Lubricants are sometimes the foundation explanation for failure when cylindrical rolling bearing system’s temperatures rise.
A typical query upkeep personnel ask bearing firms when their equipment temperature is excessive or rises is: What’s the most temperature that the bearings can deal with? The higher query to ask is: What’s the most temperature that the bearing system can deal with?
When excited about temperatures you will need to suppose when it comes to an entire cylindrical rolling bearing system.
An entire cylindrical rolling bearing system features a rolling bearing, a lubricant, and in most cases a lubricating system. The lubrication of ball and curler bearings is completed with oils, greases, or dry stable movies [graphite, molybdenum disulfide (MoS2), polytetrafluoroethylene (PTFE), oil impregnated polymer oil, and so on. Rolling bearings carry the load of rotating equipment, however can’t perform for very lengthy and not using a lubricant. If the lubricant fails the bearing will fail shortly thereafter. Lubricants are sometimes the foundation explanation for failure when a bearing system’s temperature rises.
This text is designed to assist upkeep personnel consider most temperatures {that a} bearing system can endure beneath use, somewhat than consider temperatures in relation to solely a bearing and solely the lubricant and lubricant system.
The metal utilized in cylindrical rolling bearing, each by means of hardened and case carburized steels, is processed to a minimal hardness of Rockwell C 60. Based on the American Bearing Manufactures Affiliation (ABMA) the utmost working temperature of by means of hardened steels, AISI 52100 is 16O0C (32O0F), 440-C is 18O0C (3560F), and M50 is 32O0C (60O0F). Normally for all steels, because the temperature exceeds 20O0C (3920F) the hardness begins to lower. Thus, the rolling bearing life decreases as temperatures rise past 20O0C (3920F).
As any metallic heats up a fabric part change happens and the scale turn into unstable. In different phrases the bearing components increase.
Since the most typical methodology to measure the temperature of a bearing is by studying the temperature on the skin of housing, you will need to do not forget that the temperature on the bearing floor is 10 to fifteen F decrease than bearing temperature.
Cylindrical rolling bearing cannot perform reliably and not using a lubricant. the rolling bearing system features a rolling bearing, a superb lubricant, and a lubricating system. The lubrication of ball and curler bearings is completed with oils, greases, or dry stable movies. When a machine’s temperature rises, the principle concern for upkeep personnel shouldn’t be the utmost allowable temperature the cylindrical rolling bearing can accommodate. The principle concern ought to be the utmost temperature all the bearing system can deal with. The principle focus ought to be on the utmost temperature that the lubricant and/ or the lubricating system can endure as a result of their failure will trigger the bearing to fail. A lubricant’s failure because of a excessive temperature is troublesome to detect. Subsequently, you will need to monitor the temperature of a lubricant.
With out a good provide of oil a cylindrical rolling bearing will fail earlier than its potential life (LlO life) because of friction and put on between the rolling ingredient and the raceways. Oil between the rolling ingredient (ball, spherical curler, cylindrical curler, and so on.) and the raceway reduces friction and put on, and thus decreased warmth era.
Oil may be provided to the bearing both immediately or by means of using grease. Oils used to lubricate a rolling bearing embrace base oil and generally components. Greases are made up of base oil (65-95%), thickener (3-30%), and components (0-15%). Typically as much as 5% of a stable lubricant is added to grease. It’s the base oil in grease that does the work in a bearing system, not the thickener, nor the components. A thickener holds the oil and the components enhance the properties of the thickener. The oil does the work for the rolling bearing, the thickener retains the oil in place, and the additive can improve the efficiency of the oil and/ or thickener.
Whether or not oil or grease is used to lubricate a cylindrical rolling bearing, each can solely endure a lot warmth earlier than they lose their effectiveness within the bearing system.
The kind and quantity of thickening agent used (natural, inorganic, metallic soap) and the bottom oil sort (mineral or artificial oil) and its viscosity decide the higher and decrease working temperature limits of lubricating greases.
One other factor to contemplate with excessive temperatures in a cylindrical rolling bearing is the oil’s viscosity Viscosity is the measure of the relative resistance of a fluid to move at a given temperature: the upper the viscosity, the higher its resistance to move. Viscosity is measured both in centistokes (cSt) or Saybolt Common Seconas (SUS). With greases the viscosity number is the move price of the bottom oil, not the thickener.
A viscosity of a lubricant ought to be adequate to separate components beneath working situations, however not so excessive that additional drag is created. Because the temperature rises the viscosity of oils lowers. The upper the temperature, the upper the viscosity wanted in a bearing system.
Usually in excessive temperature functions, if the oil or grease used has a decrease viscosity, the bearing system will fail prematurely As may be anticipated, typically in a excessive temperature software the next viscosity oil or grease ought to be used.
An important property of oil, from a top quality standpoint, is its chemical or oxidation stability Warmth is primarily an accelerator of oil oxidation. The speed of any chemical response, together with the oxidation of hydrocarbons will double for each 18 F (10 C) improve in temperature. It’s estimated that the lifetime of an oil is decreased 50% for each 18 F (10 C) temperature rise above 140 F (60 C). At temperatures higher than 248 F (120 C) oxidation drastically impacts grease life. The system for this is able to be 롤대리:
Lt = a*L
the place:
Lt = Oil life because of temperature higher than 60 C (140F)
α = Temperature life issue
L = Anticipated lifetime of oil at or beneath 60 C (140 F)
It doesn’t matter what is used to lubricate a cylindrical rolling bearing in a excessive temperature software and/or surroundings, the lubrication system can both lengthen the lifetime of a rolling bearing or lower it. A bearing system have to be designed to help the bearing in assembly its potential life. Consideration to the lubrication system ought to by no means be ignored or ignored.
A number of oil programs can be utilized to take away warmth from a cylindrical rolling bearing. Grease and dry stable movie don’t help in eradicating warmth from a rolling bearing. The first consideration with greases is the relubrication methodology and interval.
Within the increased pace ranges of operation, an excessive amount of grease will trigger overheating. The quantity of grease that’s acceptable for a specific excessive pace software can solely be decided by expertise. Normally, about half to a third of the open space in a bearing ought to be full of grease on startup. If extra grease within the bearing causes overheating, will probably be essential to take away some grease from the bearing. A slight present of purged grease on the bearing seals is regular and in addition helps hold contaminants out of the bearing. Extra grease may be tolerated and is mostly fascinating in low pace functions.
When establishing grease re-lubrication schedules, a small quantity of grease at frequent intervals is preferable to giant portions at rare intervals.
There are a number of lubrication programs in terms of oil; sump (bath), circulation by means of sump, circulation by means of sump with cooling, jet (injection) into bearing, mixture of bypass circulation with cooling and jet, and mist (spot). An oil bath system can be utilized to lubricate a bearing, however usually, it doesn’t help in eradicating the warmth from a bearing system. The oil degree for a sump bearing ought to come as much as the center of the rolling ingredient when it’s at its lowest place.
An entire cylindrical rolling bearing system features a cylindrical rolling bearing, a lubricant, and in most cases a lubricating system. The lubrication of ball and curler bearings is completed with oils, greases, or dry stable movies [graphite, molybdenum disulfide (MoS2), polytetrafluoroethylene (PTFE), oil impregnated polymer oil, and so on. Rolling bearings carry the load of rotating equipment, however can’t perform for very lengthy and not using a lubricant. If the lubricant fails the bearing will fail shortly thereafter. Lubricants are sometimes the foundation explanation for failure when a bearing system’s temperature rises.