TN295 
 
 No. 8832 
 
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JC^ 8832 
 
 Bureau of Mines Information Circular/1980 
 
 Automatic Fire Protection Systems 
 for Surface Mining Equipment 
 
 By William H. Pomroy and Kenneth L. Bickel 
 
 i^m^; 
 
 i UNITED STATES DEPARTMENT OF THE INTERIOR 
 
 
i4A--'- 
 
 :i 
 
 Information Circular 8832 
 
 Automatic Fire Protection Systems 
 for Surface Mining Equipment 
 
 By William H. Pomroy and Kenneth L. Bickel 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 Cecil D. Andrus, Secretary 
 
 BUREAU OF MINES 
 
 Lindsay D. Norman, Director 
 

 '^ 
 
 S)' 
 
 This publication has been cataloged as follows: 
 
 Pomroy, William H 
 
 Automatic fire protection systems for surface mining 
 equipment. 
 
 (Information circular - Bureau of Mines ; 8832) 
 
 Bibliography: p. 36-38. 
 
 Supt. of Docs, no.: I 28.27:8832. 
 
 1. Strip mining — Fires and fire prevention I. Bickel, Kennetii L., 
 joint author. II. Title. III. Series: United States. Bureau of Mines. 
 Information circular ; 8832. 
 
 TN295.U4 [TN315] 622s [622. 
 
 80-607030 
 
CONTENTS 
 
 ■Page 
 
 Abstract 1 
 
 Introduction 1 
 
 Description of prototype systems 3 
 
 Haulage trucks 3 
 
 Optical and thermal sensing, stored-pressure suppressant 5 
 
 Optical and thermal sensing, cartridge-activated suppressant.. 8 
 
 Thermal sensing, cartridge-activated suppressant 10 
 
 Thermal sensing, warning-only system 11 
 
 Fusible plastic tube sensing, cartridge-activated suppressant. 12 
 
 Coal augers 13 
 
 Dozers 16 
 
 Front end loaders 18 
 
 Thermal sensing, cartridge-activated suppressant 18 
 
 Thermal sensing, stored-pressure suppressant 20 
 
 Blasthole drills 22 
 
 Open-deck drills 23 
 
 Enclosed electric drills 24 
 
 Diesel hydraulic shovels 28 
 
 Electric mining shovels 30 
 
 Summary and conclusions 35 
 
 References 36 
 
 ILLUSTRATIONS 
 
 1 . Typical mine vehicle fire 2 
 
 2. Manually activated fixed fire-suppression system 2 
 
 3. First-generation prototype automatic fire protection system for 
 
 haulage trucks 4 
 
 4. Fire test of first-generation fire protection system for haulage 
 
 trucks 4 
 
 5 • Automatic fire protection system for coal haulers 6 
 
 6. Test of coal hauler fire protection system 7 
 
 7. Solenoid-activated spring cartridge-type actuator for 
 
 fire protection systems 8 
 
 8. Automatic fire protection system for mine haulage vehicles 9 
 
 9. Test of automatic fire protection system on an ash hauler 10 
 
 10 . Fire warning system for mine haulage trucks 11 
 
 11 . Fusible plastic tube fire-sensing system 12 
 
 12 . Automatic fire protection system for coal augers 14 
 
 13. Actuator for the coal auger fire protection system 15 
 
 14. Test of coal auger fire protection system 16 
 
 15. Automatic fire protection system for mining dozers 17 
 
 16. Explosive squib-type actuator for automatic fire suppression 
 
 systems 17 
 
 17. Test of mining dozer automatic fire protection system 18 
 
 18. Automatic fire protection system for large front end loaders 19 
 
 19. Test of large front end loader fire protection system 20 
 
 20. Automatic fire protection system for large front end loaders 21 
 
ii 
 
 ILLUSTRATIONS— Continued 
 
 Page 
 
 21. Dashboard-mounted fire protection system control panel 22 
 
 22. Automatic fire protection system for open-deck mining drills 23 
 
 23. Test of open-deck mining drill fire protection system 24 
 
 24. Automatic fire protection system for large enclosed blasthole 
 
 drills 25 
 
 25. Halon 1301 concentration test results using delayed discharge 
 
 technique 27 
 
 26. Halon 1301 concentration test results using extended discharge 
 
 valve technique 28 
 
 27 . Automatic fire protection system for hydraulic shovel 29 
 
 28. Magnetic latch- type actuator for fire suppression systems 30 
 
 29. Automatic fire protection system for an electric mining shovel 32 
 
 30. Test fire burning in a mining shovel machinery house 34 
 
 31. Test fire extinguished by discharge of Halon 1301 34 
 
 32. Halon 1301 concentration test results in the mining shovel 35 
 
AUTOMATIC FIRE PROTECTION SYSTEMS FOR SURFACE 
 MINING EQUIPMENT 
 
 by 
 
 William H. Pomroy ^ and Kenneth L. Bickel ' 
 
 ABSTRACT 
 
 Fire on surface mining equipment is a serious hazard to life and property. 
 The Bureau of Mines, through a program of contract and in-house research, has 
 developed and in-mine demonstrated reasonably priced, reliable automatic fire 
 protection systems to deal with this problem. This report reviews the devel- 
 opment and subsequent testing of systems for haulage trucks, front end loaders, 
 coal augers, dozers, drills, and shovels. A variety of fire sensors, extin- 
 guishing agents, and control systems are discussed in the context of mine 
 equipment designs and operating environments. 
 
 INTRODUCTION 
 
 Fire on surface mining equipment is a serious hazard to life and property. 
 The large size of this equipment magnifies the problem by increasing the poten- 
 tial for fires, obstructing the operators' view of fire hazards, and restrict- 
 ing their egress from the vehicles. Serious personal injuries frequently 
 result, and property damages in excess of $100,000 per fire are not uncommon 
 (fig. 1). In addition, production drops until the damaged equipment is 
 repaired or new equipment is delivered. 
 
 To avoid these problems, regulatory agencies and insurance companies 
 require fire protection hardware on these machines. Usually, a portable 
 extinguisher is mounted in or near the operator's cab, with perhaps another 
 mounted elsewhere on the vehicle. With the increasing size of vehicles, 
 however, portable extinguishers do not provide adequate protection. 
 
 Many manufacturers offer manually activated, fixed fire-suppression sys- 
 tems to supplement portable extinguishers. These systems consist of one or 
 more containers of fire suppressant (usually a dry chemical) connected by a 
 fixed plumbing network to nozzles directed at specific, predetermined fire 
 hazard areas (fig. 2). To use the system, the operator must detect the fire 
 and activate a cab-mounted electric or pneumatic releasing device, but the 
 large size of this equipment makes it difficult for an operator to see the 
 
 Mining engineer. Bureau of Mines, Twin Cities Research Center, Twin Cities, 
 Minn. 
 
FIGURE 1. - Typical mine vehicle fire. 
 
 Manual actuator 
 
 Instruction 
 nameplate 
 
 Dry chemical 
 discharge nozzle 
 
 Manual actuator 
 
 Instruction 
 nameplate 
 
 Dry chemical container 
 
 FIGURE 2. - Manually activated fixed fire-suppression system. 
 
fire until it has grown out of control. Operators often panic, fail to acti- 
 vate the system, and in their haste to escape, jump from the cab to the 
 ground, sustaining serious injury. 
 
 To avoid the problems of manually activated systems, the Bureau of Mines 
 developed automatic fire sensing and suppression systems for mining equipment. 
 This program sought to demonstrate, through in-mine tests, that rugged, reli- 
 able, cost-effective automatic systems for mine equipment could be developed 
 from existing fire protection technology. Whenever possible, off-the-shelf 
 components were used. Numerous combinations of components were tested to 
 demonstrate the flexibility of available design options. Although each system 
 was designed for a specific application, it should be noted that — 
 
 (1) Any given fire system design could be well suited to protecting many 
 different types of vehicles, and 
 
 (2) Several alternative fire system designs could be used effectively on 
 one vehicle. 
 
 Haulage trucks were selected for initial development because their fire 
 hazards are typical of most mine equipment and because they compose the larg- 
 est class of mine vehicles. Using hardware developed for military and petro- 
 chemical applications, a system was installed and tested on a 100-ton haulage 
 truck at the Cyprus Pima copper mine near Tucson, Ariz. (9^). 2 This first gener- 
 ation prototype system, which protected the truck's engine and dynamic brake 
 grids, used optical and thermal fire sensors to trigger stored-pressure dry 
 chemical extinguishers (fig. 3). Automatic controls with manual override were 
 provided. A second-generation prototype system was installed at the Erie 
 taconite mine near Hoyt Lakes, Minn., for cold weather testing. These tests 
 culminated in actual fire tests (fig. 4) and demonstrated that such automatic 
 systems are feasible. The successful demonstration of this prototype hardware 
 on haulage trucks led to the development of improved systems that were tai- 
 lored to the specific fire protection needs of many types of mining equipment. 
 
