MINE MONITORING FOR SAFETY AND HEALTH Ian D. Unwin, M. Phil, B.Sc., D.I.S. [email protected] © 2007 CONTENTS List of diagrams ii List of Tables iii Preface iv Chapter 1 The management of the environment and safety and health in coal mines 1 Chapter 2 Coal mining technology 7 Chapter 3 The ventilation of coal mines 13 Chapter 4 Blackdamp or chokedamp 18 Chapter 5 Firedamp 25 Chapter 6 The hazard posed by the gaseous products of 47 explosions and fires Chapter 7 The environmental impact of shot firing 66 Chapter 8 Diesel engines underground 70 Chapter 9 Respirable dust 75 Chapter 10 Ionising radiation 94 Chapter 11 Heat and humidity 98 Chapter 12 Lighting in coal mines 110 Chapter 13 Noise 120 Chapter 14 General conclusions 126 APPENDICES Appendix I The general properties of air and gases found underground A1 Appendix II Surface laboratory gas analysis techniques A5 Appendix III The Wheatstone bridge circuit A9 Appendix IV Heat and humidity - general terms A10 Appendix V Lighting - general terms A11 ACKNOWLEDGEMENTS i LIST OF DIAGRAMS 2.1 Sort wall, or pillar and stall method of working 8 2.2 The long wall system of mining 9 2.3 Breaking coal from the sold 9 2.4 Cutter loader 10 2.5 Underground conveyor belt 10 4.1 A schematic diagram of the Bergman cell 21 4.2 A schematic diagram of the City Technology oxygen cell 21 4.3 The Sieger OXD-2M oxygen monitor 22 5.1 A flame safety lamp 31 5.2 Garforth’s lamp 33 5.3 Probe lamp 33 5.4 Naylor Spiralarm 34 5.5 Sigma recording methanometer 34 5.6 The McLuckie methanometer 35 5.7 The Ringrose automatic firedamp alarm 36 5.8 Liveings gas detector 37 5.9 The MSA W8 methanometer 38 5.10 The English Electric automatic firedamp detector 39 5.11 The pellistor 40 5.12 The MSA GP methanometer 40 5.13 The MSA D6 methanometer 41 5.14 The Sieger automatic firedamp detector 41 5.15 The MRE type 225 four headed methane monitoring system 42 5.16 The BM1 methane monitor 43 5.17 Interferometer gas detector 44 6.1 The Haldane cage 52 6.2 Hoolamite gas detector 54 6.3 The City Technology 2T carbon monoxide cell 56 6.4 The tube bundle system 57 6.5 The BCO1 carbon monoxide monitor 59 6.6 Emcor 59 6.7 The Minerva T86 smoke detector 60 6.8 The Trolex P3270 smoke detector 61 6.9 Firant 62 9.1 Dust size selection curves 78 9.2 A schematic diagram of a konimeter dust sampler 82 ii 9.3 Exposed konimeter slides 83 9.4 The Soxhlet thimble dust sampling apparatus 84 9.5 The PRU hand-pump 85 9.6 Green and Watson’s thermal precipitator 85 9.7 The short running thermal precipitator 86 9.8 The Mk III short running thermal precipitator 86 9.9 The MRE long running thermal precipitator 87 9.10 The dust collector in the long running thermal precipitator 87 9.11 The Hexhlet sampler 88 9.12 The NCB/MRE Gravimetric Dust Sampler Type 113A 88 9.13 The MRDE Gravimetric Dust Monitor 89 9,14 Simslin 90 11.1 Thermohygrograph 103 11.2 Mason’s wet and dry bulb hygrometer 104 11.3 Storrow’s whirling hygrometer 104 11.4 The kata thermometer 106 11.5 A basic effective temperature nomogram 107 12.1 The flint mill 110 12.2 Early flame safety lamps 110 12.3 Protector CT33A lamp 112 12.4 Electric miners lantern 112 12.5 A cap lamp 112 12.6 The shadow photometer 115 12.7 The grease spot photometer 115 12.8 A colliery photometer incorporating a phototronic cell 116 12.9 An integrating sphere cap lamp photometer 116 12.10 An ambient light meter 117 13.1 A portable sound level meter 124 AII.1 NCB Sampling pump A5 AII.2 Haldane’s apparatus A6 AIII.1 The Wheatstone bridge circuit A9 LIST OF TABLES 8.1 The constituents of undiluted diesel exhaust fumes 70 AII.1 Reagents used in absorption gas analysers A6 iii PREFACE In 1994, as a prelude to privatisation, the British Coal Corporation closed its Technical Services and Research Executive (TSRE). This brought to an end a forty-seven year period during which Britain’s state owned coal industry had carried out its own research into mining related problems. The amounts of money spent had been huge. For example, in one arbitrarily chosen year, 1988/9, it was £16m (1). Whilst some went on projects that had a direct impact on the productivity of mines, for example the development of improved coal getting machines, some was also spent on more philanthropic activities. Examples included investigations of the underground environment and its impact on the safety and health of miners. As part of these studies many new and improved instruments were produced for the assessment of atmospheric ‘pollutants’. For the purposes of this monograph all such devices will be called ‘environmental instruments’, or ‘environmental monitors’. In 1974 I joined an expanding team of physicists at the NCB’s Mining