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Questions and Answers
Journal bearings are designed to support and mount non-rotating shafts.
Journal bearings are designed to support and mount non-rotating shafts.
False (B)
The life of a journal bearing is typically limited by metal fatigue.
The life of a journal bearing is typically limited by metal fatigue.
False (B)
A journal is the stationary part of the bearing that surrounds the shaft.
A journal is the stationary part of the bearing that surrounds the shaft.
False (B)
A lubricant's role is to facilitate metal-to-metal contact within a bearing.
A lubricant's role is to facilitate metal-to-metal contact within a bearing.
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In hydrodynamic bearings, fluid pressure is generated from an external source.
In hydrodynamic bearings, fluid pressure is generated from an external source.
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Hydrostatic bearings rely on pressure self-generated by the shaft’s rotation.
Hydrostatic bearings rely on pressure self-generated by the shaft’s rotation.
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In a fully hydrodynamic bearing, there is theoretical contact between the moving parts.
In a fully hydrodynamic bearing, there is theoretical contact between the moving parts.
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This standard provides guidelines for the selection of bearing types for agricultural machines.
This standard provides guidelines for the selection of bearing types for agricultural machines.
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The standard PAES 305:2000 is about Engineering Materials for Gears.
The standard PAES 305:2000 is about Engineering Materials for Gears.
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The word should indicates an action that must be adhered to, without exceptions.
The word should indicates an action that must be adhered to, without exceptions.
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This standard was prepared in accordance with PNS 01-4:1998 (ISO/IEC Directives Part 3:1997).
This standard was prepared in accordance with PNS 01-4:1998 (ISO/IEC Directives Part 3:1997).
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The AMTEC initiated the formulation of the National Standard under a project funded by the Bureau of Forestry.
The AMTEC initiated the formulation of the National Standard under a project funded by the Bureau of Forestry.
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The standard provides technical information for proper application of all types of machine bearings.
The standard provides technical information for proper application of all types of machine bearings.
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The standard uses the word must to indicate requirements strictly to be followed.
The standard uses the word must to indicate requirements strictly to be followed.
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The standard includes references to Mark’s handbook for mechanical engineers by Theodore Baumeister.
The standard includes references to Mark’s handbook for mechanical engineers by Theodore Baumeister.
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The primary focus of this standard is to discuss the best practices for designing advanced bearing systems in agricultural machinery.
The primary focus of this standard is to discuss the best practices for designing advanced bearing systems in agricultural machinery.
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Hydrostatic bearings necessitate relative motion between bearing surfaces to function correctly.
Hydrostatic bearings necessitate relative motion between bearing surfaces to function correctly.
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In boundary lubrication systems, the lubricant should not adhere to the surfaces involved.
In boundary lubrication systems, the lubricant should not adhere to the surfaces involved.
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Dry bearings require the presence of a significant fluid film to separate the moving surfaces.
Dry bearings require the presence of a significant fluid film to separate the moving surfaces.
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Journal bearings are designated by bore diameter, length, and wall thickness.
Journal bearings are designated by bore diameter, length, and wall thickness.
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Tin babbitt has a higher tensile strength than lead babbitt.
Tin babbitt has a higher tensile strength than lead babbitt.
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Polycarbonate has a higher hardness value than polymide.
Polycarbonate has a higher hardness value than polymide.
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Cemented tungsten carbide exhibits a lower hardness value than fused aluminum oxide.
Cemented tungsten carbide exhibits a lower hardness value than fused aluminum oxide.
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Cast iron has a greater tensile strength than steel.
Cast iron has a greater tensile strength than steel.
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A journal with a diameter of 76 mm requires a minimum clearance of 0.10 mm.
A journal with a diameter of 76 mm requires a minimum clearance of 0.10 mm.
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A journal with a diameter of 152 mm needs clearance more than 0.10 mm.
A journal with a diameter of 152 mm needs clearance more than 0.10 mm.
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A journal with a diameter of 51 mm has the largest clearance requirement.
A journal with a diameter of 51 mm has the largest clearance requirement.
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A journal with a diameter of 229 mm requires the smallest clearance according to the chart.
A journal with a diameter of 229 mm requires the smallest clearance according to the chart.
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A journal diameter of 254 mm requires a minimum clearance of about 0.20 mm.
