IMPROVEMENTS IN CONVEYOR BELT FIRE SUPPRESSION SYSTEMS 

FOR U.S. COAL MINES 

Kara A. Teacoach, NIOSH, Pittsburgh, PA, USA 

James H. Rowland, NIOSH, Pittsburgh, PA, USA 

Alex C. Smith, NIOSH, Pittsburgh, PA, USA 

Abstract 

Current regulations for fire suppression systems in 

underground coal mines to protect conveyor belt 

installations have been in place since the Coal Mine 

Health and Safety Act of 1969 was enacted. Over time, 

the coal conveyer equipment being used and ventilation 

conditions underground have changed significantly, 

particularly the width of the conveyor belts and the use of 

belt air at the face. The effect of these new conditions on 

the effectiveness of suppression systems during a fire is 

not known. The National Institute of Occupational Safety 

and Health (NIOSH) conducted a study to evaluate the 

effect of air velocity, water sprinkler activation 

temperature, and a limited water application time on the 

effectiveness of water sprinkler fire suppression systems 

to extinguish large-scale conveyor belt fires. 

The fire tests were conducted using both new and 

used 1.8-m-wide, fire-resistant rubber belt that met the 

Mine Safety and Health Administration (MSHA) flame 

resistant requirement specified in Title 30, Code of 

Federal Regulations, part 18, section 18.65 (also known 

as the 2G test). Tests were conducted using standard 

response sprinklers with activation temperatures of 68 °C 

and 141 °C at air velocities of 0.5 and 5.1 m/s. Two tests 

were conducted at both air velocities for each sprinkler 

activation temperature, one using a new belt and one with 

a used belt. 

The results showed that the suppression system was 

able to suppress the fires in ten minutes to the point that a 

miner could extinguish it with a fire hose. However, in 

several of the tests, the fire reestablished itself a few 

minutes after the sprinkler water supply was cut off and 

quickly grew out of control. This report discusses the 

large scale experimental configuration, the installation 

specifications of the fire suppression system, and the 

results and conclusions regarding the effect of air 

velocity, sprinkler activation temperature, and limited 

water application on the suppression system performance. 

Disclaimer: the findings and conclusions in this 

report are those of the authors and do not necessarily 

represent the views of NIOSH.

Introduction 

Fire Suppression systems are the first line of defense 

after a conveyor belt fire has started in an underground 

coal mine. Between 2000 and 2009, twenty-five fires in 

underground coal mines were caused by friction of 

conveyor belts against pulleys, drives, rollers, idlers, and 

bearings (MSHA). These fires were often not detected for 

long periods of time after ignition, making manual fire 

fighting difficult or impossible. The success of the 

suppression system in extinguishing or controlling the fire 

is extremely important in preventing injuries and fatalities 

to miners, as well as preventing extensive damage and 

disruption to the mining operation. 

When water sprinkler systems are used in 

underground coal mines, they must be installed in 

accordance with The U.S. Code of Federal Regulations 

(30 CFR 75.1101-7, 75-1107-8, and 75.1103-9(d)). These 

standards provide specifications on sprinkler type, 

location, and water discharge requirements. However, 

these systems are designed and installed according to 

guidelines for aboveground installations where no 

ventilation airflow exists. In addition, these standards 

were developed when the typical width of belts used in 

underground mines was 1.07 m, or narrower. Currently, 

many mines with multiple mining sections have gone to 

main line belts of 1.8 m width and some are even 
considering the move to 2.44-m-wide main line belts. 

