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Bureau of Mines Information Circular/1985 
 
 Improved Stench Fire Warning 
 for Underground Mines 
 
 By William H. Pomroy and Terry L. Muldoon 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
 c 
 9^ 
 
 75 
 
 1^/NES 75TH A^^'^ 
 
Information Circular 9016 
 
 Improved Stench Fire Warning 
 for Underground Mines 
 
 By William H. Pomroy and Terry L. Muldoon 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
 Donald Paul Model, Secretary 
 
 BUREAU OF MINES 
 Robert C. Morton, Director 
 

 UNIT OF MEASURE ABBREVIATIONS 
 
 USED IN 
 
 THIS REPORT 
 
 
 
 atm 
 
 atmosphere, standard 
 
 Vim 
 
 micrometer 
 
 
 °F 
 
 degree Fahrenheit 
 
 pet 
 
 percent 
 
 
 
 ft 
 
 foot 
 
 ppb 
 
 part per billion 
 
 
 ft5 
 
 cubic foot 
 
 ppm 
 
 part per million 
 
 
 ft^/min 
 
 cubic foot per minute 
 
 psi • 
 
 pound per 
 
 square 
 
 inch 
 
 h 
 
 hour 
 
 psla 
 
 pound per 
 absolute 
 
 square 
 
 inch, 
 
 in 
 
 inch 
 
 
 
 
 
 
 
 psig 
 
 pound per 
 
 square 
 
 inch. 
 
 lb 
 
 pound 
 
 
 gauge 
 
 
 
 Ib/MMft^ 
 
 pound per million 
 cubic foot 
 
 s 
 
 second 
 
 
 
 
 
 wt pet 
 
 weight percent 
 
 
 mg/kg 
 
 milligram per kilogram 
 
 yr 
 
 year 
 
 
 
 mi 
 
 mile 
 
 
 
 
 
 min 
 
 minute 
 
 
 
 
 
 Library of Congress Cataloging in Publication Data: 
 
 Pomroy, William H 
 
 
 
 
 
 
 
 Improved stench fire warning for 
 
 underg 
 
 roun 
 
 d mines. 
 
 
 
 
 (Information circular / United 
 
 States 
 
 Dc 
 
 partment of 
 
 the 
 
 Interior, 
 
 Bureau of Mines ; 9016) 
 
 
 
 
 
 
 
 Bibliography: p. 33. 
 
 
 
 
 
 
 
 Supt. of Docs.: I 28.27:9016. 
 
 
 
 
 
 
 
 1. Mine fires— Prevention and control. 
 
 2, 
 
 Stench firc- 
 
 warning 
 
 sys- 
 
 tems in mines. I. Muldoon, T. L. 
 
 II. T 
 
 tie. 
 
 III. Series 
 
 In 
 
 formation | 
 
 circular (United States. Bureau of V 
 
 ines ; 
 
 9016) 
 
 
 
 
 TN295.U4 [TN315] 622s 
 
 [622' 
 
 .8] 
 
 84-600274 
 
 
 

 CONTENTS 
 
 Page 
 
 Abstract 1 
 
 Introduction 2 
 
 "^ Alternatives to stench warning 4 
 
 0^ Electrical systems 4 
 
 ^ Messenger systems 4 
 
 ^ Radio systems 4 
 
 J* Deficiencies of existing stench warning systems 5 
 
 Development of improved stench system 6 
 
 .^^ Selection of stench agent 6 
 
 ^ Stench injector development 8 
 
 Existing stench-inj ection methods 8 
 
 Design concepts 8 
 
 Pressurized canister with metering orifice 11 
 
 Pressure balanced with metering orifice 12 
 
 Variable-rate injection pump 14 
 
 Concept evaluation 14 
 
 Testing the improved stench system 16 
 
 Laboratory testing >. 16 
 
 Field testing 16 
 
 Mine ventilation and compressed-air analysis 16 
 
 Injector locations and installation 17 
 
 Test procedures 18 
 
 Results 19 
 
 Design and development of second-generation stench injector 25 
 
 Deficiencies in design of the improved stench injector 25 
 
 Design features of the second-generation injector 26 
 
 Remote-control system for injector actuation 27 
 
 Testing of second-generation stench system 28 
 
 Installation 28 
 
 Test procedures 28 
 
 Results 28 
 
 Summary and conclusions 30 
 
 References 33 
 
 ILLUSTRATIONS 
 
 1. Evacuation time versus maximum depth of main shaft 2 
 
 2. Size of underground workforce versus depth of mine 3 
 
 V) 3. Reactivity of ethyl mercaptan with iron oxide 5 
 
 ^ 4. Vial-breaking stench injector 10 
 
 rv^ 5. Components of vial-breaking stench injector 10 
 
 '^ 6. Pressurized-canister stench injector 11 
 
 \ 7. Components of pressurized-canister stench injector 12 
 
 V9 8. Pressurized-canister injector with metering orifice 12 
 
 9. Use of pressure-balancing line to equalize pressure across metering 
 
 Vo orifice 13 
 
 10. Variable-rate injection pump 14 
 
 11. Improved stench injector design 15 
 
 12. Layout of haulage levels, boreholes, and main shaft in test mine 17 
 
 13. Sampling points and transit times for compressed-air system tracer gas 
 analysis 18 
 
 14. Main shaft ventilation-air injector location 18 
 
 ^ 
 
XI 
 
 ILLUSTRATIONS—Continued 
 
 Page 
 
 15. Remote venthole injector location 18 
 
 16. Compressed-air injector location 19 
 
 17. Compressed-air injector mounted on receiver tank 20 
 
 Stench test results, improved system, first shift: 
 
 18. 1-4 level 20 
 
 19. 1-5 level 21 
 
 Stench test results, improved system, second shift: 
 
 20. 1-4 level 21 
 
 21. 1-5 level 21 
 
 Stench test results, existing system, third shift: 
 
 22. 1-4 level 22 
 
 23. 1-5 level 22 
 
 Previous stench test results, existing system, first shift: 
 
 24. 1-4 level 22 
 
 25. 1-5 level 23 
 
 Previous stench test results, existing system, second shift: 
 
 26. 1-4 level 23 
 
 27. 1-5 level 23 
 
 28. Locations of air sampling points 24 
 
 29. Stench concentration versus time for air samples collected during stench 
 
 tests 25 
 
 30. Refilling improved stench injector 26 
 
 31. Second-generation stench injector design 26 
 
 32. Refilling second-generation injector 27 
 
 33. Second-generation injector for compressed air 29 
 
 34. Second-generation injector for ventilation air installed at main shaft.. 29 
 
 35. Wireless remotely controlled stench injector for ventilation air in- 
 
 stalled at remote venthole 30 
 
 36. Master panel installed in hoist room 30 
 
 37. Remote-control telemetry system installed on leg of emergency-escape- 
 
 hoist headf rame at remote venthole 31 
 
 Stench test results, second-generation system, first shift: 
 
 38. 1-4 level 32 
 
 39. 1-5 level 32 
 
 Stench test results, second-generation system, second shift: 
 
 40. 1-4 level 32 
 
 41. 1-5 level 33 
 
 TABLES 
 
 1. Properties of industrial gas odorants evaluated against ethyl mercaptan. 7 
 
 2. Stench fire-warning system specifications 9 
 
 3. Evaluation matrix for new injection-method design concepts 16 
 
IMPROVED STENCH FIRE WARNING FOR UNDERGROUND MINES 
 
 By William H. Pomroy and Terry L. Muldoon 
 
 ABSTRACT 
 
 This report describes Bureau of Mines research that led to the de- 
 sign, prototype fabrication, and successful proof-of-concept testing of 
 an improved stench fire-warning system for underground noncoal mines. 
 
 Stench systems are the most widely used means of warning miners in 
 underground noncoal mines of fires or other emergencies. A stench sys- 
 tem alerts miners that an emergency condition exists by injepting an 
 odorant into the mine air. Although stench warning systems have been 
 used successfully for over 60 yr , present systems suffer several seri- 
 ous shortcomings, including odorant toxicity, unreliability of warn- 
 ings, widely varying stench concentrations, and others. 
 
 In 1980, the Bureau began a research program to upgrade the stench 
 warning system. The resultant system overcomes the deficiencies of ex- 
 isting systems by substituting tetrahydrothiophene for the commonly 
 used ethyl mercaptan stench odorant, and through the use of a specially 
 designed stench injector. The improved injector reliably meters stench 
 fluid into either ventilation-air or compressed-air streams at a pre- 
 cisely controlled rate. Prototype hardware has been fabricated and 
 proof-of-concept tested under both laboratory and in-mine conditions. 
 
