education mine ventilation docs36
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Outline
• Airflow Measurements
– How to take air readings
– Measuring areas
– Mean Entry Velocity
• Principals of Airflow
• When and Where to take Air Measurements
• Actions for Excessive Methane
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Three categories of Airflow
Measurements
• Low Velocity (0 to 120 fpm)• Medium Velocity (120 to 2000 fpm)
• High Velocity (>2000 fpm)
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The principal mechanism for taking
medium air velocity measurement is the
Anemometer.
A high speed
anemometer ismost often used
for high velocity
air measurements!
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Taking Anemometer Measurements
• Make sure to zero dial!
• Make sure air flow is into the back of the
anemometer.
• Press lever to start dial movement.
• Take reading for 1 Minute.
• Press lever to stop.
• For precise measurements, use a wand or
extension rod to minimize effects of hand, arm,
and body.
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Traverse the whole entry when taking an
anemometer reading.
Start
15
Sec.
30 Sec.
45
Sec.
End
60 Sec.
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Take care to record correct dial reading.
Dial Reading = 239 feet per minute.
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Correct reading per
correction chart.
Correction factor = +43
Note
Calibration
Due Date
Dial Reading = 239
Velocity = 282
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Take multiple height measurements for
irregular roof.
5’ 0” 5’ 0” 6’ 6”
Average Height = 5’ 6”
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Estimate Gob Areas.
4 Feet
Gob area = 1/2 * 3 *4 = 6 feet2
Triangular shaped gob
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Estimate area of obstruction!
Crib area = 3 * 2.5 * 6 * 50% = 22.5 feet2
Taking air reading between 3 rows of cribs. You have to
estimate the effect of the cribs.
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Narrow, high
velocity
openings may
require you
to take out
the area of your body !
Air velocity has an impact on the amount of
obstructions you should consider!
Remove 3 feet2 for body and 3 feet2 for timber!
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Calculations Example
5’ 0” 5’ 0” 6’ 6”
Average Height = 5’ 6” Q = V A
20’
Area = 5.5 X 20 - 6 = 110 ft.2 - 6 ft.2 = 104 ft.2
Q = V A = 282 X 110 = 31,020 cfm
4 Feet
Gob area = 1/2 * 3 *4 = 6 feet2
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Regulator
Take Air Readings Upwind of Obstructions!
Try to take air readings a few
feet inby corners.
Recommendedlocations to take
air readings.
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O.67 ft.2
1.33 ft.2
Area of block = 0.67 X 1.33 = 0.89 ft.2
Area of Reg. = 8 X 0.89 = 7.2 ft.2
If cannot take air reading upwind of regulator then take
centerline reading in regulator and multiply by 0.9.
Anemometer Reading = 100 fpmVelocity =100 X 0.9 = 90 fpm
Q = 90 X 7.2 = 648 cfm
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How to take smoke readings!
It takes two!
Measure how long it takes smoke totravel over a pre-determined distance!
Best for upstream
(smoker) to look down
path of smoke with light.
Divide distance
traveled by time
required to get the
velocity. Multiply by60 to get fpm.
Example: 6 seconds to travel 10 feet.
10/6 = 1.67, 1.67 X 60 = 100 fpm
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1
2
3
4
5
6
7
8
9
Divide the entry into quadrants to take smoke
readings.
The number of quadrants is flexible!
OR take centerline reading and multiply by 0.9!
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Mean Entry Velocity
1) Measure area
behind curtain.
2) Take anemometer
reading behind curtain.
3) Calculate airflow
behind curtain.
4) Measure remaining
area of entry.
4 ft.
5 ft.
16 Ft.
5) Divide airflow reading
behind curtain by entry area.
4 X 5 = 20 Ft.2
Velocity = 272 fpm16 X 5 = 80 Ft.
2
272 X 20 = 5,440 cfm
5,440/80 = 68 fpm
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Ventilation Tubing Area
R 2 Area =
= 3.14
Pie are square!
