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VESPELUSING VESPEL BEARINGS
DESIGN AND TECHNICAL DATA
g
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Putting VESPEL* towork in your system
DuPont VESPEL SP polyimidebearings have been hard at workfor more than twenty years, keep-ing equipment running longer
and with less maintenance thanconventional bearing materials.VESPEL bearings are the cost-effective choice in thousands ofapplications, because theyretough and lightweight, and resistwear and creepeven at ex-tremes of temperature. Theycan outperform metals and otherengineering plastics under awide range of conditions.
The design guide is providedto help you choose the VESPEL
bearing that is best suited to yourapplication. Inside you will find:
general information aboutbearing design;
a method for determiningpressure-velocity (PV) loadingin your application;
guidelines for selecting thecorrect SP polyimide for PVloadings found in practice;
considerations for use in the
design of VESPEL bearings; and
a sample bearing designproblem.
If you have any questions onbearings that are not answered inthis brochure, contact your localVESPEL sales engineer or thesales office nearest you.
* DuPont registered trademark forpolyimide parts and machining stock.
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Table of Contents
VESPEL Bearings vs. Other Materials 2 & 3
How To Choose a Bearing Material 4
PV LoadingA Prime Factor in Material Selection 4
Determining Your PV Requirements 4
PV Limits of Unlubricated Bearing Materials 5
Designing VESPEL Bearings 6
Effects of Surface Temperature on Wear Characteristics 6
Wear Transition Temperature 6
Frictional Behavior 7
Mating Material and Surface Finish 8
Lubrication and Other Bearing Design Considerations 9
Proportions 10
Running Clearances for Journal Bearings 10
Wall Thickness for Journal Bearings 11
Installation of Journal Bearings 11
Sample Design Problem 12 & 13
1
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VESPEL Bearings vs. Other Materials
The ability of a bearing to perform in a given application depends,in general, on:
the operating environment, including temperature and lubrication
load or pressure on the bearing surface sliding velocity of the mating surface relative to the bearing
hardness and finish of the mating surface
frictional behavior of the bearing material
thickness of the bearing material combined with the materials abilityto dissipate heat of friction.
VESPEL parts, made from DuPonts SP polyimide resins, performwell with or without lubrication under conditions that destroy most otherplastics and cause severe wear in most metals. VESPEL bearingsreduce or eliminate problems with abrasion, corrosion, adhesion,fatigue and wear that plague conventional bearing materials, especially
when used without lubricants.VESPEL bearings can accommodate higher pressure-velocity (PV)
loading than most high-performance engineering plastics. In addition,VESPEL bearings excel over a wide range of temperatures andstresses because they retain their outstanding creep resistance, abra-sion resistance and strength. They have performed successfully in thefollowing adverse environments:
air and inert gases at 700F (371C)
gamma and electron beam radiation
high vacuum (1010torr)
hydraulic fluids and jet fuels
liquid hydrogen
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Unlike ordinary ball, needle and roller bearings, VESPEL* bearings:
need no external lubrication
perform at temperatures where lubricants break down
perform well in dirty environments
can reduce noise, weight and costs
Compared with bronze, brass and porous metal bearings, VESPELbearings:
extend the life of other components by eliminating metal-to-metalwear
withstand combinations of temperature, prssure and surfacevelocity beyond the reach of unlubricated metals
resist creep and poundout eliminate problems of lubricant loss in the presence of paper dust
or lint
Compared with other polymer bearings, VESPEL bearings:
perform at temperatures, pressures and surface velocities thatother plastics cannot survive
increase creep and poundout resistance
machine like brass and hold tighter tolerances
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How to Choose a Bearing Material
PV LoadingA Prime Factor
in Material Selection
PV is the product of load or pressure(P) and sliding velocity (V). A plasticbearing subjected to increasing PV
loading will eventually reach a pointof failure known as the PV limit. Thefailure point is usually manifested byan abrupt increase in the wear rateof the bearing material.
As long as the mechanical strengthof the bearing material is not ex-ceeded, the temperature of the bear-ing surface is generally the mostimportant factor in determining PVlimit. Therefore, anything that affectssurface temperaturecoefficient of
friction, thermal conductivity, lubrica-tion, ambient temperature, runningclearance, hardness and surface finishof mating materialswill also affectthe PV limit of the bearing.