 ^Supervisory mining engineer, Twin Cities Research Center, Bureau of Mines, Minne- 
 apolis, MN . 
 
 ^Program manager, Foster-Miller Associates, Inc., Waltham, MA. 
 
INTRODUCTION 
 
 Fires In underground noncoal mines are 
 a serious hazard to life and property. 
 From 1965 to 1979, there were 115 report- 
 able fires (at least 30 min in duration 
 or resulting in injury) in U.S. under- 
 ground noncoal mines, accounting for 119 
 fatalities (J_).-^ Countless millions of 
 dollars were spent on rescue and recovery 
 efforts, equipment repair and replace- 
 ment, and mine rehabilitation. In addi- 
 tion, mines shut down by fires were 
 forced to forego hundreds of millions of 
 tons of mineral production. 
 
 ^Underlined numbers in parentheses re- 
 fer to items in the list of references at 
 the end of this report. 
 
 The primary safety hazard in an under- 
 ground fire is contaminated air. Since 
 the mine's limited fresh-air supply can 
 be rapidly consumed and replaced by smoke 
 and toxic gas, the mine must be evacuated 
 as quickly as possible in the event of 
 fire. However, mine evacuation is often 
 a very time-consuming process. 
 
 In a recent survey of 50 underground 
 noncoal mines, emergency evacuation times 
 ranged from 5 to 85 min, with a strong 
 correlation between the time required for 
 evacuation and the maximum depth of the 
 main shaft (fig. 1) (2^). Compounding the 
 problem of longer evacuation times for 
 deeper mines is the fact that work forces 
 in deeper mines are usually larger than 
 
 to 
 O 
 
 < 
 
 X 
 
 z 
 < 
 
 IJ. 
 o 
 
 Q. 
 Ul 
 O 
 
 20 
 
 70 
 
 30 40 50 60 
 
 EVACUATION TIME, min 
 
 FIGURE 1. - Evacuation time versus maximum depth of main shaft. 
 
work forces in shallower mines (fig. 2). 
 The average work force in mines between 
 3,600 and 7,700 ft deep is 195 miners per 
 shift, whereas the average work force 
 for mines less than 1,800 ft deep is only 
 84 miners per shift. As mines become 
 deeper with the depletion of shallower 
 ore bodies , these problems of long evacu- 
 ation times and more miner exposure to 
 fire hazards will tend to get worse. 
 
 Mine fire evacuation must begin as 
 soon as possible after a fire has been 
 detected. The miners must be warned, and 
 they must then follow an emergency escape 
 preplan. Since time is of the essence, 
 detection, warning, and escape must all 
 be accomplished as reliably and quickly 
 as possible. However, fire-warning tech- 
 nology, the essential link between detec- 
 tion and evacuation, has not kept pace 
 with advances in detection and evacuation 
 planning. 
 
 In a typical stench system, ethyl mer- 
 captan, a highly odoriferous organic com- 
 pound, is released from the surface into 
 
 the compressed-air and/or ventilation- 
 air streams of the mine. The liquid is 
 quickly vaporized, and the stench is car- 
 ried in the airstreams to the working 
 areas underground. Miners, upon smelling 
 the stench, evacuate the mine according 
 to the emergency preplan. 
 
 Although the stench system has been 
 used successfully for over 60 yr, it suf- 
 fers several serious shortcomings owing 
 to certain chemical properties of ethyl 
 mercaptan and certain performance char- 
 acteristics and limitations of present 
 injection systems. These shortcomings 
 include (1) toxicity of the odorant which 
 can lead to debility in miners; (2) re- 
 activity of the odorant with iron ox- 
 ide, which can result in unreliable warn- 
 ings because the odor may fade when 
 transported long distances in steel pipe; 
 (3) lack of control over the rate of 
 agent release into the airstream, with 
 the result that some work areas may re- 
 ceive unbearably high stench concen- 
 trations while other areas are missed 
 
 200 r- 
 
 50 
 
 X 
 
 cr 
 
 LU 
 Q. 
 0} 
 QC 
 UJ 
 
 I 100 
 
 u. 
 O 
 oc 
 
 UJ 
 
 m 
 
 i 50 
 
 1,800 3,600 
 
 MINE SHAFT DEPTH, ft 
 
 FIGURE 2. - Size of underground workforce versus depth of mine. 
 
 7,200 
 
altogether; (4) lack of visual indica- 
 tions of system status, valve positions, 
 and proper system operation; and (5) ex- 
 cessively long stench transit times. 
 
 In 1980, the Bureau of Mines embarked 
 on a research program to upgrade the 
 stench warning system. The objectives of 
 this program were to improve the safety. 
 
 reliability, and effectiveness of stench 
 systems. The work done under this pro- 
 gram was accomplished through a research 
 and development contract with Foster- 
 Miller Associates, Inc., Waltham, MA O- 
 4^) , and is described in detail in this 
 report. 
 
 ALTERNATIVES TO STENCH WARNING 
 
 Although the primary thrust of the re- 
 search program was to upgrade the stench 
 system, the following sections are in- 
 cluded to acquaint the reader with avail- 
 able and near state-of-the-art mine warn- 
 ing system options. Subsequent analyses 
 of existing stench warning technology and 
 the improved stench warning system devel- 
 oped by the Bureau are more meaningful 
 when considered in the context of mine 
 warning systems in general. 
 
 Two alternatives to stench systems are 
 now used on a limited basis: electrical 
 and messenger systems. Radio systems, 
 although not in current use, are often 
 mentioned as a possible successor to the 
 stench system. 
 
 ELECTRICAL SYSTEMS 
 
 Electrical warning systems are used 
 where compressed-air equipment is not 
 used extensively and where ventilation 
 velocities are low. Bells, flashing 
 lights, gongs, and horns have been tried 
 and have achieved limited success. How- 
 ever, these systems are not effective 
 when miners are working outside the vis- 
 ible or audible range of the alarm or 
 when mine power fails. Where electrical 
 equipment is used extensively in the min- 
 ing operation, interruption of the power 
 supply has sometimes been used to signal 
 an emergency. However, this system is 
 also unreliable because power interrup- 
 tions are common in many mines, and elec- 
 trical equipment may not be in use when 
 an emergency occurs. 
 
 MESSENGER SYSTEMS 
 
 A messenger system depends on the 
 miners to physically communicate the 
 emergency warning from person to person. 
 
 Some mines use a messenger system as the 
 primary warning system, but more commonly 
 a messenger system is used as a backup to 
 the primary system. Messenger systems 
 are particularly common in small mines 
 where personnel are not spread out over a 
 large area and/or where telephone systems 
 are both reliable and extensive. The 
 chief disadvantage of the messenger sys- 
 tem is the time required for the signal 
 to be passed to each worker. 
 
 RADIO SYSTEMS 
 
 Prototypes of high frequency (HF) , 
 very high frequency (VHF) , and ultrahigh 
 frequency (UHF) leaky-feeder wireless 
 radio-transmission communication systems 
 have been constructed and tested in sev- 
 eral noncoal underground mines. Although 
 originally designed for the geometry of 
 coal mines, it was hoped these systems 
 would find application in noncoal mines 
 as well. However, test results showed 
 signal ranges were limited to 30 to 50 ft 
 from the transmission cable (5) . 
 
 An alternative to the leaky-feeder ap- 
 proach is provided by medium frequency 
 (MF) transmission. MF has the unique 
 capability to couple into, and reradiate 
 from, continuous conductors in the mine 
 (rails, trolley lines, water pipes, air 
 lines, phone lines, etc.) in such a way 
 that these conductors become not only the 
 transmission lines, but also the antenna 
 system for the signals (6^). 
 
 Although this parasitic coupling ef- 
 fect provides greater signal-transmission 
 coverage, in comparison with leaky-feeder 
 systems, MF systems have problems in 
 reliably receiving the transmitted sig- 
 nal. Large, protruding antennas are re- 
 quired on vehicular transceivers, and 
 users of personal transceivers must wear 
 
a specially designed vest containing an 
 antenna and radio-circuit modules. In 
 addition, total mine coverage is not as- 
 sured due to limits on signal range and 
 through-the-rock transmission. Miners in 
 
 remote stopes and development headings 
 that are not linked to the rest of the 
 mine by continuous conductors are most 
 vulnerable, yet typically they are faced 
 with the longest evacuation times. 
 