 This Bureau of Mines report discusses the development of these systems 
 and illustrates their use in mines. It is divided into seven sections, cover- 
 ing haulage trucks, coal augers, dozers, front end loaders, blasthole drills, 
 diesel hydraulic shovels, and electric mining shovels. Each section describes 
 the factors that were considered in the design of the system, development of 
 hardware components, and subsequent in-mine, on-vehicle tests. 
 
 DESCRIPTION OF PROTOTYPE SYSTEMS 
 
 Haulage Trucks 
 
 T3^ical fire hazard areas on mine haulage vehicles include the engine, 
 transmission, fuel tanks, and in some cases, dynamic brake grids. Parking 
 brake and dashboard electrical fires are common, but usually are small enough 
 
 ^Underlined numbers in parentheses refer to items in the list of references 
 at the end of this report. 
 
Extinguishers 
 
 FIGURE 3. - First-generation prototype outomatic fire protection system for haulage trucks. 
 
 
 FIGURE 4. - Fire tests of first-generation fire protection system for haulage trucks. 
 
to be put out with a portable extinguisher. The worst fires generally are 
 caused when ruptured high-pressure hoses spray combustible fluids onto hot 
 surfaces. The resulting fast-growing class B fires are difficult to extin- 
 guish and significantly impede safe operator egress, especially in larger 
 trucks, where the cab-to-ground distance can be as far as 12 feet. 
 
 Optical and Thermal Sensing, Stored-Pressure Suppressant 
 
 The long-term ruggedness and reliability of the first-generation auto- 
 matic vehicle fire protection system developed under two Bureau of Mines 
 contracts 0-6^) were evaluated by installing a system of both optical and 
 thermal fire-sensing and stored-pressure dry chemical suppression on a 120-ton 
 Wabco^ bottom-dump coal hauler in the Jim Bridger mine near Rock Springs, 
 Wyo . (18 ) . 
 
 Dual fire sensing was selected to provide both rapid response and high 
 reliability. Optical sensors trade off rapid detection for low reliability, 
 while thermal sensors trade off high reliability for slow detection. Both 
 sensor tjrpes were used to combine the positive features of each. Four near- 
 infrared optical flame detectors were mounted above and away from the mud- 
 slinging tires and under the engine hood and A-frame to observe the exhaust 
 and turbocharger areas. A thermistor-core detection cable was used with the 
 optical sensors. The 16-foot-long, steel-sheathed cable, 5/64 inch in diam- 
 eter, contained two electrical conductors separated by a semiconductor 
 material whose electrical resistance varied sharply with the temperature. 
 The resistance between the two conductors indicated temperature. (This 
 extremely rugged sensor is common on commercial aircraft and marine vessels.) 
 On the mine equipment, the heat-sensing cable was arranged in a U-shaped 
 looped circuit, with legs extending forward orer the exhaust manifolds, then 
 routed under the A-frame at the rear of the engine. An ambient temperature 
 probe was installed near the truck ladder to automatically adjust the alarm 
 setting of the thermal sensor, depending on the ambient temperature. The 
 control panel assembly consisted of an ON-OFF-TEST/RESET switch, audible and 
 visual fire warning indicators, and a manual override discharge button. The 
 manual override discharge button initiated discharge of extinguishant even 
 when the control panel power switch was off. Current was supplied directly 
 by the vehicle's battery. If an optical sensor detected a fire, a yellow 
 FAULT/FLAME warning light on the control panel illuminated and the audible 
 alarm sounded. There was no automatic discharge of the dry-chemical powder 
 if fires were sensed only by the optical sensors. If the thermal device alone 
 sensed a fire, the red FIRE warning illuminated and an alarm sounded. The 
 system automatically discharged the agent after a lO-second delay, during 
 which time the driver could stop, turn off the engine, and test the system 
 for malfunctions. Moving the control panel switch to TEST/RESET during the 
 10-second delay reset the discharge delay to provide an additional 10 seconds 
 after the control panel switch was released from the test position. 
 
 ^Reference to specific trade names is made for information only and does not 
 constitute endorsement by the Bureau of Mines. 
 
When optical and thermal sensors detected a fire simultaneously, the dry 
 chemical was immediately discharged to suppress the probable flash fire situ- 
 ation. Immediate discharge also could be initiated manually by striking the 
 discharge button. 
 
 A remote system discharge switch, located at the base of the ladder, per- 
 mitted manual actuation of the system without any fire signals, regardless of 
 the position of the control panel switch or of the truck's master switch. 
 
 The integrity of the control circuit was monitored constantly, and the 
 operator was alerted to any electrical malfunction by the yellow light and 
 pulsing horn. 
 
 Multipurpose dry chemical (monoammonium phosphate) was selected as the 
 fire suppressant agent. This agent is effective in suppressing A, B, and 
 C class fires (ordinary combustibles, flammable and combustible fluids, and 
 electrical), but is particularly effective on class B fires, which are the 
 most common class of fires on haulage trucks. The agent was contained in two 
 25-pound-capacity cylinders, pressurized to 500 pounds per square inch (psi) 
 with dry nitrogen. A switch monitored nitrogen pressure and if the pressure 
 fell below 450 psi, a yellow fault light on the control panel illuminated. 
 The cylinders were prepressurized to avoid caking of the dry chemical. Each 
 cylinder was fitted with a solenoid valve to discharge the suppressant. The 
 cylinders were housed in two protective enclosures mounted on the right front 
 corner of the truck's operator deck. A manifold connected to the outlet port 
 
 Thermal wire 
 sensor 
 
 FIGURE 5. - Automatic fire protection system for coal haulers. 
 
of each cylinder divided the flow of dry chemical through four flexible, steel- 
 brald-relnforced hydraulic hoses to fixed nozzles. Four nozzles from one cylin- 
 der each with a 180° fan-shaped discharge pattern, were directed so that the 
 flow of extinguishing agent was divided half above and half below the exhaust 
 manifolds in the engine area. Two of the four nozzles from the second cylin- 
 der had the same fan pattern and were directed to obtain equal flow over the 
 transmission. The remaining two units were 360° cone-shaped nozzles, one 
 pointed to the oil reservoir and one to the diesel fuel tank saddle mounted 
 to the rear frame. A schematic of the system design is shown in figure 5. 
 
 The system was installed on a bottom-dump coal hauler in January 1977 
 for a 10-month endurance test. After that time, the system was fire-tested 
 by applying a torch to the thermal wire sensor. An optical sensor detected 
 the presence of flame immediately and in spite of an ambient temperature of 
 40° F and cross winds through the engine area exceeding 40 mph, the thermal 
 wire responded to the heat in approximately 30 seconds. The system then 
 discharged and distributed sufficient powder to all protected areas of the 
 machine (fig. 6). 
 
 However, during this 10-month period, several weaknesses were identified 
 in the system design. The system was susceptible to false alarms during 
 periods of low vehicle-battery voltage. Although the suppressant was not 
 discharged, the fire and fault lights illuminated and the alarm sounded. In 
 addition, inductive voltage or electrical transients occasionally cycled th.e 
 
 FIGURE 6. - Test of coal hauler fire protection system. 
 
system through the test sequence. Also, during the first 2 months of the 
 endurance test, pressure was lost from the suppressant cylinders. Starting 
 the third month of the test, the originally installed neoprene seals in the 
 solenoid valve were replaced with specially manufactured cast urethane seals, 
 which corrected this problem. The optical sensors proved unreliable because 
 of dirt buildup on the lenses. The optical sensor that detected the flame 
 during the fire tests of the system responded only because its lens had been 
 wiped clean immediately prior to the test. During previous in-mine tests of 
 this sensor, false alarms caused by red sunsets, welding, etc., were a prob- 
 lem. However, no false alarms attributable to the optical sensors were 
 encountered during this test program, probably because of the rapid buildup 
 of dirt. 
 
 Optical and Thermal Sensing, Cartridge-Activated Suppressant 
 
 The same fire protection system design was tested on a 170-ton Wabco ore 
 haulage truck at the Cyprus Pima mine near Tucson, Ariz. This second system 
 was identical to the one tested on the coal hauler at the Jim Bridger mine. 
 
 Drive spring 
 
 Plunger 
 
 Drive spring plug 
 
 Puncture pin 
 
 FIGURE 7. - Solenoid-activated spring cartridge-type actuator for fire protection systems. 
 
