Mine Ventilation and Air Conditioning E-Book

Howard L. Hartman

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 980

Veröffentlichungsjahr: 2012

Beschreibung

This revised edition presents an engineering design approach to ventilation and air conditioning as part of the comprehensive environmental control of the mine atmosphere. It provides an in-depth look, for practitioners who design and operate mines, into the health and safety aspects of environmental conditions in the underground workplace.

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

Dedication

Preface

Acknowledgments

List of Mathematical Symbols

List of Map Symbols

Part I: Introduction

Chapter 1: Environmental Control of the Mine Atmosphere

1.1 Purpose And Importance

1.2 Control Processes

1.3 Coordination of Mining and Ventilation Systems

1.4 Foundations of Mine Ventilation and Air Conditioning

Chapter 2: Properties and Behavior of Air

2.1 Nature and Composition of Air

2.2 Properties of Air

2.3 Gas Laws: Behavior of Air

2.4 Pressure/Head Relationship

Problems

Part II: Mine Air-Quality Control

Chapter 3: Mine Gases

3.1 Contaminants

3.2 Threshold Limit Values

3.3 Mine Gases

3.4 Gas Detection and Monitoring

3.5 Control of Gases Underground

3.6 Determining Dilution Requirements

3.7 Methane Drainage

Problems

Chapter 4: Dusts and Other Mine Aerosols

4.1 Aerosol Types and Definitions

4.2 Dynamic Behavior of Aerosols

4.3 Classification of Mineral Dusts and Other Relevant Aerosols

4.4 Physiological Effects of Mineral Dusts

4.5 Factors That Determine Dust Harmfulness

4.6 Explosive Dusts

4.7 Threshold Limit Values

4.8 Aerosol Measurement

4.9 Sampling of Diesel Particulate Matter

4.10 Sources of Dusts in Mines

4.11 Aerosol Control Technology

4.12 Personal Protection Devices

4.13 Medical and Legal Means of Dust Control

Part III: Mine Ventilation

Chapter 5: Airflow through Mine Openings and Ducts

5.1 Energy Changes in Fluid Flow

5.2 Head Losses and Mine Heads

5.3 Head Gradients

5.4 State of Airflow in Mine Openings

5.5 Calculations of Head Losses

5.6 Air Power

5.7 Compressibility Effects

5.8 Thermodynamic Approach To Mine Ventilation

Problems

Chapter 6: Ventilation Measurements and Surveys

6.1 Introduction

6.2 Temperature Measurement

6.3. Air Specific-Weight Determinations

6.4 Velocity Measurement

6.5 Air Quantity Measurement

6.6 Air-Pressure Measurement

6.7 Ventilation Surveys

6.8 Continuous Monitoring and Remote Control of the Mine Environment

6.9 Organization for Ventilation Functions

Problems

Chapter 7: Mine Ventilation Circuits and Networks

7.1 Relationship Between Head and Quantity

7.2 Kirchhoff’s Laws

7.3 Series Circuits

7.4 Parallel Circuits

7.5 Ventilation Networks

7.6 Solution of Simple Networks with Natural Splitting

7.7 Analysis of Complex Networks

7.8 Generalized Network Model

7.9 Networks with Fixed-Quantity Branches

7.10 Simplified Application of the Hardy Cross Algorithm

7.11 Additional Network Insights

Problems

Chapter 8: Natural Ventilation

8.1 Characteristics of Natural Ventilation

8.2 Quantification of Natural Ventilation

Problems

Chapter 9: Air-Moving Equipment

9.2 Classification of Air-Moving Equipment

9.3 Centrifugal Fans

9.4 Axial-Flow Fans

9.5 Fan Characteristics

9.6 Fan Noise

9.8 Fan Laws

9.9 Fan Testing

9.10 Other Air-Moving Equipment

Problems

Chapter 10: Fan Application to Mines

10.1 Application of the Fan to the System

10.2 Fan Heads and Head Gradients

10.3 Fan EvaséS and Diffusers

10.4 Fans in Combination

10.5 Fans and Natural Ventilation

10.6 Fan Selection

10.7 Fan Drive and Control

10.8 Characteristics of Multiple-Fan Systems

Problems

Chapter 11: Auxiliary Ventilation and Controlled Recirculation