 DEFICIENCIES OF EXISTING STENCH WARNING SYSTEMS 
 
 The air-carried-stench system is the 
 most popular means of emergency warning 
 in noncoal mines because it is the most 
 practical, versatile, and effective means 
 currently available. Despite several se- 
 rious shortcomings , its use and accept- 
 ance is widespread because the alterna- 
 tives offer lower levels of safety and 
 reliability. Stench system deficiencies 
 addressed through this research include 
 the following: 
 
 1. Ethyl mercaptan is highly reactive 
 with iron oxide (fig. 3). There- 
 fore, the odor tends to fade when 
 it is transported in steel pipe. 
 (For this reason, ethyl mercaptan 
 is no longer used as an odorant in 
 the natural gas industry.) 
 
 2, Ethyl mercaptan is highly toxic. 
 The 8-h time-weighted average con- 
 centration limit (threshold limit 
 value, or TLV) established by the 
 
 0.5 
 
 .4 r- 
 
 0} 
 
 © 
 
 o 
 a 
 
 3 
 CO 
 
 .3 - 
 
 .2 I- 
 
 .1 - 
 
 80 120 
 
 Time, min 
 FIGURE 3. - Reactivity of ethyl mercaptan 
 with iron oxide. 
 
 200 
 
 National Institute for Occupational 
 Safety and Health (NIOSH) and the 
 American Conference of Governmental 
 and Industrial Hygienists (ACGIH) 
 is 0.5 ppm. As a comparison, the 
 NIOSH TLV for hydrogen cyanide is 
 also 0.5 ppm. An absolute limit of 
 2 ppm has been set by ACGIH for ex- 
 posures of 15 min or less. In low 
 concentrations, ethyl mercaptan can 
 cause headaches and nausea. At 
 higher levels, it can irritate the 
 skin and eyes, affect liver func- 
 tion, affect amino acid levels in 
 the blood, and retard redox 
 processes. 
 
 3. The odor intensity of ethyl mercap- 
 tan tends to increase steadily with 
 increasing stench concentration. 
 When personnel are exposed to high 
 concentrations of stench, the odor 
 can be overwhelming. 
 
 4. Ethyl mercaptan is highly corro- 
 sive to injection equipment and air 
 lines. Prolonged use of ethyl mer- 
 captan can damage injectors to the 
 extent that proper function may be 
 impaired. 
 
 5. The injection methods release the 
 stench in a totally uncontrolled 
 fashion. As a result, areas of the 
 mine near the injection point may 
 be overwhelmed by the stench odor, 
 and miners in those areas are like- 
 ly to be exposed to potential- 
 ly toxic concentrations of ethyl 
 mercaptan. 
 
 6. The injection methods have been un- 
 reliable. Injection equipment is 
 often "homemade" and "free lanced." 
 "Designs" are often strongly influ- 
 enced by the availability of mis- 
 cellaneous parts at the mine site. 
 
Typical problems include operat- 
 ing procedures that are complex 
 and therefore improperly followed, 
 frozen valves , mismatches in size 
 and shape between major system 
 components and stench-fluid refill 
 containers, and unsatisfactory 
 and/or incompatable materials of 
 construction. 
 
 Available injection equipment does 
 not permit visual system status 
 checks. An empty or nonfunctional 
 injector is not readily apparent, 
 and if unnoticed until needed dur- 
 ing an actual emergency, precious 
 time could be lost while refilling 
 it or performing repairs. 
 
 Current systems do not have visual 
 indications of valve positions. It 
 is difficult for personnel to know 
 if valves are completely open or 
 completely closed, especially when 
 valves are frozen or sluggish. 
 
 Available systems have no immediate 
 visual indications of proper system 
 operation. The only positive con- 
 firmation that the odorant has been 
 released is to contact personnel 
 underground, and this is often a 
 time-consuming process. 
 
 10. 
 
 Current systems seldom achieve to- 
 tal mine coverage. Remote work- 
 places, workplaces not using air 
 equipment , and dead-end headings 
 are often missed. 
 
 11. 
 
 Stench transport times 
 acceptably long. 
 
 can be un- 
 
 In addition, certain functional defi- 
 ciencies in the stench system are in- 
 herent due to its reliance on moving 
 airstreams to carry the warning signal. 
 The heat-induced buoyancy effects of a 
 mine fire, for example, may cause throt- 
 tling or reversals of ventilation flows. 
 Stench injected into intake air may be 
 exhausted if the intake air flow is 
 reversed. Areas with poor or slow ven- 
 tilation and/or areas distant from 
 compressed-air equipment may not receive 
 the stench warning signal. It was beyond 
 the scope of this research to treat such 
 inherent limitations. However, as mines 
 become deeper, as workings become more 
 complex, and as diesel and electric 
 equipment displace compressed-air equip- 
 ment, the need for novel warning systems 
 that will address these problems will 
 grow. 
 
 DEVELOPMENT OF IMPROVED STENCH SYSTEM 
 
 The development of an improved stench 
 system capable of safely, effectively and 
 reliably warning underground personnel 
 of an emergency was accomplished in two 
 steps: First, a stench agent was se- 
 lected; and second, an improved injector 
 was developed. 
 
 SELECTION OF STENCH AGENT 
 
 A survey of industrial gas odorizing 
 agents was undertaken to identify a suit- 
 able substitute for ethyl mercaptan. 
 Many compounds were surveyed, and five 
 were selected for detailed evaluation: 
 isopropyl mercaptan, amyl acetate (ba- 
 nana oil), dimethyl sulfide, tertiary 
 butyl mercaptan, and tetrahydrothiophene 
 (THT). Factors considered were boiling 
 
 point, freezing point, vapor pressure, 
 flashpoint, flammability limits, reac- 
 tivity, solubility in water, toxicity, 
 odor threshold, availability, cost, and 
 past industrial uses. The results of 
 the final evaluations are summarized in 
 table 1, 
 
 THT emerged as the most desirable agent 
 for use in the stench system. THT is 
 widely used in Europe as a natural gas 
 odorant and has been used successfully on 
 a limited basis in this country for the 
 same application. THT is not reactive 
 with iron oxide, so it is not subject to 
 "odor fade." The odor intensity of THT 
 tends to stabilize at a moderate, easily 
 recognizable level, and it is much less 
 corrosive than ethyl mercaptan. 
 
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In addition, available data suggest 
 that THT may be far less toxic than ethyl 
 mercaptan. Although ACGIH and NIOSH have 
 not established a TLV for THT, the lethal 
 concentration (LC50) for inhaled vapors 
 of THT is 44,200 ppm (for rats), compared 
 with an LC50 of 4,420 ppm for ethyl mer- 
 captan. Based on this finding, and a 
 NIOSH search of its TOXLINE computer- 
 ized data bank of toxic substances, the 
 Mine Safety and Health Administration 
 (MSHA) has approved the use of THT in 
 mine stench systems, provided the injec- 
 tion equipment maintains agent concen- 
 trations at nontoxic levels, (The sub- 
 stitution of THT for ethyl mercaptan in 
 existing stench systems thus does not 
 satisfy the conditions established by 
 MSHA for the use of THT in mine stench 
 fire-war ling systems), 
 
 Othe"^ pertinent chemical and physical 
 properties made THT a favorable choice 
 for use in the stench system. However, 
 like ethyl mercaptan, THT is flammable 
 (flashpoint 55° F) and needs to be mixed 
 with an inerting agent to avoid possible 
 explosion hazards. This potential hazard 
 is greatest if stench is injected into 
 compressed air. Numerous incidences of 
 compressor fires and explosions have been 
 recorded. Most were caused by ignition 
 sources, such as glowing carbon deposits, 
 igniting combustible lubricating oils in- 
 side the compressor, lines, or receiver. 
 The introduction of a flammable liquid 
 (such as a flammable stench odorant) into 
 the compressed air system would only com- 
 pound the hazard. 
 
 Laboratory flammability tests were con- 
 ducted, and it was determined that a mix 
 of 10 parts Freon 113'^ refrigerant and 1 
 part THT is totally noncombustible. Ac- 
 cordingly, the stench fluid selected and 
 used throughout the program was a 10:1 
 mix of Freon 113 and THT. 
 
 STENCH INJECTOR DEVELOPMENT 
 
 Prior to hardware development, numer- 
 ous mining companies and mine safety 
 specialists were contacted to help 
 
 set performance specifications for the 
 improved stench warning system. Both 
 performance-range and general design 
 specifications were thus developed. The 
 specifications are summarized in table 2, 
 The development program began with a com- 
 prehensive analysis of existing stench- 
 injection systems. 
 