The first step in evaluating a bear-ing material consists of determiningwhether the PV limit of that materialwill be exceeded in your application. Itis usually prudent to allow a generoussafety margin in determining PV limits,because real operating conditionsoften are more rigorous than experi-
mental conditions.
Determining Your PV
Requirements
1. First determine the static loadingper unit area (P) that the bearingmust withstand in operation.
For journal bearing configurations:
P = W/(d b)
P = pressure, psi (kg/cm2)
W = static load, lb (kg)
d = bearing surface ID, in. (cm)
b = bearing length, in. (cm)
N = rotation speed, rpm
For thrust bearing
configurations:P = 4W/(D2 d2)
P = pressure, psi (kg/cm2)
W = static load, lb (kg)
d = bearing surface ID, in. (cm)
D = bearing surface OD, in. (cm)
N = rotation speed, rpm
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For either bearing configuration, pressure (P) should not exceed thevalues shown here at room temperature:
Allowable Static Bearing Pressure
Composition SP-1 SP-21 SP-22 SP-211
Fabrication Direct Direct Direct DirectProcess Mach. Formed Mach. Formed Mach. Formed Mach. Formed
P, psi 7,400 4,800 6,600 4,900 6,000 3,700 5,400 4,000P, kg/cm2 520 337 464 345 422 260 380 281
2. Next, calculate the velocity (V) of the bearing relative to the matingsurface:
Journal Bearing Thrust Bearing
Continuous Rotation V = (DN) V = (DMN)
Oscillatory Motion V = (dN) (/180) V = (DMN) (/180)
where:
N = speed of rotation, rpm or cycles/minDM = (D + d)/2, in. (cm)
= angle between limits of oscillation, degreesV = surface velocity, in./min (cm/min)
3. Finally, calculate PV:
PV(psi-ft/min) = P(psi) V(in/min) / 12or, in metric units:
PV(kg/cm2-m/sec) = P(kg/cm2) V(cm/min) / 6000
PV Limits of Unlubricated Bearing Materials
Table 1 shows the maximum PV limits for unlubricated VESPEL partsand several other unlubricated bearing materials under conditions ofcontinuous motion. Properly lubricated VESPEL parts can withstandapproximately 1 million psi-ft/min.
TABLE IPV LIMIT GUIDELINES**
Maximum
lb-ft kg-m Contact Temperature
Material Filler in2-min cm2-sec F C
SP-21 15% Graphite 300,000 107 740 393
SP-22 40% Graphite 300,000 107 740 393
SP-211 15% Graphite 100,000 36 500 260
10% PTFEPTFE* Unfilled 1,800 0.64 500 260
PTFE* 1525% Glass 12,500 4.5 500 260
PTFE* 25% Carbon 20,000 7.1 500 260
PTFE* 60% Bronze 18,500 6.6 500 260
Nylon Unfilled 4,000 1.4 300 217
Acetal PTFE 7,500 2.7 250 201Unfilled 3,500 1.2
*At 100 fpm.
** These guideline values are supplied for reference only. PV limits for any materialvary with different combinations of pressure and velocity as well as with other testconditions. Consult manufacturers literature for detailed information.
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Designing VESPEL Bearings
Effects of Surface
Temperature on Wear
Characteristics
PV is a very useful measure indetermining the suitability of amaterial for a bearing application.However, contact pressure andsliding velocity alone do notadequately characterize bearingmaterials. Temperature, systemgeometry and mating surfacematerial also play significantroles in wear of bearings.
Of the factors just named,temperature is generally the mostimportant, because it not only
affects the coefficient of frictionbut also determines the usablecombinations of pressure andsliding velocity, or PV. Wearcharacteristics of VESPELbearings will be moderate evenat high PVs if sufficient cooling isprovided. Wear can be severe atany PV if the ambient tempera-ture is too high. The wear resis-tance of a VESPEL bearingoperating at a temperature belowits limit can be predicted from an
experimentally determined WearFactor.The wear factor is derivedfrom an equation relating thevolume of material removed bywear in a given time per unit ofload and surface velocity.
v = KFVT
where:
V = wear volume, in3(cm3)
K = wear factor, in3-min/ft-lb-h(cm3-min/m-kg-h)
F = supported load, lb (kg)
T = time, h
V = velocity, ft/min (m/sec)
For flat surfaces the equation ismodified so that:
X = KPVT
where:
X = wear depth, in. (cm)
P = pressure, psi (kg/cm2)
Wear Transition
Temperature
The wear rate of a plastic mate-rial operating in air is proportional
to the product of pressure andvelocity (PV) if the surfacetemperature does not exceed acritical value called Wear Transi-tion Temperature.Above thewear transition temperature, wearincreases dramatically. For SPresins, the wear transition tem-perature is in the range 900to1000F (482to 538C) invacuum or inert gases, and 700to 750F (371to 399C) in air.
