3_1 operating multiple fans

8/3/2019 3_1 Operating Multiple Fans

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AMC - The Business of Mining(C) AMC Consultants Pty Ltd 2005 1

Basic Mine VentilationBasic Mine Ventilation

Understanding FansUnderstanding Fans

Operating Multiple FansOperating Multiple Fans


Series fansSeries fans


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Operate in the samesystem and handle the

same air

Fans may be bolted

together or spaced

along the duct

Pressure increases for

the same volume

PTotal = P1 + P2

Series fansSeries fans

Quantity (m3/s)

Pressure

(Pa)

0

0

5 10 15 20

500

100

0

PA

PB

P A+B

Fan A

Fan B

Fan A + B

0 5

A B


Example

Airflow increase is minimal

Pressure increase is x2

Assuming the motors are250 kW, would you

recommend this?Increase circa 10 m3/s


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Fans & NVPFans & NVP

Quantity (m3/s)

Pressure

(Pa)

0

0

5 10 15 20

500

1000

Operating point varies on a

daily and seasonal basis

NVP -100

-200

NVP +110

Fan - NVP

Fan + NVP

Fan


Operating fans in parallelParallel fansParallel fans


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Fans installed alongside each other

and operate on the same system

Volume increases for the same

pressure

QTotal = Q1 + Q2

Parallel fansParallel fans

Quantity (m3/s)

Pressure

(Pa)

00

5 10 15 20

50

0

1000

QA

QB

Q A+B

Fan A

Fan B

Fan A + B

A

B


Example

Pressure increase is minimal

Quantity increase is something

less than x2

Assuming the motors are 250

kW, would you recommend

this?

How would you configure the

fans?

Increase circa 30 m3/s

NOT x2


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If fans that intake (exhaust) air through the same system are in parallel,

then fans that intake (exhaust) from the same place but through different

systems are in partial parallel

Both fans must have sufficient pressure to overcome the resistance of the

common airway.

Partial parallel fansPartial parallel fans

Fan 1A

B

C

Fan 2


PartialPartial--parallel fansparallel fans

0

500

1000

1500

2000

2500

3000

0 25 50 75 100 125 150 175 200 225 250 275 300

Volume (Q) (m3/s)

Pressure(Pa)

Fan 1

Fan 2

A

B

C

Fan1

Fan2

System

A

System

B

Syste

mC


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0

500

1000

1500

2000

2500

3000

0 25 50 75 100 125 150 175 200 225 250

Volume (Q) (m3/s)

Pressure

(Pa)

Fan1

System

AFan pressure available

Pressure used by the system

2214

810

Residual fan pressure

2214 810 = 1404Fan pressure exactly

overcomes the system

resistance and the residual

pressure is ZERO

Fan 1 in System AFan 1 in System A Residual fan curveResidual fan curve

Fan 1

Fan 2

A

B

C


Plotting the residual curvesPlotting the residual curves

0

500

1000

1500

2000

2500

3000

0 25 50 75 100 125 150 175 200 225 250 275 300

Volume (Q) (m3/s)

Pressure

(Pa)

Fan1

Fan2 System

A

System

B

SystemC

Fan1-SysA=R

1

Fan2-SysB=R2Fan 1

Fan 2

A

B

C

Paralle

lresidualcu

rve

Q1

Q1+2

Q2


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0

500

1000

1500

2000

2500

3000

0 25 50 75 100 125 150 175 200 225 250 275 300

Volume (Q) (m3/s)

Pressure

(Pa)

Fan1

Fan2 System

A

System

B

Syste

mC

Fan1-SysA=R1

Fan2-SysB=R2

R1+

R2=

Resid

ualcu

rve

Partial parallel fansPartial parallel fans --The solutionThe solution

Fan 1

Fan 2

A

B

C


When one fan passes the air to another the fans are said to be in

series. But if air enters or leaves the system between the fans the

fans are only in partial series

Because Fan 1 (System A) is assisting Fan 2 (System C) the curve

of Fan 1 needs to be subtracted from the system curve (A) to

determine the residual system curve.

Partial series fans (Circuit booster)Partial series fans (Circuit booster)

Fan 1A

B

C

Fan 2


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0

500

1000

1500

2000

2500

3000

0 25 50 75 100 125 150 175 200 225 250

Volume (Q) (m3/s)

Pressure

(Pa)

Fan1

System

A

Fan pressure exactly

overcomes the systemresistance and the residual

pressure is ZEROPressure for system

Fan pressure2214

640

Residual system pressure

640 2214 = 1574-934

Fan 1

Fan 2A

BC

Fan 1 in System AFan 1 in System A Residual system curveResidual system curve


Plotting the residual system curvesPlotting the residual system curves

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

3000

0 25 50 75 100 125 150 175 200 225 250

Volume (Q) (m3/s)

Pressure

(Pa)

Fan 1

Fan 2A

BC

Fan1

Syste

mA

System

B

SysA

Fa

n1

Parallelsy

stemc

urve

Q1

Q2

Q1

Q1+2

System A and System B are in parallel


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Partial series fansPartial series fans --The solutionThe solution

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

3000

0 25 50 75 100 125 150 175 200 225 250

Volume (Q) (m3/s)

Pressure

(Pa)

Fan1

Fan2

Syste

mASy

stem

B

SysA

Fa

n1System B

40 m3/sSystem A

130 m3/sSystem A+B

170 m3/s

Paralle

lsyste

mcurv

eFan 1

Fan 2A

BC


Primary Installations

Parallel at the the same shaft

Partial parallel if at different shafts

Single fan installations are generally less expensive than multiple fan installations.

Multiple fan installations have the advantage of airflow redundancy, i.e. a percentage of

airflow will always be available whilst a fan is off line for maintenance or component

change out.Single fan options do not provide any capacity for redundancy airflow. The purchase of

spares (motor, impeller, shafts, bearings, blades etc) is good management and should be

included as upfront capital expenditure.

Circuit Booster

Partial series

Sometime installed to act as a regulator

Relative merits of single and multiple fan installationsRelative merits of single and multiple fan installations


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Acknowledgements

DALY, B.B., 1978 Woods Practical Guide to Fan Engineering

(Published by Woods of Colchester 1978)

Le ROUX, W., Le Rouxs Notes on Mine EnvironmentalControl Fourth Edition. (The Mine Ventilation Society of South

Africa).

JORGENSEN, R. 1983 Fan Engineering Eighth Edition (Buffalo

Forge Company. Buffalo, New York.)

BURROWS, J., 1989 Environmental Engineering in South African

Mines (The Mine Ventilation Society of South Africa)

Tien, J.C., 1999 Practical Mine Ventilation Engineering (Intertec

Publishing Corporation. Chicago, Illinois.)

3_1 operating multiple fans

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