 Existing Stench-Injection Methods 
 
 Two methods of stench injection are now 
 in common use: the vial-breaking method 
 and the pressurized-canister method. The 
 vial-breaking method employs a glass vial 
 that contains the stench fluid. The vial 
 is placed inside an airtight steel cylin- 
 der (fig. 4), which is connected in par- 
 allel to 'the compressed-air line by two 
 hoses fitted with globe valves. The sys- 
 tem is activated as follows: First, the 
 globe valves are opened to allow air to 
 pass over the vial; then, a steel plunger 
 is screwed into the cylinder to break 
 the vial (fig. 5). The broken vial re- 
 leases the stench fluid into the air- 
 stream. The practices of throwing a bot- 
 tle of stench fluid down the ventilation 
 shaft or "puddling" the fluid at the col- 
 lar of the downcast shaft are simply mod- 
 ified forms of the vial-breaking method. 
 
 Where the pressurized-canister method 
 is used, the stench fluid is contained in 
 a canister pressurized to 400 psi with a 
 fluorinated hydrocarbon propellant (fig. 
 6). The canister is connected to the 
 compressed-air line or emptied into the 
 ventilation airstream through a short 
 length of tubing (feed line in figure 7). 
 Both, systems use an ethyl mercaptan-Freon 
 mix as the stench agent. 
 
 Functional analysis and actual experi- 
 ence indicated that neither the vial- 
 breaking method nor the pressurized- 
 canister method was satisfactory because 
 they were fundamentally unable to meet 
 the established performance-range or gen- 
 eral design specifications. Alternative 
 design concepts were therefore developed. 
 
 Design Concepts 
 
 '^Reference to specific products does 
 not imply endorsement by the Bureau of 
 Mines. 
 
 Three design concepts were developed 
 and evaluated relative to the performance 
 specifications: pressurized canister 
 
TABLE 2. - Stench fire-warning system specifications 
 Performance-range specifications 
 
 Airflow, ft^: 
 
 Ventilation air 50,000-2,000,000 
 
 Compressed air 2,000-20,000 
 
 Compressed-air pressure psig. . 80-150 
 
 Stench gas concentration, ppm: 
 
 In compressed-air line '0.5-2.0 
 
 In ventilation air '0.1-2.0 
 
 Minimum duration of stench injection, min: 
 
 Into compressed air 30 
 
 Into ventilation air 10 
 
 Air temperature, °F: 
 
 Ventilation -30-125 
 
 Compressed -30-200 
 
 Equipment operating specifications: 
 
 Temperature °F. . -30-125 
 
 Humidity pet. . 20-100 
 
 Vibration (applied) ' None 
 
 Environmental corrosion pH. . 4.0-9.0 
 
 General design specification 
 
 Reliability Extremely high. (Sys- 
 
 stem should be simple 
 with a minimum number 
 of moving parts.) 
 Life expectancy Indefinite with per- 
 iodic maintenance. 
 
 Ease of operation Simple — requiring 
 
 minimal training. 
 
 System status indication Visual , including 
 
 "Ready to operate," 
 "Operating correct- 
 ly," and "Needs to be 
 refilled." 
 Injector costs, maximum: 
 
 Hardware ^$h , 900 
 
 Installation worker-h. . 8 
 
 Maintenance worker-h/month. . 0. 5 
 
 'As an added safequard, the maximum design concentration of THT is the same as that 
 of ethyl mercaptan, even though available data suggest that THT is far less toxic. 
 
 ^Median from field survey; however, a much lower figure is probably more realistic. 
 This figure does not include telemetry for remote injector activation, although tele- 
 metry may represent the single largest expense for remotely operated systems. 
 
10 
 
 FIGURE 4. - Vial-breaking stench injector. 
 
 Flexible hose 
 
 Valve 
 
 Stench fluid 
 
 Vial-breaking plunger 
 
 Screen 
 
 FIGURE 5. - Components of vial-breaking stench injector. 
 
11 
 
 FIGURE 6. - Pressurized-canister stench injector. 
 
 with metering orifice, pressure balanced 
 with metering orifice, and variable-rate 
 injection pump. Each of these concepts 
 is described below. 
 
 Pressurized Canister 
 With Metering Orifice 
 
 This concept, which provides for meter- 
 ing of the stench flow, is a logical 
 extension of the pressurized-canister in- 
 jection method already in use. The me- 
 tering capability could be added simply 
 by installing a metering orifice in the 
 stench-delivery tube of a pressurized- 
 canister injector (fig. 8). 
 
 Although the design is simple and in 
 theory could satisfy the system perform- 
 ance specifications, injector reliability 
 
 would be low. Low reliability would re- 
 sult because an extremely small orifice 
 would be required to meter the contents 
 of the pressurized canister (at 400 psi) 
 into the airstream over the desired time 
 period (10 min for ventilation air; 30 
 min for compressed air) . Internal canis- 
 ter pressurization to at least 400 psi is 
 necessary to assure complete discharge of 
 the canister contents. Orifices sized 
 O.OOI to 0.013 in would be required to 
 achieve the desired stench flow rates. 
 Particles as small as 25 vim could plug an 
 orifice of this size, and the probability 
 of encountering particles 25 yra in diam- 
 eter or larger is very high, even in a 
 clean environment. Since nothing ap- 
 proaching clean-room conditions exists at 
 a typical mine, the chances of a plugged 
 
12 
 
 Stench canister 
 
 Valve 
 
 Feed line 
 
 Bali valve 
 
 Compressed-air line 
 
 FIGURE 7. - Components of pressurized- 
 canister stench injector. 
 
 Manual valve 
 
 Pressurized canister 
 
 Pressure indicator 
 
 Filter 
 
 Solenoid valve 
 
 Metering orifice 
 
 FIGURE 8. • Pressurized-canister injector v/ith 
 metering orifice. 
 
 orifice (and, therefore, an interrupted 
 stench discharge) are also very high. In 
 addition, a wide variation in stench flow 
 rate would result owing to canister pro- 
 pellant pressure decay. The flow rate 
 could be expected to vary by as much as 
 50 pet over the period of the discharge. 
 
 Pressure Balanced With Metering Orifice 
 
 The pressure-balanced concept was de- 
 veloped to take advantage of the positive 
 features of the previous concept while 
 eliminating its undesirable features. 
 Orifices much larger than those mentioned 
 above can be used if the high pressure 
 differentials across the orifice are 
 eliminated. This can be accomplished by 
 introducing line pressure on both sides 
 of the orifice via a pressure-balancing 
 line. The concept is illustrated in 
 figure 10. The pressure difference be- 
 tween point 1 in figure 9 (just below the 
 orifice at the entry to the pressure- 
 balancing line) and point 2 (at the 
 bottom of the standpipe) is negligibly 
 small. 
 
 During steady-state flow, the fluid 
 pressure at point 2 is also roughly equal 
 to the air pressure at point 1 because 
 the fluid pressure and air pressure at 
 point 2 are in equilibrium. Since the 
 fluid pressure at point 2 is roughly 
 equal to the air pressure at point 1 , the 
 driving head exerted at the orifice is 
 equal only to the weight of the column of 
 fluid between point 2 and the orifice. 
 This driving head remains constant for 
 nearly the entire discharge, meaning the 
 flow through the orifice (the stench- 
 injection rate) is also constant during 
 nearly the entire discharge. 
 
 During startup, before the standpipe is 
 emptied of stench mixture, the flow rate 
 is greater than the steady-state flow 
 value. This does not last very long and 
 is easily minimized by making the stand- 
 pipe cross-sectional area as small as 
 possible. When the stench-mixture sur- 
 face drops below the tip of the standpipe 
 near the end of the run, the flow rate 
 begins to decrease, since effective head 
 decreases. Eventually, both the flow 
 rate and effective head drop to zero. 
 
13 
 
 Canister body 
 
 Standpipe 
 
 Mixture surface 
 
 Pressure- 
 balancing 
 loop 
 
 Airflow 
 (very slow) 
 
 Orifice 
 
 Stench mixture stream 
 (enters either compressed- 
 air line or ventilation system) 
 
 FIGURE 9. - Use of pressure-balancing line to equalize pressure across metering orifice. 
 
 This effect can be lessened by minimizing 
 the internal area of the canister below 
 the tip of the standpipe. 
 
 The important features of this concept 
 are as follows: 
 
 1. The pressure below the orifice is 
 balanced by an equal pressure above 
 the orifice so that the pressure of 
 the airstream into which the stench 
 is injected has no affect on injec- 
 tor operation. 
 
 The driving head across the orifice 
 is very low, so the size of the 
 orifice can be relatively large 
 (0.015 to 0.070 in) and still 
 achieve the desired stench flow 
 rates. 
 
 The driving head is independent of 
 the amount of stench fluid in the 
 injector canister. Therefore, the 
 injection rate does not decay as 
 the fluid level in the canister 
 drops. 
 
