1 2 Outline Airflow Measurements –How to take air readings –Measuring areas –Mean Entry...

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

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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.

Start

15 Sec.

30 Sec.

45 Sec.

End60 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

3 F

eet

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

3 F

e et

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.

Recommended locations 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 to travel 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 by 60 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 fpm 16 X 5 = 80 Ft.2

272 X 20 = 5,440 cfm

5,440/80 = 68 fpm

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Ventilation Tubing Area

R2Area =

= 3.14

Pie are square!

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Vent Tubing Example

R2Area =

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 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.

100,000CFM

2 inchesW.G.

200,000CFM

8 inchesW.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

A B

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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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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 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

Where is Last Open Crosscut?

R

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LOC


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 dilute and carry away smoke from blasting and any flammable or harmful gasses.

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LOC LOC


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LOC

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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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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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Where is Intake End

of Pillar Line?

Intake

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Where is immediately inby Split Point?

Inby Inby

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LOC

LOC

Where is Last Open

Crosscut?

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Where is Last Open

Crosscut?

LOC

LOC

LOC

LOC

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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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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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Where are Intake Air Readings required?

Velocity

Velocity locations as required by

approved federal ventilation plan.

Volume

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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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Section 1

Where are weekly air readings required?

Main Intake

LOC

Main Return

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Section 1

Section 2

Where are weekly air readings required?

Main Intake

Intake Split

Intake Split

LOC

LOCReturn Split

Return Split

Main Return

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Section 1 Where are weekly methane test required?

Main Return

LOC

Main Intake

Methane Test

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Section 1 Where are weekly Air Readings required?

Main Return

LOC

Main Intake

ML @Top End

Entrance toGOB

RML 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 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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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.

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Methane Example

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1.2 %

1. Stop Work in No. 2

2. Kill power to Miner.

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 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).

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Methane Example

1.6 %

R

2. Withdraw all other personnel.

1. Work to reduce CH4 concentration.

3. De-energize power.

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R

1.8 %

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 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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Affected Area

Active 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

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Active 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.

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R

Active Section

2.5 %

Methane Example

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!

1 2 Outline Airflow Measurements –How to take air readings –Measuring areas –Mean Entry...

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