11.1 Importance of Face and Auxiliary Ventilation

11.2 Check Curtains and Line Brattice

11.3 Auxiliary Fans and Vent Pipe Or Tubing

11.4 Other Options for Face and Auxiliary Ventilation Systems

11.5 Equipment Selection and Design Considerations

11.6 Booster Ventilation

11.7 Controlled Recirculation

Problems

Chapter 12: Economics of Airflow

12.1 Basis of Economic Design

12.2 Effect of Airway Characteristics On Power Consumption

12.3 Economic Design of Airways

12.4 Economic Design of the Overall Network

Problems

Chapter 13: Coal Mine Ventilation Systems

13.1 Introduction

13.2 Coal Mine Versus Metal Mine Ventilation Systems

13.3 General Considerations

13.4 Overview of Mine and Ventilation System Design

13.5 Ventilation Controls

13.6 Leakage Considerations

13.7 Laws Affecting Mine Ventilation

13.8 Location of Fan and Principal Airways

13.9 Room and Pillar Ventilation

13.10 Longwall Ventilation

13.11 Shortwall Ventilation

13.12 Bleeders

13.13 Design of the Mine Ventilation System

13.14 Ventilation Data from Operating Mines

13.15 Design Example

Problems

Chapter 14: Metal Mine Ventilation Systems

14.1 General Considerations

14.2 Laws Affecting Metal Mine Ventilation

14.3 Ventilation for Various Mining Methods

14.4 Case Studies of Ventilation Systems

14.5 Design of Ventilation Systems

14.7 Design Example

Problems

Chapter 15: Control of Mine Fires and Explosions

15.1 Prevention Strategies

15.2 Mine Monitoring

15.3 Responses To Fires and Explosions

Problems

Part IV: Mine Air Conditioning

Chapter 16: Heat Sources and Effects in Mines

16.1 Need For Air Conditioning in Mines

16.2 Sources of Heat in Mines

16.3 Physiological Effects of Heat and Humidity

16.4 Heat Indexes and Standards

16.5 Calculation of Mine Heat from Human Metabolism

Problems

Chapter 17: Mine Air Conditioning Systems

17.1 Psychrometric Processes

17.2 Chilled-Water Sources

17.3 Other Heat-Transfer Processes

17.4 Mine Cooling Load

17.5 Mine Cooling Plants

17.6 Mine Heating Systems

Problems

Appendix A: Reference Tables and Figures

Appendix B: SI Units in Mine Ventilation

B.1 Basics of the SI System

B.2 Advantages of the SI System

B.3 Tables of Conversion Factors

Appendix C: Laboratory Experiments

C.1 Laboratory Equipment Needs

C.2 Outline of Experiments

C.3 Laboratory Reports

Appendix D: Computer Applications and Software

D.1 Scope of Computer Applications

D.2 Network Analysis Software

References

Answers to Selected Problems

Index

MINE VENTILATION AND AIR CONDITIONING

Copyright © 1997 by John Wiley & Sons, Inc. All rights reserved.

Published simultaneously in Canada.

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, [phone], fax [phone]. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, [phone], fax [phone].

Library of Congress Cataloging in Publication Data:

Mine ventilation and air conditioning / Howard L. Hartman … [et al.].—3rd ed.p. cm.Rev. ed. of: Mine ventilation and air conditioning / Howard L. Hartman. 2nd ed. 1991.“A Wiley-Interscience publication.”Includes bibliographical references and index.ISBN 0-471-11635-1 (cloth : alk. paper)1. Mine ventilation. 2. Air conditioning. I. Hartman, Howard L.TN301.M554 1997622′.42—dc21 97-547

To our wives,Bonnie, Diane, Geetha, and Janetwhose support, understanding, and patience on the home front enabledus to write this book.

PREFACE

That this book has enjoyed a modicum of success and evolved into a third edition was hardly anticipated when the original work was published in 1961. The second edition, issued in 1982, was a group effort by 25 contributors and modernized and expanded the coverage. When it was decided to revise the book again, four of us agreed to undertake the task.