14 
 
 Variable-Rate Injection Pump 
 
 Concept Evaluation 
 
 The variable-rate injection pump con- 
 cept is the most precise method for 
 stench injection. A precision diaphragm 
 metering pump placed between the stench 
 canister and the airstream can effective- 
 ly control stench-fluid flow rates to ex- 
 tremely close tolerances (fig. 10). The 
 primary disadvantages of this system are 
 its complexity and its reliance on elec- 
 tric power. These factors could lead to 
 very low system reliability. In addi- 
 tion, the cost of such a system would be 
 quite high compared to that of the other 
 two concepts. 
 
 The three design concepts were sub- 
 jected to a systematic evaluation to 
 weigh their respective advantages and 
 disadvantages. The concept-evaluation 
 matrix showing the parameters evaluated 
 and the resultant ratings is shown in ta- 
 ble 3. Based on this evaluation, the 
 pressure-balanced with metering orifice 
 concept was selected for further develop- 
 ment. Detailed design and prototype fab- 
 rication followed. A drawing of the re- 
 sulting injector is shown in figure 11, 
 and operating data are shown in table 3. 
 
 Pressurized canister 
 
 Solenoid valve 
 
 Volume-metering 
 pump 
 
 Electric motor 
 
 Back-pressure valve 
 
 Pressure indicator 
 
 Filter 
 
 Metering nozzle 
 
 Manual valve 
 
 FIGURE 10. - Variable-rate injection pump. 
 
15 
 
 Standpipe 
 
 Stench fluid 
 
 Driving head 
 
 Ball valve 
 
 Pressure-balance line 
 
 To compressed air or ventilation air 
 
 FIGURE 11. - Improved stench injector design. 
 
16 
 
 TABLE 3. - Evaluation matrix for new injection-method design concepts 
 
 Parameter 
 
 Pressurized 
 canister with 
 
 Pressure 
 balance with 
 
 Variable-rate 
 injection pump 
 
 
 metering orifice 
 
 metering orifice 
 
 Rating 
 
 Value ' 
 
 
 Rating 
 
 Value' 
 
 Rating 
 
 Value' 
 
 
 Stench concentration 
 
 range. 
 
 Complexity 
 
 Filtration level required 
 Number of injector sizes 
 
 required. 
 
 Status indication 
 
 Ease of manual operation. 
 Initial cost, estimated.. 
 Operating cost, estimated 
 Number of significant 
 
 leak points. 
 Electric power required.. 
 Remote-operation 
 
 capability. 
 Temperature sensitivity.. 
 
 Reliability 
 
 Maintainability 
 
 Training requirements.... 
 
 Life expectancy 
 
 Safety 
 
 Acceptable 
 
 Low 
 
 Very high. 
 5 
 
 Fair 
 
 Good 
 
 $800 
 
 $100 
 
 15 
 
 (2) 
 
 Yes 
 
 High 
 
 Very low.. 
 
 High 
 
 Low 
 
 High 
 
 Medium. . . . 
 NAp 
 
 3 
 
 3 
 
 
 
 1 
 
 2 
 3 
 3 
 
 2 
 
 1 
 
 3 
 3 
 
 1 
 
 3 
 3 
 3 
 2 
 
 Acceptable 
 
 Low 
 
 Medium. . . . 
 3 
 
 Fair 
 
 Good 
 
 $1,800.... 
 
 $50 
 
 1 
 
 3 
 
 3 
 2 
 2 
 
 2 
 3 
 2 
 3 
 3 
 
 3 
 3 
 
 3 
 3 
 3 
 2 
 3 
 3 
 
 Acceptable 
 
 Medium. . . . 
 
 High 
 
 2 
 
 3 
 
 2 
 1 
 3 
 
 Poor 
 
 Good 
 
 $3,000.... 
 
 $100 
 
 15 
 
 Yes 
 
 Yes 
 
 Medium. . . . 
 
 Low 
 
 Low 
 
 High 
 
 Low 
 
 Low 
 
 NAp 
 
 1 
 3 
 
 1 
 2 
 1 
 
 (2) 
 
 Yes 
 
 Low 
 
 High 
 
 High 
 
 Medium. . . . 
 
 High 
 
 High 
 
 NAp 
 
 1 
 3 
 
 2 
 
 1 
 1 
 1 
 1 
 1 
 
 Total 
 
 36 
 
 46 
 
 28 
 
 NAp Not applicable. 'Maximum total = 51. ^For remote-operation capability only, 
 
 TESTING THE IMPROVED STENCH SYSTEM 
 
 A prototype of the entire improved 
 stench system was fabricated and proof- 
 of-concept tested in the laboratory and 
 at an operating underground mine to val- 
 idate its performance and highlight any 
 design deficiencies. 
 
 LABORATORY TESTING 
 
 FIELD TESTING 
 
 The improved stench system was field 
 tested at Kerr-McGee Corp.'s Church Rock 
 No. 1 uranium mine near Gallup, NM. 
 
 Mine Ventilation and 
 Compr e ssed-Air Analysi s 
 
 The system was thoroughly tested fol- 
 lowing fabrication. Tests involved 
 discharges of nonodorized liquids as 
 well as the THT-Freon 113 mixture se- 
 lected for stench warning use. Tests in 
 both ventilation-air and compressed-air 
 streams were performed. Parameters mea- 
 sured included fluid flow rates, dis- 
 charge times, and stench concentrations 
 in the airstreams. All tests indicated 
 conformance with the system performance 
 specifications (table 2). 
 
 The improved stench system releases 
 odorant into both the ventilation-air and 
 compressed-air streams, relying on these 
 airstreams to transport the waraing sig- 
 nal to the various workplaces. There- 
 fore, a thorough knowledge of these sys- 
 tems and their interactions was essential 
 in order to plan and lay out an effective 
 stench warning system. 
 
 The test mine has two main levels, des- 
 ignated 1-4 and 1-5, the 1-5 level being 
 about 300 ft below the 1-4. Raises are 
 
17 
 
 driven from these levels to the ore, 
 which is 50 to 100 ft above the level in 
 each case. Figure 12 presents the layout 
 of the haulage levels, along with the lo- 
 cations and flow rates of the ventilation 
 shaft and boreholes. 
 
 The ventilation scheme has intake air 
 downcasting through the main shaft and 
 borehole 6 to the haulage levels. The 
 air travels along the haulage drifts, up 
 the raises, through the stopes, and fi- 
 nally through a network, of exhaust drifts 
 in the ore horizon and out the exhaust 
 boreholes. Exhausting fans are located 
 on the surface at the exhaust boreholes. 
 
 For both ventilation purposes and ad- 
 ministrative reasons, the 1-4 level of 
 the test mine is divided into two seg- 
 ments. The area to the east of the two 
 air doors (fig. 12) has its own hoist- 
 ing plant, compressed-air supply, and 
 ventilation system. The two doors form 
 an airlock, and are normally closed; how- 
 ever, there is a minor leakage flow 
 from the east side to the west. The two 
 compressed-air systems are connected, and 
 there is normally a small net flow, again 
 from east to west. Thus, the stench 
 
 Venthole 2 
 95,000 ftVmin 
 upcast 
 
 Main shoft ^ 
 
 22!,00Gft7min^ 
 
 total downcast 
 
 1-4 level 
 
 tests were conducted in the west side of 
 the mine without disturbing the east 
 side. 
 
 A tracer gas technique was used to 
 determine the effectiveness of the 
 compressed-air system in transporting the 
 warning signal. The tracer gas was re- 
 leased at the point where the new stench 
 injector was to be installed, at 9:55 
 a.m. , a time when compressed-air usage 
 is usually at a maximum. Starting at 
 10:00 a.m., air samples were taken at 
 3-min intervals for 30 rain, at four loca- 
 tions underground and on the surface at 
 venthole 1. 
 
 Tracer gas was detected at all sampling 
 points. The locations of the sampling 
 points as well as the transit time of the 
 tracer gas to each point are indicated in 
 figure 13. 
 
 The rapid appearance of the tracer gas 
 in the exhaust borehole (after 8 min) in- 
 dicated that leakage from the compressed- 
 air line into the ventilation air was 
 originating not very far downstream from 
 the injection point and that the stench 
 first reached most areas of the mine 
 through the ventilation air rather than 
 in the compressed air. It is also proba- 
 ble that a large percentage of the stench 
 injected into the compressed-air line was 
 exhausted through venthole 1 after having 
 passed through only a small part of the 
 total workings. However, some stench was 
 retained in the compressed air, indicat- 
 ing that this mode of stench transport 
 can effectively supplement ventilation- 
 air transport. 
 
