between theassumed values and those calculated from the CFD do not matchthe percentage differences noted from the pressure drops over thesection considered, it does raise a concern as to the accuracy ofthe factors used for the theoretical evaluation.

Simulation T07 (i.e. when the pipes are assumed to be flanged)showed significant increases in the pressure losses for all the shaftsfor the CFD analysis. However, even with the flanges included inthe simulation, there is still a significant difference between the calculated pressures losses and those from the CFD simulations.

Simulations T08, T09 and T10 showed significantly better correlations between the theoretical pressure losses and those ofthe CFD analysis.

To try and discern the reason for this, the pressure losses calculatedfor the previous tests for the piping and buntons were subtractedfrom the overall pressure value. This showed an additional unaccounted for pressure loss of approximately 30% of the overallpressure loss. The only reason that could be found for this pressureloss is the interaction between the various components in the shaft.This is not consistent with the theory and indicates a flaw in theprimary assumptions made for the theoretical analysis.

The final evaluation relates to the placement and movement ofthe skips and cages (conveyances) in the shaft. In this instance thereis good correlation between the data obtained for the movement ofthese conveyances in the shaft and the theoretical data. It is,however, worth noting that the overall pressure loss as a result ofthe conveyance moving or blocking the shaft is not large, assumingeach of the conveyances is alone in the shaft. This is attributed tothe fact that none of the conveyances in the shaft is considered tobe especially large in comparison with the shaft size. The maximum coefficient of fill was 30%.

It should be noted at this point, that while the results from theCFD analysis are interesting, the final results should be calibratedagainst physical measurements of shafts. This validation wasundertaken by testing 5 shafts at Impala Platinum The details ofthis comparison can be found in Kempson et al, 2012. The measurement detailed in this work did validate the CFD approachdescribed above.

6. CONCLUSIONS FROM THE CFD SIMULATIONRESULTS6.1. Discussion of the CFD results

The following specific conclusions can be drawn from the CFDsimulations:

1. The overall correlation between the pressure drops predicted bythe theory and those taken from the CFD simulations showedgood correlation when evaluating the complete shaft system,including all the buntons and fittings within the shaft.

Table 4. Comparison of Measure Data vs Calculated Data vsCFD Data

Shaft PLoss PLoss PLoss PLoss PLoss PLoss

No. (measured) (calculated) (calc) (CFD) (CFD) (CFD)

(Pa/m) (Pa/m) /PLoss (Pa/(meas) m) (calc) (meas)

No.14 1.81 1.26 70% 1.22 97% 68%

No.11 1.22 0.95 77% 0.87 92% 71%

No.1 0.47 0.55 118% 0.42 76% 89%

No.11C 0.69 0.59 85% 0.38 63% 53%

No.12N Bratticed Shaft, the measured results were not reconcilable


There was however very poor correlation between the pressuredrops predicted by the theory and those taken from the CFD simulation for the individual items in the shaft.

This difference was attributed to the fact that the theory requiresthe evaluation of individual items and does not take into consideration the effect each of these items has on the other. Thiseffect is taken in to consideration by the CFD simulations.

These results highlight the primary flaw in the theoretical calculation assumptions and that is that the pressure loss for eachof the shaft fittings can be calculated separately and arithmeticallyadded to obtain the final pressure loss for the shaft.

The CFD evaluations show that the inter-related effect of these fittings is more significant than anticipated and can increase thepressure losses in the shaft by approximately 30%.

The technique developed here allows for the inclusion of theseinter-related effects and therefore for potentially optimisation ofthe shaft pressure losses.

2. The inclusion of pipes in the shaft resulted in a small decreasein the overall pressure drop in the shaft. This decrease was onlyapparent in the shafts that had comparatively fewer pipes. Oncethe shaft had more than 2 to 3 pipes in it, no reduction in pressureloss was apparent.

The current theory evaluates the pressure losses in the shaft as aresult of the pipes by evaluating the rubbing surface the pipes present to the ventilation flow. This rubbing surface is increased tomake an allowance for the flanges which are of greater diameterthan the pipe itself. The CFD evaluation showed that shaft pressure losses associated with the use of flanges was higher thanthat predicted by the theory.

During the CFD evaluation, it was also noted that the pressurelosses associated with certain pipes changed depending on theirposition in the shaft, this was seen to be a potential source for savings.

3. The theoretical calculations of the pressure losses resulting fromthe conveyances in the shaft showed good correlation when compared with those predicted by the simulation results. These arehowever sufficiently small to be not be considered further.