As Figure 1 shows, the wearfactor of VESPEL bearings madewith SP-21 resin is essentiallyconstant over a wide range ofoperating conditions, as long assurface temperature does notexceed the wear transitiontemperature.
FIGURE 1Wear Factor vs. Surface Temp for SP-21vs. Carbon Steel Thrust Bearing TesterNo Lubrication PV of 1,000 to 500,000 lb/in2ft/min (310-155,000 N/cm2m/min)
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FIGURE 2Wear Factor and Friction Coefficient for Unlubricated Operation AgainstMild Carbon Steel
Frictional Behavior
Temperature, pressure and velocity all affect the dynamic coefficient offriction. Typical coefficients of friction for various SP polyimide composi-tions are shown in Table 2 below.
The coefficients of friction for filled SP compositions undergo atransition at about 300F (149C), as shown in Figure 2. Below thistemperature the frictional behavior is similar to that of 66 nylon, but
above 300F (149C) the frictional forces drop sharply, and in the rangeof 400to 1000F (204to 538C), the friction characteristics of SPcompositions remain independent of temperature. The friction transitionis not associated with wear transition. The magnitude of the transition,and the wear rate below 300F (149C), are greatly reduced in SP-211.
The designer must allow for the higher frictional forces, resulting fromtwo separate phenomena, which may be present during start-up. Oneis the transfer of a layer of SP polyimide resin/filler composition to themating surface and the second is the temperature transition for SPpolyimide resins. During restart, it may not be necessary under serviceconditions to break in a new layer, but the temperature effect is revers-ible and will continue to operate at each restart.
TABLE 2Typical Coefficients of FrictionUnlubricated Thrust Bearing Test
MEASUREMENT COMPOSITION
Conditions SP-21 SP-22 SP-211British (SI) Units polyimide polyimide polyimide
Static 0.30 0.27 0.20
P = 50 psi (0.34 MPa)V = 500 fpm (2.54 m/s) 0.24 0.20 0.21
P = 100 psi (0.69 MPa)V = 100 fpm (0.51 m/s) 0.30 0.24 0.24
P = 100 psi (0.69 MPa)V = 300 fpm (1.52 m/s) 0.28 0.21 0.20
P = 100 psi (0.69 MPa)V = 1000 fpm (5.08 m/s) 0.12 0.09 0.08
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Mating Material and Surface Finish
The wear performance of VESPELparts can be substantiallyaffected by the hardness of the mating material and its surface finish.Unlubricated bearing wear rates can be reduced by increasing thehardness and decreasing the roughness of the mating surface. Ingeneral, a ground surface finish on the mating material is preferable
to a turned surface. A fine polishing operation is often beneficial. Thefinishing operation should be in the same direction as the bearingmotion relative to the mating surface.
Aluminum and zinc are not good mating surfaces for plastic bearingsbecause the softness of these materials can lead to rapid wear. If used,aluminum should be hardened or, preferably, anodized. Die-cast alumi-num with high silica content is very abrasive to VESPEL. Chromeplating is not necessary and may cause greater wear than a polishedsteel surface. The porosity of the chrome tends to micro-machine theVESPEL surface. In general, the metal surface should be as hard andsmooth as is practical.
Plastic is not a good mating material for VESPEL bearings and, if
used, should be limited to low PV conditions. The softness of a plasticmating surface can lead to high wear. In addition, since plastics arerelatively poor thermal conductors, plastic-to-plastic bearing interfacesrun hotter than plastic-to-metal interfaces, so metal plastic bearingsystems have higher PV limits than plastic-plastic bearing systems.Figure 3 illustrates the effects of mating material hardness and finishon wear performance.
FIGURE 3Effect of Mating Material Hardness on Wear
Thrust Bearing Tester No Lubrication
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Lubrication and
Other Bearing Design
Considerations
When determining whetherbearings need to be lubricated,the following points should beconsidered:
A one-time lubrication, consist-ing of an initial greasing or use ofdry lubricant, generally reducesbreak-in wear and improvesoverall wear resistance.