 Injector Locations and Installation 
 
 Venthole I 
 35,000 ftVmin 
 upcast 
 
 Main shaft 
 75,000 ftVmin 
 upcast 
 
 'Venthole 3 
 85,000 ftVm in 
 upcast 
 
 1-5 level 
 
 Venthole 6 
 45,000 ftVmin 
 downcost 
 
 FIGURE 12. - Layout of haulage levels, boreholes, 
 ond main shaft in test mine. 
 
 Ventilation-air injectors were in- 
 stalled at each of the two intake-air 
 shafts. One injector was installed in a 
 crawl space located just below ground 
 level near the top of the main shaft 
 (fig. 14). Because there was a high rate 
 of activity near the employee and sup- 
 ply hoist, the crawl space location was 
 chosen to minimize the possibility of ac- 
 cidental system activation. Approximate- 
 ly 10 ft of copper tubing was suspended 
 from the injector down into the shaft to 
 carry the stench agent. 
 
18 
 
 rrr 
 
 LEGEND 
 Main shaft 
 Exhaust borehole 
 Sampling pointin stope 
 Sampling point on haulage level 
 Transit time, minutes 
 
 1-5 level 
 
 FIGURE 13. - Sampling points and transit times for compressed-air system tracer gas analysis. 
 
 Shaft collar 
 
 Wire mesh 
 
 Copper tube 
 
 Intake air 
 
 Shaft lining 
 
 FIGURE 14. - Main shaft ventilation-air injector 
 location. 
 
 The other ventilation-air injector was 
 installed on a leg of an emergency- 
 escape-hoist headframe positioned over 
 venthole 6 about 1 mi from the main shaft 
 (fig. 15). This injector was mounted 
 approximately 7 ft above ground level to 
 discourage tampering. 
 
 Injector 
 
 Ventilation shiaft intake 
 
 FIGURE 15. - Remote venthole injector location. 
 
 The compressed-air injector was mounted 
 on the main receiver for the compressed- 
 air system (figs. 16-17). A piece of 
 copper tubing approximately 2 ft long 
 joined the injector to the main com^ 
 pressed-air line through a shutoff valve. 
 
 Test Procedures 
 
 The in-mine test consisted of using the 
 improved stench system to issue the warn- 
 ing signal during two regularly scheduled 
 fire drills. The mine's routine practice 
 was to conduct drills during all three 
 
19 
 
 From air compressor 
 
 Injector 
 
 Pressure-balancing line 
 
 Compresses-air line to mine 
 
 FIGURE 16. - Compressed-air injector location. 
 
 shifts over the course of 1 week. The 
 improved system was used for the drill 
 during the first shift (day shift) and 
 for the second-shift (afternoon) drill. 
 For comparison, the mine's existing vial- 
 breaking system was used for the third- 
 shift drill. This arrangement afforded 
 the opportunity to evaluate and compare 
 the performance of the two systems under 
 constant mine conditions. 
 
 The emergency plan at the mine is dif- 
 ferent from that of most mines in that it 
 does not call for immediate evacuation. 
 Standard procedures require miners to 
 proceed to a dead-end drift or stope with 
 an air line and build a barricade. 
 
 The standard procedure for fire drills 
 (of which the miners are always informed 
 beforehand) requires miners to note the 
 time they smell stench and proceed to a 
 dead-end drift or stope with an air line 
 and barricade materials. (Barricades are 
 not actually built.) 
 
 Environmental samplers visit each work 
 area and fill out a form showing the 
 location of each worker, the time he or 
 she smelled stench, the strength of the 
 stench, the action taken by the miner, 
 and the miner's comments. This procedure 
 was followed during all tests. 
 
 Results 
 
 The main criteria for evaluating the 
 performance of the improved stench system 
 were (1) degree of coverage, (2) elapsed 
 time between actuation of the injectors 
 and the detection of odor at various lo- 
 cations, and (3) stench concentrations 
 measured at various locations. 
 
 To give an overall view of the perform- 
 ance of both the improved system and the 
 existing system, stench transit times to 
 various areas of the mine were plotted on 
 maps of the haulage levels. These tran- 
 sit times were based on the stench arriv- 
 al times recorded by the mine's environ- 
 mental samplers during the drills. 
 
 Figures 18-21 show the results of the 
 tests of the improved system (during the 
 first- and second-shift drills and on 
 both haulage levels.) Figures 22 and 23 
 show the results of the test of the 
 existing system during the same week. 
 Since this test was run on the third 
 shift, there were fewer active workplaces 
 for which arrival times could be re- 
 corded. Therefore, the results of two 
 earlier tests of the existing system 
 were reconstructed from mine records to 
 provide a better comparison of the old 
 
20 
 
 FIGURE 17. - Compressed-air injector mounted 
 on receiver tank. 
 
 and new systems. The earlier tests of 
 the mine's existing system are illus- 
 trated in figures 24-27. 
 
 During the first-shift test of the im- 
 proved system, air samples were taken at 
 several locations in the mine while the 
 stench was noticeable at those locations. 
 These samples were then analyzed to ob- 
 tain their quantitative stench concentra- 
 tions (expressed as parts per million of 
 THT in air). The locations of the sam- 
 pling points are shown in figure 28. 
 Stench concentration versus time is 
 plotted in figure 29. Figure 29 also 
 shows the upper and lower system design 
 limits for stench concentration (from 
 table 2). Only 2 of the 10 samples col- 
 lected exceeded the 2.0-ppm upper design 
 limit, and no samples fell below the 0.1- 
 ppm lower design limit. 
 
 Of 23 miners who were interviewed dur- 
 ing the second-shift test of the improved 
 system, only 2 rated the stench as reach- 
 ing an annoying level , and none rated it 
 as reaching a sickening level, indicating 
 that odorant levels were probably very 
 near the 2.0-ppm design goal. One envi- 
 ronmental sampler commented that the 
 miners thought the new stench (THT) was 
 not as sickening as the old (ethyl 
 mercaptan) . 
 
 Mine management was pleased with the 
 improved system not only because of im- 
 provement in warning times , but also be- 
 cause of the ease and simplicity of oper- 
 ation of the new injectors. The valve 
 
 4 
 
 10 
 
 LEGEND 
 Main shaft 
 
 Sampling pointin stope 
 Sampling pointon haulage level 
 Transit time, minutes 
 
 FIGURE 18. - Stench test results, improved system, first shift, 1-4 level. 
 
21 
 
 LEGEND 
 Main shaft 
 1^ Sampling pointinstope 
 4 Sampling point on haulage level 
 10 Transittime, minutes 
 
 FIGURE 19. - Stench test results, improved system, first shift, 1-5 level. 
 
 ^ 
 
 i 
 
 14 taNo smel 
 
 LEGEND 
 Main shaft 
 ^ Sampling point in stope 
 4 Sampling pointon haulage level 
 1 Transit time, minutes 
 
 FIGURE 20. - Stench test results, improved system, second shift, 1-4 level. 
 
 LEGEND 
 
 <S) Main shaft 
 
 ^ Sampling point in stope 
 
 5 Transittime, minutes 
 
 FIGURE 21. - Stench test results, improved system, second shift, 1-5 level. 
 
22 
 
 LEGEND 
 (S) Main shaft 
 ^ Sampling point in stope 
 4 Sampling point on haulage level 
 10 Transittime, minutes 
 
 FIGURE 22. - Stench test results, existing system, third shift, 1-4 level. 
 
 LEGEND 
 Main shaft 
 ^ Sampling pointon haulage level 
 15 Transittime, minutes 
 
 FIGURE 23. - Stench test results, existing system, third shift, 1-5 level. 
 
 LEGEND 
 (^ Main shaft 
 ■^ Sampling point in stope 
 ^ Sampling point on haulage level 
 10 Transittime, minutes 
 
 FIGURE 24. - Previous stench test results, existing system, first shift, 1-4 level. 
 
23 
 
 LEGEND 
 Main shaft 
 1^ Sampling point in stope 
 ^ Sampling point on haulage level 
 1 5 Transit time, minutes 
 
 Previous stench test results, existing system, first shift, 1-5 level. 
 
 smel 
 
 4 
 
 * 
 
 LEGEND 
 Main shaft 
 
 Sampling pointin stope 
 Sampling pointon haulage level 
 
 1 5 Transit time, minutes 
 FIGURE 26. - Previous stench test results, existing system, second shift, 1-4 level. 
 
 30 
 FIGURE 27 
 
 LEGEND 
 Main shaft 
 W^ Sampling pointin stope 
 ^ Sampling point on haulage level 
 10 Transittime, minutes 
 
 Previous stench test results, existing system, second shift, 1-5 level. 
 