6.2 General conclusions and recommendation

This section briefly summarises the most significant conclusionsarising out of this work. While the background to this work hasnot been covered in this report, we think it is important to demonstrate the practical results of the CFD analysis. The detailand methodology by which these conclusions are reached is discussed in the original paper (Kempson et al, 2012).

The CFD evaluation method was used to evaluate the following:

1. A typical shaft configuration with different buntons shapes.

2. A typical shaft configuration, with the piping placed in variouspositions around the shaft.

A schematic of this shaft cross section which was used is shown inFigure 3.

Figure 3. Cross section of typical shaft

The typical shaft used has the following dimensions:

• Shaft diameter: 9 m

• Shaft depth: 2 000 m

• Ventilation velocity: 10 m/s

The pressure losses associated with the configurations describedabove were evaluated and the associated difference in pressurelosses reconciled to electrical energy costs. The results are presented in Table 5 and Table 6 (Kempson et al, 2013).

Table 5. CFD simulation for Bunton Arrangement

As can be seen from Table 5, a significant saving can be madethrough the judicious choice of the bunton shape. These savingscan be realised without a significant increase in the capital costs.

Airflow Buntons 822 1.00 -

Streamlined Buntons 774 0.94 -5 738

Square Buntons 1 608 1.92 94 046

I-beam Buntons 1 324 1.61 60 413

Descr. Shaft Ratio of Rand SchematicPLoss PLoss (Savings (Pa) over 20

Years LOM) vs Baseline(R × 1000)


As can be seen from Table 6 the result shows that the judiciousplacement of the piping in the shaft can have an effect on theresistance in the shaft. The results also show that, once the mostefficient position has been chosen for the piping, the use of flangesto join the pipes can also increase the cost of supplying air to themine. This demonstrates the importance of ensuring that the crosssection of the pipe is increased by as little as possible when choosing a pipe joining method.

7. ACKNOWLEDGEMENTSThis work was possible as a result of the efforts of the followingpeople:

1. James Janse van Rensburg, Group Ventilation Manager atImpala Platinum, who facilitated use being able to various shafts atImpala Platinum.

2. Prof R.C.W. Webber-Youngmann, for his patience and guid-ance in the completion of this work.

3. Prof J.P. Meyer for his patience and guidance in the completionof this work.

REFERENCESChasteau, V.A.L., (1962). Equipment and techniques used for scale modelinvestigations of mine shaft resistance to air flow in the CSIR laboratories.Journal of the Mine Ventilation Society of South Africa, May.

Craig, K., (2001). Report on CFD analysis of bunton sections. Reportprepared for Anglo Operation Limited, November.

Kempson, W.J., Webber-Youngmann, R.C.W., Meyer, P., (2012).Optimising Shaft Pressure Losses Through Computational Fluid DynamicModelling. University of Pretoria, South Africa.

Kempson, W.J., Webber-Youngmann, R.C.W., Meyer, P., (2013).Design of Energy Efficient Systems. Proceedings of the 23rd WorldMining Conference, Montreal, August

McPherson, M.J., (1987). The resistance to airflow of mine shafts.Proceedings of the 3rd Mine Ventilation Symposium, October.

Meyer, J.P., and Marx, W.M., (1993). The minimising of pressure lossesin a fan driftmine shaft intersection, using computational fluid dynamics. R&DJournal, 9(3).

Pankhurst, R.C., (1964). Introductory Survey. Dimensional Analysis andScale Factors. London: Chapman and Hall, pp 13-19, 53-55.

Wala, A., Vytla, S., Taylor, C., and Huang, G., (2007). Mine faceventilation: A comparison of CFD results against benchmark experiments forthe CFD Code validation. US: National Institute for OccupationalSafety and Health (NIOSH).

Wala, A., Yingling, J.C., Zhang, J., and Ray, R., (1997). Validationstudy of computational fluid dynamics as a tool for mine ventilation design.Proceedings of the 6th International Mine Ventilation Congress,May.

White, F.M., (1986). Fluid Mechanics, 2nd edition. New York:McGraw-Hill, pp 308-314.

Table 6. CFD Simulation for Piping Arrangement

Note:

1. The base case for this evaluation was chosen as the case withthe lowest pressure loss and is not a reflection on what is normallyfound in shaft systems.

Description Shaft Ratio of Rand (SavingsPLoss PLoss over 20 Years (Pa) LOM) vs

Baseline(R × 1000)

Piping along shaft edge 857 1.13 12 114(No Flanges)

Piping away from shaft 819 1.08 7 651edge (No Flanges)

Piping distributed around 755 1.00 -shaft (No Flanges)

Distributed piping with flange 867 1.14 13 310

Mine Ventilation Society of South AfricaTel: +27 11 482-7957 /

Email: [email protected]


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