With the use of wider belts and belt air at the working 

face, research is needed to evaluate the effect of these 

wider belts and ventilation on system effectiveness. Belt 

air used to ventilate the working section or areas where 

mechanized mining equipment is being installed or 

removed must be at a velocity no lower than 0.5 m/s and 

no greater than 5.1 m/s (30 CFR 75.350). Experiments 

testing the performance of automatic sprinkler systems for 

extinguishing incipient and propagating belt fires under 

ventilated conditions were performed by Smith, et al, in 

1995. The study utilized 1.07-m-wide styrene butadiene 

rubber conveyor belts (SBR) at airflows of 1.1 m/s and 

4.1 m/s. The sprinklers were able to extinguish the 

incipient fires, with improved performance at the lower 

air flow. The sprinklers were also successful in 

controlling propagating fires up to 10.8 megawatts (MW), 

activating earlier at lower velocities resulting in less 

damage to the belting. 

Recently, MSHA and NIOSH collaborated on a 

research project to evaluate the effect high air velocity has 

on the ability of different types of fire suppression 

systems to extinguish conveyor belt fires (Rowland, 

2009). Four different fire suppression systems were 

tested in the NIOSH Fire Suppression Facility (FSF); 

water sprinkler, deluge water spray, and two different 

types of dry chemical fire suppression systems. The 

large-scale fire tests were conducted using 1.8-m-wide 

fire-resistant SBR belt. Fire suppression tests were 

conducted at low (2.5 – 2.8 m/s) and high (6.6 – 7.6 m/s) 

air velocities. Both of the water-based systems and one of 

the dry chemical fire suppression systems were able to 

suppress the fire to the point that a miner could extinguish 

it with a fire extinguisher. However, the water-based 

systems were allowed to run until the fire was completely 

suppressed (forty to fifty minutes). The outcome of this 

study did not answer what would happen if the sprinklers 

had a limited application time. 

This paper describes the results of experiments to 

evaluate the ability of a water sprinkler suppression 

system to control conveyor belt fires under two 

ventilation rates with a ten minute application of water. 

To simulate typical mine equipment, new and used 1.8-mwide, 2G-approved SBR conveyor belts were installed on 

a conveyor structure in the FSF. Experiments were 

conducted at air velocities of 0.5 and 5.1 m/s, the lower 

and upper limits allowed by law. The regulations also 

state that sprinklers must have activation temperatures 

between 66 °C and 149 °C (30 CFR 75.1101-8). The 

sprinklers used in this study had activation temperatures 

of 68 °C and 141 °C to evaluate the effect of ventilation 

and limited water application on systems using sprinklers 

that cover the range of activation temperatures allowed by 

MSHA. In each experiment, the water was allowed to run 

for ten minutes after the first sprinkler activated. The belt 

was monitored, undisturbed, for several minutes after the 

water supply was turned off to observe if the fire would 

re-establish itself and continue to burn out of control. 

After five minutes of observation, the presence or absence 

of a propagating fire was used to determine if a ten 

minute application time was sufficient to extinguish the 

belt fire under the test conditions. 

Fire Suppression Facility 

The conveyor belt fire suppression tests were 

conducted at the Fire Suppression Facility (FSF), which is 

part of the NIOSH Lake Lynn Laboratory (LLL). The 

LLL is a world-class surface and underground facility 

located approximately 60 miles southeast of Pittsburgh, 

Pennsylvania. The FSF is constructed to simulate a U.S. 

coal mine entry and crosscut. The main tunnel is 46.6-mlong and the crosscut is 12-m-long. The entries are 2.2-

m-high and 5.5-m-wide. The roof is made of corrugated 

steel bridge planks, the ribs are made of 20.3-cm thick 

mortared solid concrete blocks, and the floor is a singlepour slab of reinforced concrete. The interior roof and 

ribs are coated with 5-cm- and 2.5-cm-thick layers of fire 

resistant material, respectively. A 1.8-m-diameter 

variable speed axi-vane fan, equipped with a pneumatic 

controller to adjust fan blade pitch, is installed at the 

closed end of the main tunnel. The fan has the ability to 

provide airflow of up to about 7.6 m/s over the crosssection of the entry. Two man doors, which permit access 

to the inside of the FSF, are located about 14.3 m from the 

fan. Figure 1 shows the exterior of the FSF. 