Our objectives in the third edition are largely the same as before: (1) to present an integrated engineering design approach to mine ventilation and air conditioning, (2) to advance an understanding of comprehensive environmental control of the mine atmosphere, and (3) to advocate total mine air conditioning through simultaneous control of the quality, quantity, and temperature–humidity of the underground atmospheric environment.

What may differ in this revision is the emphasis on an undergraduate treatment of the subject matter. We have intentionally restricted the scope and level of the coverage so that students can cover the material in one semester, assuming a background in the basic and engineering sciences and introductory mining engineering courses.

We have also directed the book to practitioners of mine ventilation in the field. It should provide adequate depth and breadth to those who design or operate mines, with responsibility for environmental engineering and especially for the health and safety of miners who rely on the underground atmosphere for survival.

To be responsive to current trends, we have again made use of dual mathematical units (English and SI) throughout.

We are indebted to our colleagues who contributed to the second edition; with their permission, we have drawn liberally in this revision from their earlier work. Additionally, sources in the current literature, manufacturers, and practicing ventilation engineers have generously provided state-of-the-art knowledge for our efforts.

To my three coauthors in this endeavor—all Penn State associates or former students of mine—I give warm thanks. To them belongs any credit for the lasting contribution this volume may make to our profession. In acknowledgment of our common educational roots, we have assigned all royalties from this book (as we also did with the second edition) to endow a mining engineering scholarship at our alma mater.

HOWARD L. HARTMAN

Sacramento, California

ACKNOWLEDGMENTS

The following persons authored chapters that appeared in the Second Edition of this book (1982) and gave permission to the present authors to draw on that material as appropriate. Their contributions to the Third Edition are gratefully acknowledged.

James L. Banfield, Jr. (deceased)Formerly of the Mine Safety and Health Administration

H. Douglas DahlEastern Associated Coal Company

Rodolfo V. de la CruzUniversity of Wisconsin at Madison

Ralph K. FosterRetired, Formerly of the Mine Safety and Health Administration

Y. S. KimPrivate Consultant

Richard J. KlineMine Safety and Health Administration

Thomas NovakThe University of Alabama

Richard L. SanfordThe University of Alabama

Stanley C. SuboleskiA. T. Massey Coal Company

Peter M. TurcicMine Safety and Health Administration

Floyd C. BossardFloyd C. Bossard & Associates, Inc.

Robert W. DalzellRetired, Formerly of the Mine Safety and Health Administration

C. Frederick EbeRetired, Formerly of Bethlehem Steel Corporation

Bruce R. JohnsonZephyrus Mining Consultants Inc.

John D. Kalasky (deceased)Formerly of Island Creek Coal Company

Edward J. MillerMine Safety and Health Administration

Thomas J. O’NeilCleveland Cliffs Inc.

Madan M. SinghEngineers International, Inc.

Pramod C. ThakurConsol Inc.

Richard W. WalliPrivate Consultant

Edwin B. WilsonBethlehem Steel Corporation

The present authors also extend thanks to John E. Urosek, Chief, Ventilation Division, Mine Safety and Health Administration, and his colleagues who read and provided technical advice on Chapter 15, Control of Mine Fires and Explosions.

LIST OF MATHEMATICAL SYMBOLS

Mathematical symbols associated with the literature and practice of mine ventilation have evolved with time. Originally, they were based on American National Standards Institute (ANSI) codes, but these standards have fallen into disuse over the years. The symbols employed in this book are representative of the ones customarily employed in mine ventilation in the United States and have been adopted because of their clarity, consistency, and recognizability.

Symbol Letters

Greek Letters

LIST OF MAP SYMBOLS

The symbols listed here alphabetically are typical, but not standard, symbols for use on mine ventilation maps. Because standards do not exist, the reader should be careful in interpreting symbols on any given ventilation map. Variations in practice are common. First, many companies use color-coded maps to help in identifying ventilation airflows. For example, intake air can be denoted by blue arrows, return air by red arrows, escapeways by green arrows, and belt air by yellow arrows. The color scheme differs from mine to mine. Second, the style of the air directional arrows differs from mine to mine with different types of arrows used to denote intake and return airstreams.