Lubrication of bearings canincrease the PV limit by reducingcoefficient of friction and helpingto remove wear debris. Circula-tion of the lubricant can furtherincrease the PV limit by coolingthe bearing.
Lubrication with a chemicallycompatible fluid to wet VESPELbearings will reduce both frictionand wear rates. The amount ofreduction increases with increas-ing fluid film thickness, which inturn increases with fluid viscosityand surface velocity, and de-creases with increasing bearingpressure. Application geometrywill also affect the reduction offriction. Even thin film lubricantscan reduce dry wear rates by a
factor of 10 or more. Thick films,which cause complete separationof the solid mating surfaces, cantheoretically reduce wear tonegligible proportions.
The frictional behavior of abearing system using thin filmlubrication is determined by theproperties of the bearing materialas well as by the properties of thelubricant. Frictional behavior isdetermined exclusively by the
lubricant properties with thickfilm lubrication.
Unlubricated bearings shouldhave surface grooves to carrywear debris out of the interface.In lubricated systems the groovescan help increase the supply oflubricant. The effect of groovingon bearing pressure should beconsidered.
Because it does not wet SPresin, water is not an effectivethin film or boundary lubricant forVESPEL bearings. In fact, watercan adversely affect the wear rateof dry VESPEL bearings. How-ever, periodic contamination bycasual water should not causeany problems.
Purging an unlubricatedVESPEL bearing with nitrogengas can reduce wear rates to
less than 20% of the correspond-ing rate in air. In addition, opera-tion in nitrogen can increase thewear transition temperature byat least 100F (56C) above thevalue in air.
For applications in dirtyenvironments, sealing or purg-ing should be considered forprevention of bearing surfacecontamination.
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Proportions
Journal Bearings: For optimumperformance of VESPEL journalbearing, l/d (length/diameter)ratios in the order of 1/2 to 3/2 aresuggested. If a long bearing isrequired, consider using twobearings with a gap betweenthem. Smaller values of l/d willresult in:
more efficient debris removal
less sensitivity to shaft deflec-tion and misalignment
better heat dissipation
cost advantages due to lowerfabrication costs
Thrust Bearings: For optimumperformance of VESPEL thrustbearings, it is best not to exceeda ratio of outside to inside diam-
eter (D/d) of 2. Ratios greaterthan 2 can cause overheating atthe outside edge, and problemsmay arise from lack of flatnessand from trapped wear debris.
Running Clearances for
Journal Bearings
Although VESPEL bearings havemuch lower coefficients of thermalexpansion than most plastics,minimal running clearances arerequired. Normal operating clear-
ances for VESPEL journal bearingsare from 0.3% to 0.5% of shaftdiameter, depending on the appli-cation. In general, heavier loadsrequire larger clearances. Closerrunning clearances can be engi-neered by slotting the bearing toallow for circumferential thermalexpansion.
Use the following formula todetermine VESPEL bearing designinside diameter adjusted for thermalexpansion of the bearing system:
Bearing design ID = shaft diam-eter at room temperature +change in shaft diameter due totemperature change + operatingclearance of shaft + change inthe bearing wall thickness due totemperature change in housingdiameter due to temperature.
ID = D(1+ ST1+C)+2t SpT2dBT3
where:
d = housing diameter
D = shaft diameter at ambienttemperature
C = shaft operating clearance,percent of shaft diameter
S = coefficient of expansion ofshaft material
Sp = coefficient of thermalexpansion of VESPEL bearing
t = VESPEL bearing wallthickness
T1 = temperature rise for the shaft
T2 = temperature rise for thebearing
T3 = temperature rise for thehousing
B = coefficient of expansion ofbore material
Running clearances for VESPELbearings usually do not have to beadjusted for moisture, because SPpolyimides absorb very little mois-ture. See the brochure Propertiesof VESPEL Parts and Shapes, formoisture absorption curves.
10
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TABLE 3Coefficient of Thermal Expansion ()
Composition SP-1 SP-21 SP-22 SP-211
Fabrication Direct Direct Direct DirectProcess Mach. Formed Mach. Formed Mach. Formed Mach. Formed
,
106in/in/F 30 28 27 23 21 15 30 23
,
106cm/cm/C 54 50 49 41 38 27 54 41
Wall Thickness for Journal Bearings
VESPEL journal bearing walls should be as thin as possible, becausethin walls:
improve dissipation of frictional heat
reduce running clearance variations resulting from thermal- andmoisture-related dimensional changes
reduce distortion under high loading
For most applications, the typical wall thickness for VESPEL bearingsranges from 0.06 in. to 0.125 in. (1.5 to 3.2 mm).
