Transcript 00ventshow.ppt

1
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 is
most 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.
60 Sec.
Start End
45
Sec.
15
Sec.
30 Sec.
6
Take care to record correct dial reading.
Dial Reading = 239 feet per minute.
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Correct reading per
correction chart.
Dial Reading = 239
Correction factor = +43
Velocity = 282
Note
Calibration
Due Date
8
Take multiple height measurements for
irregular roof.
5’ 0”
5’ 0”
6’ 6”
Average Height = 5’ 6”
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Estimate Gob Areas.
Triangular shaped gob
4 Feet
Gob area = 1/2 * 3 *4 = 6 feet2
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Estimate area of obstruction!
Taking air reading between 3 rows of cribs. You have to
estimate the effect of the cribs.
Crib area = 3 * 2.5 * 6 * 50% = 22.5 feet2
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Air velocity has an impact on the amount of
obstructions you should consider!
Narrow, high
velocity
openings may
require you
to take out
the area of
your body!
Remove 3 feet2 for body and 3 feet2 for timber!
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Calculations Example
Gob area = 1/2 * 3 *4 = 6 feet2
Average Height = 5’ 6”
Q =VA
20’
5’ 0”
5’ 0”
6’ 6”
4 Feet
Area = 5.5 X 20 - 6 = 110 ft.2 - 6 ft.2 = 104 ft.2
Q = V A = 282 X 110 = 31,020 cfm
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Take Air Readings Upwind of Obstructions!
Recommended
locations to take
air readings.
Try to take air
readings a few
feet inby corners.
Regulator
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If cannot take air reading upwind of regulator then take
centerline reading in regulator and multiply by 0.9.
O.67 ft.2
1.33 ft.2
Anemometer Reading = 100 fpm
Velocity =100 X 0.9 = 90 fpm
Area of block = 0.67 X 1.33 = 0.89 ft.2
Area of Reg. = 8 X 0.89 = 7.2 ft.2
Q = 90 X 7.2 = 648 cfm15
How to take smoke readings!
It takes two!
Divide distance
traveled by time
required to get the
velocity. Multiply by
60 to get fpm.
Best for upstream
(smoker) to look down
path of smoke with light.
Measure how long it takes smoke to
travel over a pre-determined distance!
Example: 6 seconds to travel 10 feet.
10/6 = 1.67, 1.67 X 60 = 100 fpm
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Divide the entry into quadrants to take smoke
readings.
1
4
7
2
5
8
3
6
9
The number of quadrants is flexible!
OR take centerline reading and multiply by 0.9!
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Mean Entry Velocity
4 X 5 = 20 Ft.2
272 X 20 = 5,440 cfm
3) Calculate airflow
behind curtain.
1) Measure area
behind curtain.
4 ft.
5,440/80 = 68 fpm
16 Ft.
5 ft.
5) Divide airflow reading
behind curtain by entry area.
2) Take anemometer
reading behind curtain.
Velocity = 272 fpm
4) Measure remaining
area of entry.
16 X 5 = 80 Ft.2
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Ventilation Tubing Area
Area =

 R2
= 3.14
Pie are square!
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Vent Tubing Example
Area = 3.14 X 12
Area = 3.14 ft.2
Area =
 R2
Q=VA
Q=3.14 X 2,350
Q=7,379 cfm
24 inch Diameter
Tubing
5 ft.
20 ft.
Anemometer reading = 2,350 fpm
Entry Area = 5 X 20 - 3.14 = 97 ft.2
Mean Entry Velocity = 7,379/97 = 76 fpm
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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 ventilating
system.
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 therefore
depend 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 losses
therefore are the result of changes on air direction or
of airway areas, obstructions, and regulation.
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Passageways, both intake and returns must
be provided to conduct airflow
R
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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.
A
B
R
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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 is
always 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.
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Face Ventilation
Blowing
Higher
velocity
at face.
Best
for gas.
Worse
for dust.
Exhausting
Lower
velocity at
face.
Worse
Good
for Gas.
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 is
scheduled to work in the areas during the
oncoming shift:
1 In the last open crosscut, which means the
crosscut 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 where
mechanized mining equipment is being installed
or removed.
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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 intake
and 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
R
Where is
Last Open
Crosscut?
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LOC
LOC
R
Where is
Last Open
Crosscut?
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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 dilute
and carry away smoke from blasting and any
flammable or harmful gasses.
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Where is
Last Open
Crosscut?
LOC
LOC
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LOC
Where is
Last Open
Crosscut?
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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 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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Section 45.1-161.209. On-shift Examinations.
C. Persons conducting the on-shift examination
shall determine at the following locations which
are 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 entry
furthest 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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Intake
Where is
Intake End
of Pillar
Line?
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Inby
Inby
Where is
immediately
inby Split
Point?
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Where is
Last
Open
Crosscut
?
LOC
LOC
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Where is
Last
Open
Crosscut
?
LOC
LOC
LOC
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:
2 On each longwall or shortwall in the intake
entry or entries at the intake end of the
longwall or shortwall face immediately outby
the face and the velocity of air at each end of
the face at the locations specified in the
approved ventilation plan required by the
federal mine safety law...
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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 the
intake 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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Volume
Where are
Intake Air
Readings
required?
Velocity
Velocity locations
as required by
approved federal
ventilation plan.
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Where are
Intake 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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LOC
Section 1
Where are weekly air
readings required?
Main
Return
Main Intake
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LOC
Section 1
Where are weekly air
readings required?
Intake Split
Return Split
LOC
Return
Split
Intake Split
Main
Return
Main Intake
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Section 1
LOC
Where are weekly
methane test required?
Methane
Test
Main
Intake
Main Return
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LOC
Section 1
Where are weekly Air
Readings required?
Entrance to
GOB
R
ML 1
ML @
Top End
Main
Intake
Main Return
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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 an
approved 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 except
intrinsically safe atmospheric monitoring systems
(AMS).
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1.2 %
1. Stop Work
in No. 2
Methane
Example
R
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.
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1.2 %
1. Stop Work
in No. 2
2. Kill power
to Miner.
Methane
Example
R
3. Adjust
Ventilation.
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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 reduce
the methane concentration to less than one and onehalf percent will be permitted and all other personnel
shall be withdrawn from the affected area.
Electrically powered equipment in the affected area
shall be de-energized and other mechanized
equipment shall be shut off except of intrinsically
safe atmospheric monitoring systems (AMS).
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1.6 %
1. Work to
reduce CH4
concentration.
2. Withdraw all
other personnel.
Methane
Example
R
3. De-energize
power.
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1.8 %
1. Work to
reduce CH4
concentration.
2. Withdraw all
other personnel.
R
3. De-energize
power.
Methane
Example
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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 less
than one percent
1.2 %
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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 in
a 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 perform
necessary 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.
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Active
Section
1. Withdraw everyone except
those persons required to
perform necessary work to
correct the problem !
Affected
Area
2. All equipment in the affected
area shall be de-energized at
the source.
1.8 %
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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Active
Section
1. Withdraw everyone except
those persons required to
perform necessary work to
correct the problem !
2. All equipment in the affected
area shall be de-energized at
the source.
1.9 %
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.
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Methane
Example
1. Identify
problem!
2. 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
2.5 %
R
Active Section
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