This presentation shows a demonstration of the PSI & Heath Consultants Remote Methane Leak Detector (RMLD) being applied to remote detection of methane within coal mines to supplement existing technology to further enhance coal miner safety.

1. Physical Sciences Inc. 20 New England Business Center Andover, MA 01810
Physical
Sciences Inc.
Laser-Based Standoff Methane Sensors for
Enhancing Coal Miner Safety
Mickey Frish1, Clinton Smith1, Richard Wainner1 ,
James Rutherford2, Steve Chancey2, Paul Wehnert2
1Physical Sciences Inc., 20 New England Business Center, Andover MA
2Heath Consultants 9030 Monroe Rd., Houston TX
Pittcon 2015
New Orleans, LA
March 8, 2015
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This material is based upon work supported by The Centers for Disease Control and Prevention. Any opinions, findings and conclusions
or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the CDC.

2. Physical Sciences Inc.
Overview
 Motivation
– Enhance miner safety by supplementing current methane measurement
practices with remote methane detection
 Technology: Backscatter Laser Sensor
– Hand-held sensor locates areas of increased methane
• Demonstrated in research and working mines.
• Standoff range up to > 150 ft.
• Measures path integrated concentration.
– Sensor pair maps methane concentrations via tomography
• Map actual concentration.
• Demonstrated in coal mine face simulation lab.
 Summary
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3. Physical Sciences Inc.
 During mining operations, methane emanates from the sidewalls and
ceilings.
– Can create pockets that are explosion or breathing hazards
 Point sensors utilized for methane measurement might not detect
pockets trapped in areas that are difficult to access
 Remote methane detection can provide additional knowledge
regarding the location, volume and extent of methane pockets,
enhancing miner safety.
Benefit of Remote Methane Detection
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4. Physical Sciences Inc.
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Technology Platform:
The Remote Methane Leak Detector (RMLD)
 Like a flashlight, laser beam
Illuminates a surface up to
150 feet distant
 Senses target gas between
surveyor and illuminated surface
 >3000 in use for natural gas (CH4) distribution pipeline leak surveying
– leak sensitivity comparable to commonly-used flame ionization detectors
 Being adopted for CO2 pipeline monitoring at sequestration sites
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5. Physical Sciences Inc.
Handheld Use Scenarios
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 Portable tool warns before entering a hazardous area
− Including through doors and windows
 Searches for methane pockets in inaccessible areas such
as high roof
 Manually scans mine face for abnormally high methane
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6. Physical Sciences Inc.
Tests in Research Coal Mine
 Hung a transparent 1 m2 Tedlar bag against a representative coal
mine wall
– Filled w/ 2.1% methane, nominal 12.5 cm path  ~2600 ppm-m.
– Directed laser beam at selected wall areas around and through the bag at
ranges of 50 ft., 75 ft., 100 ft., and 150 ft.
– Achieved acceptable laser return signal and detected the increased
methane from all ranges
– Established good return signals for different wall compositions
 Performed a controlled detection test using 2.1% methane released
from pressurized cylinder
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7. Physical Sciences Inc.
Targeting a Representative Coal Mine Wall
1) Brown
stone
2) Grey
stone
3) Brown/grey
stone
4) 2.1%
methane
bag
5) coal
8) coal
7) coal6)
Brown
stone
 Laser beam was directed at each of the 8 locations
 Surface of coal mine face was wet
 Measurements made from distance of 50, 75, 100, 150 ft.
 Backscatter signal strengths are sufficient to detect methane from
distances > 200 ft.
1) 2)
3)
4)
5)
6) 7)
8)
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8. Physical Sciences Inc.
Detected Methane from Remote Distance
 2.1% methane concentration in bag against mine wall
– Bag thickness (i.e., methane path) is ~5 inches
 Able to detect the methane at all distances measured
 2.1% methane pocket (5” deep) detectable from >200 ft.
– Power law extrapolation based on return signal
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4000
3500
3000
2500
2000
1500
1000
500
0
50 70 90 110 130 150
Distance From Wall (ft.)
0
10
20
30
40
50
60
70
80
90
2
1
r
1f at Methane Bag Vs. DistancePath Integrated Concentration of
Methane Bag Vs. Distance
50 70 90 110 130 150
Distance From Wall (ft.) L-3129
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9. Physical Sciences Inc.
Rock Types Have Little Impact on Signals
 Aimed RMLD away from the methane bag
 Brown stone, grey stone, and coal all return similar laser power
– Path integrated concentration increases with distance due to ambient methane
• Positions #5, #6, #8 exhibit anomalies at 150 ft. range due to laser beam sampling
only a portion of the methane bag
– Beam diameter @ 150’ is ~75 cm
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1200
1000
800
600
400
200
0
50 90 110 130 150
Distance From Wall (ft.)
70 50 90 110 130 150
Distance From Wall (ft.)