Symbol

Description

Airflow (intake) Airflow (return)

Airlock; a double-door system to allow equipment to pass through without disrupting the ventilation circuit

Auxiliary fan and vent pipe or tubing (flow direction may be indicated by an arrow)

Brattice (also called a

line brattice

); a curtain of plastic or plastic-covered fabric hung from the roof to direct air to or from a working face

Box check; a stopping with a hole in it to allow a conveyor or other equipment to pass through while limiting the airflow quantity

Check curtain; a barrier of plastic or plastic-covered fabric hung across an opening from the roof to block the flow of air

Door

Escapeway with direction of escape in the direction of airflow

Escapeway with the direction of escape in the direction opposite to the airflow direction

Fan (flow direction may be indicated by an arrow)

Fire door (normally open)

Main fan (the dotted lines show the location of the weak wall)

Overcast or air crossing; an area where roof material is taken to allow one airflow to pass over another without mixing (the parallel lines indicate the airway that goes straight through the overcast); may also be constructed as an undercast or sidecast crossing

Overcast with a built-in regulator

Pipe overcast; a method of using pipes to pass a small quantity of return air through an intake airflow without mixing the two airflows; generally used for taking belt air directly to the return in a coal mine

Regulator

Seal

Self-contained self-rescuer cache location

Shaft with a downcast flow of air (alternately, this symbol may represent an undercast)

Shaft with an upcast flow of air (note that this symbol could also represent a gas well or a borehole location on some mine maps)

Stopping (permanent); an impermeable stopping made of masonry, steel, or other flame-resistant material to block the flow of air through an opening

Stopping (temporary); a quickly erected and movable stopping normally made of brattice material to temporarily block the flow of air through an opening

Stopping with small door to allow the passage of personnel

PART I

INTRODUCTION

CHAPTER 1

Environmental Control of the Mine Atmosphere

1.1 PURPOSE AND IMPORTANCE

In the vacuum of outer space, human astronauts rely on the artificial atmosphere of a spacecraft for their life support system. While differing in locale and mission, human miners are no less dependent on an artificial atmosphere to sustain them in underground mines where the air may be stagnant and contaminated.

It is evident that both miners and astronauts confront a hostile environment, and that both groups must depend on a ventilation–air conditioning system to supply them adequate air for breathing.

Under even normal circumstances, excavation in the earth—like exploration in space—can be fraught with a variety of environmental problems and hazards. While ground support is an obvious and compelling need, the most vital aspect of the mine environment to control is the atmosphere of the workplace.

To the mining engineer, ventilation is the most versatile atmospheric control tool. It is the process relied on to accomplish most environmental control underground. Mine ventilation is essentially the application of the principles of fluid dynamics to the flow of air in mine openings. As the primary means of quantity control, ventilation is responsible for the circulation of air, in both amount and direction, throughout the mine. It is one of the constituent processes of total mine air conditioning, the simultaneous control within prescribed limits of the quality, quantity, and temperature-humidity of mine air (Anon., 1993).

Increasingly, in underground mining, environmental objectives require that we condition air to meet quality and temperature–humidity standards as well as quantity criteria. In recent years, these standards have been raised substantially. Although threshold limits are based on human safety and tolerance, increasing concern is being expressed for standards of human comfort as well. The provision of a comfortable work environment is both cost-effective and humanitarian. Worker productivity and job satisfaction correlate closely with environmental quality. Further, excessive accident rates and workers’ compensation rates are a consequence of unsatisfactory as well as unsafe environmental conditions. No mining company today can afford to be lax in its environmental and air-control practices.

Historical Perspectives and Natural Constraints

The importance of mine ventilation and air conditioning has not just newly been recognized. From the onset of underground mining in Paleolithic times, perhaps as early as 40,000 BCE (B.C.) (Gregory, 1980, p. 50), miners confronted oxygen deficiency, toxic gases, harmful dusts, and debilitating heat. As miners became more skilled, by the first millennium BCE, they learned to course the air through multiple openings or circuits to provide fresh air to the working face (Lacy and Lacy, 1992, p. 5) and to use fire-induced air currents (McPherson, 1993, p. 2).

