BEARING MAINTENANCE Mounting. Lubrication. Dismounting 1
IMPORTANCE OF PROPER MOUNTING PROCEDURES Ensure safety Simplicity and speed the process Using full bearing capabilities Get the longest possible bearing life Prevent rings from turning on 2
FACTORS CAUSING BEARING FAILURE Poor Lubrication 36% Fatigue 34% Improper mounting 16% Contamination 14% 3
1. BEARING MOUNTING Preparing of assembly elements for mounting We recommend that mounting method to include : Checking of the assembly components (dimensional, form, surface quality), such as: -Shaft -Housings -Axial fixing elements -Sealing Clean surrounding elements (clean environment); Use of correct mounting procedures; Check if bearing is mounted correctly; Operating test. 4
1. BEARING MOUNTING Working temperature: 18-22 C In mounting rooms don t have to exist: Humidity: max. 60% Sweat hands can cause bearing corrosion Use tools in good condition Grinders Dust sources Vibrations Keep Tools organized 5
1. BEARING MOUNTING BEARING preparing NEW Bearings: (original packing) -Protected against corrosion; -No need to remove preservative (washing); -Remove packing in the same day of mounting! OLDER Bearings:(damaged packing, older than 2 years, reused bearings) -Checking bearing aspect; - Washing in diesel/mineral spirt (2x); - Measure d, D, B, clearance. -Remove of corrosion smaller than 5 mm (forbidden on raceways!) -Don t rotate the bearing before washing! 6
1. BEARING MOUNTING SHAFT & HOUSING preparing - Mounting surfaces should be clean and smooth - No hit signs - No burrs (use rasp and clean) - No corrosion signs - Measure shaft/housing diameter, oval shape, tapering - Measure mounting radius (radius gauge) FORBIDDEN TO: -Mount on shafts with smaller diameters!-> (ring will turn) -Mount on shafts with bigger diameters! ->(no clearance) 7
1. BEARING MOUNTING Axial fixing elements Axial fixing of rings is done through supporting sleeves or axial lock nuts, mounted on the frontal surfaces of the shaft. At the axial fixing elements there are not accepted following defects: - Local wears; - Cracks and pinches; - Sticking marks; - Inclusions; 8
1. BEARING MOUNTING Devices for bearing mounting Mechanical tools (cold mounting) FOR: - Cylindrical Bore - Bearing with d< 50 mm (small pressing forces) Rule: Forces shouldn t be transmitted through rolling elements! Fitting tool Anti fretting paste This paste can increase interference fit between housing and bearing and can stop ring turning into housing. 9
1. BEARING MOUNTING Devices for bearing mounting FOR: - Tapered Bore - Small & Medium Bearings Hooke spanner; Impact spanner FOR: - Tapered Bore - Large Bearings Hydraulic nut and pump 10
1. BEARING MOUNTING Mounting of spherical bearings, with tapered bore The tightening is achieved through axial displacement of the inner ring mounted on adapter sleeve. The tightening is evaluated through the reduction of the radial clearance or axial displacement. Values of the radial clearance reduction after mounting according to initial clearance. -=spherical roller bearings=- 11
1. BEARING MOUNTING Devices for bearing mounting FOR: - Medium & Large Bearings (d>50 mm) - Cylindrical/spherical roller bearings - Separable bearing elements Oil bath Electric heating plate! Rotate ring! Use mounting sleeve Induction heater Remember: - Don t heat bearings over 110 C! - Don t force elements during mounting! - Don t heat bearings with open flame! 12
1. BEARING MOUNTING Check : After the mounting - if bolts have been well tight - bearing radial clearance - bearing rotation by hand (if possible) Operational test A good bearing mounted, should have: - no strange noise; - no high temperature; - no vibration; - no lubricant leakage; - no other defects. 13
2. BEARING DISMOUNTING When? Careful..! How? - faulty mounting - regular wear of bearings - accidents - machine general reparation. During dismounting..: - don t damage shaft / housing; - don t damage surrounding parts; - ensure cleanliness (good bearings); - Protect yourself: wear gloves and clean tools. Bearing dismounting is realized by mechanical, thermal and hydraulic means, in reverse order than mounting operations 14
2. BEARING DISMOUNTING Tools Jaw puller (mechanical/ hydraulic) Bearing separator 15
2. BEARING DISMOUNTING Tapered bore bearing dismounting -With tools -Mechanical -Hydraulic 16
2. BEARING DISMOUNTING Another ways to dismount a bearing Induction Heating Thermal aluminum extractor (for small and medium dimension) cylindrical bearings 17
