tire taper

8/13/2019 Tire Taper

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Industrial Kiln & Dryer Group |www.industrialkiln.com|877-316-6140

TIRE / SUPPORT ROLLER TAPER

The following is an excerpt out of the training manual authored by Roland

Sutter; Chief Engineer, for Industrial Kiln & Dryer Group. The purpose of

this article is to give some insight into the causes, and adjustments

necessary, to remedy the problem of tire taper wear on rotary dryers and

similar roller mounted equipment.

Pressure Relationship:

Before we can elaborate on the symptoms you may encounter and the causes of those symptoms, we need to

understand the pressure relationship between the Tire and Support Roller. The figures shown below give you

a visual understanding of the pressure relationship between the Tires and the Support Rollers, showing

the amplitude and relative position of the pressure load:

Figure 1 shows the force applied by the Tire to the roller by the weight of the drum. This pressure across theroller is called Hertz Contact Pressure. This calculated stress is a function of the Support Roller diameter,

Tire diameter, Tire face width, load, and the rpm of Tire. The allowable stress is a function of the steel

hardness.

Figure 2shows the normal stress level if the Tire and Support Roller are on same slope and contact is good.


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Figure 3shows the stress pattern and higher stress amplitude due to poor contact. Wear will accelerate due

to metal fatigue, resulting in the formation of a taper. If the taper is extreme, metal can extrude out the contact

points, forming a lip on the edge of the Roller or Tire.

Figure 4shows a flat area at the point of contact. The metal is deformed inward, and then springs out. This

repeated action results in fatigue of the metal, and the wear in true rolling action, is the result of fatigue rather

than sliding wear.

Common Wear Situations:

The following list describes some of the common situations that cause Tire and Support Roller wear:

1) When the Support Rollers are improperly set, such that the centerline of the Drum is not on the same

slope as the Support Rollers and Bases.

2) When the Support Rollers are not on the proper slope due to deformation of the Bases, Pier movement

improper shimming, and/or Base Shim corrosion and Grout failure.

3) When the Support Roller Bases are not at the proper elevation due to Pier settlement.

4) Tapered wear due improper skewing of the Support Rollers.

5) Tapered wear due to Tire axial runout.

6) Wear due to excessive Gear / Pinion backlash.

Figure 5 - Vertical Offset

Figure 5shows Vertical Offset. If the Support Rollers are on the correct slope, but are misadjusted in such a

manner that the centerline of the near Tire is higher, or lower, than the far Tire, the slope of the Drum will be

different than the Support Rollers, and tapered wear condition will occur.


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Figure 6 Horizontal Offset

Figure 6shows an example of Horizontal Offset. If the Support Rollers are on the correct slope, but are

misadjusted in such an manner that the centerline of the near Tire is right, or left, of the far Tire, a whirling

action will occur, (visualize putting a drill bit in a chuck off center). Sometimes the resulting taper is in twodirections across the face of the Tire and Support Roller.

Figure 7a - Rollers Off Slope.


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Figure 7b - Base Settlement Caused By Pier Settlement

Figures 7a and 7bshow the Support Rollers on different planes with each other. This condition can be

caused by Pier movement, deformed Support Roller Bases, Base Grout and Shim failure, and/or improperinitial installation.

Figure 8 - Excessive Skewing

Figure 8 shows an example of excessive skewingof the Support Roller. As an illustration, if the Support

Roller Shaft was set to be parallel with the Tire face, pure sliding would occur with very little contact. If the

Support Roller Shaft was set to be perpendicular to the Tire face, nearly pure rolling action with good contact is

achieved. Very little angular skewing will result in a sliding component resulting in normal wear. Excessive

skewing will dig into the Tire resulting in aggressive wear and a resulting taper.


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Figure 9 Tire Axial Runout

Figure 9 shows tapered wear as a result of a poor Tire axial

runout. As was shown in Figure 3 earlier, the fact that the

percentage of contact between the Tire and Support Roller is

lower increases the amount of pressure applied to a concentrated

area, resulting in that area wearing quicker than the area without

contact and a taper is developed.

Figure 10 Excessive Gear/Pinion Backlash

Figure 10 shows the wear patterns that develop due to theGear and Pinion backlash being excessive. Under normal

conditions, the Pinion will drive the Gear in a uniform motion with

one Tooth engaged, and in contact, at all times. If the backlash is

excessive, the driving Tooth will lose contact before the next Tooth

engages, resulting in a load reversal, (Drum sliding) and impact

when the next Tooth does engage. This jerking motion will leave

skid marks on the Tire and will result in flat spots wearing into the

Tire and/or Support Roller.


