kuliah 7 - mine fans

7/29/2019 Kuliah 7 - Mine Fans

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Mine Fans

Rini Novrianti Sutardjo Tui


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Axial Flow Fan

Free air -

Theimpeller is

notconfined

Vane axial -The impelleris fitted in a

casing

Tube axial- Theimpeller isconfined

in a casing


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Centrifugal Flow Fan


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Fan Comparison

Characteristic Axial Centrifugal

Size Can be fairly compactForward curved about same sizeas Axial, backward curved muchlarger.

ReversibilityLimited efficiency whenoperated in reverse direction.

Centrifugal fans cannot bereversed.

Installation Simpler and cheaper.

Complex airflow reversalarrangement may be necessary.U/G fans may need recessed

areas for set-up.

CostMajor fans are about the samein cost.

Underground centrifugal fansmore expensive

NoiseAxial flow fans noisier and at ahigher pitch.

Mechanical StabilityCentrifugal fans are morerobust than axial fans.

Power Characteristics Falling power characteristic

Forward curved draw excessivepower near free air delivery(low pressures), backwardcurved have falling powercharacteristic.

Maximum HeadMax for single stage, about3000 Pa.

Maximum can be as much as9000 Pa.

Efficiency Vane axial most efficient. Forward curved least efficient.

Flexibility Variable pitch axial flow mostflexible.


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Fan Applications

MainFan

Booster

Fan

Auxiliary

Fan

The principalfan used toproduce generalventilation air

current in mine.It is normallypermanent innature and largein capacity.

The fan whichis usuallyinstalled toventilate parts

of the minewhere the mainfans may, bythemselves, beinadequate.

The fan is usuallyof small size,portable, andtemporarilyinstalled to

ventilate workingplace throughwhich the generalventilating air maynot otherwisepass.


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Fan Stall

Stall ZoneSigns

The fan vibratesexcessively

The fan makesunusual noises

Input poweramps show rapid

oscillations orsurging at a

slower frequency

The quantity andpressure points

alter considerably

A fan will stall if the resistance of the system is (or becomes) excessive and

eventually, the pressure and quantity become unstable and fluctuate wildly.


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Fan Performance Control

Increasedresistance

Increased airflowrequirements

Power savingChange in air

density

Regulators


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Fan Arrangements

baseriesba ppp

baparallelba QQQ

Series arrangement: on thesame flow circuit, handlingthe same airflow, generating apart of total pressure required

Parallel arrangement: inseparate openings, draw airfrom the same commonpoint, deliver it to the samedestination


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Fan in Series

Two identical fans in series Two different fans in series


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Fan in Parallel

Two identical fans in parallel

Two different fans in parallel


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Fan in Combination

Each fan shares a portion of the total mineresistance load, but retains its own specific

zone of influence.


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Fan Failure

Poorpreventativemaintenance

includingregular cleaning

of guide vanesand impellers

Unrecognizedincreasing fan

pressure causedby increasing

mine resistance

Anaccumulation ofdust and salts on

impellers mayalso cause the

fan to run out ofbalance

Rocks and otherforeign

materials are

often found infan housings canbecome caughton an impeller


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Fan Efficiency

Fan

Efficiency

F

ass

P

P

F

at

t P

P

I

at

o P

P

Static Efficiency

Total Efficiency

Overall Efficiency

Total power

output of

the fan

Power input

supplied to

motor driving

the fan

Static power

output of the fan

Power input

the fan

Power input

the fan

Total power

output of the fan

W

PQ

MIP

AP


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kuliah 7 - mine fans

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