3. BEARING LUBRICATION. General considerations Lubrication effects: Reduce friction Dissipating heat and cooling Seals (from contamination) Corrosion protection Extends fatigue life For lubricant selection, we need to take in consideration followings: Bearing Size (d, D); Load (Pequiv); Temperature, T ; Speed (n); 18
3. BEARING LUBRICATION Oil advantages: - Good results at high temperatures; can be cooled - Evacuate the heat produces within the bearing. - Many ways to feed the bearing (pressurized systems, oil bath, oil mist) - Cleaner - Can be used a system that can collect foreign particles (filters); - Can allow replacement of the lubricant without dismounting the bearings. - Oil level must be periodically checked. 19
3. BEARING LUBRICATION Grease advantages: - Simple construction of the housing; - Sealing : safer and cheaper; - Bearing protection from external hazard; - Smaller danger on grease leakage (than liquids). How much Remember Full, at n/n lim < 0,2 One third, at n/n lim =0,2 0,8 Less than 1/3, at n/n lim <0,8, n=working speed, n lim=limit speed Respect relubrication intervals! Use same type of grease! 20
4. PREVENTIVE MENTENANCE Preventative maintenance techniques are employed to ensure that a bearing is operating properly. What to look for? Changes in: - noise; - vibrations; - temperature; - lubrication. These characteristics are dependent on the lubrication conditions, including speed, loading, lubrication and environment. Detecting a change form the baseline condition will indicate possible deterioration of the bearing and suggest an immediate maintenance action. 21
4. PREVENTIVE MENTENANCE Useful tools for bearing monitor : Electronic stethoscope. Can determinate noise level. Able to find parts with defects. Sound meter. Instrument for measuring sound level in decibels [db] 22
4. PREVENTIVE MENTENANCE Thermocouple. Instrument for measuring temperature. Thermocouple must be in contact with the object Infrared thermometer. Able to measure temperature from distance. This permits temperature measurement from a distance without contact with the object to be measured. A non-contact infrared thermometer is useful for measuring temperature under circumstances where thermocouples or other probe-type sensors cannot be used or do not produce accurate data for a variety of reasons. 23
4. PREVENTIVE MENTENANCE Thermal camera. Endoscope. Device which create an image with accurate temperature data, providing crucial information about condition of equipments. Can offer inspection of the equipments more safer than at peak operation. A miniature camera, with LED lightening, enveloped in a flexible tube, able to give images (directly on screen, or on a computer) from spaces hard to reach. 24
4. PREVENTIVE MENTENANCE Accelerometer. Accelerometer sensors accurately measure vibration, shock, acceleration, and motion for monitoring Many common problems in machine, such as imbalance, play, misalignment can be evaluated by measuring vibration. Vibration Analysis of a Bearing with an Outer Ring Defect. 25
5. FAILURES Failures due to Lubricant : Defect: Failure. Inner ring Crack Cause: Greasing only on one side Countermeasure: Grease both sides Right = Ungreased side Left = Greased Side 26
Failures due to Lubricant contamination: 27
Failure: Fatigue Defect: Flaking. Repeated stresses developed in the contacts elements=fatigue Cause: Structural changes and fatigue cracks, originating in the loaded zone, due to load cycles. Normal wear pattern. Countermeasure: Use a bearing with higher load carrying (if longer life is required) Flaking due to vibration (equally spaced at roller pitch). 28
Failure due to Mounting Defect: Roller end side and flange wear. Cause: - Axial overloading; - Shaft deflection Countermeasure: Check and correct axial clearance of mounted bearing Defect: Overheating. Seizure. Uneven wear. Cause: - Overloading of one raceway; - Small radial clearance Reason: Improper heating of inner ring. Countermeasure: Use proper mounting tools Inner diam. (d) Inner ring raceway Outer ring raceway 29
Storage of bearings Bearings must be - stored on special shelve, on horizontal position. - in rooms with low humidity (max 60%) - ventilated place Forbidden to - Store bearings directly on the ground! - On shelves from green lumber (undried wood)! - Near to cold and wet walls! 30
NEWS - Mesys - Life / Stress Calculus Mesys RBC Rolling Bearing Calculation. - calculates reference life, modified reference life. - fast and precise computing of loads, efforts and lubricating conditions; - calculation of the characteristics of all the bearing types. 31
THANK YOU. 32