Papernumber05080, presentedatthe SMEAnnual Meeting, Feb.28-March2.2005, Salt Lake City, Utah. Originalmanuscript accepted for publication April 2006. Discussionof this peer-reviewedand approved paper is invitedand must be submitted to SME Publications Dept. pribr to Sept. 30, 2007. Copyright 2006, Society forMining, Metallurgy. and Exploration Inc.

;OCIETY FOR MINING, METALLURGY, AND EXPLORATION 127 Vol. 320 

# - 2006TRANSACTIONS 

# Using ultrasonic anemometers 

# to evaluate factors affecting face ventilation effectiveness

C.D. Taylor, 

### R.J. Timko, 

### E.D. Thimons and T. Mal Industrial hygienist, manager RHCB monitoring team, respiratory hazards control branch (RHCB) chief and engineering technician, respectively, National Institute for Occupational Safety and Health (NIOSH),Pittsburgh Research Laboratory, Pittsburgh, Pennsylvania



### Abstract A testsystemwasdeveloped attheNationalInstitutefor Occupational Safety and Health's ventilationtest galleryfor measuringaiflow using a three-axisultrasonicanemometer. Thegallery war used tosimulate face ai$ow conditions in underground mines having a blowing curtain.Airflow data, collected at multiple sampling locations between the face and the end of the curtain, were used to draw aiflowprofiles for different curtainsetback distances, intakeflow quantities and entry widths. In addition, methane was released at the face, measured at the sampling locations and displayed as methane distributions in the
area beiween the curtain and the face. Entry geometry had a sign$cant effect on aiflowpatterns, and theflowpatterns affected thedistribution ofmethane in the entry. Flow measured at andparallel to the face was a goodpredictor ofmethane dilution and removal within 

### 0.6 m 

### (2ft) 

### of the face.



### Background In coal mines the highest methane concentrations are often found near the developmentfaces where coal is being mined. Effective face ventilation requires that methane liberated at the face be diluted and removed quickly. 

### An importantfactor affectingfaceventilationeffectivenessis thequantityofintake air deliveredto the facefromthe end of the facecurtainortubing.Tomaintainmethaneconcentrationbelow 1%, asrequired by law (30 

### CFR 75.323 (b)), an adequate quantity of intake 

### air must be supplied to the face. Normally, the quantity of air reaching the working face is determined using flow readings made at the inby end of the entry's curtain or tubing (30 

### CFR 75.325 (a)(2)). However, past studies have shown that these calculatedquantitiesmightnotbe good estimatesofhow much 

### air actually reaches the face (Thlmons et

### al., 1999).Better estimates of face airflow could be made if airflow direction and speedwere measured closerto the face.However,it is difficult to make more accurate measurements between the curtain and the face because airflow direction and speed constantly change in this area. Instruments such as a rotating vane anemometeror a pitot tube and a magnehelic gauge are used to measure airflow belund the curtain or in the tubing. 

### A vane anemometer can be used to measure flow velocity inby the tubing or curtain, but it must be aligned with the airflow to give accurate readings. Most often, smoketubes are used to determine flow direction. Although only qualitative in nature, valuable information about face airflow patterns was obtained using smoke tubes (Luxner, 1969). Apreviouspaper (Taylor, 2004)describeshow atestprocedure was developed and used for measuring airflow direction and speed in NIOSH's ventilation test galleryusing ultrasonic anemometers.Thispaperdescribesacontinuationofthatwork. Airflow directionand speed in emptyentries are measured and compared for selectedcurtain setback distances,entry widths and intake flow quantities.Theeffectsofflow on facemethane distributions are discussed.