Figure 1. Exterior of Fire Suppression Facility 

The FSF is equipped with an array of chromel-alumel 

thermocouples (type-K) projecting 3 cm from the mine 

roof. The thermocouples are spaced at 3 m intervals 
starting 3 m from the fan along the centerline to the end of 

the simulated entry. A 9-point thermocouple array, 

spaced evenly across the width and height of the entry, is 

set up 46 m from the fan to measure the temperature of 

the gas exiting the entry. These temperatures were later 

used to calculate the heat release rates of the fires. A gas 

sampling array is also located at the end of the tunnel exit 

to sample the amount of oxygen, carbon monoxide and 

carbon dioxide in the exiting gas. The array consists of 

three steel pipes located evenly across the width of the 

entry. Each steel pipe had three 3 mm holes, spaced 

evenly from the roof to the floor of the tunnel, for a total 

of nine gas sampling points. A pump draws from each 

pipe and mixes the gas prior to entering the gas analyzers. 

The FSF is equipped with two video cameras to 

record each test. The first camera is mounted roughly 

23 m from the fan in the center of the roof to give a 

frontal view of the conveyor belt structure during the belt 

burn test. The second video camera is placed on a stand 

on the left side of the tunnel (when facing the open end of 

the tunnel) to view the inside of the conveyor belt drive 

area where the belt is ignited. 

The front of the conveyor belt structure is located 

26 m from the fan and is slightly off center of the entry to 

allow for heavy equipment to pass on one side to install 

the belting on the structure. The conveyor belt structure 

measures 15.2-m-long and 2.2-m-wide. Fifty-five gallon 

steel drums are used to simulate the head roller, drive 

rollers, idler roller and take-up roller. The diameter of 

each drum is 0.6-m-wide and each drum is 1.7-m-long. 

On each end of the drums, a steel plate is welded with a 

12.7-cm-diameter hole cut out of the center to allow for a 

10.2-cm-diameter steel pipe to be inserted through the 

center of the drum. The pipe is attached to the structure 

as shown in figure 2. The trough idlers are placed at 1.5 m 

intervals. 

Figure 2. Fifty-five gallon drum as drive roller 

To ignite the belt, four sets of natural gas 

impingement burners connected in series are placed along 

the width of the belt next to the drive roller closest to the 

fan, approximately 15 cm below the belt, as shown in 

figure 3. 

Figure 3. Natural gas burners to ignite belt 

 Each burner is equipped with 60 stainless steel 

jets having a rated output of 0.042 to 0.11 BTU/s. The 

ignition area is confined by metal shields on three sides; 

the fourth side remains unshielded towards the open end 

of the fire tunnel to reduce the effect the ventilation may 

have on the ignition process. 

An 18,900 L capacity closed water system adjacent to 

the FSF provides water for the installed fire suppression 

systems, as well as to hoses that can be used to extinguish 

hot spots remaining after tests. This system is capable of 

providing the pressure and volume of water needed to 

comply with federal regulations. 

Fire Suppression System Installation 

The water sprinkler fire suppression system was 

installed on the conveyor structure in accordance with 30 

CFR 75.1101-8. In this study, glass bulb-type sprinklers 

with two different activation temperatures, 68 oC and 

141 oC, were evaluated. The sprinklers were the same 

model from a name brand manufacturer with identical 

discharge coefficients (K=5.6 GPM/psi1/2). Sixteen 

sprinklers on 2.4-m-centers were needed to protect 15.2 m 

of the structure. Two branch lines were required, one 

above the top belt and one between the top and bottom 

belt. A schematic of the installation is shown in figure 4. 

The sprinkler denoted as sprinkler 1 was located 0.7 m 

from the head roller, 1.6 m vertically from the floor and 

1.2 m horizontally to the center of the top belt. Sprinkler 

2 was installed below sprinkler 1, underneath the top belt, 

0.7 m from the head roller, 1.1 m vertically from the floor 

and offset 0.6 m towards the right from the center of the 

belt when facing the open end of the tunnel. This set up 
was repeated seven more times along the length of the 

structure at 2.4 m intervals. 

