Ventilation

Designing a Mine Auxiliary Ventilation System

Quantity of air required Physical Constraints Other considerations

Purpose Auxiliary ventilation is designed to provide adequate ventilation to a dead-end entry or tunnel, to remove or dilute hazardous gasses or dust, and to provide sufficient and clean air for individuals and equipment to work efficiently.

Considerations:

Auxiliary Ventilation

Air velocity in the entry or tunnel Air quantity for diesel equipment Air quantity for people Air quantity to dilute or remove gasses and dust Air quantity for cooling or other needs Head room over haulage or material transport equipment Length of duct Handling and hanging problems Potential for damage from blasting and other activities Duct and fans must be sized to ensure that the fans are not working in a stall (i.e., the fan is attempting to move more air than the duct will allow) A larger duct allows for a more efficient and lower horsepower system Legal and contract requirements for fans and duct Preferred direction of airflow - suction or blowing Most leakage occurs at the joints and longer lengths have significantly less leakage

Evaluate the Different Types of Duct

Steel

Fiberglass

Flexible Suction

Lay flat

Lowest initial-cost suction duct Required on some projects Holds high positive and negative

pressure Medium leakage Non-flammable

Best suited for: Moderate length ventilation runs (less than 3,000 ft.) Drill and shoot operations Single use applications

Most durable suction duct Holds up well to abuse Holds high positive and negative

pressure Low friction factor Flame resistant Light-weight

Best suited for: Short-length ventilation runs (less than 1,500 ft.) Multiple reuse operations Drill and shoot operations

Flame resistant Can expand and contract length Weight dependent on negative

pressure rating Can be stored in small area

Best suited for: Starter tunnels Short ventilation runs Flexible connections in other type of duct

Low cost Flame resistant Low leakage in long lengths Pressure rating dependent on

material, construction Requires additional fan for

reversing air flow on OSHA jobs Medium friction factor Many grades available Requires special expertise in

applications for booster fans

Best suited for: Short ventilation runs using low cost duct Long ventilation runs using high-quality long-length ducts

For all equations, the definitions are: AH = pressure loss in in. w.g. A = area of duct in square feet C = loss coefficient K = the friction factor for the V = air velocity in feet/minute material L = length in feet (Fiberglass duct is 11.7; O = perimeter in feet Steel duct is 12; Q = air quantity in 100,000 cfm Cassette duct is 15; (60,000 cfm would be .60) Lay flat duct is 18; P = air density (.075 for standard air) in lb/ft3 Flexible suction duct is 27)

Dynamic Losses The pressure loss in each fitting, inlet and outlet must be calculated separately and is based on the velocity pressure of air at that point in the system.

Velocity pressure Pv =

Calculating Losses

Friction Losses Friction loss curves, which are provided in this brochure, are designed to give the pressure loss due to friction in the duct. The curves are based on the following formula:

Loss coefficients for area changes

Type Illustration Conditions Loss Coefficient

Gradual Contraction Equal Area Transformation Flanged Entrance Duct Entrance Formed Entrance Gradual Expansion Abrupt Exit

30°              0.02     45°               0.04     60°                                                  0.07

C2

A1 = A2 C ≤ 14o 0.15 C A = ∞ 0.34 C A = ∞ 0.85 C A = ∞ 0.03 C1

5o 0.17 7o 0.22 10o 0.28 20o 0.45 30o 0.59 40o 0.73 A2 = ∞ A1/A2 = 0.0 1.00

Note: A”c” with subscript indicates the cross-section at which velocity is calculated.

Loss coefficients for elbows

Type Illustration Conditions

No

90O Round Section

Loss Coefficient Pressure Loss L/D Ratio

Rectangular or round, with or without vanes

(N/90) times value for similar 90o elbow

Miter R/D = 0.5

0.75 1.0 1.5

2.0

Miter R/D = 0.5

0.75 1.0 1.5

2.0

Reading fan curves and resistance charts

How to use the friction curves To determine the friction loss, find the average air quality in the duct (air at heading + 1/2 leakage), follow the line up to your duct diameter and read across to determine the static pressure drop per 100 feet. Multiply this number by the length of the duct to obtain the friction losses. For and oval duct, use the hydraulic diameter formula to calculate the equiva-lent round diameter: DH = For example: An application requires 28,000 cfm at the heading. We have 2,000 feet of 36” fiber-glass duct and 4,000 cfm of leakage. The average air quantity in the duct is 30,000 cfm. This gives us a friction loss of .8 in w.g./100 feet or 16” total. To calculate the total system static pressure loss, add the

ducting loss– 16”, fan loss– normally –1”, fittings loss= .5” each and duct inlet/exit loss normally-1”.