The Installation was made under a service contract in January 1977. After 
 7 months of operation on the truck, the system was converted from stored- 
 pressure to cartridge-activated extinguishers because of recurring pressure 
 losses from the original units, and to test a specially designed cartridge- 
 puncturing device. Manually activated, fixed fire-suppression systems are 
 common on this type of equipment. Such a cartridge-puncturing device would 
 allow mine operators to convert their manual systems to automatic operation. 
 The cartridge-activated suppression system consisted of the solenoid-operated, 
 gas-cartridge-puncturing device (fig. 7), and two nonpressurized 25-lb dry 
 chemical extinguishers. When supplied with an electric current, the solenoid 
 actuated, releasing a spring-loaded puncture pin. The puncture pin pierced 
 the brass seal of a high-pressure nitrogen cartridge. The nitrogen was 
 carried to the extinguishers through a short length of hydraulic hose. The 
 gas pressurized and expelled the dry chemical from the extinguishers through 
 a fixed network of hoses to eight discharge nozzles. A schematic drawing 
 depicting the layout of the system is shown in figure 8. (As noted pre- 
 viously, the problem of pressure loss was later corrected on the coal hauler 
 with the use of improved urethane valve seats.) Following this conversion, 
 the system underwent continuing endurance tests until the test vehicle was 
 removed from production service in November 1977. 
 
 Extinguishers 
 
 Nozzle 
 
 Engine 
 area 
 
 Ambient 
 temperat 
 probe 
 
 actuator 
 FIGURE 8. - Automatic fire protection system for mine haulage vehicles. 
 
10 
 
 Field performance of this system closely paralleled that of the one on 
 the coal hauler. Pressure loss from the extinguishers and dirt buildup on the 
 optical sensors were the principal operational problems. However, unlike the 
 coal hauler system, electrical transients did not interfere with system per- 
 formance. The system was discharged once by a mine mechanic who mistook the 
 ground level remote manual discharge switch for a truck ladder light switch. 
 
 Thermal Sensing, Cartridge-Activated Suppression 
 
 Due to problems of pressure loss from prepressurized extinguishers and 
 dirt on optical sensors (as described previously) , a third system was devel- 
 oped which used cartridge-activated extinguishers and thermal wire sensing. 
 This system, which was specifically designed to retrofit automatic actuation 
 to an existing manual system, was installed on an ash haulage truck at the 
 Jim Bridger mine in February 1977 ( 18 ) . Thermistor-core wire was again used 
 as the fire-sensing element and the suppressant was supplied by cartridge- 
 activated extinguishers. The control system was similar to those described 
 previously. The heat-sensing wire, control box, and suppressant nozzles were 
 mounted as they were on the coal hauler. The actuation device was mounted 
 under the left front fender. The ground level manual actuator was mounted 
 near the base of the ladder. 
 
 FIGURE 9. - Test of automatic fire protection system on an ash hauler. 
 
11 
 
 The system was fire tested in November 1977 by applying a torch to the 
 thermal wire sensor. The system sensed the fire within about 60 seconds and 
 automatically discharged the fire suppressant agent (fig. 9). Good dry chemi- 
 cal coverage was obtained despite 40 mph cross winds through the engine area. 
 
 During the 9-month endurance test period, the control system was found to 
 be sensitive to low voltage. The problem occurred only when the engine was 
 off and the lights were on. Low voltage caused the fire alarm system lights 
 to illuminate dimly and the system to sound a weak audible alarm. Several 
 discharges of the system occurred during the test program as a result of 
 manual activation by mine personnel unfamiliar with the system. 
 
 Thermal Sensing, Warning-Only System 
 
 As a low-cost alternative to an automatic system, and to provide more 
 manual control over the fire protection system, a warning-only system was 
 developed by the Bureau to be used in conjunction with a manually activated 
 fixed fire-suppression system. This system gives the vehicle operator early 
 warning of a fire condition, but it does not automatically activate a fire- 
 suppression system. Thus, if vehicle operators are not present or should they 
 panic during fire emergencies and fail to activate the fire protection system, 
 fire suppressant will not be discharged. This warning-only system consists of 
 a thermistor-core sensing cable connected to a cab-mounted control box. The 
 control box is fitted with visual and audible fire alarms and a system circuit 
 
 Control 
 panel 
 
 FIGURE 10. - Fire warning system for mine haulage trucks. 
 
12 
 
 integrity test switch. This system was installed on a 100-ton Unit Rig haulage 
 truck at the Reserve taconite mine near Babbitt, Minn., in May 1977. The con- 
 trol box was installed directly onto the vehicle dashboard to the right of the 
 driver, with the manual fire protection system activator bolted to the top of 
 the box. The sensor wire was looped through the truck's engine area (fig. 10) 
 from mounting clips attached to the vehicle frame. The system was function- 
 ally tested following the installation and at 4-month intervals thereafter. 
 It functioned without failure during an 18-month endurance trial period. 
 
 Fusible Plastic Tube Sensing, Cartridge-Actuated Suppressant 
 
 A totally nonelectric automatic fire sensing and suppression system was 
 tested on two mine haulage trucks via a memorandum of agreement between its 
 manufacturer, the Ansul Co, of Marinette, Wise, and the Bureau from 1975 to 
 1977. To avoid dependence of the system on complex and sometimes unreliable 
 vehicle electrical systems, the firm developed a fusible plastic tube sensing 
 system that triggers cartridge-actuated dry chemical extinguishers by a pneu- 
 matic signal. The fire detector consists of three elements: detection tubing, 
 a pressure make-up device (PMD) , and a detection actuation device (DAD) 
 (fig. 11). The ij-inch-outside-diameter detection tubing, made of nylon 
 approved by the Department of Transportation for air brakes on over-the-road 
 
 Pressure 
 regulator 
 
 Acfuotion 
 spring 
 
 High-pressure 
 N2 cartridge 
 
 FIGURE n. - Fusible plastic tube fire-sensing system. 
 
13 
 
 trucks, is strung between the PMD and DAD so that it passes through all fire 
 hazard areas to be protected. A high-pressure (1,800-psl) nitrogen gas car- 
 tridge is then attached to the PMD, pressurizing the detection tubinp, through 
 a regulator to about 80 psi. As the detection tubing loses pressure through 
 slow leaks at connections Cwhich are almost impossible to avoid), the PMD 
 automatically "bleeds" in nitrogen from the high-pressure cartridge to main- 
 tain the 80 psi in the tubing. This pressure acts on a piston and puncture 
 pin assembly in the DAD to compress an actuation spring. When the heat from 
 a fire softens the detection tubing (at about 355° F) , the internal gas pres- 
 sure causes the tube to burst. The rapid release of gas allows the actuation 
 spring force to overcome the nitrogen pressure on the piston in the DAD, caus- 
 ing the puncture pin assembly to pierce the brass seal of a second high- 
 pressure nitrogen cartridge. This gas operates a cartridge-actuated fixed 
 dry chemical suppression system. The system may also be manually activated. 
 
 Both hot weather and cold weather in-mine tests of the system were per- 
 formed to determine the rate of pressure loss from the PMD cartridge. One 
 system was installed on a 150-ton ore haulage truck at the Pinto Valley copper 
 mine in Arizona. A second system was installed at the Minntac taconite mine 
 in northern Minnesota. Gas pressure inside the PMD of each system was meas- 
 ured daily with a pressure gage on the high-pressure side of the regulator. 
 Readings were taken on the Pinto Valley system for 17 months and the Minntac 
 system for 2 months. Pressure loss was approximately 2.5 psi per day at Pinto 
 Valley, indicating that a new PMD cartridge would be required after about 
 24 months of use. No pressure loss was observed on the Minntac truck. 
 
 All of these haulage truck automatic fire sensing and suppression systems 
 are now commercially available for from $850 to $5,000, depending on design 
 and capability. 
 
 Coal Augers 
 
 Primary fire hazard areas on coal augers include the auger engine com- 
 partment and (on certain machines) the auxiliary engine used to position auger 
 flights. Typical combustible fluids involved are hydraulic oil, lubricating 
 oils and greases, and diesel fuel. Also present are electrical controls and 
 ordinary combustibles such as electrical insulation, hoses, accumulations of 
 coal dust and other debris. Because people must be near both fire hazard 
 areas to operate the machine and because fast growing class B fires in these 
 areas can be expected, a reliable automatic fire suppression system is 
 essential . 
 
 In 1974, a research contract was issued to develop and in-mine test such 
 a system. The system featured spot-type, fixed-temperature thermal bimetallic 
 sensors in the two engine areas and cartridge-activated multipurpose dry 
 chemical suppression (fig. 12). When the sensors were exposed to a tempera- 
 ture of 300° F, an electrical circuit was completed which energized a solenoid- 
 operated valve. This valve released high pressure COj gas, which made a 
 puncture pin pierce a brass seal on a second COj gas cartridge (fig. 13). 
 This gas fluidized and pressurized the dry chemical in the extinguisher shells. 
 The pressurized dry chemical was piped through thin-walled steel tubing into 
 
14 
 
 Dry powder 
 extinguisher 
 
 Auxiliary engine 
 compartment 
 
 Dry powder 
 extinguisher 
 
 Nozzle 
 
 Auger engine 
 compartment 
 
 FIGURE 12. - Automatic fire protection system for coal augers. 
 
 both engine and transmission areas and also around the hydraulic control 
 panels. Semidirectional cone spray nozzles totally flooded these areas while 
 directing powder away from the operators. 
 