24 
 
 1 -4 level 
 
 LEGEND 
 
 ® Ventilation-air injection 
 point 
 
 p Sampling point in stope 
 
 i 
 
 Sampling point on haulage 
 
 FIGURE 28. 
 
 level 
 2 Sampling point number 
 
 Locations of air sampling points. 
 
 stem that breaks the vial in the existing 
 system is very difficult to turn. In ad- 
 dition, it is necessary to open two globe 
 valves whose positions are not readily 
 apparent. The improved system, which re- 
 quires only the manipulation, in any or- 
 der, of two easy-to-turn 90° valves, was 
 regarded as far superior. 
 
 The most dramatic improvement in tran- 
 sit times occurred at the western end of 
 the 1-5 level. No doubt this was due to 
 the injection of stench into intake ven- 
 tilation air at venthole 6. Substantial 
 improvement also occurred at the west- 
 ern end of the 1-4 level. This was prob- 
 ably due to the injection of stench into 
 the intake air at the main shaft. In the 
 central area of the 1-4 level, transit 
 
 times for the two systems were about the 
 same. The reason for this may have been 
 that when the existing system was used, 
 stench reached this area by leakage from 
 the compresssed-air system into the ven- 
 tilation air. This hypothesis is sup- 
 ported by the rapid appearance of tracer 
 gas that was observed in venthole 1 
 during the tracer gas test of the 
 compressed-air system. Both systems had 
 some trouble providing rapid coverage to 
 the area near the eastern boundary of the 
 1-4 level. This area is at the extremes 
 of both the ventilation and compressed- 
 air systems. Changes in the ventilation 
 system to increase airflow to these areas 
 would probably improve coverage of these 
 areas. 
 
25 
 
 3 - 
 
 E 
 o. 
 
 Q. 
 
 o 
 ^ 2 
 
 o 
 o 
 
 
 
 I 
 
 ▲ 
 
 
 I 
 
 I 
 
 KEY 
 
 A Sampling point No. 1 
 ■ Sampling point No. 2 
 
 
 
 
 
 
 A 
 
 o Sampling point No. 3 
 
 Upper design 
 
 limit 
 
 
 A 
 
 
 A 
 
 ■ 
 
 
 
 
 
 
 o 
 
 o 
 
 
 ° Lower design 
 
 limit 
 
 
 
 1 
 
 
 1 
 
 1 
 
 
 10 
 
 30 
 
 20 
 Tl ME, min 
 
 FIGURE 29. - Stench concentration versus time for air samples collected during stench tests. 
 
 40 
 
 DESIGN AND DEVELOPMENT OF SECOND-GENERATION STENCH INJECTOR 
 
 Field testing of the prototype stench 
 system was successful in that the in- 
 jectors performed according to specif- 
 ication, providing faster, more consist- 
 ent, and more controlled concentrations 
 of stench in the mine. However, the 
 field testing also highlighted certain 
 design aspects of the injector needing 
 improvement. 
 
 DEFICIENCIES IN DESIGN OF THE IMPROVED 
 STENCH INJECTOR 
 
 The following deficiencies in the de- 
 sign of the improved stench injector were 
 noted : 
 
 1. Fluid levels in the canister body 
 were not visible, and valve posi- 
 tions alone are not a reliable in- 
 dicator of system readiness. An 
 injector design that permits visual 
 system status checks is needed. 
 
 2. Refilling the injectors was a nui- 
 sance. The injectors had to be 
 removed from the mounting brackets 
 and refilled from a special con- 
 tainer (fig. 30). 
 
 3. The injector had to be removed from 
 the mounting bracket and dismantled 
 to inspect the orifice and screen. 
 
 4. Because two valves have to be 
 opened, operation of the injector 
 by remote control is somewhat com- 
 plicated. (Remote-control injector 
 operation is an extremely attrac- 
 tive feature under certain circum- 
 stances. In the field tests of 
 the improved system, significantly 
 shorter stench transit times were 
 achieved in the part of the mine 
 near the remote downcast vent 
 shaft, due to the injection of 
 stench into the ventilation 
 
26 
 
 FIGURE 30. - Refilling improved stench injector. 
 
 airstream at this location. But 
 this time advantage would be lost 
 if someone had to travel to the 
 remote shaft during a mine emer- 
 gency to manually operate the in- 
 jector. The need for remote opera- 
 tion is particularly acute where 
 distance and/or inclement weather 
 make timely access to a remote site 
 impossible. ) 
 
 5. The overall cost of the injector 
 ($1,800) was judged to be too high. 
 
 DESIGN FEATURES OF THE 
 SECOND-GENERATION INJECTOR 
 
 The deficiencies listed above formed 
 the basis for additional performance 
 and general design specifications. Based 
 
 ^^ ven 
 
 Filling 
 
 Stench 
 fluid 
 
 Delivery tube to 
 compressed oir or 
 ventilation streom 
 
 FIGURE 31. 
 design. 
 
 Second-generation stench injector 
 
 on these additional specifications, a 
 second-generation stench injector design 
 was developed (fig. 31). Although func- 
 tionally identical to the original injec- 
 tor, the second-generation unit also sat- 
 isfies these additional requirements: 
 
 1. The canister body for ventilation- 
 air injectors is made of clear 
 polycarbonate, permitting visual 
 inspection of the injector fluid 
 level. Also, during injector oper- 
 ation, bubbles can be seen rising 
 through the fluid — proof positive 
 of unhindered fluid flow, 
 
 2. A refilling standpipe permits re- 
 filling without removing the injec- 
 tor from the mounting bracket (fig. 
 32). 
 
27 
 
 3. The orifice plate and screen can 
 be quickly inspected through a 
 port on the side of the injector. 
 
 4. The injector is operated by a sin- 
 gle easy-to-turn 90° ball valve. 
 
 thus facilitating remote-control 
 actuation. 
 
 5. Widespread use of commercial compo- 
 nents reduces the overall cost of 
 the injector. 
 
 REMOTE-CONTROL SYSTEM FOR INJECTOR ACTUATION 
 
 As previously noted, improvements in 
 stench times were greatest near the re- 
 mote vent shaft. To insure that this 
 rapid warning could be duplicated in an 
 actual emergency, some form of remote- 
 control injector operation would be 
 required . 
 
 The following performance specifica- 
 tions were developed to guide the design 
 of a remote system: 
 
 1. The system telemetry must be wire- 
 less or hard-wired, as conditions 
 dictate. 
 
 2. The system must provide positive 
 feedback to the operator to indi- 
 cate successful actuation of the 
 injector(s) . 
 
 3. The system must be capable of man- 
 ual operation should remote opera- 
 tion fail. 
 
 4. The system telemetry must be capa- 
 ble of being tested for continuity 
 without actuating an injector. 
 
 5. The system must provide emergency 
 backup power to insure proper sys- 
 tem function if mine power is lost. 
 
 6. The system must be designed in ac- 
 cordance with appropriate MSHA and 
 National Fire Protection Associa- 
 tion (NFPA) standards covering 
 warning systems. 
 
 7. The system must be designed to op- 
 erate reliably in harsh mine en- 
 vironments and not be adversely 
 affected by dust, high humidity, 
 varying temperatures, and electri- 
 cal transients. 
 
 8. The system must be capable of re- 
 motely actuating one injector with 
 the capability to add additional 
 remote units if desired. 
 
 The remote system described below was 
 designed to satisfy the specific require- 
 ments of the Kerr-McGee Church Rock No. 1 
 Mine, where the second-generation stench 
 system was field tested. However, the 
 concept for the remote system is flexible 
 and can be adapted to suit differing lo- 
 cal conditions. 
 
 ^^• 
 
 FIGURE 32. - Refilling second-generation injector. 
 
28 
 
 Since no power or phone lines con- 
 nect the site of the remote vent shaft 
 with the mine office, a wireless (radio- 
 frequency) remote-control system was se- 
 lected. Wireless signal transmission be- 
 tween the two sites was provided by a 
 digital-scan-type telemetry system uti- 
 lizing frequency-shift-keyed (FSK) tone 
 telemetry. VHF FM radio transceivers 
 were used to transmit signals between the 
 two sites. 
 
 Signals were transmitted between the 
 two sites continuously to verify the 
 functional readiness of the telemetry 
 system. Fault lights were provided on a 
 master control panel (master panel) to 
 indicate telemetry failure, power loss, 
 
 etc. Battery backup power was provided 
 at the master panel and at the remote 
 site. 
 