### Test conditions Tests were conducted in the NIOSH Pittsburgh Research Laboratory's ventilation test gallery (Fig. 1). One side of the gallery was designedto simulateamining entry with a 2.2-m- (74%) high roof and with ribs 5 m (16.5 ft) apart. For half of thetests, theentry width was reduced to 4

### m (13 ft)by building
a wall 1m 

### (3.5 ft) from the right rib. The exhaust fan draws approximately 5.9 m3/s (12,500 cfm) of 

### air through the gallery. To simulate airflow in 

### an underground mine, air was directed toward the entry face using a 2.2-m- (7-ft-) high curtain that was supported by a wood frame consmcted 0.6 m (2 ft)from the left side of the2006 TRANSACTIONS Vol. 320 

### 28 SOCIETY FOR MINING, METALLURGY,AND EXPLORATION Regulator / doFigure 1


### - Ventilation Test Gallery.

L- I I 

# ?:- o2 03 *' 4' 

### I

- 

### - o5 o6 o7 08 4'

F-0 9 20 

## 21 :2 4'

- o13 014 015 4' 1-

- .17 28 29 om 4' 

### I-- ,21 023 .24 4' I_-,= o= 02" om 4'

- p om 031 032 

# - 1.s

# c

- 033 O34 O35 O3a 3.5YBlowingCumin

KEY r oJ6Sanp6ng-- Figure 2


### - Sampling locations.

Figure 3

- Three-axis ultrasonic anemometer. Figure 4


### - Overhead support system.

entry. The curtain was positioned so that setback distances between the curtain and the face were 10.7 m (35 ft), 7.6 m (25 ft) and 4.6 m (15 ft). Regulator doors were adjusted to provide intake flows behind the curtain of either 2.8 or 

### 4.7 m3/s (6,000 or 10,000 cfm). Flow velocity behind the curtain
was measured with a vane anemometer held at the centerline of the curtain. Flow quantity was determined by multiplying the average velocity times the cross-sectional area behind the curtain. Flow and methane measurements were made for two entry widths of 4 and 5 m (13 and 16.5 ft), two intake flows of 2.8 and 4.7 m3/s (6,000 and 10,000cfm) and three curtain setback distances of 4.6,7.6 and 10.7 m (15.25 and 35 ft).


### Airflow and methane measurements Methane concentrations and airflow measurements were made at the same sampling locations. The number of sampling locations between the curtain and the face varied from 36 (for the 35-ft setback tests) to 16 (for the 15-ft setback tests). The sampling locations for the 10.7-111 (35-ft) setback distance and two entry widths are shown in Fig. 2. Airflow measurements were made between the end of the curtain and the face using "Windmaster" three-axis ultrasonic anemometers (Fig. 3), manufactured by Gill Instruments Ltd., Great Britain (references to specific products does not imply endorsement by NIOSH). The anemometer was attached to an overhead support system (Fig. 4), which was used to move the anemometer toward and away from the face and right and left across the entry.The anemometer was inverted to facilitate positioning of the sensor head 1.1 m (3.5 ft) from the floor and roof. All tests were conducted with the sensor head at this elevation. To compare flow direction for data collected at multiple locations, the orientation of the anemometer with respect to a reference point or location had to be maintained for all measurements. The face was selected as the reference location. The anemometer was rotated around its vertical axis until an arrow, printed on top of the sensor head, was directed toward the face. Each time the anemometer was moved, the direction of the instrument with respect to the face was rechecked. The data collected by the anemometer pass through a power communication interface 

### (PCI) box, which powers the anemometer and resolves each flow measurement into three orthogonal components: 

### U, V and W. For these tests, flow component data were simultaneously collected from two anemometersand stored in a personal computer usingAnemvent 2003,which is adataacquisition softwaredeveloped by NIOSH specifically for use with the ultrasonic anemometers. DataVol. 320 2006 TRANSACTIONS 

### w hake Air n~w 

### Face Face

Figure 5 

## - Flow diagrams for 4.6-m (15% setback. Figure 6 

## - Flow diagrams for 7.6-m 

### (254setback. ?. / 

### -

16 % -ft entry



### from each instrument were collected at one-second intervals and the time intervalbetweenreadingsforthe two instruments
was 0.2 seconds. During each 3-minutetest, 180 setsofdatapoints were collected. The data stored in the computer were analyzed using EXCEL functions and algorithms.The 

### U and V components
wereusedtocalculatetheflow angleand speedin theWplane located 1.1 m (3.5 ft) from the floor and roof. 