Figure 4. Water sprinkler system. 

Test Procedure 

For each test, 1.8-m-wide fire resistant belt that met 

30 CFR Part 18.65 standards was installed on the 

conveyor belt structure shown in figure 5. 

Figure 5. Test set up 

 Two different 

belts were used in these experiments, a new, 3-ply, SBR 

belt and a used, 3-ply SBR belt. Thermocouples were 

installed on the belt in the center, right and left edge of 

the belt at the following locations: 9.1 m and 12.2 m from 

the head roller on the top belt, 7.6 m and 13.7 m from the 

head roller on the bottom belt, 7.6 m and 13.7 m from the 

head roller on the belt between the drive rollers and takeup rollers, and 9.1 m from the head roller between the 

drive area and take up area. Each thermocouple was 

placed just below the surface of the belt to measure the 

temperature of the belt when the flame spread reached 

that location on the belt. Thermocouples were placed on 

each sprinkler next to the glass bulb to determine the air 

temperature when the sprinkler activated. Before each 

test, the air velocity was established using a handheld 

vane anemometer to measure the air flow. The 

anemometer was positioned above the top belt over the 

drive area approximately 0.3 m from the roof. Two 

measurements were taken and averaged together. If the 

measurement was not within ten percent of the desired air 

velocity, the pitch of the fan blades was adjusted until the 

airflow was correct. Once the air velocity was 

established, the fan was not turned off or adjusted until 

the test was completed. After the fan was set at the 

desired airflow, measurements were taken in front of the 

belt structure and in front of each thermocouple on the 

array located at the open end of the tunnel. The air 

velocities at each array point were averaged together to 

determine the average exit velocity. 

To ignite the belt, the gas burners were lit with a 

propane torch and allowed to burn for ten minutes. If the 

fire appeared to be sustainable without the burner after ten 

minutes, the burners were turned off. If not, the gas was 

left on until the belt appeared to be ignited, at which time 

the burners were turned off. For six of the nine tests the 

sprinkler system activated before the end of the ten 

minute ignition period. If this occurred the gas supply to 

the burners was immediately shut off when the 

suppression system activated. 

Once the fire suppression system activated, the time 

was noted, and the water was left on for ten minutes. 

After ten minutes, the water was turned off and the belt 

and ventilation were left undisturbed for five more 

minutes. The test was monitored from inside the control 

room to determine if the fire was extinguished, under 

control, or not under control. The tests were concluded 

once the belt reignited into a propagating fire (fail) or 

after five minutes if the belt was no longer on fire (pass). 

Results and Discussion 

Full scale fire suppression experiments were 

conducted with two changing variables: activation 

temperature of the sprinklers and airflow velocity in the 

FSF. For this experimental configuration, both of these 

parameters had an effect on the characteristics of the fire 

and the ability of the water system to suppress it. The 

amount of water used during the experiments was 

dependent on the number of sprinklers that activated 

during the fire. The results for all tests are shown in 

Table 1. 

The initial test was conducted using new conveyor 

belt, an air velocity of 0.5 m/s, and sprinklers with an 

activation temperature of 141 °C. The sprinklers 

activated 8.3 min after the burners were ignited and the 

fire had grown to 0.034 MW. The suppression system 

failed to suppress the fire in ten minutes under these 

conditions. The next test, conducted under the same 

ventilation conditions and with the same sprinklers, but 

with used belt also resulted in a failed test. The sprinklers 

activated at 20.3 min and a fire size of 0.014 MW. 
Table 1. Results from full-scale suppression tests