By the Middle Ages, mine ventilation enjoyed the status of a mining art. In the most celebrated early mining treatise, Georgius Agricola (1556, p. 200), a respected German scholar and scientist, decried the evils of the foul atmospheric environments in which miners had to work and pictured their still-primitive efforts to combat these conditions:

I will now speak of ventilating machines. If a shaft is very deep and no tunnel reaches to it, or no drift from another shaft connects with it, or when a tunnel is of great length and no shaft reaches to it, then the air does not replenish itself. In such a case it weighs heavily on the miners, causing them to breathe with difficulty, and sometimes they are even suffocated, and burning lamps are also extinguished. There is, therefore, a necessity for machines which the Greeks call and the Latins, spiritales—although they do not give forth any sound—which enable the miners to breathe easily and carry on their work.*

Figures 1.1a-c, taken from Agricola’s book, portray some of these early “ventilating machines.” A contemporary history of mine ventilation is presented by McPherson (1993, pp. 1-7).

FIGURE 1.1 Mine ventilation machines of Agricola’s day: (a) deflectors; (b) bellows; (c) fans.

[Parts (a)-(c) from Agricola, 1556. By permission from Dover Publications, Inc., copyright 1950.]

Technology has vastly improved mine ventilation, although environmental challenges underground still abound. Depth, the most serious natural constraint, sets the ultimate limit, specifically through rock pressure and rock temperature. Not only do rock pressures rise inexorably with depth but temperatures do also, with subsequent deterioration of the atmosphere. According to Spalding (1949, p. 238):

Of all the factors which affect mining operations, high rock temperature is the one most often likely to limit the depth to which those operations can be extended. The science of ventilation is therefore rapidly becoming the most important branch of deep mining.

At great depths, ventilation requirements and costs eventually climb to unsustainable levels. To preserve mine atmospheric quality under these intense heat conditions, ventilation at great depths must be supplemented by air conditioning.

Although heat generated by depth imposes the ultimate limit, the mine and its atmosphere have other detrimental conditions to withstand. These consist usually of airborne contaminants such as gases and dusts. As mines expand in size, complexity, manpower, and mechanization, demands on the ventilation–air conditioning system to maintain more stringent standards of environmental quality likewise rise. Fortunately, advances in mining science and technology tend to keep pace with worsening hazards underground. The struggle, however, is a continuous one reflected in both human safety and operating costs.

1.2 CONTROL PROCESSES

Lest confusion arise in the mind of the reader, it is well to clarify some of the terms related to environmental control of the mine atmosphere. Used alone, in mining parlance, air conditioning denotes only the function of temperature–humidity control, generally cooling or heating. To signify total mine air conditioning and all the functions of environmental control it entails, the qualifier term “total” should be used.

To reiterate, the functions encompassed by total air conditioning are (1) quality control, (2) quantity control, and (3) temperature–humidity control of the atmosphere. To accomplish these objectives, individual conditioning processes are employed; in mining, they consist of the following:

1. Quality control (purifying air and removing contaminants)

a. Gas control—vapors and gaseous matter, including radiation

b. Dust control—particulate matter

2. Quantity control (regulating magnitude and direction of airflow)

a. Ventilation

b. Auxiliary or face ventilation

c. Local exhaust

3. Temperature–humidity control (controlling latent and sensible heat)

a. Cooling

b. Heating

c. Humidification

d. Dehumidification

Control processes may be applied individually or jointly. If the objective is total air conditioning of the mine, then all three goals must be met, and multiple processes may be applied simultaneously. Several processes can serve more than one function; for example, ventilation, the most common one in mining, performs mainly quantity control but may serve also for quality control and temperature–humidity control.

In coping with atmospheric environmental hazards in mining, certain engineering principles are fundamental and applicable to control of any contaminant. These contaminants consist mainly of gases and dusts but include heat and humidity as well. In order of preference of their application, engineering control principles consist of the following (Hartman, 1968):

1. Prevention or avoidance

2. Removal or elimination

3. Suppression or absorption

4. Containment or isolation

5. Dilution or reduction

For example, if quality control of a dust hazard is the objective, then these five steps should be evaluated and, as appropriate, applied in the order given. Ventilation, a dilution measure, may be the ultimate solution, but it should be employed in conjunction with prevention, removal, suppression (by water), and containment (by suitable enclosure of the source).