### EXCEL chart functions were used to draw, on a single sheet, flow vectors for all locations sampled. Each vector indicatesflow direction and is proportional in length to the flow speed. Airflow and methane measurements were made in the test gallery for the same set of operating conditions,but the measurements were made at separatetimes. To make methane measurements, methane gas was released into the test area through four 3-m- (104%) long horizontal copper pipes that
were located at the mining face. The pipes were located 100
mm (4 in.) 

### away fromIhe face and equally spacedhorizontally to provide a relativelyuniform release of gas. On the top and bottom of each ofthe 3-m- ( 

### 10-ft-) longpipes, 1.6-mm- (1116- in.-) diameter holes were drilled 65 

### rnrn (2.5 in.) apart. For most tests, the methane flow into the gallery was 16Us (34 cfm). However, during some tests (see below) the flow rate
was reduced to 3.2 Ws (6.8 cfm) to prevent methane levels in the gallery from exceeding 2.5%. A rotameter was used to set gas flows at either 3.2 or 16Us(6.8 or 34 cfm). While methane measurements were being made, four air

### sampling tubes were suspended from the overhead support system.Thehose inlets werepositioned 1.1 

### m (3.5 ft) from the roof andfloor.Avacuurnpumpcontinuouslypulled air

### samples through each tube to one of four Bacharacch combustible gas monitors, and concentrationswere measured at four locations during each test Methane concentrations were monitored (one reading per second) for eight minutes at each sampling location, and the individual readings were averaged. Each test condition was repeated once, and the results of the two tests were averaged. Data were stored using a commercial computer-based data acquisition system. \



### Face

. 

### Face,

Key mks Air Flow

Figure 7 

## - Flow diagrams for 10.7-m (354

### setback.



### Results and 

### discussion Airflow patterns and methane distribution. Drawings showing the flow profiles and methane concentrationsin the
area between the blowing curtain and the face were made for each set of the test operating conditions. Data were collected for intake flows of 2.8 and 4.7 m3/s (6,000 and 10,000 cfm). However, to limit the material included 

### in this paper, airflow profiles and methane concentrationsare only shown for tests conducted with an intake flow of 4.7 m3/s (10,000 cfm). The vector drawn at each sampling location shows the direction of airflow. The length of the vector is proportional to the air speed (seeFigs. 5.6 and 7).

### Flow directionwas similar for the 2.8 and 4.7 m3/s (6,000 and 10,000cfrn) intake flows when the entry width and setback distances were the same. However, vectors atthe same samplinglocationswere shorter for intake flows of 2.8 m3/s (6,000 cfm).2006 TRANSACTIONS 

# .Vol. 320 130 SOCIETY FOR MINING, METALLURGY, AND EXPLORATION Figure 8 

## - Methane profile for 4.6-m (15-ft) setback, 4.7 m3s (10,000 cfrn) intake. 

# Ilk Bbhg ClulEh

Figure9 

## - Methane distribution for 7.6-m (25-ft) setback, 4.7 m3s (10,000 cfrn)intake. C; 

### -",


## -zk Bbwhy) Cwoin

Theeffectofentrywidthonflowdictionwas sigmficantfor 10.7- and 7.6-m (35- and 25-ft) setbackdistances. The airflow pattern in the 4-m (13-ft) entry was similar to a figure "8." 

### In contrast, air 

### in the 5-m (16.5-ft) entry moved up the curtain side of the entry to the face and returned on the opposite side of the entry. For all tests with the 4.6-m (15-ft) setback, 

### air moved up the curtain sideof the entry to the face and returned
on the opposite side. ThemethaneprofilesinFigs. 8,9and 10showhowmethane concentrationsvaried between the end of the curtain and the facefortests where intake flow was 4.7 m3s (10,000cfm). The methane concentrations 

### in figs. 8, 9 and 10 were meas~ed for the same operating conditions used for the airflow tests described above (Figs. 5,6and 7). 

### 16 

### lit

### entry 134

### enhy 

# "6

Figure 10-Methane distribution for 10.7-rn (353)setback, 4.7 m3s (10,000cfm) intake.