A journal diameter of 254 mm requires a minimum clearance of about 0.20 mm.
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The chart shows that a journal diameter of 102mm requires a clearance of about 0.12 mm.
The chart shows that a journal diameter of 102mm requires a clearance of about 0.12 mm.
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A journal with 127 mm diameter requires minimum clearance less than 0.15 mm.
A journal with 127 mm diameter requires minimum clearance less than 0.15 mm.
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A smaller journal diameter requires a proportionally larger minimum clearance for steadily loaded bearings.
A smaller journal diameter requires a proportionally larger minimum clearance for steadily loaded bearings.
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For a 25 mm journal diameter, the minimum diametral clearance for dynamically loaded bearings is approximately 0.07 mm.
For a 25 mm journal diameter, the minimum diametral clearance for dynamically loaded bearings is approximately 0.07 mm.
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A sliding velocity is not a significant factor in frictional heating.
A sliding velocity is not a significant factor in frictional heating.
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When using Figure 2, a bearing with a 100 mm journal diameter requires a minimum diametral clearance around 0.10 mm at 1000 rpm.
When using Figure 2, a bearing with a 100 mm journal diameter requires a minimum diametral clearance around 0.10 mm at 1000 rpm.
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The minimum diametral clearance for dynamically loaded bearings is always greater than that of steadily loaded bearings for any given journal diameter.
The minimum diametral clearance for dynamically loaded bearings is always greater than that of steadily loaded bearings for any given journal diameter.
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The maximum operating speed of a steadily loaded bearing is directly proportional to its journal diameter.
The maximum operating speed of a steadily loaded bearing is directly proportional to its journal diameter.
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According to Figure 3, a 200 mm diameter journal should have about 0.125 mm of minimal clearance when dynamically loaded.
According to Figure 3, a 200 mm diameter journal should have about 0.125 mm of minimal clearance when dynamically loaded.
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The standard dictates that bearings operating in high-temperature environments must use a lubricant with a low coefficient of friction.
The standard dictates that bearings operating in high-temperature environments must use a lubricant with a low coefficient of friction.
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Bearing pressure is not a contributing factor to the heat generated from friction.
Bearing pressure is not a contributing factor to the heat generated from friction.
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The provided graph assumes that bearing material type has no influence on minimum diametral clearance.
The provided graph assumes that bearing material type has no influence on minimum diametral clearance.
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Frictional heating in bearings is independent of the coefficient of friction.
Frictional heating in bearings is independent of the coefficient of friction.
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The unit for minimum diametral clearance in figures 2 and 3 is millimeters.
The unit for minimum diametral clearance in figures 2 and 3 is millimeters.
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The graph for dynamically loaded bearings shows that a larger journal diameter always needs greater minimal clearance than smaller diameters.
The graph for dynamically loaded bearings shows that a larger journal diameter always needs greater minimal clearance than smaller diameters.
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Frictional heat generated is a function of sliding speed only and unrelated to bearing pressure.
Frictional heat generated is a function of sliding speed only and unrelated to bearing pressure.
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Figure 2 shows that a journal diameter of 150mm needs to have about 0.133 mm of diametral clearance when steadily loaded.
Figure 2 shows that a journal diameter of 150mm needs to have about 0.133 mm of diametral clearance when steadily loaded.
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If the coefficient of friction is constant, the PV factor provides a rough indication of the heat load.
If the coefficient of friction is constant, the PV factor provides a rough indication of the heat load.
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Exceeding the stated PV limits always ensures normal bearing life.
Exceeding the stated PV limits always ensures normal bearing life.
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The 'PV' in 'PV limits' refers to Potential Velocity.
The 'PV' in 'PV limits' refers to Potential Velocity.
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Lead-bronze has a higher PV limit than bronze, according to the provided data.
Lead-bronze has a higher PV limit than bronze, according to the provided data.
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Hardenable copper-iron has the highest static bearing pressure limit among the materials listed in Table 3.
Hardenable copper-iron has the highest static bearing pressure limit among the materials listed in Table 3.
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TFE Fabric has a higher PV limit than filled TFE in Table 4.
TFE Fabric has a higher PV limit than filled TFE in Table 4.
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The PV limit for Nylon is higher than that of Acetal.