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Vent Tubing Example
R 2 Area =
24 inch Diameter Tubing
Area = 3.14 X 12
Area = 3.14 ft.2
Entry Area = 5 X 20 - 3.14 = 97 ft.2
20 ft.5 ft.
Anemometer reading = 2,350 fpm
Mean Entry Velocity = 7,379/97 = 76 fpm
Q=VA
Q=3.14 X 2,350
Q=7,379 cfm
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Airflow in a mine is induced by pressure
differences between intake and exhaust
openings.
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The pressure difference is caused by
imposing some form of pressure at one
point or a series of points in the ventilatingsystem.
Exhausting Fan
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The pressure created must be great enough
to overcome frictional resistance and shock
losses.
• Friction pressure losses are caused by the resistance of
the walls on the airstream. Friction losses thereforedepend upon the conditions and roughness of
individual wall surfaces and velocity of air.
• Shock pressure losses are caused by abrupt changes
on the velocity of air movement. Shock lossestherefore are the result of changes on air direction or
of airway areas, obstructions, and regulation.
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Airflow follows a square-law relationship
between volumes and pressures, that is,
twice the volume requires four times the
pressure.
100,000
CFM
2 inches
W.G.
200,000
CFM
8 inches
W.G.
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The pressure drop for each split leaving
from a common point and returning to a
common point will be the same regardless
of the air quantity flowing in each split.
R
AB
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Mine ventilation pressures, with respect to
atmospheric pressures, may be either
positive (blowing) or negative (exhausting).
• Total Pressure = Static Pressure + Velocity Pressure
• Static Pressure is the pressure exerted in all directions.
Tire pressure is static pressure. Can be negative or
positive.
• Velocity pressure is directional pressure. You feel
velocity pressure when you feel the wind. VP isalways positive.
• Exhausting fans are generally rated on Static Pressure.
• Blowing fans are generally rated on Total Pressure.
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Air always flows from a point of higher to
lower pressure.
* Blowing fans create a high
pressure point immediately inby
the fan. Air travels from this high
point through the mine to the
surface.
* Exhausting fans create a low
pressure point immediately inby
the fan. Air travels from the
surface through the mine to this
low pressure point.
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Blowing
Fan
* Neutral flows to outside. Smoke
will not travel to face area.
* Gobs are “pressurized”. Less influx
of contaminants from gobs until fan
stops.* Harder to maintain required LOC
quantities.
* Best for mining near OLD
WORKS.
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Exhausting
Fan* Neutral flows toward face. Smoke
will travel toward face area.
* Gobs are “under suction”.
Contaminants flow from gobs until
fan stops.* Easier to maintain required LOC
quantities.
* Worse for mining near OLD
WORKS.
F V til ti
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ExhaustingBlowing
Face Ventilation
Higher velocity
at face.
Best for gas.
Worse for dust.
Lower velocity at
face.
Worse for Gas.
Good for Dust.
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Section 45.1-161.208. Pre-shift Examinations.
C. During the pre-shift examination, the mine
foreman shall determine the volume of air
entering each of the following areas if a miner isscheduled to work in the areas during the
oncoming shift:
1 In the last open crosscut , which means thecrosscut in the line of pillars containing the
permanent stoppings that separate the intake and
return air courses, of each set of entries or rooms
on each working section and areas wheremechanized mining equipment is being installed
or removed.
S i 4 1 161 209 O if i i
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Section 45.1-161.209. On-shift Examinations.
C. Persons conducting the on-shift examination
shall determine at the following locations which
are underground:
1 The volume of air in the last open crosscut , which
means the crosscut in the line of pillars containing
the permanent stoppings that separate the intakeand return air courses, of each set of entries or
rooms on each working section and areas where
mechanized mining equipment is being installed
or removed.
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LOC
Where is
Last Open
Crosscut?
LOC
R
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Section 45.1-161.210. Volume of Air.
