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