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The Proper Set Up of the Tires and Support Rollers:

The following assumes that the Tire face and Support Roller face are square, either as a result of Grinding or

because they are new. (You may have figured it out by now that the act of Grinding the Tires and Support

Rollers does not fix the conditions that actually cause the tapers. If you Grind and do not fix all of the

mechanical alignment issues, your tapered condition will come back in the future) .

The Support Roller Bases must be level, no shims are under the pillow blocks, and the bases are square and

not offset.

Figure 11- Base Level, Square, and Offset

Figure 12- The objective is to place the Rollers so that the centerline of the Rollers and Tires are on the same

slope and are in the same vertical plane.


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Figure 13- Machined Base Pads are in the same plane and are square.

Figure 14 Achieve Station Geometry

CL BASE

SQUARE

OFFSET


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Key Relational Formulas:

CDR= (Dt+RDR)/2 CDR= (Dt+RDL)/2

YR= (Dt/2) - (OSR) (RDR/2) YR= (Dt/2) - (OSL) (RDL/2)

HR=CDR YR HR=CDL YL

=ANGLE= ARC TAN (YR/HR) =ANGLE= ARC TAN (YL/HL)

XL= 1/2 Dt X SIN (AR) XR= Dt X SIN (AL)

AT 30 DEGREES YR= CDR X 0.5 HR= CDR X 0.866 HTR= HR+ BR

YL= CDL X 0.5 HL= CDL X 0.866 HTL= HL+ BL

XL= 0.5 X Dt XR= 0.5 X Dt

Notes:

1. To find the center of the Tire from the Roller centerline= Dt/2- RDR/2-OSR or Dt/2-RDL-OSL

2. If the Bases at the machined Pads are in the same plane HTL=HTR

3. If the Tire and Roller are in contact, the center distance CRL or CRR will not change.

4. To find the centerline of the Support Roller Bases; measure the distance between Pillow Block hold

down bolts and divide by 2.

Example Set Up Process:

Figure 15

1. Neutralize the Rollers by making the sides of the Tire and Support Rollers parallel. (The T-TRAC is a

simple tool for this operation).

2. Measure the OD of Tires and Support Rollers with a precision Pi Tape where they are in contact. Lay

a wire over the Tire with plumb bobs on both sides and measure OSR and OSL.

3. Measure the vertical distance from the Pillow Block split to the machined Base BL and BR.


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4. Calculate the change in OSL and OSR to move the Support Rollers where they sit in a position as

originally designed: AR= AL = 30 (acceptable tolerance - 28 to 32 ). The Pillow Block Bolts should

be centered in the slots.

5. Calculate the Shim thickness to compensate for the elevation of the Pillow Block.

6. Determine the difference in elevation between the near and far Tire and the Shim thickness required to

align the Tire centerlines on the same slope as the Support Rollers.

As shown in Figure 16 below:

Move 1 & 2: Move Support Rollers at each station where the Pillow Block Bolts are centered in the

slots as close as possible install the proper Shim to compensate for this move and to place the Tire

centers at the same elevation and recheck parallelism of sides of Tire and Support Roller.

Move 3: Move both Support Rollers a one or both stations so that both sets of Support Rollers are on

the same vertical centerline.

Figure 16 Move Diagram


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Example Data Table:

Conclusion:Focused thought and analysis is required to accurately diagnose what is actually causing your Tires and

Support Rollers to develop a tapered wear pattern. Grinding alone is not a cure and will only temporarily

alleviate the issues. Also frequent grinding will significantly shorten the life of your Tires and Support Rollers,

since you are removing material during each grinding session. The focus needs to be in figuring out which

mechanical issues exist that are the root-cause of the tapered wear pattern, and steps that need to be taken to

fix these mechanical issues. Once the root-cause mechanical issues have been eliminated, the Tires and

Support Rollers should be ground square to give the best rolling surfaces and the lowest pressure points.

Note:

Roland Sutter is the Chief Engineer of Industrial Kiln & Dryer. He is a degreed Mechanical Engineer with 43+ years experience in designing, fabricating,installing, troubleshooting and servicing Rotary Kilns, Rotary Dryers, Ball Mills, Lime Processing Equipment, Hydration Systems, Slaking Systems,

Rotary Incinerators and Rotary Digesters. He is the Past President/Chief Engineer of Vulcan Iron Works and has past design experience with Allis

Chalmers and Kennedy Van Saun.

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