 The system was installed on a Compton coal auger at the Cedar Coal Co.'s 
 Chelyan, W. Va., mine in 1975. During an 8-month endurance test period, two 
 discharge tests were performed (fig. 14). In each case, discharge was suc- 
 cessful. Even with the auxiliary engine running at full throttle, powder was 
 deposited in good depth throughout the engine-transmission compartments and 
 all the hydraulic control areas. The machine operators agreed that the dis- 
 charge of the system did not interfere with safe personnel egress. 
 
 During this test period, the actuator gas cartridge lost pressure. This 
 loss was attributed to "puff-leakage" through the solenoid valve caused by 
 shock and vibration. This pressure loss would not have resulted in accidental 
 discharge of the system or impaired manual discharge capability; however, over 
 a long time period, automatic system discharge capability may have been 
 impaired. Subsequent redesign of the actuator corrected this deficiency. Sys- 
 tems based on this improved design are commercially available at from $1,000 
 to $3,000. 
 
15 
 
 Actuating 
 
 Manual override 
 plunger 
 
 Manual pull ring 
 
 Line-up sleeve 
 
 Solenoid 
 valve 
 
 Pressure 
 gage 
 
 CO2 
 regulator 
 
 Manual 
 
 electrical 
 
 switch 
 
 12-volt 
 battery 
 
 Strain- 
 relief 
 fitting 
 
 FIGURE 13. - Actuator for the coal auger fire protection system. 
 
16 
 
 FIGURE 14. - Test of coal auger fire. protection syster 
 
 Dozers 
 
 The primary fire hazard areas on a large dozer are the engine and trans- 
 mission, and hydraulic pump areas. Failure of any of the numerous lines or 
 fittings carrying high-pressure, high-temperature combustible fluids near 
 ignition sources such as hot manifolds often results in a flash fire. Because 
 egress from large dozers is difficult, such flash fires are a significant 
 safety problem. In 1975, a research contract was awarded for development and 
 testing of an automatic fire suppression system for mining dozers (12) . 
 
 The resulting system utilizes inexpensive spot-type fixed-temperature 
 thermal fire sensors and a specially designed, squib activated cartridge type 
 multipurpose dry-chemical extinguishing system (fig. 15). When any one of the 
 sensors is exposed to a temperature above 300° F, an electrical circuit is 
 closedj firing the squib. The expanding gases from this squib charge cause 
 a puncture pin to pierce the brass seal on a high-pressure nitrogen gas car- 
 tridge (fig. 16). The release of the nitrogen gas fluidizes and discharges 
 the dry chemical from the extinguisher shell. The dry chemical is piped to 
 preselected hazard areas. The system also may be manually discharged. 
 
17 
 
 Thermal fire 
 sensor 
 
 Engine 
 compartment 
 
 Dry powder 
 extinguishers 
 
 Transmission area 
 
 FIGURE 15. - Automatic fire protection system for 
 mining dozers. 
 
 Bross 
 seal 
 
 cortridqe 
 
 FIGURE 16. 
 
 Explosive squib-type actuator for auto- 
 matic fire suppression systems. 
 
 In November 1975, the 
 system was installed on a 
 Lemmons and Company Fiat 
 Allis HD 41 Tractor in 
 Boonville, Ind, The system 
 consisted of two 30-lb dry 
 chemical extinguishers, ten 
 cone spray nozzles, six 
 300° F heat sensors, a con- 
 trol box, and the necessary 
 tubing and high temperature 
 wiring. Installation 
 required approximately 
 30 manhours. 
 
 After installation and 
 a final checkout, the system 
 was successfully test fired 
 by heating one of the sen- 
 sors with a small butane 
 torch (fig. 17). Powder 
 deposition was as antici- 
 pated with good coverage on 
 the engine converter, blower, 
 fuel pump, starter, filters, 
 pumps, hoses, transmission, 
 and belly pan. The test was 
 conducted with the engine 
 running. Although some pow- 
 der was blown out of the 
 engine compartment by the 
 engine fan, this had been 
 considered in the system 
 design, and sufficient pow- 
 der remained for good cover- 
 age in all desired areas. 
 
 In February 1977, after 
 4 months of field operation, 
 a final firing test was per- 
 formed. Again a torch 
 heated one sensor and actua- 
 tion was successful . Subse- 
 quent examination of the 
 interior showed deposits of 
 power ranging from 1/32 to 
 1/4 inch over all protected 
 areas. 
 
 During the test program, 
 no operational problems with 
 
18 
 
 
 FIGURE 17. - Test of mining dozer automatic fire protection system. 
 
 the hardware were observed. This system and others with similar capabilities 
 are commercially available from $850 to $4,000. 
 
 Front End Loaders 
 
 Fire protection on large front end loaders is especially important, both 
 because of the vehicle's size and because of the relative location of the cab, 
 engine, articulation area, and egress routes. The cab on most large loaders 
 is at least 10 feet from ground level. If the operator leaps to the ground, 
 the likelihood of serious injury is quite high. Moreover, normal egress 
 routes lead past the engine and articulation areas which, owing to the presence 
 of both fuels and ignition sources, are primary fire hazard zones. To help 
 improve safety on these machines, two front end loader automatic fire protec- 
 tion systems were developed and in-mine tested. 
 
 Thermal Sensing, Cartridge Activated Suppressant 
 
 In June 1976, a research contract was awarded for development and testing 
 of an automatic fire protection system for large front end loaders. The con- 
 tractor fabricated the hardware for a Clark 675 loader, but the design is 
 flexible so the system can be used on other machines as well. The Clark 675 
 was selected for tests because of its size (24-yard capacity, overall length 
 of 50 feet, width of 17 feet, operator cab 12 feet above the ground). Four 
 extinguisher shells, each containing approximately 30 lb of multipurpose dry 
 chemical, are required to provide adequate suppressant coverage in all hazard 
 areas (fig. 18). The dry chemical is piped to the hazard areas. Cone-shaped 
 spray nozzles with hinged covers are used for agent dispersal. These nozzles 
 
19 
 
 Dry powder 
 extjnguishe 
 
 Nozzle 
 
 Engine area 
 
 Transmission 
 area 
 
 Articulation 
 area 
 
 Bucket hydraulics end parking 
 brake 
 
 FIGURE 18. - Automatic fire protection system for large front end loaders. 
 
 are relatively clog-free and disperse the agent in a wide pattern which not 
 only totally floods the interior, but also casts powder behind filters and 
 other components not directly in line with the nozzle. 
 
 Inexpensive spot-type fixed temperature thermal fire sensors are used. 
 These sensors close an electrical circuit when exposed to a temperature above 
 300° F. In the event of fire, current is supplied from a 6-volt battery 
 (independent of the vehicle's electrical system) to a squib. The squib 
 selected for this system is the same one used on the dozer, 
 from the space program and is extremely reliable. It has a 
 fire current of 1 ampere and a minimum sure fire current of 
 will not fire from two-way radio or blasting current fields, 
 gases from the squib charge causes a puncture pin to pierce the brass seal on 
 a high-pressure nitrogen gas cartridge (fig. 16). The gas is released into 
 the extinguisher shells, fluidizing and discharging the dry chemical agent. 
 Each extinguisher shell is connected to a separate battery, squib, and nitro- 
 gen cartridge; however, all the sensors are wired in series so that if any one 
 sensor detects a fire, all four extinguishing systems will discharge. This 
 design option was selected to prevent a small fire from spreading to unaf- 
 fected parts of the machine. Manual actuation is provided in the cab and on 
 the operator's deck. 
 
 It is a spin-off 
 maximum safe non- 
 2 amperes. It 
 The expanding 
 
 The system was installed on a Clark 675 loader operating at the Kellerman 
 mine near Tuscaloosa, Ala. The installation required approximately 32 man- 
 hours of labor. The system was test fired twice, once immediately following 
 
20 
 
 '^- 
 
 ■^.C*- 
 
 
 FIGURE 19. - Test of large front end loader fire protection system. 
 
 the installation and a second time following a 1-year endurance test. Both 
 discharge tests were successful with good dry chemical coverage in all hazard 
 areas (fig. 19) . 
 
 Thermal Sensing, Stored-Pressure Suppressant 
 
 The second fire protection system developed for front end loaders fea- 
 tured operator warning, greater operator control, and supervised detection and 
 actuation circuits as well as automatic actuation. Because both cartridge- 
 activated and stored-pressure dry chemical extinguishers are commonly used 
 for industrial fire protection, this design allowed the use of either extin- 
 guisher type. Also, either spot-type or thermistor-strip thermal sensors 
 could be used. The system that was actually fabricated and tested utilized 
 stored pressure extinguishers and spot-type, rate compensation thermal sensors 
 (fig- 20). 
 
