4.Kiln Supports

7/26/2019 4.Kiln Supports

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Rotary Kiln MaintenanceRotary Kiln MaintenanceSeminarSeminar

Kiln Supports


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Kiln SupportsKiln Supports

Types of Kiln Supports Roller Adjustments

Roller Inclination Roller and Tire Defects

Roller and Tire Re-conditioning


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Types of Kiln SupportsTypes of Kiln Supports


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Rigid Kiln SupportRigid Kiln Support

A kiln support consists of two rollers with bearings mountedon a base frame. This rigid support is the most common.


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Tire

Roller

Bearing

Hinge

Pivot Point

On this support the bearings aremounted on a pivoting frame.


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SelfSelf--AligningAligning Kiln SupportKiln Support

A self aligning support maintains continuouscontact between tire and roller as the kiln turns. Asa result, there is less hertz pressure on the rollerand components can be sized more economically.

Self-aligning

support

Traditional

Rigid Support


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SelfSelf--Aligning Kiln SupportAligning Kiln Support


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FLS Kiln Support Type SRBFLS Kiln Support Type SRB


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FLS Kiln Support Type RAFLS Kiln Support Type RA

FLS kilns have supports with self aligning bearings inspherical sockets.


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FLS Kiln Support Type RBFLS Kiln Support Type RB

The RB support is similar to the RAsupport, except the bearing takes the thrustload next to the roller on a thrust ring.


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Fuller Kiln SupportFuller Kiln Support

The Fuller support has rigid bearings.


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Roller AdjustmentsRoller Adjustments


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Axial Forces on a KilnAxial Forces on a Kiln

A kiln on a slope will tend to move downhill as it turns. Thatdownward movement is resisted by both the friction forcebetween rollers and tires, and by the force on the thrust roller.

2 - 4% slope

Friction Force

ThrustRoller

Force

Kilns Downhill Force


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Roller Friction ForceRoller Friction Force

When a kiln roller is not exactly parallel to the kiln axis, it

imparts an axial thrust force to the kiln. The direction ofthis force (uphill or downhill) depends on how the roller isskewed, and on the direction of kiln rotation.

Neutral

Neutral


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Roller AdjustmentRoller Adjustment

CounterCounter--Clockwise KilnClockwise Kiln

To reduce the load on the thrust roller, all rollers should be

skewed to push the kiln uphill, never downhill. Shown aboveare the correct adjustments for a kiln that turns counter-clockwise (looking from the burner floor).

Direction of Kiln Thrust


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Clockwise KilnClockwise Kiln


These are the correct adjustments for a clockwiseturning kiln.


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Rollers on the discharge pier are often adjusted forneutral thrust. This avoids excessive roller wearcaused by dust from the kiln seal.

Neutral

Neutral

FeedEnd

Discharge

End


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Good Roller AdjustmentGood Roller Adjustment

All Rollers Pushing Uphill

All Rollers Pushing Equally

Kiln FloatingBetween Upper and

Lower Thrust Rollers (or, correctpressureon hydraulic thrust cylinder)


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RollerRoller --Tire ForcesTire Forces

When the force on the tire/kiln is uphill, the force on theroller is downhill. The direction of thrust can bedetermined by observing the contact or gap at the thruststop inside the bearing.



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Bearing Thrust ArrangementsBearing Thrust Arrangements

FLS Type RA

Takes Thrust Load on Thrust Collar

FLS Type RB

Takes Thrust Load on Thrust Ring

Fuller

Takes Thrust Load on Thrust Washer

UphillBearing

DownhillBearing


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Bearing Thrust ArrangementsBearing Thrust Arrangements

FLS Type RA

FLS Type RB

Fuller

Contact

Contact

Contact

Gap

Gap

Gap

Direction ofForce on Kiln

Direction ofForce on Roller


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FLS Bearing Type RAFLS Bearing Type RA

The RA bearing takes the thrust load on a thrustplate which is bolted to the end of the shaft.

ThrustCollar


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FLS Bearing Type RBFLS Bearing Type RB

The RB bearing takes the thrust load at a ring which isshrunk onto the shaft.

Thrust

Ring


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Fuller BearingFuller Bearing

The Fuller bearing takes the thrust load on a thrustwasher which is bolted onto to the housing end cover.

ThrustWasher


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The direction of roller thrust in an RA bearing is determined byobserving the gap between thrust plate and bronze bearingliner. Contact in the uphill bearing and a gap in the lowerbearing indicates that the roller is pushing the kiln uphill.


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For FLS bearings type RA, there should always be contactbetween thrust plate and bronze bearing liner on the uphillbearing. This indicates that the roller is pushing the kiln uphill.

Contact


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Direction of roller thrust in an RB bearing isdetermined by observing the gap/contact betweenthrust ring and bronze bearing liner.


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For FLS bearings type RB, there should always be contactbetween thrust ring and bronze bearing liner on the downhillbearing. This indicates that the roller is pushing the kiln uphill.

Contact

Thrust

Ring

Bearing

Liner


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For FLS bearings type RB, a gapshould always be presenton the uphillbearing. This indicates that the roller is pushingthe kiln uphill.

Gap


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Fuller BearingFuller Bearing

For Fuller bearings, thrust direction is checked by rapping thebearing end cover with a hammer. A solid sound indicatescontact, a hollow sound indicates a gap.