Installation of Journal Bearings
VESPEL journal bearings can be installed either mechanically or withadhesive.
To press fit VESPEL bearings into metal, the suggested practice is touse a low-interference fit. After it is pressed into place, the bore of thebearing will be reduced by 90% of the calculated diametral interference,which will result in a small compressive load in the bearing wall. Atypical interference fit is 0.5%, but press-fit interference should beadjusted to the needs of the application.
VESPEL parts can be used with most commercial adhesives. TheVESPEL Adhesives Bulletin discusses selection of adhesives, surfacepreparation and other considerations. With any adhesive, it is importantto follow the manufacturers recommendations for best results.
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Sample Design Problem
VESPEL bearings are beingconsidered for a blender dryerwith the following requirements:
Two bearings on a 1.5 in. (38mm) shaft must support 4000 lb(1814 kg), at temperatures
ranging from 70F to 525F(21C to 274C).
Maximum bearing length is1.5 in. (38 mm) and maximumallowable running clearance hotor cold is 0.015 in. (0.38 mm).
To prevent product contamina-tion, the bearings cannot belubricated and they must operatewithout service 40 hours perweek for 3 years.
The blender-dryer shaft rotatesintermittently, 5% on and 95% off,at 20 rpm.
Will VESPEL bearings meetthese requirements? Refer to thetable PV LIMIT GUIDELINES,under PV Limits of UnlubricatedMaterials for temperature and PVlimits.
Solution (British Units)
1. Check temperature limit.
Limiting surface temperature ofSP-21 polyimide in air is 740F,so unless PV is very high, thesurface temperature should riseless than the 215F difference
between 525F and 740F.
2. Check PV.
Calculate bearing pressure:
P = =
= 890 psi
Calculate shaft Speed:
V = DN =
= 7.9 fpm
Calculate PV:PV = 800 psi 7.9 fpm
= 7040 psi-fpm
At this low PV, SP-21 polyimidewill operate in its mild wearregime, so PV will not limit,especially considering the inter-mittent operation.
3. Check wear resistance.
Calculate running time:
T = .05 3 yrs
= 312 hours
Radial wear = wear factor PVrunning time=
33 1010
7040 psi-fpm 312 hrs = 0.0073 in
This wear is less than themaximum allowable operatingclearance. If the difference isenough to accommodate thermalexpansion, then VESPEL Partswill meet the requirements.
4. Design-Determine RoomTemperature Clearance.
At this point, experience andjudgment play a big role, and onecan only approximate a solution.Experience dictates that the shaft,bearing surface, bearing OD andhousing will all reach differentoperating temperatures.
Assume that:
the contact surface reaches100F higher than the dryertemperature, but:
the bearing body averagetemperature is only 50Fhigher than the dryer, while:
the housing remains at roomtemperature and restrains thebearing securely, so:
the bearing will expandinward when the temperaturerises, and
the shaft will expand outward.
With these assumptions, initialroom temperature clearance, C4,can be determined with thefollowing equation:
C4= D (sT1+ C) + 2tsT2
D = shaft diameter
s = coefficient of thermalexpansion for shaft material
= 6 10-6 in/in/F
C = operating clearance,usually 0.001 in/in
t = bearing wall thickness
s = coefficient of thermalexpansion for bearing =24 106in/in/F
T1 = temperature rise for shaft
T2 = temperature rise for bearing
If one picks a wall thickness of1/16in
C4= 1.5[(6 106)(625 70) + .001]+(2 .0625 24 104)(575 70)
= 1.5 (.0043) + .0015
= .00645 + .0015
= .008 in
5. Check maximum clearance.
Initial clearance plus wear after3 years will then be 0.008 + 0.007= 0.015 in which just meets thestated requirements.
Thus, VESPEL bearings domeet the requirements to operatewithout lubrication in this elevatedtemperature situation.
If you encounter expansionproblems, slot the bearing.
