Millwright Level 2 – Bearings Questions and Answers Already Passed

Millwright Level 2 – Bearings Questions and Answers Already Passed What are the principle parts of a friction bearing housing? Base, Base bolt slots, cap and cap bolt holes. What are friction bearing housings made from adn what factors influence the choice of housing? Cast Iron, Cast Steel, Fabricated Steel. Choice depends on the Load, The Rotational Speed, the Direction of Pull and the Support Design How are friction bearing dimensions expressed? In a fraction of their nominal size. Do all new bearings of the same shaft size have the same base-to-eye measurement? If they are from the same manufacturer. What factors influence the choice of bearings? Load, Rotational Speed, Direction of the Pull and support Design What are the applications for the following bearings? a)Solid Bearings b)Split bearings c)Angle bearings d)Integrated Bearings a) Where Speed and Load are low. Where load is applied on the top part of the bearing. b) Where load is applied on the bottom portion of the bearing. Different bolt numbers for loads. c)When load is applied parallel to, or at a slight angle to, the horizontal. Or when the bearing is mounted on the vertical support d)Where the bearings are an integral part of the machine. How does friction bearing joint design affect its integrity? Position of the top half may affect the bearing tolerances and load positions. What qualities should a good bearing material have? (5 points) Softer than the shaft material, low coefficient of friction, wear-resistant, a good heat conductor and remain relatively stable with heat changes, readily available. List Metals generally used in bearing liners and their applications. (5 points) Babbitt - for general use Brass (copper zinc alloy) - for higher speeds and heavier load than babbit Bronze (coper tin alloy) - for higher speeds and heavier loading than babbitt Aluminum - hydraulic pumps Sintered Bronze - Porous bronze with a built in oil supply. 2:1 ratio. What characteristics of nylon polyurethanes and phenol laminates affect their applications? Heat, , water saturation. What is the hardest and toughest babbitt made from? Tin (90%) How does overheating affect babitt? Service life is greatly reduced How is babbitt held in bearing casting? Holes or slots. Describe the procedure for pouring a babbitt bearing using a mandrel. (6 Steps) 1. Gather Equipment ( oxyacetylene torch putt pliers, babbitt) 2. Fit the torch with a large tip and melt out the remaining babbitt in the casting 3.Smoke the shaft with a straight acetylene flame. 4.Put a putty dam around the shaft and bearing 5. Hold the babbitt with the pair of pliers 6. Melt it into the bearing with the torch. What must be checked when fitting a bearing? (4 points) surface finish area of contact, running clearance, lubrication entry, and grooves Describe the purpose of tinning. To secure a thin skin of babbitt to a metallic backing. Describe the tools used to fit a friction bearing. Scraper, files, groove chisels. Describe procedure for fitting a bearing. 1. Chamfer the top edges or cut an oil groove 2. check bearing for contact by coating mandrel in bluing and rotating mandrel 3. Shave down high spots indicated by bluing Describe the procedure fro shimming a bearing to the correct amount of clearance. Insert shims, make sure they do not make contact with the shaft or the chamfer. Tighten bolts to specs and rotate the shaft. Add shims or realign the cap. Describe the procedure for checking bearing clearance with a dial indicator, Pastigage and lead wire. (3 points) 1. Place indicator on both ends of the shaft and adjust to acquire an even reading. 2. Insert plastigage and tight cap to proper torque and measure width to determine clearance. 3.Same way as plastigage Described how preformed bearings are installed and held in place. Press preformed bearing into housing with the cap. Or press fit Describe procedure for installing bushings. Pressure fit or crushed into housing Describe how thrust is controlled with plain bearings for both low and high speed applications. Oil wedges. Describe radial and axial load. Radial is horizontal load, axial is vertical. Describe the basic design of Kingsbury bearings. Faces have a minor pivoted shoes and oil is injected to so during operation the shaft is centered in clearance accurately. What styles do kingsbury bearings come in? (2 points) Fixed pad and floating or tilting pads. What are the merits of anit-friction bearings? A lot less friction occurring. Less energy, less heat. List the main parts of anti-friction bearings? (3 points) 2 hardened steel rings, the hardened balls or rollers (rolling elements) and the separator. Describe the operating principle of ball bushings. Guide rails/shafts using recirculating ball bushings. List the three styles of rolling elements. Ball, Roller and needles Describe the applications for open bearings, shielded bearings, sealed bearings and sealed and shielded bearings. Open bearings - oil bath or open lubrication Shielded bearings- keep out solid contaminates Sealed - Keeps out solid contaminates and liquid contaminants. How are directions of bearing loads expressed? Radial and thrust and combination What are the normal speed ranges for ball bearings and roller bearings? Ball - 40,000 rpm Rolling - 2000-20,000 rpm How are bearings classified according to their service use? Type, Service Weight, Bore size. (X, X, XX) What measurements are matched to the code markings on a bearing? Last two numbers correspond with bore diameter. (00-10mm, 01-12mm, 02-15mm, 03-17mm) Above 20mm