In addition to engineering control, there are other measures at the disposal of mine officials responsible for safety, ventilation, and air conditioning. Medical control principles consist of education, physical examinations, lung x-rays, personal protective devices, prophylaxis, and therapy. Last are legal control principles, which consist of statutory and regulatory provisions and workers’ compensation laws. All are resources to employ in combating environmental hazards.

Up to this point, the stated or implied reason for air conditioning or other environmental control processes is the preservation or enhancement of human life. Conditioning that controls the atmosphere that human beings breathe is termed comfort air conditioning. Nearly all mine air conditioning systems are of this type. On occasion, however, product air conditioning is employed when the objective is preservation of the plant or quality of the product. Examples are air temperature or moisture reduction to prevent slaking of coal mine roofs, absorption of water by drying to preserve deliquescent minerals, heating of water lines in downcast shafts during winter, and dehumidification of air in wet upcast shafts.

1.3 COORDINATION OF MINING AND VENTILATION SYSTEMS

Notwithstanding its criticality to the life support process, environmental control in mines poses a paradox. It does in all industry. On the one hand, environmental control is essential to the preservation of human life and necessary for the conduct of underground operations. On the other hand, it is ancillary to the primary objective of mining: the production of ore, rock, or coal from a mineral deposit. The paradox is that environmental control contributes nothing to production directly and yet makes the production cycle possible.

As stated previously, the two most vital environmental control measures in mining are (1) ventilation and air conditioning and (2) roof support and ground control. Ideally, they should be performed with minimum interference and cost to the production operation. Realistically, they are essential and must carry top priority in the entire mining system.

How is the dilemma resolved? The answer is that environmental control measures are auxiliary operations that are programmed into and performed as an integral part of the production cycle. Thus they receive the attention they must but are managed to optimize the productivity of the overall mining operation. The matter receives more detailed consideration in Chapters 13 and 14.

There is also a unique interdependency between the mine production system and the environmental control system (Hartman, 1973). In mine ventilation, air is coursed through the mine workings and openings themselves (and for auxiliary purposes through vent tubing and ducts). Quite clearly, joint optimization of the two systems can lead to the most satisfactory environment and to the most cost-effective mining.

Through the centuries, recalling Agricola’s discourse, and into more recent years, ventilation systems and mining systems have tended to evolve together. Probably the prime example of the evolution is in room and pillar mining of bedded or tabular mineral deposits, especially coal. Here constraints of the ventilation system have imposed numerous changes in the configuration of the mining plan in response to technological progress in machines and methods. For example, ventilation requirements have led to the provision of special underground openings, called bleeders. And in all mining systems, one finds concessions to ventilation needs in the form of air shafts, escapeways, multiple openings, and various airflow control devices.

Much of the joint evolution of mining and ventilation systems, however, has been fortuitous and unplanned. In spite of the progress that has been made, the safety record in underground mining remains one of the poorest of all U.S. industries. There is now reason to believe that the situation may be changing (Hartman, 1982). Four highly important developments in the last three decades, two technological and two nontechnical, are responsible:

1. The high-speed, electronic digital computer, permitting advanced solutions to ventilation circuits and networks heretofore unsolvable

2. The systems approach, which optimizes complex industrial operations, permitting personnel, materials, and methods to be coordinated in the most efficient way

3. Extensive federal legislation, embodying a strict code of regulations to improve the safety of mining operations

4. The advent of socioengineering, the applying of technology with full consideration of the social, political, economic, and environmental consequences as well as the technical benefits

Their application is considered as appropriate in succeeding chapters; the literature now is replete with examples. It is worth noting that none of these developments existed (or certainly not as state-of-the-art technology) at the time the first edition of this book appeared in 1961. This progress alone necessitates and justifies the current revision.

