SABCO TRADERS

  • info@sabcotraders.com
  • +92-42-32182325
  • +92-321-8333177
Menu
Menu

BEARING TIPS

All the research and development and the latest state of the art manufacturing techniques and the eventual quality of the bearing are of no use if the bearings are not correctly mounted, lubricated and appropriate maintenance procedures are not implemented/followed.

We have identified some areas and under each area we have listed some very basic suggestions which are often ignored by the relevant engineering and maintenance personnel that lead to premature bearing failures.

  • Properly clean the shaft and abutment shoulder and check the bearing seat tolerances prior to mounting.       
  • The mounting environment should be free from metal particles, sawdust, sand, cement, corrosive substances and other contaminants.
  • In general, only bearings of inner diameter up to 80mm should be cold mounted.
  • Never use hammer or chisel directly on the bearing.
  • Never use wooden mallets since nicks or burrs may come out of them and enter the bearings.   
  • Bearings with inner diameter greater than 80mm should preferably be mounted by thermal methods. For larger inner diameters, hydraulic methods are the better choice. Always mount the bearing by transmitting force through the ring that is being mounted. Never exert force through the other ring or the cage.    
  • In case of an oil bath, use fresh clean oil with a flash point below 250°C. e.g. transformer oil or low-viscosity hydraulic oils.          
  • Never use an oil bath for shielded (2ZR) or sealed (2RSR) bearings.
  • In case of adapter sleeves, do not exceed the recommended tightening torques.  
  • In case of bearings with eccentric locking collars, if the direction of rotation is not known, bearings at either end should be locked in opposing directions.
  • A large number of end-users presume that dismounting is not that significant. This is not the case as a wrong dismounting method or technique may substantially damage the shaft.
  • As with the mounting precautions, always dismount the bearing directly from the ring to be dismounted and never from the cage, other ring, shield etc.
  • Do not use flame or electric arc for cutting since it could damage the shaft too.
  • Never apply direct blows on either the shaft or the bearing.
  • In case of using a mechanical or hydraulic puller, check its reach & spread.
  • The puller must be accurately centered & continuously turned during the process.          
  • As a thumb rule, the diameter of the shaft from which bearing has to be dismounted should not be more than 2.5 times the diameter of the stud of the puller.
  • Please handle bearings with utmost care. Do not remove the wrapping since it will make way for contamination.
  • The bearing must be taken out of its box and wrapper only when you are ready to mount it.
  • Avoid inspecting the bearing by taking out of the packing as it will not tell you much. The best way to ensure that the bearings are genuine is to buy them from the right source.
  • Make sure that your suppliers deliver/dispatch the bearings to you appropriately packed.
  • Manufacturers recommend that the warehouse temperature should not exceed 35°C. Relative humidity should be below 60%.
  • Avoid excessive stacking of the bearings (bearings on top of each other).  
  • Use FIFO (The “First In First Out” rule)
  • Place the boxes in such a manner that the bearing label on the box should be clearly visible.
  • Large size bearings should not be stored upright but flat and supported over their entire circumference.
  • Warehouse/store should be kept clean. Keep chemicals and other corrosive material away from the bearings.
  • Store bearings in their original package in order to protect them against contamination and corrosion.
  • According to a survey, around 55% of premature bearing failures are due to lubrication related issues.
  • All necessary parameters such as rpm, dmN factor, operating temperature, vibration factor, load factor, contamination factor, base oil type, viscosity index, NLGI number should be taken into consideration when selecting grease/oil.
  • Initial fills quantities, re-greasing quantities & intervals should be according to the recommendations of either the OEM or the bearing / lubricant manufacturers.
  • Care should be taken to protect the grease/oil containers from contaminants.
  • Greases are generally preferred to oils because they simplify maintenance and can be used as sealants.         
  • Oil, however, has its advantages – it readily feeds into all areas of contact and dissipates heat.
  • In a humid environment, condensate can form in rolling element bearings and cause corrosion, leading to a reduction of the bearing life. With careful choice of the grease lubricant, the effect of the condensed moisture can be reduced. Greases thickened with sodium soap will absorb (emulsify) large quantities of water but this may soften the grease to such an extent that it flows out of the bearing. Lithium soap greases do not emulsify water, but with suitable additives can provide good protection against corrosion. There are also a number of greases available which have synthetic thickeners that offer excellent protection against corrosion, prolonging the bearing life.
  • Bearing greases of higher consistency (NLGI numbers) are used to avoid water washout, bleed/separation and leakages.
  • When running grease-packed bearings at higher speeds (in excess of 5000 rpm), experiment with the quantity of grease in the bearing. A 10 percent change in the quantity of grease can drastically affect the amount of heat generated by the bearing (even as much as 25 degrees C depending on how close to optimum it is). If there is too much grease for the bearing to push out to surrounding pockets, the bearing will heat up quickly. Often the optimum amount of grease is less than you might think.