 Operation of the remote injector was 
 accomplished by depressing a button on 
 the master panel. A digital coded signal 
 was transmitted to the remote site, where 
 it was received, decoded, and verified. 
 The valve on the injector was then ro- 
 tated. The rotation of this valve initi- 
 ated the stench release and also tripped 
 a switch that prompted the transmission 
 of a return digital coded signal to the 
 master panel. When the return signal was 
 decoded and verified, a light appeared on 
 the master panel, indicating that the in- 
 jector valve had been operated. 
 
 TESTING OF SECOND-GENERATION STENCH SYSTEM 
 
 Prototypes of all the second-generation 
 stench system components, including the 
 remote system, were built and proof-of- 
 concept tested in the laboratory and in 
 the Church Rock No. 1 Mine. The in-mine 
 tests of the complete system are summar- 
 ized below. 
 
 INSTALLATION 
 
 One complete second-generation stench 
 system, consisting of one manual com- 
 pressed-air injector (fig. 33), one man- 
 ual ventilation-air injector for the main 
 shaft (fig. 34), and one wireless remote- 
 control injector for the remote vent 
 shaft (fig. 35) was installed at the 
 Church Rock Mine. Antennas for the re- 
 mote system were installed on top of the 
 emergency-escape-hoist headframe at the 
 remote site and on the roof of the hoist 
 building near the main shaft. The two 
 antennas were in a direct line-of-sight . 
 The master panel (fig. 36) was installed 
 in the hoist building within sight of the 
 hoist operator. The telemetry equipment 
 at the remote site (fig. 37) was mounted 
 on a leg of the emergency-escape-hoist 
 headframe near the injector. 
 
 TEST PROCEDURES 
 
 Following hardware checkout, two func- 
 tional (fire-drill) tests of the system 
 
 were conducted, one during the first 
 shift and one during the second. (The 
 mine was not working a third shift at the 
 time of these tests). For both tests, 
 all three injectors were actuated si- 
 multaneously. The main shaft and com- 
 pressed-air injectors were operated manu- 
 ally. The injector at the vent shaft was 
 actuated remotely at the same time by de- 
 pressing the button at the master panel. 
 
 RESULTS 
 
 All three injectors and the remote ac- 
 tuation system performed according to the 
 specifications. The injector at the main 
 shaft had a release time of 11-1/2 min, 
 the injector at venthole 6 took 12-1/2 
 min, and the compressed-air injector took 
 32 min. The light on the master panel 
 indicated successful actuation of the 
 remote injector about 10 s after the re- 
 lease button was depressed. 
 
 The main criteria for evaluation of the 
 second-generation stench system were 
 (1) degree of coverage and (2) elapsed 
 time between actuation of the injectors 
 and the detection of the odor at various 
 locations. Since the test conditions 
 were almost identical to those present 
 during the first-generation injector 
 tests, air samples were not collected and 
 analyzed for stench concentration. 
 
 mm 
 
29 
 
 FIGURE 33. - Second-generation injector for 
 compressed air. 
 
 FIGURE 34. - Second-generation injector for 
 ventilation air installed at main shaft. 
 
30 
 
 FIGURE 35. - Wireless remotely controlled 
 stench injector for ventilation air installed 
 at remote venthole. 
 
 For the first-shift test, the elapsed 
 times from actuation to detection ranged 
 from 2 to 23 rain on both the 1-4 and 
 1-5 levels (figs. 39-40). The maximum 
 time was recorded at a location 3,400 ft 
 from the remote vent shaft injection 
 point on the 1-4 level. All recorded 
 times compared closely to those recorded 
 
 FIGURE 36. - Master panel installed inhoistroom. 
 
 during the tests of the first-generation 
 injector. 
 
 During the second-shift tests, elapsed 
 times ranged from 1 to 30 min on both the 
 1-4 and 1-5 levels (figs. 40-41). Again, 
 the maximum time was recorded at a loca- 
 tion on the 1-4 level, 3,400 ft from the 
 remote vent shaft injection point. 
 
 Mine management was pleased with the 
 improved injector design and the new re- 
 filling system. Other significant im- 
 provements over the original design were 
 one-valve actuation, the clear bowl on 
 the ventilation-air injectors, and a new 
 orifice plug for easier orifice removal. 
 Based on the success of the laboratory 
 and field testing of this system, a pro- 
 duction version is now being commercially 
 marketed. The injector is available for 
 about $1,300, and a THT refill kit is 
 available for about $100. 
 
 SUMMARY AND CONCLUSIONS 
 
 An improved stench warning system for 
 underground noncoal mines has been de- 
 veloped and succesfully in-mine tested. 
 
 The system utilizes a superior stench 
 agent (THT) and employs an injector 
 that dispenses a controlled volume of 
 
31 
 
 FIGURF 37. - Remote-control telemetry system installed on leg of emergency-escape- 
 hoist headframe at remote venthole. 
 
32 
 
 Ventholee 
 (g) . 
 
 Venthole 1 
 (g) 
 
 LEGEND 
 Main shaft 
 l| Sampling point in stope 
 4 Sampling point on haulage level 
 10 Transit time, minutes 
 FIGURE 38. - Stench test results, second-generation system, first shift, 1-4 level. 
 
 FIGURE 39. 
 
 LEGEND 
 <S) Main shaft 
 ^ Sampling point in stope 
 4 Sampling point on haulage level 
 Ventholee io Transit time, minutes 
 
 Stench test results, second-generation system, first shift, 1-5 level. 
 
 Ventholee 
 (8> 
 
 LEGEND 
 Main shaft 
 i( Sampling point in stope 
 4 Sampling point on haulage level 
 10 Transit time, minutes 
 FIGURE 40. - Stench test results, second-generation system, second shift, 1-4 level. 
 
 ^ 
 
33 
 
 5 
 
 Ve 
 
 nthole 1 \ 
 
 LEGEND 
 Main shaft 
 
 Sampling point in stope 
 Transit time, minutes 
 
 Venthole6 
 FIGURE 41. - Stench test results, second-generation system, second shift, 1-5 level. 
 
 stench fluid into either compressed or 
 ventilation air. The system is simple, 
 easy to use, requires little maintenance, 
 is easy to recharge, and is designed for 
 
 high reliability. It can be remotely op- 
 erated by either wireless ' or hard-wired 
 means. The system is commercially avail- 
 able for about $1,300 per injector. 
 
 REFERENCES 
 
 1. Baker, R. M. , J. Nagy, L. B. McDon- 
 ald, and J. Wishmyer. An Annotated Bi- 
 bliography of Metal and Nonmetal Mine 
 Fire Reports. Final report (contract 
 J0295035, Allen Corp. of America). Vol- 
 ume 1: BuMines OFR 68(1)-81, 1980, 64 
 pp., PB 81-223729; Volume 2: BuMines OFR 
 68(2)-81, 1980, 284 pp., PB 81-223737; 
 Appendix: BuMines OFR 63(3)-81, 1980, 
 390 pp. , PB 81-223745. 
 
 2. FMC Corp. Mine Shaft Fire and 
 Smoke Protection System. (Final report). 
 Volume I. — Design and Demonstration (con- 
 tract H0242016). BuMines OFR 24-77, 
 1975, 407 pp.; NTIS PB 263 577. 
 
 3. Muldoon, T. L. , T. Lewtas, and 
 T. E. Gore. Upgrade Stench Fire Warning 
 System — System Development and Prototype 
 Tests (contract H02292002, Foster-Miller 
 Associates, Inc.). BuMines OFR 136-81, 
 1981, 142 pp.; NTIS PB 82-122128. 
 
 4. Muldoon, T. L. , and K. Heller. Up- 
 grade Stench Fire Warning System, Volume 
 
 2 — Second Generation System Development 
 and Prototype Test. Final report on Bu- 
 Mines contract H0292002 with Foster- 
 Miller Associates, Inc., 1983, 96 pp.; 
 available upon request from William H. 
 Pomroy, BuMines, Minneapolis, MN. 
 
 5. Bergeron, A. A., R. L. Collins, and 
 J. L. Michels. A Communication and Moni- 
 toring System for an Underground Coal 
 Mine, Iron Ore Mine, and Deep Underground 
 Silver Mine (contracts S0133035 and 
 J037 707 6, Rockwell Int.). BuMines OFR 
 156-82, 1981, 293 pp.; NTIS PB 83-115865. 
 
 6. Dobroski, H. , and L. G. Stolarszyk. 
 A Whole-Mine Medium Frequency Radio Com- 
 munications System. Paper in Proceedings 
 of the 52nd Annual Technical Session 
 (Mines Accident Prevention Association of 
 Ontario, Toronto, Canada, May 25-27, 
 1983). MAPAO, North Bay, Ont . , Canada, 
 1983, pp. 3-15. 
 
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