Bearings Sleeves deserve respect

By D.Nayar (Bob) A.Nairsons Industries (India)

In today world industry is more reliant on bearings than ever before. Machine builders are putting increasingly higher demands on bearing manufacturers – requiring bearings that are smaller, carry greater loads at higher speeds, and last longer.

“Bearing manufacturers, particularly the world leaders, have responded by producing bearings with performance levels that could only have been dreamt of years ago,” “For example our KT design Sleeves & locknuts made on CNC machines with Good Quality Steel ,Forging /Annealing Quality, Higher accuracy, Excellent Durability, Better life for Bearings, hence increase in productions..”

Unfortunately when it comes to the maintenance of bearings, there are a number of issues that need to be addressed – taking shortcuts is one of them.

Our Taper developed sleeve by forging process in figure below.

“There will always be a conflict between production and maintenance in many plants and this is where perhaps one of the most common shortcuts takes place,” .And that is not rectifying the problem when it occurs but delaying maintenance until a window opens in the production cycle.
“For instance, a fan gets out of balance and, rather than fix it, maintenance is delayed. This creates an artificial, out of balance mass in the fan which, in turn, puts an undue load on the bearings and shortens their useful life.”
“One of the common ones we see is for the defective bearing to be replaced with an identical bearing – but the sleeve, shaft and housing will not be measured to ensure that the fit is still correct. Ninety percent of the time you’ll get away with this, but if the housing and/or shaft is worn, or the fit incorrect to start with, then you’ll have premature failure on your hands.”

“Bearing lubrication is also a big issue. Industry does not appear to value the importance of correctly lubricating bearings and reducing contamination.”
Bearing installation and removal is yet another huge issue. “And running machines smoothly so there’s no unbalance, misalignment or resonance is critically important.”
We believe there’s a need to study the ‘forensic science’ of bearings and determine why they fail. “Rather than cutting bearings off and scrapping them, their correct removal and analysis of the patterns on the bearing surface should provide clear indication of why the bearing failed. If you know why it failed you can take action to avoid the failure in the future.
“Being proactive in the first place to give the bearing the best possible chance of surviving, and then determining why it failed and correcting the root cause has to be the best formula for success,” .
“Not providing the right grade and type of lubrication to get the best possible expected and designed life out of the bearing is a real issue.
“Often engineers have no idea the damage moisture within the oil has on the life of the bearing either.
“Contamination of lubricant is also of major concern. It is a proven fact that lubrication related plant failures can be drastically reduced by improving the control of lubricants.”
Some bearing failures cause catastrophic damage. In Paper Industry, One “significantly large coupling” that was thrown across a machinery room due to the shaft bending. “Heat had been generated to such a degree that the steel shaft had become plastic-like. Lubrication-related issues could have played a part in this failure, as could poor fit and tolerances.”
Bearings sleeves are often mistakenly regarded as just a commodity that fit in a hole and go around. “KT Bearing sleeves are a very precise product made to exacting standards with tolerances and clearances in the order of microns. They must be treated with all due respect.”
Proper training is absolutely paramount if plant operators are going to get anywhere near the theoretical life of their bearings.

“Tradesman must understand that sleeves ,shaft and housing tolerances are critically important.
The condition of the shafts and sealing devices are also important if lubrication is going to be retained correctly and contaminants excluded.
“One of the most misunderstood aspects of maintenance we have come across is the way that bearing clearances are adjusted to attain the correct running clearances in spherical roller bearings. This is a highly skilled operation. There are measurements and calculations required to ensure that the correct clearance is arrived at. Quite often arbitrary ‘hit and miss’ methods are used, resulting in very poor bearing life.”

Proper Training should be given.
Bearings fail for a variety of reasons. Some research shows that 14 percent fail due to contamination; poor installation practices cause 16 percent to fail; 34 percent of failures are due to premature fatigue; and the biggest cause of failure, at 36 percent, is lubrication issues. We believe that understanding all these areas is critical to get the best out of bearings – but if there has to be a single focus, his money’s on understanding lubrication.
“Too often the role of machine lubrication is left to a person who may not really understand that different applications running at different speeds and different temperatures require greases that are significantly different in their makeup. Greases are complex chemical mixes with a wide range of bases and oils, which are not necessarily compatible with one another. Mixing greases incorrectly can lead to absolute disaster when the resulting product fails to perform as it should.
“Correct lubrication selection for a given application and correct re-lubrication intervals are absolutely essential if ultimate bearing life is to be achieved.”