Bearings, Gaskets and Seals

1. Bearings, Gaskets and Seals • What is a Bearing? • Component used to reduce friction between rotating parts in a machine. • Types of bearings: • Plain bearing • Ball bearing • Angular ball bearing • Roller bearing

2. Bearings, Gaskets and Seals • Plain bearings are the simplest • Cylindrical sleeve used to support a rotating shaft • Shaft slides on the surface of the plain bearing • Film of lubricant forms between shaft and plain bearing while shaft rotates

3. Bearings, Gaskets and Seals • 3 types of Plain bearings • Sleeve Bearing • Flange Sleeve Bearing • Thrust Plain Bearing

4. Bearings, Gaskets and Seals • Bearing choice dependent upon the load. • 2 types of load • Radial – Loads that are perpendicular to the shaft • Axial – loads that are parallel to the shaft

5. Bearings, Gaskets and Seals • Bearing Choice: • Sleeve Bearing - Radial Loads • Thrust Bearing - Axial Loads • Flange Sleeve Bearing - Combination of both • Lubrication is key • Lubricate through a hole on the outside of the sleeve bearing • Permanent lubrication from porous metal impregnated with oil. • Sometimes grooves machined on the sleeves to provide lubricant path.

6. Bearings, Gaskets and Seals • Ball Bearings • Type of Antifriction Bearing • Friction reduced due to rolling motion rather than sliding motion in plain bearings * Balls roll on a “raceway” (Not shown at left)

7. Bearings, Gaskets and Seals • 5 types of Ball Bearings • Radial Open • Open to the environment • Radial Shielded • Protected from the environment • Radial Sealed • Seal retains lubricant • Prevents relubrication

8. Bearings, Gaskets and Seals • Angular Ball Bearing • Same principle as radial • Shoulders designed for a combined radial and axial loads. • Most common in pumps/compressors • Thrust Ball Bearing • 2 flat washers and a cage • Balls positioned between the washers • Axial load applications

9. Bearings, Gaskets and Seals • Roller Bearings • Another type of Antifriction Bearing • Friction reduced due to rolling motion rather than sliding motion in plain bearings • Use rollers instead of balls • Rollers have greater contact area than balls • Higher load capacity than ball bearings of same size • More contact area – more friction • Used for heavy duty – moderate speed application • Car axles common use

10. Bearings, Gaskets and Seals • 3 types of Roller Bearings • Tapered Roller Bearing • Inner & outer cones (rings), rollers, cage • Rings can separate to assist assembly • High radial and axial loads • Radial Needle Bearings • Support high load in limited space • No raceway • Rollers make direct contact with the shaft.

11. Bearings, Gaskets and Seals • Thrust Needle Bearing • Perform same as thrust ball bearings. • Capable of higher loads

12. Bearings, Gaskets and Seals • Gaskets & Seals • Used to prevent leaks and contamination • 2 categories • Static seals • Dynamic seals • Static Seals • Gaskets - Used when there is no movement between the mating surfaces • Dynamic Seals • Mechanical Seals – used to seal moving surfaces

13. Bearings, Gaskets and Seals • Gaskets • Prevent fluid leakage • Block out dirt and contaminants • Deform under pressure to seal small irregular surfaces • Material – cork, metals, fibers, Teflon, rubber. • Material choice depends on pressure, temperature and chemical properties of the medium • Identified by the thickness of the material in fraction of an inch.

14. Bearings, Gaskets and Seals • O-Rings • Prevent fluid leakage between mating parts • Operation – O-Ring deforms when it is subject to a “squeeze” between 2 surfaces • Flattens whens comes in contact with the surfaces to be sealed • Excessive squeeze – wears O-Ring out too quickly • Insufficient squeeze – leakage • Buna-N, Teflon, Silicone, ethylene propylene, polyurethane

15. Bearings, Gaskets and Seals • Mechanical Seals • Used in pumps to prevent leakage • Prevents fluid from leaking from the fluid side to dry side • 4 components • Holder • Spring • Seal Head • Seat • Dynamic seal • Seals by the rotation of the seal head on the seat • Flat faces held together by the spring and fluid pressure