Research and Development Establishment (later to become TSRE) to work on environmental monitor development. Some twenty years later, when redundancy occurred, I felt the need to look back at what I had done and to ask why and so what? Only when these ghosts had been exorcised would I be able to move forward with confidence to a new and exciting career. This monograph is the result of my research. In it an attempt is made to answer a number of questions: * What underground environmental factors have an adverse impact on the safety and health of coal miners? * How were these hazards discovered, investigated and controlled? * What influence did the availability of appropriate monitoring instrumentation have on this process? * Were there any underground environmental hazards that required (in 1994) continued research into their control and monitoring? * Were there (in 1994) any environmental monitoring or control procedures that could be relaxed? Before considering the history of environmental hazards in coal mines, this monograph begins with chapters containing general background information for the discussions that follow; Chapter 1 looks at the attitudes of colliery management and governments towards underground safety and health and how they affected the introduction of hazard control measures; Chapter 2 outlines the development of mining technology, showing how it led to the appearance of new pollutants and sources of danger. Environmental hazard control has frequently been achieved by ventilating the workings. Chapter 3 contains a brief review of technology applied. Following these general reviews are chapters that consider the identified hazards. These include: Blackdamp - Chapter 4, Firedamp - Chapter 5, Gaseous products of explosions and fires - Chapter 6, Shot firing - Chapter 7, Diesel engines - Chapter 8, Respirable dust - Chapter 9, Ionising radiation - Chapter 10, Heat and humidity - Chapter 11, Lighting - Chapter 12, Noise - Chapter 13. Answers to the questions identified above are given as a set of general conclusions in Chapter 14. Although falls of ground have been a major danger underground, they are usually considered a ‘geological’ hazard rather than environmental. Consequently the subject has not been reviewed in this monograph. I D Unwin 22 October 1999 Reference 1. British Coal Corporation. Report and Accounts 1988/89. iv Chapter 1 The management of the environment and safety and health in coal mines In Roman times, men working below ground experienced hazardous environments created by the presence of noxious gases. In response, they developed monitoring and control techniques, as evident from Agricola (1). He reports that in the first century AD Pliny had noted that ‘aluminous or sulphurous fumes dangerous to diggers’ sometimes occurred in wells. They were detected by observing the behaviour of a dog or lighted candle when lowered down the shaft. They were removed by directing a current of fresh air into the workings. That is through the application of ventilation. In Britain, the first coal mines were formed from shallow pits dug into seams exposed at the surface. Sometimes the air in these workings became so stagnant that men could not breathe and candles would not burn. Such conditions were said to be caused by the presence of a gas given the descriptive names ‘chokedamp’ or ‘blackdamp’. The danger this gas has represented to miners is discussed in Chapter 4. By the seventeenth century a rising demand for coal had resulted in the construction in Britain of relatively large mines. In some places two shafts were sunk, linked underground by the workings. As described in Chapter 3, such an arrangement could lead to the spontaneous flow of a current of air. This reduced the likelihood that blackdamp would appear. From about the middle of the seventeenth century the presence of another gas began to be noted in some of the deeper coal mines. Rather than preventing candles from burning, it caused their flames to grow. Sometimes violent explosions occurred, leading to massive devastation underground and large loss of life. Given the name ‘firedamp’, the danger this gas has represented to coal miners is considered in Chapter 5. A feature of the early blackdamp hazard was that if its appearance did lead to any fatalities, they tended to be few in numbers. Further, there was no structural damage caused to the mine. Consequently the events were rarely noted outside the immediate locality. Explosions of firedamp, on the other hand, were very different. By the beginning of the eighteenth century the devastation being caused was sufficiently newsworthy for descriptions to begin appearing on a wide scale.