multiply last two digits by 5. Above 480mm, size is directly placed in Briefly describe: a) non-separable bearings b)separable bearings c)non-aligning bearings d)self aligning bearings a)Non-sperable - designed in single peice b)Separable- Can pull bearing, consist of either 2 or 3 separable parts c)non-aligning - used in machines where the bearings are held in alignment by the bores of the housing d)self-aligning - may be internal or external. outer race is more concave to allow for pivot. Define the following bearing codes: a) SKF06106 b) SKF-22310 c)FAG-6108K a)skf=manufacturer 06=rolling element 6=service weight 06=30mm b)skf=manufacturer 22=rolling element 3=service weight 10=50mm c)FAG=manufacturer 6=rolling element 1=service weight 8=40mm k=taper Why is there a need for bearing clearance? (3 Points) It compensates for expansion of inner ring or contraction of outer ring. It compensates for differential expansion of the two rings when internal operates at a higher temp than the outer. It affects the end play of ball journal bearings and their capacity for carrying axial loads. the greater the clearance the greater the load. Define: a) Initial Clearance b)installed clearance c)running clearance a) uninstalled clearance; as it comes out of the box b) clearance left on the bearing after installation and fixed c) clearance when machine is operating at temperature and lubrication is supplied Which bearing has the most clearance, a standard bearing or C4? c4 Which bearing is more accurately manufactured? c1 What checks should be made before fitting a bearing? diameter, roundness, shaft deflection, surface damage, general finish, any damage to the shoulder supporting the inner ring, cracks in the housing Define the following: a)push fit b)pressure fit c)interference fit a) bearing is installed by hand without mechanical aid b) use a tube to distribute the force evenly. Always apply pressure on part that is being secure. (ie place pressure on inner ring if pressure is on the shaft) c)description on how tightly the bearing fits around the shaft. How does and interference fit affect the bearing clearance? it will decrease the clearance. Which bearing ring has the press fit on a straight bore bearing? Inner Race Describe the procedure for pressing a bearing onto a shaft and pressing a shaft through a bearing. 1. Apply a coating of oil 2.Put the bearing on the shaft, makes sure its perpendicular 3.Place a clean pipe or mounting tube slightly larger than the shaft diameter on the inner ring of the bearing pressure by hand to start the bearing moving 5.Check the position of the bearing to see that it is still squarely on. 6.Press it on final position 7.As bearing moves down the shaft rotate the outer ring by hand to check for drag or loss of clearance. Describe the procedure for chilling to shrink fit a bearing. Shrink the bearing with dry ice/ alchohol or compressed air. What is the maximum temperature that a bearing should be heated to for expansion purposes? 120 degrees celcius Briefly describe: a)Heat lamps b)oven c)induction heater d)oil bath a) Heat bearing. Used on small bearings b) Can heat up bearing saftely becuase of temperature control c) Uses electricity to heat up bearing, no way of determining heat. use heat crayon d) Bathe large bearings in a heated oil. make sure bearing doesnt touch bottom of the pot. Describe the procedures for installing a hot bearing on a shaft and installing the bearing outer ring in a housing. Place bearing on shaft as quick as possible and hold. if resistance is felt, remove and reheat. Describe the methods used to positively position the inner ring and the outer ring in its axial position. inner ring - snap ring in a groove cut in the shaft or housing; large washer witha lock nut. outer ring - End caps for positive position w/ or w/out shims; snap ring is in the housing Define fixed bearing and floating bearing. * fixed bearings do not allow for axial variance. floating do What is the reason for having one fixed and one floating bearing on most shafts? to allow a minimal amount of axial clearance and stop the journal Describe how axial clearance is adjusted using shims. shims can be applied either by the end cover and the bearing cup OR between the end cover and machine housing Describe the applications for the following angular-contact bearing arrangements: a) back-to-back b)face-to-face c)tandem a)back to back - What is the purpose of using tapered-bore bearings with tapered sleeve adapters? Briefly describe how the taper sleeve adapter positively positions the bearing. Describe the procedure for installing or mounting the following bearings: a)ball bearing, using tapered sleeve adapter b)tapered-bore bearing, using hydraulic unit c)spherical roller bearing, used tapered sleeve adapter What is the rule of thumb for setting the standard-clearance on a spherical roller bearing if there are no tables available? Describe the non-destructive removal of bearings using the following methods: a)press b)bearing splitter and puller c)cup or inside puller Compare withdrawal sleeves to adapter sleeves. Describe the non-destructive removal of bearings which are mounted on adapater and withdrawal sleeves. Describe the destructive removal of bearings and cups. Describe the process and procedure for removing bearings with oil injection. Describe the construction of horizontally split, vertically split and one piece pillow block bearing housing. Describe the installation and removal of pillow block bearings. Describe the installation or mounting of flange bearings, needle bearings and thrust bearings.