70
0
20
40
60
80
100
120
140
160
Methane Concentration for Different Surfaces Vs. Distance
L-3130
1. Brown stone 2. Grey stone 3. Brown/grey stone 5. Coal
6. Brown stone 7. Coal 8. Coal
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10. Physical Sciences Inc.
Controlled 2.1% Methane Release:
Search for Source
Search wall area away
from source
Search wall area away
from source
Methane Pocket
Concentration increases
near methane source
 Manually scanned from 50 ft. range
 Methane pocket created by release from bottle was readily detected
Methane released in back corner
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11. Physical Sciences Inc.
Dual-Sensor Tomography
 Operator scans two tripod-mounted laser beams across the mine face
– Employs two sensors on rotational stages to make in-plane horizontal scans over the region of
interest.
– Pathlength retrieval with rangefinders.
 Log signals to rugged laptop for software processing
 A Graphical User Interface computer displays methane spatial concentration
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Tomography: Coal Mine Face Simulation Lab Tests
• Performed tomographic scans with varying
flow rates and leak sources (2.1% methane)
− 20 ft. distance from wall
− Single source (0.5 L/min)
− Single source (>2 L/min)
− Three sources (> 2 L/min)
• 2.1% methane flow at 2 L/min is equivalent
to 0.08 scfh pure methane
− Less than a pilot light
X2X1
X=RMLD + laser rangefinder
mounted on tripod (~4ft. High)
40ft.roomdepth
16.5 ft. room width
Control cables
Simulated coal face with leak(s)
single source
Three sources
X1
X2
leak sources
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13. Physical Sciences Inc.
Tomographic Scan of Single Leak Source – 20 ft. away
Single source high flow (>2L/min.)Single source low flow (0.5 L/min.)
 Leak source is located in the middle of the face; Background methane is less than 15 ppmv
– Methane collects near far wall (conforms with historical observation)
 Tomographic low flow peak is ~25 ppmv; high flow peak is ~60 ppmv
– Note: These values are 2-3 orders-of-magnitude below concentrations of concern at coal
mine faces
 Electrochemical sensors deployed for comparison
– Detected high flow (~2% methane) when placed at leak source
• Could not detect methane several inches from leak source
– Could not detect low (0.5L/min.) flow
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14. Physical Sciences Inc.
Three sources high flow (sources near scan plane)
Tomographic Scan of Three Leak Sources – 20 ft. away
X2X1
X=RMLD + laser rangefinder
mounted on tripod (~4ft. High)
40ft.roomdepth
16.5 ft. room width
Control cables
Simulated coal face with leak(s)
Three sources
 2.1% methane; Flow rate > 2 L/min.
 Peak of 0.01% (100 ppm) detected from stronger (upstream) source
– All three sources are distinguishable
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15. Physical Sciences Inc.
Coal Mine Face Simulation Lab Tests – 40 ft. away
X2X1
X=RMLD + laser rangefinder
mounted on tripod (~4ft. High)
40ft.roomdepth
16.5 ft. room width
Control cables
 2.1% methane flow rate of > 2 L/min.
 Peak of 0.08% (800 ppm) detected from stronger
(upstream) source
 Two sources are distinguishable
Three sources high flow (sources near scan plane)
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16. Physical Sciences Inc.
Summary
1. Successful remote methane detection inside an experimental mine
– Single laser backscatter sensor readily identified areas of increased
methane from distances > 150 ft.
– Successfully located the source of a controlled 2.1% methane release from a
distance of 50 ft.
• Tests were done against wet coal faces and a fresh coal mine face
2. Tomographic scans located and quantified methane near
simulated mine faces from distances of 20 ft. to 40 ft.
– Identified releases of 2.1% methane at 0.5 L/min and 2 L/min
– Sensitivity > 100x better than concentrations of concern in mines
– New application for backscatter TDLAS laser sensor systems.
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17. Physical Sciences Inc.
Acknowledgments
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Research funded by CDC/NIOSH Contract #200-2011-40565
and Heath Consultants Inc.
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18. Physical Sciences Inc.
Questions?
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19. Physical Sciences Inc.
Machine Mounted Mapping Tool Scenario
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 Automated tool installed on mining machine that continuously
maps methane concentrations at mine face
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20. Physical Sciences Inc.
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Absorption Spectroscopy Fundamentals
• Gas molecules absorb light at
specific colors (“absorption lines”)
Beer-Lambert law
Iν = Iνo exp [S(T) g( - o) N]
where:
 = optical frequency (= c/l)
o = line center frequency
g() = lineshape function
 = path length
N = absorbing species number density
S(T) = temperature dependent linestrength
Iνo = unattenuated laser intensity
I = laser intensity with absorption
DI = change in intensity (= I0-I)
c = speed of light
l = wavelength of light
Absorbance = - ℓn (I /Io)
≈ DI/I0 ( with small DI)
CH4 Spectrum
Mid-IR fundamental
Near-IR overtone
200x linestrength advantage is
the mid-IR appeal
(when deployed judiciously)
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