ALPHAIR Ventilating Systems Notes on Fan Applications and
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Transcript ALPHAIR Ventilating Systems Notes on Fan Applications and
ALPHAIR
Ventilating Systems
Notes on Fan Applications
and Selection For Mine
Ventilation
Presented By Ron Prevost Derbecker
Basic Concepts
Volume - Flow
Pressure
Power - Energy
Volume
Quantity of Gas, Typically Air
Standard Air - at 70° F., 0.0 feet
above sea level, .075 lb/ft3
Pressure
Static Pressure [Ps]
Velocity Pressure [Pv]
Total Pressure [Pt]
Bernouli’s Equation:
Pt = Ps + Pv
At any given point only one value for
total pressure can exist
Fan Pressure
Fan performance is defined by the
pressure differential across the fan
There are 3 definitions:
Fan Total Pressure = FTP= Pto - Pti
Fan Static Pressure = FSP= Pso - Pti
Static Pressure Rise = SPR= Pso - Psi
Where o=fan outlet i=fan inlet
Power / Work
hp – Horsepower rating, typically the
maximum power of the fan motor
BHP - Brake Horsepower, the actual
shaft power consumed by fan
(in SI kW – kiloWatts are used, the term
brake kiloWatts is not common)
Effects of Environment
Altitude
Temperature
Degree of Saturation with Moisture
Positive & Negative Pressure
Altitude
Gas density decreases as elevation
increases
Standard Barometric pressure at Sea
Level is 29.92” Hg ( mercury)
Barometric pressure varies by +/- 1”
Hg per 1000’ change in elevation
Air density varies by +/- 3% per
1000’
Temperature
Gas density decreases as
temperature increases
Density varies as a ratio of absolute
temperature
Density at temperature “T” =
(460+70)
X .075
(460+T)
Note: Use 273 Deg C in place of 460 F for SI
Moisture Saturation
Water vapor is lighter than air and
displaces air when present, reducing
gas density
At standard conditions, the density of
saturated air is 0.073 lb/ft3
Positive & Negative Pressure
Air density varies with the fan
pressure applied, exactly as it varies
with barometric pressure.
An exhaust fan develops a negative
pressure at the inlet therefore the
density of the air is decreased
Fan Laws
Flow varies directly with speed
change ratio
Pressure varies as a square of speed
change ratio
Power varies as a cube of speed
change
Fan Laws
Flow:
Q2 = Q1 x N2 / N1
Pressure:
P2 = P1 x (N2 / N1)^2 x ρ2 / ρ1
Power:
HP2 = HP1 x ( N2 / N1 )^3 x ρ2 / ρ1
Where ρ (rho) = density
System Line Curve
System line refers to a single formula
that represents all of the losses in the
vent circuit
It is characterized by the following
parabolic formula:
P2 = k Q^2
System Line Curve
Volume / Pressure System Lines
35
Based on 40,000
ACFM at 5.0"
30
Pressure, in Wg
25
Based on 50,000
ACFM at 5.0"
20
15
Based on 60,000
ACFM at 5.0"
10
5
0
0
20,000
40,000
60,000
Volume, CFM
80,000
100,000
120,000
Basic Equations
Atkinson Equation
Velocity Pressure
Air Horsepower
Actual Horsepower
Fan Efficiency
Atkinson Equation
Equation for calculation of loss
through a system or system element
Hf = KPLQ2
5.2A3
Hf=Friction head - inches W.G.
• Q= Volume in
ACFM
K= Loss coefficient
• A=Area of airway
P= Perimeter of airway in feet
in square
feet
L=Length of airway in feet
Velocity Pressure
Energy contained in moving air
Standard Air Pv = (Velocity/4005)2
Non Standard Air Pv
= (Velocity/1097)2 x density
Air Horsepower
Energy required to obtain a given
flow and pressure
AHP= (Q x Pt) / 6354
SI: AHP = Q X Pt
where Q=m3/s & Pt = kPa, AHP= kW
Brake or Fan shaft Horsepower
Energy required to obtain a given
flow and pressure including fan
efficiency
BHP = (Q x Pt) / (6354 x ηt)
where ηt = fan total efficiency
Fan Efficiency
Ratio of Air power supplied to the
mechanical power absorbed
ηt = AHP / BHP
where AHP is calculated using fan Total Pressure
For static efficiency, calculate AHP using
Fan Static Pressure
Fan Types
Centrifugal
Axial
Centrifugal Fans
Centrifugal Fan Rotor Types
Airfoil
Backward Curved / Inclined
Forward Curved Radial Tip
Full Radial - Shrouded or Un-Shrouded
(Sopladores)
Typical Centrifugal Fans
Axial Fans
Tube Axial
Vane Axial
Tube Axials
Low Efficiency
Low Pressure Capability
Low Cost
Reversible Flow
Vane Axials
High Efficiency
High Pressure Capability
Preferred Type for Mining Applications
Fan Curves
Centrifugal - Non-Overloading
Centrifugal - Overloading
Axial
Vane Axial Fan Curve
Each curve
represents a
specific blade
angle
Performance can
be varied by:
Blade angle,
Fan speed
Basic Fan Systems
Supply
Exhaust
Booster
Single Fan
Parallel Fans
Fans in Series
Parallel Fans
Two fans in parallel will create twice
the volume at the pressure of one
fan
Fans in parallel should not be
selected close to peak pressure
Special consideration must be made
to prevent instability of parallel fans
during start-up
Fans in Series
Two fans in series will create the
volume of one fan at twice the
pressure
Multiples of fans greater than 2
may be installed
Multiple fans and/or multi-stage
fans are common at higher
elevation
Supply Fan Systems
Clean Air
Easy Access for Maintenance
Accessible in the event of an
underground fire
Easy to silence if sound is a
consideration
Must provide heat in cold climates
Exhaust Fan Systems
Air is tempered by mine, same
conditions at all times
Accessible in the event of a fire or
emergency
Produce moisture, corrosive air
Difficult to silence
Higher maintenance
Booster Fan System
Air is tempered by mine, same
conditions at all times
Sheltered from weather extremes
Difficult to access in the event of a
fire
Costly to install and maintain
Sample Installations
Cameco - McArthur River Project –
Uranium
Ventilación Primaria - Extractor
3, 10150 AMF 6100, Ventiladores Axiales,(Extractores)
300,000 cfm, 9.5 in Wg, 880 rpm, 700 hp
IMC Salt - Goderich Mine - Sel
Ventilación Primaria - Booster
2, 96-58-1180, Ventiladores Axiales, (Ventiladores
booster subterráneos)
400,000 cfm, 15.5 inWg,1180 rpm, 1250 hp
Codelco - El Teniente, Inyector y
Extractor
Ventilación Primaria –
Inyector y Extractor
2, 148” Ventiladores Axiales
1,000,000 cfm, 6.5 in Wg, 735
rpm, 1308 hp
Canalización, Codos y
Apagadores fabricante en Chile
Placer Dome – Zaldivar –
Processos de Cobre
• Sopladores que
promueven actividad
bacteriana en el proceso
de lixiviación
• 6,000 cfm, 85” wg, 119 bhp
Questions?
Please ask for clarification or
additional information on any aspect
of the presentation