### In Figs. 8, 9 and 10 the methane concentration at each sampling location is indicatedby the pattern of the block that surrounds the sampling location. The distributionof methane for the 2.8 and 4.7 m3s (6,000 and 10,000 cfm) intake tests
was similar, but the concentrationsmeasured during the 2.8 m3/s(6,000cfm) testswerehigher. Thedistributionofmethane between the curtain and the face in general corresponds to the dow patterns. When 

### aii moved along the intake side of the entryto the face, moremethaneaccumulatedon the return side ofthe entry. When airflow moved tothereturn sideofthe entry before reaching the face, the higher methane concentrations,
were on the intake side of the entry.



### Flow at the face. The airflow and methane profiles described above help to explain how 

### air moves between the blowing curtain and the face. However, the most critical area for the dilution and removal of methane is within 0.6 m (2 ft)of the face. The effectiveness of a face ventilation system depends
on how quickly methane is diluted and removed from this
area. Therefore, data collected closest to the face (for these tests Locations 1, 2, 3 and 4) provide important information for comparing ventilation systems and evaluating factors 

### affecting flow to the face. Thevectors shownin Figs.5,6and 7 illustratethe direction of the airflow and the 

### air speed in the direction indicated.

### An easier and more direct way to compare 

### air movement at the face is to look atthe magnitude of the flow as it moves parallel to the face. Specifically, one shouldconsiderthe componentof flow that isparallel to the face.The data collected atLocations 1, 2, 3 and 4 were used for this analysis.

The ultrasonic anemometer is designed to measure the 

### U and V flow components in a plane that has been rotated 30" counterclockwisefrom the referencedirection (Fig. 11). To measure the airflow speed moving parallel to the face, the 

### U and V axes were mathematically rotated 30" clockwise using rotation of the axes equations (Flanders, 1985). The magnitude of the rotated V flow componentwas then equal to the speed of the airElow moving parallel to the face. Figures 12, 13, 14 and 15 show the speed of the airflowSOCIETY FOR MINING, METALLURGY, AND EXPLORATION 131 Vol. 320 2006 TRANSACTIONS W, Reference Direction

W - Figure 11 

## - Anemometer and directional components.

moving parallel to the face at samplingLocations 1.2.3 and 4. Data are given for 7.6- and 10.7-m (25- and 35-ft) setbacks and 2.8 and 4.7 m3/s (6,000 and 10,000 cfm) intake flows. Airflow speed was higher for the higher intake flow, regardless of direction across the face. The highest airflow speed occurred near the center of the face (Locations2 and 

### 3). For the same intake flows, 

### air speed across the face was significantly lower in the 4-m- (13-ft-) wide entry. As seen earlier with the flow profiles, 

### air moved left to right across the face in ,the 5-m (16.5-ft) entry and right to left across the face in the 4-m- (13-ft-) wide entry. Figures 16,17,18 and 19show the methaneconcentrations measured at sampling Locations 1,2,3and 4 for both entry widths. Operatingconditionsused duringthesetests correspond to the operating conditions used during the airflow measurements (Figs. 12,13,14and 15).Methaneconcentrationsvaried depending on the speed and directionof the 

### air moving across the face. The higher velocities resulted in lower methane concentrations. For both entry widths the highest methane concentration was measured on the "downwind" side of the

- face. The highest concentrationswere on the right side of the

face for the 5-m (16.5-ft) entry tests and on the left side of the face for the 4-m- (1 3-ft) entry tests. One cautionary note must be given when comparing data presented in Figs, 16through 19. Themethaneconcentrations measured during 4-m (13-ft) entry tests were lower than during the 5-m- (16.5-ft-) wide entry tests, for both the 7.6- and 10.7-m (25- and 35-ft) setback data. However, to maintain methane levels in the gallery below 2.5%, the gas flow rate through the pipe manifold had to be reduced from 16to 3.2 Us (34 to 6.8 cfm) during tests where the entry width was 4
m (13 ft). For all 5-m (16.5-ft) tests, the flow rate was 16Us (34 cfm). Direct comparisons, therefore, should not be made for ventilation effectivenessin the 4- and 5-m- (13- and 16.5- ft-) wide entries using the measured methane concentrations. However, the fact that methane levels could be maintained below 2.5% methane in the 5-m (16.5-ft) entries at the higher gas flow rates indicates that more ventilation 