 The system's dash-mounted control panel assembly consisted of an ON-OFF- 
 TEST/RESET switch, audible and visual fire warning indicators, and a manual 
 discharge button (fig. 21). If any one of the thermal sensors sensed a fire, 
 the red FIRE warning illuminated and an audible alarm sounded . The system 
 automatically discharged the agent after a 10-second delay, during which time 
 the driver could stop, shut down the engine, and test the system for 
 malfunctions. 
 
 Moving the panel switch to TEST/RESET during the delay would delay the 
 discharge 10 seconds longer . 
 
 Discharge could be initiated immediately by striking the manual discharge 
 button. The control panel did not have to be in the ON position because the 
 battery supplied power directly. A remote system discharge switch mounted at 
 
21 
 
 Extinguisher 
 
 Nozzle 
 
 FIGURE 20. - Automatic fire protection system for large front end loaders. 
 
 the rear of the loader at ground level permitted manual actuation of the sys- 
 tem without any fire signals, regardless of the position of either the control 
 panel switch or the loader's master switch. The integrity of the control cir- 
 cuit was constantly monitored and the operator was alerted to any electrical 
 malfunction by a yellow light and a pulsing horn. 
 
 The six thermal sensors were mounted in the engine and transmission 
 areas. These areas were identified as prime fire hazard zones due to the 
 presence of large amounts of flammable liquids, wire insulation and hose, and 
 such ignition sources as electrical components and hot engine or transmission 
 surfaces. Four 225° F sensors were mounted in the upper four corners of the 
 engine area. The two remaining sensors were mounted in the transmission area. 
 Because this area operated at higher normal operating temperatures than the 
 open engine space, 325° F sensors were used. 
 
 Two stored-pressure cylinders, each containing 30 pounds of ABC dry- 
 chemical extinguishing agent, were mounted on the operator's platform. The 
 four nozzles from each cylinder were mounted on the engine hood. Six 180° 
 fan-type nozzles pointed toward the engine with the discharge flow divided 
 over top and bottom. Two nozzles pointed forward into the transmission area. 
 Removing two 3/4-inch hose connections separated the nozzle manifold from the 
 hood for engine maintenance. 
 
 This system was designed, fabricated, and installed on a Caterpillar 
 992 loader at the Jim Bridger surface coal mine near Rock Springs, Wyo., by 
 
22 
 
 FIGURE 21. - Dashboard-mounted fire protection system control panel. 
 
 the FMC Corporation under a 1977 Bureau contract. This system underwent an 
 endurance test on the loader for 10 months. During the first four months, 
 both extinguishers lost significant pressure. This loss was attributed to 
 leaking Teflon seals. These were replaced with cast urethane seals and no 
 further leaking was observed. Automatic fire protection systems for loaders 
 are available from several suppliers for from $1,700 to $2,600, installed. 
 
 Blasthole Drills 
 
 The Bureau has developed and tested automatic fire protection systems for 
 two types of blasthole drills commonly used by the surface mining industry: 
 (1) smaller, open-deck diesel drills and (2) larger electric drills with 
 enclosed machinery houses. 
 
23 
 
 Open-Deck Drills 
 
 Fire hazard areas on open-deck blasthole drills include the diesel 
 engine, hydraulic pumps, compressors, controls, and miscellaneous class A 
 materials such as electrical insulation, coal dust, and debris. The most 
 severe fires generally are caused by ruptured high-pressure lines which spray 
 combustible fluids onto hot surfaces, often igniting secondary combustibles as 
 well. Safe operator egress is often impaired by such fires. 
 
 The Bureau developed and tested an automatic fire sensing and suppression 
 system for open-deck blasthole drills. The system design features spot-type, 
 fixed-temperature thermal fire sensors and multipurpose dry chemical extin- 
 guishant. The sensors are positioned above the engine and compressor areas 
 (fig. 22). They are designed to close an electrical circuit when exposed to a 
 temperature in excess of 300° F. Automatic discharge of the system is accom- 
 plished with an actuation device similar to that tested on the loader, but 
 with certain design refinements. 
 
 In the event of fire, current is supplied directly from a 6-volt battery 
 (independent of the vehicle's electrical system) to a squib. The expanding 
 gases from the squib charge causes a pin to pierce a brass seal on a high- 
 pressure nitrogen gas cartridge (fig. 16). The gas then discharges the dry 
 chemical suppressant from the extinguisher shells . Each extinguisher shell 
 is connected to a separate battery, squib, and nitrogen cartridge; however, 
 all the sensors are wired in series so if any one detects a fire, both 
 
 Drill mast 
 
 Compressor 
 
 Operator cab 
 
 Dry chemical extinguishers 
 
 Suppressant nozzle 
 Diesel engine 
 
 Heat sensor 
 
 Control box 
 
 FIGURE 22. - Automatic fire protection system for open-deck mining drills. 
 
24 
 
 FIGURE 23. - Test of open-deck mining drill fire protection system. 
 
 extinguishing systems discharge. Manual system actuation capability is pro- 
 vided in the cab, on the deck, and at ground level. 
 
 The system was installed for an endurance test on a Bucyrus-Erie 30R 
 drill operating at AMAX's Ayrshire mine near Evansville, Ind. This machine 
 is principally used for drilling coal. Installation of the system required 
 approximately 40 man-hours of labor. It was functionally tested immediately 
 after installation and again after a 1-year endurance test. Both discharges 
 were satisfactory, with powder deposited from 1/32 to 1/4 inch in all pro- 
 tected areas (fig. 23). During the endurance test period, the system was 
 partially dismantled for normal drill maintenance and reassembled by mine 
 maintenance personnel without supervision. No operational problems with 
 this system were encountered. 
 
 Enclosed Electric Drills 
 
 Large, enclosed, electrically powered blasthole drills present complex 
 fire protection problems. The machinery house and operator cab contain high- 
 voltage electrical apparatus, so an electrically conductive agent such as 
 water or foam cannot be used safely. These areas also contain delicate 
 electrical switching gear, which would be severely damaged by the residual 
 deposits of dry chemical if that agent was used. However, these areas are 
 
25 
 
 completely enclosed, so a "clean," electrically nonconductive gas-type agent 
 like COj (carbon dioxide) or Halon 1301 (bromotrifluoromethane) can be used 
 safely and effectively. Because of the life safety hazard of using COj in an 
 enclosed, occupied area, Halon 1301 was preferred. On most machines, the 
 transformer room is not adequately enclosed for Halon because the floor is 
 made of an expanded metal material that allows leaking dielectric fluids to 
 drain to the ground. However, the transformer room does not house delicate 
 electrical switching gear, so use of a dry chemical agent can be permitted. 
 Therefore, the optimum fire protection system design for most enclosed, elec- 
 trically powered drills requires both dry chemical and Halon 1301. 
 
 In June 1976, the Bureau contracted for installation and in-mine testing 
 of a system based on the above conceptual design (fig. 24). The hardware was 
 assembled and installed on a BE 61R drill operating in the Ayrshire mine near 
 Evansville, Ind. 
 
 The system offers automatic activation with manual override controls, and 
 uses spot- type, rate compensation thermal sensors to detect fires. Operation 
 of the dry chemical subsystem is identical to that on the open-deck drill sys- 
 tem described previously. Operation of the Halon 1301 subsystem is more com- 
 plex because of the nature of the agent. When any sensor in the operator cab, 
 hydraulics room, or machinery house reaches a temperature of 300° F, the 
 Halon 1301 system automatically begins an actuation sequence. First, a bell 
 sounds to warn the operator and the machine is automatically shut down through 
 the ground fault interrupter circuit. Af ter a 40-second delay, a horn sounds 
 and 50 lb of Halon 1301 is discharged through a solenoid-operated valve to 
 nozzles in each area. The 40-second delay is necessary to allow time for 
 
 Visual and 
 audible alarms 
 
 Nozzle 
 
 Thermol sensor 
 
 Transformer 
 room 
 
 Dry chemical 
 extinguisher 
 
 Halon extinguisher 
 
 Hydraulics room 
 
 Operator 
 cab 
 
 FIGURE 24. - Automatic fire protection system for large enclosed blosthole drills. 
 
26 
 
 the ventilation fans to stop completely to avoid blowing the Halon gas out of 
 the machine. 
 
 The system was designed to Induce a minimum 5 vol-pct concentration of 
 Halon 1301 as required by NFPA 12A. The maximum Halon 1301 concentration 
 allowed by NFPA 12A is 7 pet for total flooding systems in normally occupied 
 areas where egress cannot be accomplished in 1 min. Where egress can be 
 accomplished in less than 1 min, a 10 pet maximum concentration is allowed. 
 Research has demonstrated that lower effective extinguishing concentration for 
 Halon 1301 to be 2.5 pet for PVC wire insulation (1^) and transformer oil (7^). 
 