A The quantity of air passing through the last open
crosscut shall be not less than 9,000 cubic feet per
minute; provided, however, that the quantity of air
reaching the last open crosscut in pillar recovery
sections may be less than 9,000 cubic feet per minute,if at least 9,000 cubic feet of air per minute is being
delivered to the intake end of the pillar line.
B The air current at working faces shall under all
conditions have a sufficient volume to readily diluteand carry away smoke from blasting and any
flammable or harmful gasses.
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LOC LOC
Where is
Last Open
Crosscut?
LOC
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Where is
Last Open
Crosscut?
LOC
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Section 45.1-161.208. Pre-shift Examinations.
C. During the pre-shift examination, the mine
foreman shall determine the volume of air entering
each of the following areas if a miner is scheduled to
work in the areas during the oncoming shift:
3 The volume of air at the intake end of any
pillar line
1 where a single split of air is used, in the intake
entry furthest from the return air course,
immediately outby the first open crosscut outbythe line of pillars being mined, or
2 if a split system is used, in the intake entries of
each split immediately inby the split point.
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Section 45.1-161.209. On-shift Examinations.
C. Persons conducting the on-shift examination
shall determine at the following locations whichare underground:
4 The volume of air at the intake end of any pillar line
1 where a single split of air is used, in the intake entryfurthest from the return air course, immediately
outby the first open crosscut outby the line of pillars
being mined, or
2 if a split system is used, in the intake entries of each
split immediately inby the split point.
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Where is
Intake Endof Pillar
Line?
Intake
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Where is
immediately
inby Spli t
Point ?
Inby Inby
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LOC
LOC
Where is
Last
Open
Crosscut
?
Wh i
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Where is
Last
Open
Crosscut?
LOC
LOC
LOC
LOC
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S ti 45 1 161 209 O hift E i ti
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Section 45.1-161.209. On-shift Examinations.
C. Persons conducting the on-shift examination
shall determine at the following locations which
are underground:
2 The volume of air on a longwall or shortwall,
including areas where longwall or shortwall
equipment is being installed or removed, in theintake entry or entries at the intake end of the
longwall or shortwall.
3 The velocity of air at each end of the longwall or
shortwall face at the locations specified in the
approved ventilation plan required pursuant to the
federal mine safety law;
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Where are
Intake Air
Readings
required?
Velocity
Velocity locations
as required by
approved federal
ventilation plan.
Volume
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Where areIntake Air
Readings
required?
Volume
Velocity
Velocity locations
as required by
approved federal
ventilation plan.
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Section 45.1-161.210. Weekly Examinations.
D. At least every seven days , a certified person
shall:Determine the volume of air entering the main
intakes and in each intake split;
Determine the volume of air and test for methane in
the last open crosscut in any pair or set of developing
entries or rooms, in the return of each split of air
immediately before it enters the main returns and
where the air leaves the main returns; and Test for methane in the return nearest each set of seals
immediately after the air passes the seals.
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Section 1
Where are weekly air
readings required?
Main Intake
LOC
Main
Return
Where are weekly air
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Section 1Where are weekly air
readings required?
Main Intake
Intake Split
Intake Split
LOC
LOCReturn Split
Return
Split
Main
Return
Wh klLOC
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Section 1Where are weekly
methane test required?
Main Return
LOC
Main
Intake
Methane
Test
Wh kl AiLOC
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Section 1Where are weekly Air
Readings required?
Main Return
LOC
Main
Intake
ML @
Top End
Entrance to
GOB
R
ML 1
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Actions for Excessive Methane
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45.1-161.222. Actions for excessive methane.
Paragraph A
A Tests for methane concentration under this
section shall be made by certified or
qualified persons trained in the use of anapproved detecting device which is
properly calibrated. Tests shall be made at
least twelve inches from the roof, face,ribs, and floor.
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45.1-161.222. Actions for excessive methane.