12
F
LD
2000 lb (per bearing)
1.5 in 1.5 in
1.5 in 20 rpm
12 in/ft
40 hrs
wk
52 wks
yr
in min
ft lb hr
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The earlier youTHINK VESPEL,the more cost-effectiveyour total designcan be
The engineers and sales staff atDuPonts VESPEL Division are
ready to help you make the bestuse of the superior performanceof VESPEL parts. Just write to theVESPEL Sales Office nearestyou, or call your VESPEL SalesEngineer. In the US, you can alsocall our Customer Service line at800-222-VESP.
DuPont CompanyVESPEL Parts Marketing SectionWilmington, DE 19898
Solution (SI Units)
1. Check temperature limit.
Limiting surface temperature ofSP-21 polyimide in air is 666K,so unless PV is very high, thesurface temperature should riseless than the 119K difference
between 547K and 666K.
2. Check PV.
Calculate bearing pressure:
P = =
= 6160 kPa
Calculate shaft Speed:
V = DN = .038 m 20 rpm
= 2.39 m/min
Calculate PV:
PV = 6136 kPa 2.41 m/min= 14,720 kPa-m/min
At this low PV, SP-21 polyimidewill operate in its mild wearregime, so PV will not limit,especially considering the inter-mittent operation.
3. Check wear resistance.
Calculate running time:
T = .05 3 yrs
= 312 hoursRadial wear = wear factor
PVrunning time=
40 109
14,720
312 hrs 104
= .0184 cm
This wear is less than themaximum allowable operating
clearance. If the difference isenough to accommodate thermalexpansion, then VESPEL Partswill meet the requirements.
4. Design-Determine RoomTemperature Clearance.
At this point, experience andjudgment play a big role, and onecan only approximate a solution.Experience dictates that the shaft,bearing surface, bearing OD and
housing will all reach differentoperating temperatures.
Assume that:
the contact surface reaches56K higher than the dryertemperature, but:
the bearing body averagetemperature is only 28Khigher than the dryer, while:
the housing remains at roomtemperature and restrains thebearing securely, so:
the bearing will expandinward when the temperaturerises, and
the shaft will expand outward.
With these assumptions, initialroom temperature clearance, Cd,can be determined with thefollowing equation:
Cd= D (sT1+ C) +2tsT2
D = shaft diameter
s = coefficient of thermalexpansion for shaft material
= 10.8 10-6 m/m/K
C = operating clearance,usually .001 cm/cm
t = bearing wall thickness
s = coefficient of thermal
expansion for bearing =43 106m/m/K
T1 = temperature rise for shaft
T2 = temperature rise for bearing
If one picks a wall thickness of.159 cm:Cd= 3.8[(10.8 10
6)(602294) + 0.01]+ (2 .159 43 104) (575 294)
= 3.8 (.0043) + .0038
= .0163 + .0038
= .020 cm
5. Check maximum clearance.
Initial clearance plus wear after3 years will then be 0.20 + 0.18 =0.38 mm which just meets thestated requirements.
Thus, VESPEL bearings domeet the requirements to operatewithout lubrication in this elevatedtemperature situation.
If you encounter expansionproblems, slot the bearing.
F
LD
8900N (per bearing)
.038 m .038 m
40 hrs
wk
52 wks
yr
cm3min
m N hrkPa m
minm2
cm2
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g
More information on the benefits and propertiesof VESPELparts is available in these brochures:
Introduction to VESPEL Parts(E-61486)
Summary of Typical Properties(E-61477)
VESPEL Shapes: Machining Stock of SP Polyimide(E-61482)
Using VESPEL Seal RingsDesign Considerations and Technical Data
(E-73911)
VESPEL and Radiation. A Guide for Users(E-73910)
This information is offered without charge as part of the DuPont Companys service to its customers, butDuPont cannot guarantee that favorable results will be obtained from the use of such data. It is intended for
use by persons having technical skill, at their discretion and risk. DuPont warrants only that the materialitself does not infringe the claims of any United States patent; but no license is implied nor is any furtherpatent warranty made.
In the United States
DuPont CompanyFabricated Products Department
VESPEL Parts Marketing SectionWilmington, DE 19898
Telephone (800) 222-VESP
In EuropeDuPont de Nemours International SA
Fabricated Products DepartmentAntoon Spinoystraat 6
B-2800 Mechelen, BelgiumTelephone (015) 4014 11
In the Far East
DuPontJapan Ltd.Fabricated Products Department
Kowa Building No. 211-39 Akasaka 1-chome
Minato-kuTokyo 107, JapanTelephone: 03-585-5511