Sprinkler 

Activation 

Temperature 

Air 

Velocity, 

m/s 

Belt 

Used 

Initiation 

Time, min 

Heat 

Release 

Rate at 

Activation, 

MW 

Amount 

of Water 

Used, L 

Outcome 

141 °C 0.5 New 8.3 0.034 2,915 Fail 

141 °C 0.5 Used 20.3 0.014 3,634 Fail 

141 °C 5.1 New 6.3 0.83 2,574 Fail 

141 °C 5.1 Used 10.9 0.85 4,315 Fail 

68 °C 0.5 New 3.5 0.040 Not 

Available 

Pass 

68 °C 0.5 New 5.7 0.010 2,536 Fail 

68 °C 0.5 Used 5.8 0.011 2,112 Pass

68 °C 5.1 New 5.4 1.9 Not 

Available 

Fail 

68 °C 5.1 Used 8.0 1.0 4,353 Fail

When the air velocity was increased to 5.1 m/s and 

sprinklers with 141 °C activation temperatures were 

installed, the suppression system in both the new and used 

belt tests failed to suppress the fire. During the test with 

the new belt the sprinklers activated at 6.3 min and a fire 

size of 0.83 MW, while the test with the used belt 

activated at 10.9 min and a fire size of 0.85 MW. 

The tests using a suppression system with sprinklers 

with an activation temperature of 68 °C and airflow of 

5.1 m/s also failed. The test with new conveyor belt had a 

heat release rate of 1.9 MW when the sprinklers activated 

at 5.4 min. The sprinklers activated at 8.0 min when the 

used belt was tested. The fire size at sprinkler activation 

was 1.0 MW. 

Three tests were conducted using an air velocity of 

0.5m/s and sprinklers with an activation temperature of 

68 °C; two with new conveyor belt and one with used 

belt. In the first test with new belting, the first sprinkler 

activated at 3.5 min and a fire size of 0.040 MW. The 

sprinkler system successfully suppressed this fire. 

However, when the test was repeated, the sprinklers 

activated at 5.7 min and a fire size of 0.010 MW, but the 

suppression system was unable to put out the fire. The 

third test at 0.5 m/s, with sprinklers with an activation

temperature of 68 °C, was conducted with used belt. The 

fire was 0.011 MW when the sprinklers activated at 

5.8 min. In this test, the suppression system was 

successful in extinguishing the fire. 

Effect of Sprinkler Activation Temperature 

Five experiments were conducted with sprinklers that 

activated at 68 °C, while four experiments used 141 °C 

sprinklers. The sprinklers with the higher activation 

temperature typically activated later during the test 

(between 6.3 min and 20.3 min) than the sprinklers with 

the lower activation temperature (between 3.5 min and 

8.0 min). In all cases for a particular belt (new versus 

old) at the same airflow, the sprinklers with activation 

temperatures of 68 °C sprinklers activated earlier than the 

sprinklers with activation temperatures of 141 °C. The 

locations of the sprinklers that activated were not 

dependent on the activation temperature. 

Effect of Airflow 

The nine experiments were conducted under two 

airflow conditions. Five experiments had a ventilation 

rate of 0.5 m/s and four experiments had a rate of 5.1 m/s. 

The difference in airflow caused several variations in the 

size of the fires and the response of the suppression 

system. At the lower airflow the largest fire was 

0.040 MW when the suppression system activated. At the 

higher air velocity the smallest fire was 0.83 MW when 

the sprinklers activated. For the four tests at high air 

velocity the heat release rates at the time of activation 

were higher because more belting was involved in the fire 

before the system activated. 

Figure 6 shows the heat release rate and time of 

sprinkler activation at the two airflows in tests using new 

belt and sprinklers with activation temperatures of 141°C. 

Testing at the high air velocity, sprinkler 10 was the first 

to activate at 6.3 min. This sprinkler was located between 

the top and bottom belts, 3 m downstream from the 

burners. Because of the sprinkler location, the shielding 

from the rollers prevented the water from reaching the fire 

in the ignition area. After ten minutes, the water supply 

was turned off but the belt was still burning in the drive 

roller area. As shown in figure 6, the fire continued to 

grow, reaching a maximum of 12.5 MW at ten minutes 

after sprinkler activation. 

