INDUCED DRAFT FAN

RITESH KUMAR CONSTRUCTION , M6K221 MECHANICAL ENGGINEER

Reference : shaft alignment hand book", john piotrowski.Ritesh Kumar M6K2211

DRAFT SYSTEM

Supply air for combustion Remove air from furnace Transporting pulverized coal to furnace Maintain speed for heat transfer

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DRAFT SYSTEM

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TYPES OF FANSAxial fan Fluid comes axially . Get compressed while

Centrifugal fan Fluid comes axially. Get compressed because of

moving axial. Move out axially.

centrifugal action. Comes out of fan radially.

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CENRIFUGAL FANS

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ERECTION OF INDUCED DRAFT FANS Blue matching Erection of packer plates Primary alignment Secondary alignments Inlet cone erection Erection of casing

Blue matching of machine foot , wedge plates and packer plates is doneRitesh Kumar M6K2216

Leveling devicePacker plate

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Erection of packer plate Elevation

Flatness Co planarity positioning

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Master level

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Installation of induced draft fan

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Result of improper installation Lose of production Premature failure of machine components Loss of energy

To insure ,before alignment some primary checks are done

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Preliminary checks Coupling half runout Soft footing Bearing

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Runout checkRunout standardsShaft speed Maximum runout 0.13 mm

0-1800 rpm

1800-3600 rpm

0.08 mm

3600+ rpm

0.05 mm

Maximum times these standards are provided by manufacturer

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Ways of detecting soft footDial indicator shims

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Checking procedureDial indicator First tight the bolt Place dial indicator Loose bolts See dial show less then 0.06

shims Check gap between foot and

mm.

pedestal by shims at four sides of foot. They should come same other wise soft footing is there.

Repeat this for all footsEliminating soft footing is most time consuming and skilled job. Machines on maximum occasion have vibration problem due soft footing This is very much a trial and error method because every time you need to put shims as per calculation and check for soft footing till you eliminating.

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Example of soft footing

This condition is outcome of

bad blue matching, leveling and complaining of packers

Reasons of soft footingInsufficient contact between machine foot and pedestal. Noncoplanarity foot or pedestal .Ritesh Kumar M6K22116

Alignment basics

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Types of misalignments

Measured in mm

Measured in degree of angle

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Calculation of angular misalignment

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Alignment methods Face to Rim method Reverse indicator method

There other method to align shafts but these are predominantly used. Reverse indicator method is more accurate then Face to Rim method.Ritesh Kumar M6K22120

Face to Rim methodAdvantage of Face to Rim method above reverse indicator method , it can be used for alignment when rotating both shaft is not possible

Both shafts are moving so facial reading is going to be effected. To overcome ,we are using two extra dial indicator .Ritesh Kumar M6K22121

Set of readings

Making compensation for shaft movement is important .Ritesh Kumar M6K22122

Other arrangement used in Face to Rim method

Axial reading = A1- A2/2

Why compensation is this?Ritesh Kumar M6K22123

Dimension required

Accuracy of Face to Rim method depends on diameter at which facial reading is taken.Ritesh Kumar M6K22124

How to align Electrical machines have magnetic center , so motor shaft first

needs to be positioned to it magnetic center , only then alignment is done. With above mentioned formula calculate position of Driver and Driven machine inboard and outboard foots. Find out movement of inboard and outboard foots to make shafts collinear and coplanar. This can easily be done by using graph paper Individuals do it on hit and trial basis but by using above process can be done in less time.Magnetic center of electric machines is specified by manufacturer 25

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Interpretation of dial reading in 3-D view

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Example

Page 361Ritesh Kumar M6K22127

Reverse indicator method

Same process of finding movement of Drive and Driven machine inboard and outboard foot to align shafts we follow here.Ritesh Kumar M6K22128

Why to rotate both shaft

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Alignment specification Most of time provided by manufacturer

Depends on coupling ,speed and power.NTPC allowable tolerance Parallel misalignmentOutput of rotor in KW Coupling Speed rpmBelow 400 (mm) 400-1000 (mm) Over 1000 (mm)

Angular misalignmentOutput of rotor in KW Coupling Speed rpmBelow 400 (mm) 400-1000 (mm) Over 1000 (mm)

2500-4000

0.01 0.025 0.04 0-01 0.015

0.02 0.04 0.06 0.02 0.03

0.03 0.06 0.10 0.03 0.04 Rigid coupling Flexible coupling

2500-40001300-2500 Below 1300 2500-4000 Below 2500

0.020.06 0.08 0.02 0.03

0.030.07 0.10 0.03 0.04

0.040.10 0.15 0.04 0.05

Flexible coupling

1300-2500 Below 1300

Rigid coupling

2500-4000Below 2500

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OPERATION PROBLEM Part load Fluctuating weather

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FLOW CONTROLING Dampers Inlet vane Hydraulic variable speed coupling Variable frequency drive

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Inlet vane

Damper

Inlet control valve is also controlled by motor actuatorsActuator

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Mechanical comparisonSpeed (flow) 100 % 90% 80% 70% 60% Hours 400 800 4000 2000 800 Load KW 933 680 477 320 201 Fluid coupling KWh 439,000 725,000 2,935,000 1,143,000 350,000 Variable speed coupling 439,000 648,000 2,229,000 780,000 201,000

Annual KWhAnnual energy cost Maintenance costs Total annual costs Capital costs Total five year cost Total ten year cost

5,559,000$279,600 $20,000 $299,600 $235,000 $1,733,000 $3,231,000

4,367,000$218,350 $10,000 $228,350 $295,000 $1,436,000 $2,578,000

Cost summaryRitesh Kumar M6K22135

The application considered above is an induced draft fanHorse power 1250 hp. Cost of energy is $0.05.

Reference :Fan drive system efficiencies", Universal Dynamics Limited, ADAM CREERY .Ritesh Kumar M6K22136

THANK YOU

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