Division of Mines

1
Division of Mines
DMME
Ventilation Section
2
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

3
Three categories of Airflow Measurements

• Low Velocity (0 to 120 fpm)
• Medium Velocity (120 to 2000 fpm)
• High Velocity (2000 fpm)

4
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!
5
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.

6
Traverse the whole entry when taking an
anemometer reading.
60 Sec.
Start
End
45 Sec.
15 Sec.
30 Sec.
7
Take care to record correct dial reading.
Dial Reading 239 feet per minute.
8
Correct reading per correction chart.
Dial Reading 239
Correction factor 43
Velocity 282
Note Calibration Due Date
9
Take multiple height measurements for irregular
roof.
Average Height 5 6
10
Estimate Gob Areas.
Triangular shaped gob
3 Feet
4 Feet
Gob area 1/2 3 4 6 feet2
11
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
12
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!
13
Calculations Example
Gob area 1/2 3 4 6 feet2
Q V A
Average Height 5 6
Area 5.5 X 20 - 6 110 ft.2 - 6 ft.2 104 ft.2
Q V A 282 X 110 31,020 cfm
14
Take Air Readings Upwind of Obstructions!
Regulator
Try to take air readings a few feet inby corners.
15
If cannot take air reading upwind of regulator
then take centerline reading in regulator and
multiply by 0.9.
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 cfm
16
Divide distance traveled by time required to get
the velocity. Multiply by 60 to get fpm.
How to take smoke readings!
It takes two!
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
17
Divide the entry into quadrants to take smoke
readings.
The number of quadrants is flexible!
OR take centerline reading and multiply by 0.9!
18
Mean Entry Velocity
4 X 5 20 Ft.2
272 X 20 5,440 cfm
1) Measure area behind curtain.
3) Calculate airflow behind curtain.
5,440/80 68 fpm
5) Divide airflow reading behind curtain by entry
area.
2) Take anemometer reading behind curtain.
4) Measure remaining area of entry.
Velocity 272 fpm
16 X 5 80 Ft.2
19
Ventilation Tubing Area
20
Vent Tubing Example
QVA Q3.14 X 2,350 Q7,379 cfm
24 inch Diameter Tubing
Anemometer reading 2,350 fpm
Entry Area 5 X 20 - 3.14 97 ft.2
Mean Entry Velocity 7,379/97 76 fpm
21
Principals of Airflow
22
Airflow in a mine is induced by pressure
differences between intake and exhaust openings.
23
The pressure difference is caused by imposing
some form of pressure at one point or a series of
points in the ventilating system.
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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.

25
Passageways, both intake and returns must be
provided to conduct airflow
26
Airflow follows a square-law relationship between
volumes and pressures, that is, twice the volume
requires four times the pressure.
100,000 CFM
200,000 CFM
2 inches W.G.
8 inches W.G.
27
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
28
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.

29
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.

30
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.

31
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.

32
Face Ventilation
Exhausting
Blowing

• Higher velocity at face.
• Best for gas.
• Worse for dust.

• Lower velocity at face.
• Worse for Gas.
• Good for Dust.

33
?
Where to take air readings?
34
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

• 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.

35
Section 45.1-161.209. On-shift Examinations.C.
Persons conducting the on-shift examination shall
determine at the following locations which are
underground

• 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.

36
LOC
Where is Last Open Crosscut?
R
37
LOC
LOC
Where is Last Open Crosscut?
R
38
Section 45.1-161.210. Volume of Air.

• 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.
• 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.

39
Where is Last Open Crosscut?
LOC
LOC
40
LOC
Where is Last Open Crosscut?
41
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

• The volume of air at the intake end of any pillar
  line
• 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
• if a split system is used, in the intake entries
  of each split immediately inby the split point.

42
Section 45.1-161.209. On-shift Examinations.C.
Persons conducting the on-shift examination shall
determine at the following locations which are
underground

• The volume of air at the intake end of any pillar
  line
• 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
• if a split system is used, in the intake entries
  of each split immediately inby the split point.

43
Intake
Where is Intake End of Pillar Line?
44
Where is immediately inby Split Point?
45
Where is Last Open Crosscut?
LOC
LOC
46
Where is Last Open Crosscut?
47
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

• 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...

48
Section 45.1-161.209. On-shift Examinations.C.
Persons conducting the on-shift examination shall
determine at the following locations which are
underground

• 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.
• 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

49
Where are Intake Air Readings required?
50
Where are Intake Air Readings required?
51
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.

52
LOC
Section 1
Where are weekly air readings required?
Main Return
Main Intake
53
Where are weekly air readings required?
LOC
Intake Split
Return Split
LOC
Return Split
Section 2
Intake Split
Main Return
Main Intake
54
LOC
Where are weekly methane test required?
Section 1
Main Intake
Main Return
55
LOC
Where are weekly Air Readings required?
Section 1
Entrance to GOB
ML 1
R
Main Intake
Main Return
56
Actions for Excessive Methane
57
45.1-161.222. Actions for excessive
methane.Paragraph 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.

58
45.1-161.222. Actions for excessive
methane.Paragraph 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).

59
Methane Example
1.2
1. Stop Work in No. 2
2. Kill power to Miner.
R
60
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.
3. Adjust Ventilation.
Methane Example
R
62
45.1-161.222. Actions for excessive
methane.Paragraph 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 one-half
  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).

63
1.6
1. Work to reduce CH4 concentration.
2. Withdraw all other personnel.
3. De-energize power.
Methane Example
64
1.8
1. Work to reduce CH4 concentration.
2. Withdraw all other personnel.
3. De-energize power.
Methane Example
R
65
45.1-161.222. Actions for excessive
methane.Paragraph 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.

66
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
Methane Example
67
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.

68
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.
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
69
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.
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
70
45.1-161.222. Actions for excessive
methane.Paragraph 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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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. Identify problem!
Methane Example
Active Section
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The End