Figure 6. Heat release rates plots of fires using 

sprinklers with an activation temperature of 141 °C and 

air velocity of 0.5 m/s and 5.1 m/s. 

In the test at the lower airflow, 0.5 m/s, sprinkler 7 

was the first to activate at 8.3 min. This sprinkler is 

located directly above the ignition area. The sprinkler 

kept the fire size to about 1 MW or less for ten minutes. 

However, the top belt shielded the flames from the water 
so that the fire was never completely extinguished. When 

the water supply was turned off after ten minutes, the fire 

was able to re-establish itself and grow out of control, 

failing the test criteria. 

Conclusion 

Water sprinkler systems with two different activation 

temperatures (68 °C, 141 °C) were tested under two air 

velocity conditions (0.5 m/s, 5.1 m/s) using both new and 

used 2G approved SBR conveyor belt. Water is a very 

effective method for suppressing and extinguishing belt 

fires; however, a sufficient supply of water is a necessity. 

MSHA regulations require a constant flow of water for 

ten minutes with all sprinklers functioning. For this 

experiment the amount of water was not limited, but the 

suppression system was allowed to run for only ten 

minutes no matter how many sprinklers activated. Under 

these parameters, and with the set up used, this was not a 

sufficient amount of water to extinguish the fire. While 

the extinguishing system was running, sprinklers were 

able to reduce the fire to a level that a miner could 

extinguish it with a hose. However, during the failed tests 

it took less than five minutes after shutting off the water 

for the fire to reestablish to a size similar to or greater 

than it was prior to the system activating. 

The two tests that resulted in suppressed fires both 

had low air flow (0.5 m/s) and sprinklers with a low 

activation temperature (68 °C). This air velocity allowed 

the sprinklers over the drive (fire) area to activate first, 

and the lower activation temperature initiated the 

suppression system earlier than higher activation 

temperature sprinklers. While the ventilation and 

sprinkler activation temperature affected the outcome of 

this experiment, it is important to note that the limited 

water application was a significant reason for the failed 

tests. Because of previous research, it can be assumed 

these test fires could have been suppressed if a 

substantially longer duration of water was available. 

The large number of failed tests reaffirms the need to 

conduct additional belt fire suppression research under 

current typical mine conditions (ventilation, conveyor belt 

type, conveyor belt width). In addition, engineeringbased data is needed to establish guidelines for 

improvements to the federal regulations (sprinkler 

spacing, sprinkler types, water supply) and development 

of new suppression system technologies. 

Acknowledgement 

The authors would like to thank our colleagues at 

NIOSH Pittsburgh Research Laboratory and Lake Lynn 

Laboratory and the contractors from Wolverine for 

conducting and setting up the experiments. 

References 

1. www.msha.gov/drs/drshome.htm Accessed

December 2009 

2. U.S. Code of Federal Regulations. Title 30-Mineral 

Resources; Chapter I-Mine Safety and Health 

Administration, Department of Labor; Subchapter O-Coal 

Mine Safety and Health; Part 75-Mandatory Safety 

Standards-Underground Coal Mines, Subpart L-Fire 

Protection, 1991. 

3. Smith, A.C., R. W. Pro, and C. P. Lazzara. 

Performance of Automatic Sprinkler Systems for 

Extinguishing Incipient and Propagating Conveyor Belt 

Fires Under Ventilated Conditions. USBM RI 9538, 1995, 

pp. 3, 4, 18. 

4. Rowland, J.H., Verakis, H., Hockenberry, M.A., 

Smith, A.C. 2009 Effect of Air Velocity on Conveyor 

Belt Fire Suppression Systems. SME Preprint No. 09-

135. Denver: SME.