1.4 FOUNDATIONS OF MINE VENTILATION AND AIR CONDITIONING

The foundations of the field of ventilation and air conditioning are laid on many disciplines. Without being identified solely with any one, they apply basic concepts of physical chemistry, thermodynamics, fluid mechanics, and mechanical design to control of the physical, chemical, and thermal properties of air.

Mining engineers, in coping with the more specialized field of mine ventilation and air conditioning, further draw from their knowledge of mining methods in designing underground conditioning systems. They are more limited in their practice than mechanical engineers in dealing with industrial air conditioning, however; as just described, their major conduits for airflow must coincide with the openings driven in the rock for mining purposes. Understanding of mine ventilation and air conditioning thus requires a knowledge of mining technology as well as basic science.

The goal of this book is to instruct mining engineers in the principles and practices of ventilation and air conditioning applicable to the underground atmosphere and the unique environmental conditions found in mines. If they employ the latest available technology, mining’s myriad challenges of depth, size, complexity, manpower, and mechanization can be adequately met today.

Since total mine air conditioning is conveniently divided into three sub-areas or functions, the theory and practice of each are presented in separate parts of this volume. For mining engineers who need to develop competence in the design of mine conditioning systems, the application of basic theory to practical design is of the utmost importance. To this aim, the book is dedicated.

Accuracy of Calculations

In mine ventilation and air conditioning calculations, it is a general rule to express numerical values to three or preferably four significant figures. This is because the precision of most ventilation and air conditioning measurements does not exceed that range. Thus there is no need for a high degree of accuracy in the bulk of mine ventilation and air conditioning work. This is not to say, however, that the speed, capacity, and precision advantages of digital or other types of computers are not utilized; complex ventilation networks can be solved only by programmable computers. For routine, basic calculations, pocket calculators are generally employed and are entirely adequate. Although answers may be rounded off to four significant figures, intermediate steps should be carried to the capacity of the calculator.

Mathematical Units

It is a reflection of the times and the complexities of socio-politico-technological change that this third edition retains the practice of employing both English and SI mathematical units adopted in the second edition (the first edition adhered strictly to English units). The authors considered alternatives but in the end elected to make no significant change. While virtually all the sciences have adopted SI usage, some technologies, especially the American mining industry, remain attached to English units.

Even with dual units, English usage still receives some preference in this book. English units generally appear first with SI in parenthesis. Formulas are stated in both units if necessary, with English first. Examples and problems also employ both units. If, for space reasons, illustrations and tables lack dual units, applicable conversion factors appear in the captions or footnotes.

For a more detailed explanation of unit usage and conversion practice as well as a table of conversion factors, see Appendix B.

Mathematical Symbols

Symbols generally employed in scientific notation as well as those peculiar to the fields of air conditioning and mine ventilation have been standardized and adopted throughout this book. They are listed in the front matter of this book preceding the list of Map Symbols.

Map Symbols

Standardized symbols for fans and control devices are customarily employed in mine ventilation mapping and surveying. Those adopted in this book appear in the front matter following the list of Mathematical Symbols.

* By permission from Dover Publications, Inc.

CHAPTER 2

Properties and Behavior of Air

2.1 NATURE AND COMPOSITION OF AIR

The fluid substance of chief concern in the mine environment is air. Air is a gaseous mixture, existing as a vapor, that constitutes the natural atmosphere at the surface of the earth. Thermodynamically, it may be thought of as a mechanical mixture of dry air and water vapor, whose behavior is complicated by changes of state in the water vapor. Chemically, the composition of so-called dry air at sea level is as follows (where vol% and wt% are percents by volume and by weight, respectively) (Bolz and Tuve, 1973):

Gas

Vol%

Wt%

Nitrogen

78.09

75.55

Oxygen

20.95

23.13

Carbon dioxide

0.03

0.05

Argon, other rare gases

0.93

1.27

For calculations involving quality control, it is customary to assume dry air and compute problems on a volume basis, taking the composition approximately as

Oxygen

21%

Nitrogen and “inert” gases

79%

The various rare gases are grouped with nitrogen because they are chemically and physically inert insofar as air conditioning is concerned. For problems involving carbon dioxide, use 0.03% or the actual content by volume.