How to use the fan curve Read across at the total pressure, then up from the quantity to determine if the intersection point falls on or under the fan curve. To obtain the total pressure require-ment for the fan, add the friction losses, dynamic losses and one velocity pressure to obtain the total pressure in the system. In the above example, if we also have 16” friction loss, 8” of dynamic losses and 1.25” velocity pressure, we would have a total pressure loss of 25.25” and a fan quantity of 32,000 cfm. Therefore, by using a fan chart we can see that a 21 x 100 HP 33” fan will meet the requirements.

ALTITUDE ATMOSPHERIC TEMPERATURE IN DEGRES FAHRENHEIT

PRESSURE -20 0 20 40 60 80 100

-1000 31.02 0.0936 0.0886 0.0858 0.0824 0.0792 0.0762 0.0735

0 29.92 0.0903 0.0854 0.0827 0.0794 0.0764 0.0735 0.0709

1000 28.86 0.0871 0.824 0.0798 0.0766 0.0736 0.0709 0.0684

2000 27.82 0.0839 0.0794 0.0769 0.0738 0.071 0.0684 0.066

3000 26.81 0.0808 0.0765 0.0741 0.0712 0.0684 0.0659 0.066

4000 25.84 0.0779 0.0738 0.0715 0.0686 0.066 0.0635 0.0635

5000 24.89 0.0751 0.071 0.0688 0.0661 0.0635 0.0611 0.0612

6000 23.98 0.0723 0.0684 0.0663 0.0636 612 0.0589 0.0569 7000 23.09 0.0697 0.0659 0.0639 0.0613 0.0589 0.0546 0.0526

8000 22.22 0.0671 0.0634 0.0614 0.059 0.0567 0.0546 0.0526 9000 21.38 0.0644 0.061 0.0591 0.0568 0.0546 0.0525 0.0506

10000 20.58 0.062 0.0587 0.0569 0.0546 0.0525 0.0495 0.0488

QUANTITY STANDARD STANDARD STANDARD OTHER UNITS

UNITS ENGLISH UNITS METRIC (SI) UNITS in. wg pscals psi

inwg 1 248.36 0.03602 pascals 0.00103 1 0.00015

PRESSURE psi 27.761 6894.7 1

inHg 13.635 3386.4 0.49116

mm WG 0.03937 9.7779 0.00142 MM Hg 0.53681 133.32 0.01934 Bar 407.98 101325 14.696

cfm m3/s m3/min

VOLUME Cfm 1 0.00472 0.02832 FLOW M3/s 2118.9 1 60

M3/min 35.314 0.01337 1 ft/min m/s m/min

Ft/min 1 0.00508 0.3048

M/s 196.85 1 60 VOLCITY M/min 3.2808 0.01667 1

Kph 0.05468 0.00028 0.01667 Mph 88 0.44704 26.822

Knots 101.34 0.51479 30.887

VEL. VP VEL. VP VEL. VP

FPM In. Water FPM In. Water FPM In. Water

500 0.016 1800 0.202 4400 1.21

600 0.022 2000 0.249 4600 1.32

700 0.031 2200 0.302 4800 1.44

800 0.404 2400 0.359 5000 1.56

900 0.05 2600 0.421 5200 1.69

1000 0.062 2800 0.489 5400 1.82

1100 0.075 3000 0.561 5600 1.96

1200 0.09 3200 0.638 5800 2.1

1300 0.105 3400 0.721 6000 2.24

1400 0.122 3600 0.808 6200 2.4

1500 0.14 3800 0.9 5400 2.55

1600 0.16 4000 0.998 6600 2.72

1700 0.18 4200 1.1 6800 2.88

Velocity Pressures Conversion Factors Air density at different altitudes and temperatures

Steel Duct Friction Loss Chart

Fiberglass Duct Friction Loss Chart

Flexible Suction Duct Friction Loss Chart (Spiral)

Flexible Forced Duct Friction Loss Chart (Lay Flat)

Over half a century of worldwide engineering experience goes into manufacturing a complete line of integrated products designed for all types of ventilation projects.

2233 Sanford Drive Grand Junction, CO 81505 U.S.A. T (970) 245-9400 F (970) 245-9402

188 Van Kirk Drive #4 Fairmont, WV 26554

U.S.A.

T (304) 363-0868 F (304) 363-0875

Info@Schauenburg.us www.schauenburg.us

Ventilation Products Flexible Ventilation Lay Flat, spiral, forced, exhaust, shaft, dispersion, cassettes and fittings Fiberglass Ventilation Round, oval, forced, exhaust, fittings and accessories Steel Ventilation 18 & 20 gauge, corrugated & smooth, fittings and coupling bands Fans & Fan Silencers Axial flow, permissible, accessories and center pod silencers Dust Collectors Brattice Plain rolls, curtains, fly pads, pogo sticks, special products Inflatable Stoppings