The PV limit for Nylon is higher than that of Acetal.
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The maximum operating temperature for phenolic bearings is 260 degrees Celsius.
The maximum operating temperature for phenolic bearings is 260 degrees Celsius.
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The manufacturer's trademark and address must be marked on the bearings themselves.
The manufacturer's trademark and address must be marked on the bearings themselves.
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Both the manufacturer's name and designation are required to be marked on the bearings.
Both the manufacturer's name and designation are required to be marked on the bearings.
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Figure 6 provides the maximum load a particular bearing can carry, based on its PV rating.
Figure 6 provides the maximum load a particular bearing can carry, based on its PV rating.
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According to Figure 6, for a 76.20 mm shaft diameter a unit load of 10,342,200 Pa is possible at a shaft speed of 70 rpm.
According to Figure 6, for a 76.20 mm shaft diameter a unit load of 10,342,200 Pa is possible at a shaft speed of 70 rpm.
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A shaft diameter of 20.32 mm can support significantly more load at a surface velocity of 0.76 m/s than at a surface velocity of 1.52 m/s.
A shaft diameter of 20.32 mm can support significantly more load at a surface velocity of 0.76 m/s than at a surface velocity of 1.52 m/s.
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Periodic drive inspection is a safety recommendation, not a mandatory action.
Periodic drive inspection is a safety recommendation, not a mandatory action.
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The PV factor is calculated by multiplying the pressure in MPa by the sliding speed in km/s.
The PV factor is calculated by multiplying the pressure in MPa by the sliding speed in km/s.
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Study Notes
Philippine Agricultural Engineering Standard - Journal Bearings
- This standard specifies and provides technical information for journal bearings in agricultural machinery.
- It was developed by the Agricultural Machinery Testing and Evaluation Center (AMTEC) with funding from the Bureau of Agricultural Research (BAR).
- It adheres to international standard guidelines (PNS 01-4:1998 & ISO/IEC Directives).
Application
- Journal bearings support rotating shafts in machinery needing quietness and rigidity.
- They are cost-effective, require less space, and handle shock loads well.
- Their longevity isn't limited by fatigue.
Definitions
- Journal bearing (sleeve bearing): A cylindrical sleeve filled with lubricant surrounding the shaft.
- Journal: The rotating part of the shaft, axle, roll or spindle.
- Lubricant: A substance preventing metal-to-metal contact.
Nomenclature
- Journal bearing nomenclature is illustrated in Figure 1.
Types
- Hydrodynamic bearings: Fluid pressure between moving parts separates them, creating no contact and minimal wear.
- Hydrostatic bearings: Fluid pressure is externally supplied and sustains the load – useful for static or low-motion situations.
- Boundary lubrication bearings: Lubricant "wets" the surfaces for reduced friction without a continuous fluid film.
- Dry bearings: No significant fluid film to separate surfaces; uses low friction materials or materials with added lubricant.
Materials
- Material properties (hardness and tensile strength) for various journal bearing materials are presented in Table 1.
Specifications
- Table 2 presents size ranges (bore and wall thickness) and length-to-bore ratios of journal bearings.
- Different materials have different PV limits, related to the maximum load and speed a bearing can handle without exceeding a safe operating PV limit.
Recommended Design Practices – Bearing Clearance
- Clearance values depend on load type (steady or dynamic) and speed; these are illustrated in Figure 2 and 3.
Heat Generation
- Frictional heating (PV factor) during bearing operation is an important factor in bearing life.
- PV limits for various bearing materials are given in Tables 3 and 4.
Markings
- Bearing casings and bearings need markings, including manufacturer's name, trademark, address, and designation.
Safety
- Regular inspections are recommended for bearings, including examining wear, lubricant quality and tightness of mounting screws.
- Follow appropriate regulations for bearing use and shaft specifications from PAES 305:2000.
Annex - Procedure for Determining Bearing Dimensions
- This provides a procedure for determining bearing dimensions for a given shaft speed, diameter, and load using PV limits from Figure 6 and specified tables.
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Description
This quiz covers the Philippine Agricultural Engineering Standard regarding journal bearings in agricultural machinery. It includes information on definitions, applications, and types of journal bearings, as well as their technical specifications and international guidelines. Test your knowledge on this essential aspect of agricultural engineering!