 Following installation, a Halon discharge test was performed to measure 
 agent concentrations in the operator cab, hydraulics room, and machinery 
 house. Gas concentrations were measured in all three rooms with a Cardox 
 Halon Analyzer. The concentration was excessive in the cab, but insufficient 
 in the machinery house. The low machinery-house concentration was attributed 
 to the many unclosable openings in this area such as ventilation louvers, fan 
 openings, and pipe and cable runs. 
 
 To correct these problems, the operator cab nozzle orifice was reduced 
 and a second "make-up" Halon bottle was added to the system. The actuation 
 sequence was then modified to discharge the 20-lb "make-up" bottle approxi- 
 mately 1-1/2 min after the 50-lb primary discharge to boost the concentration 
 in the machinery house. These system design changes were tested and resulted 
 in satisfactory concentrations of from 2.5 to 7 pet for about 4 min in all 
 three areas. After an approximate 1-year endurance test, the system was again 
 discharge-tested to measure agent concentrations. Concentration varied from 
 2.5 to 8.5 pet for 2 to 6 min in the machinery house with slightly lower 
 values in the other two areas (fig. 25). Although the design concentrations 
 were achieved, the soaking time may not have been adequate to extinguish 
 certain class A materials. 
 
 In an effort to lengthen the Halon soaking time without causing unsafe 
 (high) agent concentrations, a research contract was issued to test an 
 extended discharge Halon valve. This system, tested on a Bucyrus-Erie 61R 
 drill, also utilized two Halon bottles. However, unlike the design described 
 above, both a 46-lb primary charge and a 19-lb make-up charge are discharged 
 simultaneously. In this case, the make-up bottle is connected to the primary- 
 agent-distribution piping network through a metering orifice. Halon flow 
 through this tiny orifice is matched closely to the estimated rate of escape 
 of Halon through the unclosable openings in the drill. In this way, a more 
 consistent Halon concentration can be maintained over a longer time period. 
 In tests of the extended discharge system, Halon concentrations of 2.5 to 
 7 pet were maintained in the machinery house for more than 10 min (fig. 26). 
 Measured concentration in the hydraulics room dropped below 2.5 pet after 
 about 2 min. Actual concentrations were probably slightly higher owing to 
 the extreme elevation of the sampling points. 
 
 In addition to measuring agent concentrations, these tests involved 
 extinguishing test fires with the system. Two steel fire test cannisters, 
 approximately 5 in tall by 3 in in diameter, containing a cleaning solvent 
 
27 
 
 4 5 6 
 TIME, minutes 
 
 FIGURE 25. - Halon 1301 concentration test results using delayed discharge technique 
 (blasthole drill). 
 
 used on the drill, were placed in the operator's cab and hydraulic enclosure. 
 A third cannister approximately 8 in tall by 5 in in diameter containing 
 cleaning solvent and a bundle of plastic insulated electrical wire was placed 
 in the machinery house. The fires were allowed to burn for about 3 min, then 
 the system was manually discharged. All three fires were extinguished in 8 to 
 10 seconds from the start of the discharge. Extinguishment of these test 
 fires is indicative of the suppression capability of the system in an actual 
 fire situation. After a 2-year endurance test period, no operational failures 
 of this system have occurred. These automatic fire protection systems for 
 blasthole drills are now available commercially and vary in cost from $1,700 
 to $3,500. 
 
28 
 
 10 
 
 LlI 
 
 o 
 
 o 
 (J 
 
 o 
 
 rO 
 
 _i 
 < 
 
 KEY 
 Machinery house 
 Hydraulic room 
 Lower effective Haion 1301 
 concentrotion, PVC wire insulation 
 
 and transformer oil 
 
 Design concentration 
 
 Maximum allowable Halon 1301 
 
 concentration m normally occu- 
 pied areas 
 
 12 3 4 5 6 
 
 TIME, minutes 
 
 FIGURE 26. - Halon 1301 concentration test results using extended discharge valve technique 
 (blasthole drill). 
 
 II 
 
 Diesel-Hydraulic Shovels 
 
 Fire protection on hydraulic shovels is essential because of the presence 
 of large amounts of combustible hydraulic fluids and diesel fuel at high tem- 
 peratures and pressures. A thorough analysis of the fire hazards on these 
 shovels was conducted to determine which areas most needed protection. The 
 rear upper structure of the machine, which houses the diesel engine and 
 hydraulic pumps, was designated the primary hazard zone because it has exces- 
 sive loading of fuels and such ignition sources as exhaust manifolds, blowers, 
 and frictional heat sources. The ring gear area where grease can accumulate 
 was designated a secondary hazard zone because fires originating in other 
 parts of the machine could spread to this area. The design developed called 
 for protection in both hazard zones. 
 
 The system included a thermistor core, thermal wire sensor strung 
 throughout the rear upper structure; a cartridge-operated, eight-nozzle dry 
 chemical suppression system; supervised sensing and actuation circuits with 
 manual override controls in the cab and at ground level; and automatic engine 
 shutdown upon system actuation (fig. 27). 
 
29 
 
 Suppressant 
 
 distribution 
 piping 
 
 Contro 
 panel 
 
 Thermal 
 
 sensor 
 
 coble 
 
 Nozzle 
 
 Ground level 
 manual actuation 
 
 Automatic 
 actuation 
 device 
 
 Extinguisher shells 
 with pressurizing 
 gas cartridges 
 
 FIGURE 27. - Automatic fire protection system for hydraulic shovel. 
 
 The fire sensor is the same as that used on the ash hauler. It consists 
 of two electrical conductors housed in a thin steel casing. The conductors 
 are separated by a thermistor material whose resistance varies inversely with 
 temperature. The resistance between the two wires is monitored by the sys- 
 tem "^s control panel. This type of thermal sensor has been commercially avail- 
 able for many years and is commonly used in military, aerospace, and other 
 rugged applications. When the cable is exposed to a temperature of 240° F, 
 a current is supplied to the suppression system actuation device. This actua- 
 tion device (fig. 28) consists of a puncture pin fixed to a piston. Also 
 attached to the piston is a spring held in compression by the magnetic attrac- 
 tion between the piston and a permanent magnet. When a current is supplied 
 to the actuation device, an electromagnet energizes, disrupting the field of 
 the permanent magnet and releasing the piston. The puncture pin fixed to the 
 piston pierces the seal of a high-pressure nitrogen gas cartridge. The gas 
 thus released pressurizes the suppression system's pnetmiatic actuation circuit 
 and 40 lb of multipurpose dry chemical fire suppressant is expelled through 
 fixed distribution lines to eight nozzles located in the rear upper structure 
 and ring gear area. The vehicle batteries supply the 12-volt electrical power 
 for system operation. The control panel circuits are completely supervised 
 to warn the operator of any electrical malfunctions in the system. Manual 
 override controls are in the cab and at ground level. The actuation circuit 
 
30 
 
 Solenoid 
 
 Actuation 
 spring 
 
 Ng e 
 port 
 
 N2 cartridge 
 
 Brass 
 seal 
 
 FIGURE 28. 
 
 Magnetic latch-type actuator for fire 
 suppression systems. 
 
 also is fitted with an 
 interlock to shut down the 
 engine in the event of fire. 
 
 The complete system was 
 installed on a Poclain HC300 
 hydraulic shovel at Pitts- 
 burg and Midway Coal Co.'s 
 Empire mine near Pittsburg, 
 Kans . The system underwent 
 1 year of endurance testing 
 without failure. 
 
 Electric Mining Shovel s 
 
 Primary fire hazard 
 areas on electric mining 
 shovels are the electrical 
 apparatus and lubricants in 
 the machinery house and the 
 roller path/collector ring 
 area inside the crawler 
 base. A fire in either of 
 these areas could impede 
 safe operator egress and 
 result in considerable 
 property damage. A research 
 contract was awarded to 
 develop and in-mine fire 
 test an automatic fire pro- 
 tection system for electric 
 loading shovels . 
 
 The suppression system 
 design requirements for the 
 machinery enclosure of a mining shovel were analyzed. Because the possibility 
 of human occupancy exists during shovel maintenance work and periodically dur- 
 ing machine operation, only fire control agents that are nontoxic when used in 
 recommended fire extinguishing concentrations could be considered. The pres- 
 ence of electric controls and equipment (in some instances solid state 
 controls) also demands consideration of agent residue removal. A gaseous 
 agent such as Halon 1301 satisfies both toxicity and cleanliness requirements. 
 However, almost complete enclosure integrity must be insured if Halon alone is 
 to be used safely and effectively, and significant differences exist in the 
 degree of enclosure integrity between the various shovel types and sizes. The 
 rope opening, the major unclosable opening in the machinery enclosure, can 
 vary from a 4- to 5-sq-ft area to an area several feet wide and extending the 
 height of the machine. 
 
 Two alternatives for protection of mining shovel machinery spaces were 
 developed. Where enclosure is adequate, a Halon 1301 system is recommended. 
 