### air was reaching the face. This was conhedby the flow measurements discussed above.


### Conclusions In some cases, the results of this study confirm earlier ob

### SAMPLING LOCATION
Figure 12-Airflow parallel totheface,7.6-m (25-ft)curtain setback,4-m- (13-ft-)wide entry.



### SAMPLING 'LOCATION Figure 13-Airflow parallel totheface,7.6-m (25-ft)curtain setback, 5-m- (16.5-ft-)wide entry.



### SAMPLING LOCATION Figure 14 

## - Aitflow parallel to the face, 10.7-m (35-ft) curtain setback, 4-m- (13-ft-1wide entry.

servations codcerning face airflow, e.g., increased intake I 2 3 4 flow results in more 

### air reaching the face. However, past 

### SAMPLING LOCATION studies have depended largely on methane measurements to estimate ventilation effectiveness. The quantitativedata col- Figure 15 

## - Airflow parallel to the face, 10.7-m (35-ft) lected with the three-axis ultrasonic anemometer provides a curtain setback, 5-m- (16.5-ft-)wide entry.2006 TRANSACTIONS 

# .Vol. 320 132 SOCIETY FOR MINING, METALLURGY, AND EXPLORATION 0.40 10,000 cfm 

## UJs 0.75 

# gs 10.000 cfm 

# 2u. 0.30 

# 2 9 0.50 

# L 

# 5 0.20 

### wo 20 0.10 0.25

n 0 1 2 3 4 SAMPLING LOCATION - 1 2 3 4 SAMPLING LOCATION Figure 16 

### -Methane concentrations, 7.6-m (25-ft) curtain Figure 18 

### -Methane concentration, 10.7-rn (35-ft)curtain setback, 4-m (13-ft) entry. setback, 4-m (13-ft)entry.

LL! 1 .SO 

# s 0.75 

# s 

# f 2 1.00 10,000 cfrn Qcj E S 6.000 cfrn Z 0.50 

### wo 

### wo EL36,000 cfrn

0.50 0.25

0 0 

### - 1 2 3 4 1 2 3 4 SAMPLING LOCATION SAMPLING LOCATION Figure 17 

## -Methane concentration, 7.6-m (254curtain Figure 19- Methane concentration, 10.7-rn (354 curtain setback, 5-m (16.54 entry. setback, 5-m (16.5-ft) entry.

means to directly calculate ventilation effectivenessbased on airflow readings. Past observations indicated that increasing the entry width should result in greater flow to the face, but the magnitude of the increase, indicatedby the flow readings,
was greater than expected. Thus, entry width is a factor that should be considered when evaluating the effectiveness of a . face ventilation system. Future testing will examine airflow patterns in entriescontainingmodels ofminingequipment.Theeffectsofwaterspray and scrubberuse on flowpatterns and levels of turbulencewill be examined using a model of a mining machine. The effects of ventilation flow on the removal of methane liberated from holes drilledin the roof willbe studiedwith a model roof-bolting machine located near the face. Collectingventilationdata with the ultrasonic anemometer is relatively simple, but work in the gallery with the present test protocol is labor-intensive. For example, special care is needed to ensure proper orientation of the instrument at each sampling location. The present test matrix was based on the mostefficientuse ofpersonneland instrumentation.Sampling at more locations will improve the measurementof flow pat- ' terns. Further testing will look at improved ways to sample at more locations. The data obtained with the ultrasonic anemometers will also be used to help develop computer aided ventilation models that will supplementdata obtained in the ventilation gallery.


### References Flanders. H., 1985, Calculus, W.H. Freeman and Company, New York. 984 pp. Luxner, J.V., 1969. "Face ventilation in underground biiuminous coal mines." U.S. Bureau of Mines. R1 7223. 16 pp. Taylor, C.D., Tmko, R.J., Senk M.J.. and Lusin, A.. 2004, 'Measurement of airflow in a simulated underground mine environment using an ultrasonic anemometer," Transaction of the Society for Mining, Metallurgyand Erploration, Vol. 316. Thimons. E.D.. Taylor, C.D., and Zirnmer J.A., 1999, "Evaluating the Ventilation of a 40-Foot Two-Pass ExtendedCut" NlOSH Report of lniestigations IR1 9648).