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Measuring Roller ThrustMeasuring Roller Thrust

Important!Rollers and tire surfaces must be completelyfree of oil when skewing adjustments are made. Onlygraphite block lubrication is permitted.

GraphiteBlock


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Rollers should be adjusted to float the kiln between theupper and lower thrust rollers.



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For kilns with hydraulic thrust rollers, support rollers areadjusted to keep the hydraulic pressure within specification.

Pressure Gage



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The force on the thrust roller can be calculated from thehydraulic pressure indicated on the gage.

Hydraulic PressureHydraulic Pressure

Force = Pressure x Area

Area = (Piston Diameter) 2 x

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Calculation of Hydraulic PressureCalculation of Hydraulic Pressure


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Calculation of Hydraulic PressureCalculation of Hydraulic Pressure

When All Rollers Are NeutralWhen All Rollers Are Neutral Calculate the weight of the rotating parts of the kiln (shell,

tires, gear, refractory, material load).

Multiply by the % kiln slope to get the force on the thrust roller.

Divide by the total piston area of all thrust rollers.

Example:

1000 short ton kiln x 2,000 pounds/short ton = 2,000,000 pounds

2,000,000 pounds x 3% slope = 60,000 pounds force on thrust roller

Area of single 10 diameter piston = (10) 2 x = 78.5 inches 2

4

Pressure = 60,000 = 764 PSI

78.5


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Rollers are skewed by moving bearings in or out asrequired. Note that the adjusting screws shown aregreased and wrapped to prevent corrosion.


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Jacks for Roller AdjustmentJacks for Roller Adjustment

Pancake Jacks are available with forces over 100 tonsto aid in pushing bearings in for roller adjustment.


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Moving a bearing out is easier.A small jack may be needed.


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Always measure and record every bearing adjustment.To keep from changing the kiln center, make equal andopposite movements on each bearing.



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Measuring precise roller thrust is possible on FLSbearings using this axial measuring device.


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The axial measuring device consists of a hand jack withpressure gage, a mounting fixture, and an adapter withbearing to enable readings when the roller is turning.



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The jack is pumped up until the roller begins to moveuphill off its thrust stop. At this point a pressure readingis taken and the reading is then converted to tons force.


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FLS

Type RB

FLS

Type RA

Data assumes a

jack piston with16.6 cm2 surfacearea.

M i R ll Th


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Caution!It may not be possible to accurately measureroller thrust if tire and roller surfaces are notcylindrical or if roller shafts or bearings are grooved.

Step-worn Roller and Tire Grooved Roller Shaft

D t i i R ll Th tD t i i R ll Th t


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Determining Roller ThrustDetermining Roller Thrust

Trial and Error MethodTrial and Error Method

Find the rollers neutral point (parallel to kiln axis)

by adjusting the roller skew in small incrementsuntil the bearing thrust contact/gap changes fromone bearing to the other.

Once the neutral point is determined, make asmall adjustment to push the kiln uphill.

While making an adjustment of an individual roller,

always observe the kilns thrust rollers to ensurethat they are not being overloaded.


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Roller InclinationRoller Inclination

R ll I li iR ll I li i


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Just like horizontal skewing, vertical skewing of a roller,i.e., having a roller slope different than the kiln slope, willalso create a thrust force.

R ll I li iR ll I li ti


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Roller slope must not deviate from the kiln slope bymore than 0.02% (0.04% for old kilns). The direction ofallowable deviation must be such that the roller pushesthe kiln uphill.

Measuring Roller SlopeMeasuring Roller Slope


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Measuring Roller SlopeMeasuring Roller Slope

Roller slope is measured with an inclinometer.

InclinometerInclinometer


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100 mmSpacing

1 mmmicrometer

scale

Due to its dimensioning, the inclinometer reads thepercent slope directly.



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When the leveling bubbles are centered, thepercent slope is read on the micrometer dial.



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Magnets allow mounting the inclinometer onhorizontal or vertical surfaces. The inclinometerhas a precision bubble level for each position.



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Check the roller slope with the inclinometer mounted on theshaft end. Take readings on both ends of the shaft andaverage them to eliminate the effect of roller shaft deflection.



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This arrangement can be used to measurethe roller slope while the kiln is turning.


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Roller and Tire DefectsRoller and Tire Defects

Tire and Roller DefectsTire and Roller Defects


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If kiln rollers are skewed too much thewear rate can be quite severe.



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The old practice of running a roller in a water bath is nowthought to promote surface pitting and is no longerrecommended.




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When rollers are misaligned or conical-shaped, the kilnload is spread over too small an area. This causes highsurface stresses resulting in pitting.



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A defect on a roller may transferto the tire, and vice-versa.



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Roller or tires may wear to a conical shape.



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A tire running off the roller for a long time will wearinto a step pattern.



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Tire wobble can create a concave roller surface.


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Roller and Tire ReRoller and Tire Re--conditioningconditioning



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Roller and Tire ReRoller and Tire Re conditioningconditioning

Rollers and tires may be re-conditioned by machining orgrinding. Shown above is a lathe adapted for this purpose.



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o e a d e e co d t o gg

Rollers are re-conditioned while the kiln is in operation.


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The machinist is protected with a heat shield.



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This roller is being resurfaced by grinding ratherthan machining.



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Re-surfacing a tire by grinding



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Tire and roller edge defects must also beremoved. Edges should then be chamfered.

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4.Kiln Supports

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