Paragraph B
B When one percent or more methane is present in a
working place or an intake air course, including
an air course in which a belt conveyor is located,
or in an area where mining equipment is being
installed or removed, work shall cease and
electrical power shall be de-energized in the
affected working place at the equipment exceptintrinsically safe atmospheric monitoring systems
(AMS).
1 2 %
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Methane
Example
R
1.2 %
1. Stop Work
in No. 2
2. Kill power
to Miner.
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45.1-161.222. Actions for excessive methane.
Paragraph B Continued
• Changes or adjustments shall be made to the
ventilation system to reduce the concentration to
below one percent. Only work to reduce the
concentration of methane below one percent shall
be permitted . This does not apply to other faces in
the entry or slope in which work can safely
continued.
1.2 %
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Methane
Example
R
1.2 %
1. Stop Work
in No. 2
2. Kill power
to Miner.
3. AdjustVentilation.
45 1 161 222 A ti f i th
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45.1-161.222. Actions for excessive methane.
Paragraph C
C When one and one-half percent or more methane is present in a working place or an intake air course,
including an air course in which a belt conveyor is
located, or an area where mining equipment is being
installed or removed, only work necessary to reducethe methane concentration to less than one and one-
half percent will be permitted and all other personnel
shall be withdrawn from the affected area.
Electrically powered equipment in the affected areashall be de-energized and other mechanized
equipment shall be shut off except of intrinsically
safe atmospheric monitoring systems (AMS).
1.6 %
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Methane
Example
1.6 %
R
2. Withdraw all
other personnel.
1. Work to
reduce CH4
concentration.
3. De-energize
power.
1.8 %
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R
Methane
Example
2. Withdraw all
other personnel.
1. Work to
reduce CH4
concentration.
3. De-energize
power.
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45.1-161.222. Actions for excessive methane.
Paragraph D
D When one percent or more methane is present in a
return or split between the last working place on a
working section and where that split of air meets
another split of air, or the location at which the
split is used to ventilate seals or worked out areas,
changes or adjustments shall be made to the
ventilation system to reduce the concentration of methane in the return air to less than one percent.
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Section 1
Methane
Example 1.2 %
Changes or adjustments shall be
made to the ventilation system
to reduce the concentration of
methane in the return air to lessthan one percent
1.2 %
45 1 161 222 Actions for excessive methane
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45.1-161.222. Actions for excessive methane.
Paragraph D
• When one and one-half percent or more methane is present ina return air split between the last working place on a working
section and where that split meets another split or air or the
location where the split is used to ventilate seals or worked-out
areas, everyone except those persons required to performnecessary work to correct the problem shall be withdrawn
from the affected area. Other than intrinsically safe
atmospheric monitoring systems (AMS), all equipment in the
affected area shall be de-energized at the source. No other
work shall be permitted in the affected area until the
concentration of methane in the return air is less than one
percent.
Active
Section
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AffectedArea
Section
1.8 %
2. All equipment in the affected
area shall be de-energized at
the source.
1. Withdraw everyone except
those persons required to
perform necessary work to
correct the problem !
3. No other work shall be
permitted in the affected area
until the concentration of
methane in the return air is less
than one percent
Active
Section
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Section
1.9 %
2. All equipment in the affected
area shall be de-energized at
the source.
1. Withdraw everyone except
those persons required to
perform necessary work to
correct the problem !
3. No other work shall be
permitted in the affected area
until the concentration of
methane in the return air is less
than one percent
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45.1-161.222. Actions for excessive methane.
Paragraph G
G The concentration of methane in a bleeder split of
air immediately before the air in the split joins
another split of air, or in a return air course other
than described in subsections D and E, shall not
exceed two percent.
2. Changes or adjustments shall
b d t th til ti1. Identify
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R
Active Section
2.5 %
Methane
Example
be made to the ventilation
system to reduce the
concentration of methane in the
return air to less than one
percent
problem!
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