31 
 
 In cases where the cable opening size prohibits use of a gaseous agent alone, 
 dry chemical is used to protect the main room while Halon 1301 is piped into 
 the electrical enclosures. This arrangement insures complete agent penetra- 
 tion in these enclosures and also prevents dry chemical from contacting elec- 
 trical controls. This eliminates a significant portion of the cleanup effort. 
 In either design alternative, the suppression system is designed to totally 
 flood a 5 pet minimum concentration of Halon 1301 and maintain an extinguish- 
 ing concentration for approximately 10 minutes. To compensate for the unclos- 
 able ventilation openings and rope opening, the concentration is maintained 
 through application of the extended discharge technique described in NFPA 
 12A, A-2-5.3. The extended discharge is provided by a separate Halon supply 
 connected to the distribution piping through a metering orifice. The orifice 
 is sized to correct for the anticipated leakage through unclosable openings. 
 The length of the extended discharge will vary from approximately 8 to 10 min- 
 utes, depending on the initial pressure and temperature of the storage cylin- 
 der. Environmental and operating conditions support the use of fixed- 
 temperature thermal detectors to sense the fire. 
 
 In operation, both systems shut down the ventilation system and sound an 
 audible alarm upon detection of a fire. Following a delay to allow the oper- 
 ator time to safely stop the motion of the shovel and evacuate the machine, 
 power is removed via the ground fault system and the agents are released. The 
 alarm continues to function until disconnected from the emergency power supply. 
 
 Protection of the collector ring area beneath the machinery deck is best 
 accomplished with dry chemical because of this area's open construction. 
 Detection, agent storage, and distribution are dependent on access to the 
 collector ring area and power, if available in the crawler base. 
 
 A system conforming to these conceptual design criteria was fabricated 
 and installed on a Bucyrus-Erie 150B shovel operating in the Peabody Coal Co., 
 Lynnville mine near Evansville, Ind. (fig. 29). The particular machine 
 selected for tests offered adequate enclosure integrity for Halon 1301 to 
 be used alone in the machinery house. 
 
 The Halon storage reservoirs are DOT 4BW-500 cylinders equipped with dif- 
 ferential pressure valves. The initial discharge cylinder, containing 90 lb 
 of Halon 1301, is equipped with a solenoid actuator. Two extended discharge 
 cylinders, containing 75 lb each of Halon 1301, are equipped with slave pneu- 
 matic operators. Both extended-discharge cylinders discharge to a common 
 orifice plate located in the distributing piping. 
 
 Fire detection is provided by 190° F spot-type, rate compensation thermal 
 fire detectors. The detectors are above the motor-generator sets, the lubri- 
 cation storage area, the main transformer cabinet, and centrally above the 
 rope-handling machinery. Manual actuators are in the operator's enclosure 
 and near the main exit from the machinery house. Alarm horns are within the 
 machinery and operator enclosures. Also controlled are the ventilation and 
 equipment shutdown and three magnetic door holders. Because of the particular 
 ventilation arrangement of this machine, the doors must be open during periods 
 of warm weather. The function of door holders is to hold the doors in the 
 
32 
 
 Rope drum thermal sensor 
 
 Electrical cabinets thermal sensor 
 Warning horn 
 
 Manual discharge control 
 Control box 
 
 Dry chemical nozzle 
 Linear thermal sensor 
 
 System actuator 
 
 Dry Chemical extinguisher 
 
 Lubricant storage thermal sensor 
 
 Fan control 
 
 Motor - generator set thermal sensors 
 
 Collector ring/ roller path area 
 
 FIGURE 29. - Automatic fire protection system for on electric mining shovel. 
 
 open position when desired. When activated, the magnetic holders release the 
 doors, which are then closed by spring hinges. At all times, the doors can be 
 manually released by pulling them away from the holder. 
 
 The Halon system distribution piping system is described in figure 25. 
 It contains approximately 30 ft of llg-inch piping and one centrally located 
 Halon 1301 nozzle. The nozzle and piping are hydraulically balanced to pro- 
 vide an initial discharge of less than 10 sec. The piping also distributes 
 the agent during the extended discharge. 
 
 The collector ring system supplies 20 lb of multipurpose dry chemical to 
 four nozzles through hydraulic hose. The chemical storage container, 
 
33 
 
 distribution hose, and nozzles are mounted on the revolving frame of the 
 shovel, and are installed to flood the volume housing the collector rings and 
 center pin by injecting the chemical above the shovel swing rollers. Each 
 nozzle produces an approximately 180° flat pattern which, when aimed at the 
 center pin from the four nearly equally spaced points, assures complete 
 coverage . 
 
 The dry chemical system detection and actuation device is a self- 
 contained pne'omatic unit employing heat-sensitive pneumatic tubing for detec- 
 tion. This is the same system described earlier for the haulage truck (p. 12). 
 The two main components of the system are the pressure make-up device (PMD) 
 used to pressurize the detection tubing, and the detection actuation device 
 (DAD). 
 
 Upon rapid loss of pressure in the detection tubing, which bursts when 
 exposed to a temperature of 355° F, the DAD punctures a nitrogen cartridge and 
 sends a pneumatic actuation signal to the dry-chemical suppression system. A 
 pressure-operated electrical switch, installed in the detection line, also 
 reacts to a rapid pressure drop and sounds alarm horns in the operator cab 
 and machinery enclosure. 
 
 The installed Halon suppression system was fire tested at the Lynnville 
 mine after a 1-month shakedown period. As part of this test, two fire canis- 
 ters, approximately 8 in tall by 5 in in diameter were placed in the machinery 
 enclosure. Cleaning solvent and wiring in the canister were ignited and 
 allowed to burn until established (fig. 30). The system was then actuated 
 using the pull station located near the exit from the machinery enclosure. 
 Immediately upon actuation, the alarms sounded, the doors closed, and the 
 ventilating fan was shut down. Following a 30-second delay, the motor- 
 generator sets were shut down and the Halon discharge began. The test fires 
 were completely extinguished in 8 to 10 seconds after the discharge started 
 (fig. 31). The concentrations during the initial and extended discharge 
 period were recorded on a Cardox Halon analyzer from sampling points near 
 the ceiling of the compartment, one approximately midway along the side of 
 the enclosure, and the other at the rear of the machine near the fan opening. 
 
 The initial discharge quickly achieved the design concentration. (The 
 test fires were extinguished in 8 to 10 sec after the start of the discharge.) 
 However, during the extended discharge, the concentration fell quickly to 
 approximately 2.5 pet (fig. 32). The most probable causes for the drop in 
 measured concentration are the height of the sampling points and the failure 
 to account for the combined effects of the smaller openings. 
 
 After 1^ years of continuous use on the shovel, no operational system 
 failures have occurred. Automatic systems based on this and similar designs 
 are now commercially available from several suppliers for about $5,500. 
 
34 
 
 FIGURE 30. - Test fire burning in a mining shovel machinery house. 
 
 'J*^i5ti»S*t«)?«Kf?to.'».^?1?i«««-<' 
 
 FIGURE 31. - Test fire extinguished by discharge of Halon 130T 
 
35 
 
 o 8 
 
 Q. 
 
 , 7 
 
 o 
 
 ^ 6 
 cc 
 
 I- 
 z 
 
 liJ c 
 CJ --' 
 
 O 
 
 o 
 
 _ 4 
 o 
 ro 
 
 < 
 ^ 2 
 
 I - 
 
 T 
 
 T 
 
 KEY 
 
 Midway along side of enclosure 
 Near reor fan opening 
 Design concentration 
 
 Lower effective Holon 130! 
 concentration, PVC wire insul- 
 ation and transfornner oil 
 Maximum allowable Halon 1301 
 
 concentration in normally occu- 
 pied areas 
 
 I 2 3 4 5 6 7 8 
 
 TIME, minutes 
 FIGURE 32. - Halon 1301 concentration test results in the mining shovel. 
 
 10 
 
 SUMMARY AND CONCLUSIONS 
 
 Fires on mobile surface mining equipment are a serious safety hazard and 
 interfere with normal mine production. Automatic fire sensing and suppression 
 systems that use off-the-shelf components have been developed by the Bureau of 
 Mines for this equipment. Based on in-mine trials on haulage trucks, first 
 generation prototypes have been refined to improve their performance and modi- 
 fied to adapt to the specialized fire protection needs of a wide variety of 
 mine equipment types and mining conditions. Long-term in-mine evaluations 
 have proven the ruggedness and reliability of these systems in the harsh min- 
 ing environment. Systems patterned after Bureau-developed designs are now 
 commercially available to the mining industry. System hardware and installa- 
 tion costs vary from about 1 pet of equipment capital cost for haulage trucks 
 to about 0.4 pet for electric mining shovels. 
 
36 
 
 REFERENCES 
 
 Cholin, R. R. How Deep Is Deep? (Use of Halon 1301 on Deep-Seated 
 Fires). Fire Journal, v. 66, No. 2, January 1972, 8 pp. 
 
 deLime, T. L. Improved Off-the-Road Vehicle Fire Protection. Pres . at 
 82d National Fire Protection Association Annual Meeting, Anaheim, 
 Calif., May 15, 1978, 22 pp. 
 
 FMC Corporation, Advanced Products Division. Improved Sensors and Fire 
 Control Systems for Mining Equipment. Phase I. BuMines Open File 
 Rept. 25(1) -74, 1972, 252 pp.; available for consultation at Bureau 
 of Mines libraries in Pittsburgh, Pa., Twin Cities, Minn., Denver, 
 Colo., and Spokane, Wash., and at the Central Library, U.S. Department 
 of the Interior, Wash., D.C. Also available from National Technical 
 Information Service, Springfield, Va., PB 232 405/AS. 
 
 . Improved Sensors and Fire Control Systems for Mining Equipment. 
 
 Phase II. Final Report. BuMines Open File Rept. 25 (2) -74, 1973, 
 178 pp.; available for consultation at Bureau of Mines libraries in 
 Pittsburgh, Pa., Twin Cities, Minn., Denver, Colo., and Spokane, Wash., 
 and at the Central Library, U.S. Department of the Interior, Wash., 
 D.C. Also available from National Technical Information Service, 
 Springfield, Va., PB 232 406/AS . 
 
 _. System Modification and Validation Testing of Fire Protection 
 
 Systems for Mine Haulage Trucks. BuMines Open File Rept. 33-74, 1974, 
 170 pp.; available for consultation at Bureau of Mines libraries in 
 Pittsburgh, Pa., Twin Cities, Minn., Denver, Colo., and Spokane, Wash., 
 and at the Central Library, U.S. Department of the Interior, Wash., D.C. 
 Also available from National Technical Information Service, Springfield, 
 Va., PB 234 577/AS. 
 
 . A Guide to the Selection of Automatic Fire Protection Systems for 
 
 Mine Haulage Equipment. BuMines Open File Rept. 34-74, 1974, 8 pp.; 
 available for consultation at Bureau of Mines libraries in Pittsburgh, 
 Pa., Twin Cities, Minn., Denver, Colo., and Spokane, Wash., and at the 
 Central Library, U.S. Department of the Interior, Wash., D.C. Also 
 available from National Technical Information Service, Springfield, Va., 
 PB 234 575/AS. 
 
 Ford, C. L. An Overview of Halon 1301 Systems. Proc. ACS Sjnnp. on 
 Halogenated Fire Suppressants, San Antonio, Tex., Apr, 23-24, 1975, 
 63 pp. 
 
 Jewett, J. W, Fire Suppression Systems. Pres. Soc. of Automotive Engi- 
 neers Off-Highway Vehicle Meeting, Milwaukee, Wise, Sept. 5-8, 1979. 
 SAE Technical Paper Series 790779, 16 pp. 
 
 Johnson, G. A., and D. R. Forshey. Automatic Fire Protection Systems for 
 Large Haulage Vehicles: Prototype Development and In-Mine Testing. 
 BuMines IC 8683, 1975, 16 pp. 
 
37 
 
 10. . Improved Fire Protection Systems for Surface Coal Mining Equip- 
 ment. Pres. at Society of Automotive Engineers Off-Highway Vehicle 
 Meeting, Milwaukee, Wise, Spet. 12-15, 1977. SAE Technical Paper 
 770744. 
 
 11. Kasten, A. E., G. R. Reid, and R. Plog. Develop and Test an Automatic 
 
 Fire Control System for Surface Mining Machinery. Final Report, 
 Volume I. BuMines Open File Rept. 119-78, 1977, 163 pp.; available 
 for consultation at Bureau of Mines libraries in Pittsburgh, Pa., 
 Twin Cities, Minn,, Denver, Colo., and Spokane, Wash., and at the 
 Central Library, U.S. Department of the Interior, Wash., D.C. Also 
 available from National Technical Service, Springfield, Va., 
 PB 293 983/AS. 
 
 12. Lease, W. D. Development and Testing of Fire Protection System for Coal 
 
 Augers. BuMines Open File Rept. 25-76, 1975, 13 pp.; available for 
 consultation at Bureau of Mines libraries in Pittsburgh, Pa., Twin 
 Cities, Minn., Denver, Colo., and Spokane, Wash., and at the Central 
 Library, U.S. Department of the Interior, Wash., D.C. Also available 
 from National Technical Information Service, Springfield, Va., 
 PB 249 865/AS. 
 
 13. . Development, Installation, and Testing Services for an Automatic, 
 
 Point-Type Thermal Sensor Fire Protection System on a Mining Dozer. 
 BuMines Open File Rept. 71-77, 1976, 18 pp.; available for consulta- 
 tion at Bureau of Mines libraries in Pittsburgh, Pa., Twin Cities, 
 Minn., Denver, Colo., and Spokane, Wash., and at the Central Library, 
 U.S. Department of the Interior, Wash., D.C. Also available from 
 National Technical Information Service, Springfield, Va., PB 266 075/AS. 
 
 14. Pomroy, W. H. Improved Automatic Fire Protection System for Off-Highway 
 
 Mine Vehicles. Pres. at Society of Automotive Engineers Off-Highway 
 Vehicle Meeting, Milwaukee, Wise, Sept. 5-8, 1979. SAE Technical 
 Paper Series 790880. 
 
 15. Reid, G. R. Fire Protection System for Mobile Underground Metal Mining 
 
 Equipment. BuMines Open File Rept. 111(1) -77, 1976, 235 pp.; available 
 for consultation at Bureau of Mines libraries in Pittsburgh, Pa., 
 Twin Cities, Minn., Denver, Colo., and Spokane, Wash., and at the 
 Central Library, U.S. Department of the Interior, Wash., D.C. Also 
 available from National Technical Information Service, Springfield, Va., 
 PB 268 735/AS. 
 
 16. . Automatic Fire Protection System for Mobile Underground Metal 
 
 Mining Equipment. Selection and Use Manual. BuMines Open File Rept. 
 Ill (2) -7 7, 1976, 16 pp.; available for consultation at Bureau of Mines 
 libraries in Pittsburgh, Pa., Twin Cities, Minn., Denver, Colo., and 
 Spokane, Wash., and at the Central Library, U.S. Department of the 
 Interior, Wash., D.C. Also available from National Technical Informa- 
 tion Service, Springfield, Va., PB 268 769/AS. 
 
38 
 
 17. Roehlich, F., Jr. Demonstration of Fire Suppression Systems on Under- 
 
 ground Mining Equipment. BuMines Open File Rept. 20-78, 1977, 68 pp.; 
 available for consultation at Bureau of Mines libraries in Pittsburgh, 
 Pa., Twin Cities, Minn., Denver, Colo., and Spokane, Wash., and at the 
 Central Library, U.S. Department of the Interior, Wash., D.C. Also 
 available from National Technical Information Service, Springfield, Va., 
 PB 278 904/AS. 
 
 18. Stevens, R. B. Automatic Fire Sensing and Suppression Systems for Mobile 
 
 Mining Equipment. BuMines Open File Rept. 34-79, 1978, 166 pp.; avail- 
 able for consultation at Bureau of Mines libraries in Pittsburgh, Pa., 
 Twin Cities, Minn., Denver, Colo., and Spokane, Wash., and at the 
 Central Library, U.S. Department of the Interior, Wash., D.C. Also 
 available from National Technical Information Service, Springfield, Va., 
 PB 234 577/AS. 
 
 19. Stevens, R. B., and W. S. Oda (assigned to U.S. Dept. of the Interior). 
 
 Fire Prevention System. U.S. Pat. 3,993,138, Nov. 23, 1976. 
 
 20. U.S. Bureau of Mines, Mining Research Staff. Metal Mine Fire Protection 
 
 Research. Proc. Bureau of Mines Technology Transfer Seminar, Tucson, 
 Ariz., March 18, 1977. BuMines IC 8752, 1977, 51 pp. 
 
 21. U.S. Bureau of Mines. Automatic Fire Protection Systems for Large Mobile 
 
 Vehicles, Technology News, No. 11, 1974. 
 
 22. . Automatic Fire Protection for Surface Coal Augers. Technology 
 
 News, No. 27, 1976. 
 
 23. . Bulldozer Fire Protection. Technology News, No. 50, 1978. 
 
 24. . Fire Protection For Blasthole Drill. Technology News, No. 70, 
 
 1979. 
 
 25. . Fire Protection for Front End Loaders. Technology News, No. 74, 
 
 1979. 
 
 26. . Loading Shovel Fire Protection. Technology News, No. 77, 1980. 
 
 27. . Fire Protection for Hydraulic Excavators. Technology News, 
 
 No. 78, 1980. 
 
 28. . Automatic Fire Protection for Mining Trucks. Technology News, 
 
 No. 79, 1980. 
 
 «U.S. GOVERNMENT PRINTING OFFICE: 1981-703-002/41 int.-bu.of mines,pgh.,p a. 24878 
 
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