Posts Tagged ‘bearing lubrication’

Bearings In The News – November 2016

Friday, November 11th, 2016

This month we are featuring two articles: “Randall Bearings of Lima Showcases Robotic Arm” and “Impala Towboats Use Water-Lubricated Bearings.”

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Myths Regarding Bearing Lubrication

Friday, December 4th, 2015

This is part 3 in a 3 part series. The first part was Myths About Bearing Installation. The second part was Myths Surrounding Bearing Applications.

If your bearings aren’t properly lubricated, then disaster is sure to follow. Unfortunately, not everyone understands how or when to lubricate their bearings.

Here are a few common misconceptions on the subject you should make a point of avoiding.

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Lubrication Methods for Roller Bearings

Friday, January 30th, 2015

For rolling bearings to operate properly, they must be effectively lubricated to prevent metal to metal contact of the rolling elements, raceways, and cages. Thus, the primary function of adding lubricant is to separate these surfaces.

The lubricant also will protect the bearing’s surfaces against corrosion. Along with its other functions, a lubricant may also provide sealing against contaminants, or act as a heat transfer medium. It is important to choose a well-suited lubrication for each bearing application.

Operating conditions will determine the correct choice of lubricant, i.e. temperature range, speeds, and surroundings. Note that because the lubricant in a bearing arrangement loses its properties as a result of working, aging, and the build-up of contaminants, it will need to be changed and renewed at regular intervals for proper bearing function. This is called “relubrication”.

Oil is generally used for rolling bearing lubrication when there are rather high speeds, high temperatures, or when heat has to be removed from the bearing position. The most important property of lubricating oil is its viscosity. The lubricant’s viscosity is directly related to the amount of film thickness it can generate, which is the most critical component to achieving separation of the bearing’s rolling and sliding surfaces.

Mineral oils are typically favored for rolling bearing lubrication, with rust and oxidation inhibitors as additives. Synthetic oils can be considered for lubrication in extreme cases such as very low or very high operating temperatures.

Methods of oil lubrication for roller bearings:

Oil bath: Can be used for low to moderate speeds. The oil stays in a pool at the bottom of the bearing, and as the bearing rotates, the oil is distributed and then flows back to the oil bath at the base.

Oil pick-up ring: For bearings operating at higher speeds and temperatures, the pick-up ring circulates oil by hanging loosely to the shaft and rotating with it to transport oil. The oil then flows through the bearing back into the reservoir at the base.

Circulating systems: This method is preferred for high speed operations. With the aid of a pump, oil is circulated to the bearing, drains and returns to the reservoir where it is then filtered and cooled before returning to the bearing.

Oil jet: For very high speed applications, where a jet of oil under high pressure is directed at the side of the bearing. For this, the oil jet’s velocity must be high enough to break through the turbulence surrounding the rotating bearing.

Oil mist: Used today only in unique conditions, oil and air under suitable pressure are supplied to the bearing housing.

Oil spot method: Uses compressed air to transport lubricant directly to the bearing. The oil is sent into the airstream supply lines to the bearing housing at set time intervals.

Lubrication of Bearings

Friday, January 24th, 2014

When a bearing is required to run under demanding conditions, the choice of lubricant is vital. Lubrication has a big impact on lifespan, torque, speed, noise, grease migration out gassing, temperature, and rust prevention of the bearing.

Proper lubrication paves the way for smooth running of equipment, with only mild wear, and without unnecessary stresses at bearings. When lubrication fails, metal or other components tend to rub destructively over one another, leading to destructive damage, heat, and failure.

About Bearing Lubrication

Monday, July 8th, 2013

When a bearing runs under extreme conditions, the lubricant selection is vital. Lubrication will have a huge impact on life, torque, speed, noise, grease migration, out-gassing, temperature and rust prevention of the bearing.

The two main types of lubricants are oil and grease. Oil is the main lubricant used for ball bearings. In the past, the majority of lubricating oil was refined from petroleum. In this day and age, synthetic oils like diesters, silicone polymers, and fluorinated compounds have become commonplace.

On the other hand, grease is an oil where a thickener has been added to in order to keep oil from migrating away from the lubrication site. It is utilized in cases where frequent replenishment of the lubricant is impossible or undesirable. The operative properties of grease rely heavily upon the base oil. Other elements being identical, grease usage instead of oil yields higher starting and running torque and can limit the bearing to lower speeds.

Petroleum Mineral Lubricants

Petroleum lubricants are known for their outstanding load carrying abilities and are excellent against corrosion. However, they are useable only at moderate temperature ranges (-25º to 250 ºF). They’re suggested for use at moderate temperatures, light to heavy loads and moderate to high speeds.

Super-Refined Petroleum Lubricants

This type of lubricants may be usable at higher temperatures as compared to petroleum oils (-65 º to 350 ºF), but they still display the same excellent load carrying capacity.

Synthetic Lubricants

The esters, diesters and poly-a-olefins are among the most widely used synthetic lubricants. They may not have the film strength of a petroleum product, but they have a wide temperature range (-65º to 350 ºF) and are oxidation resistant.

Silicone Lubricants

Silicone products are typically used over a much wider temperature range (-100 º to 400 ºF), but they happen to not have the load carrying capacity of the petroleum types and other synthetics.

Perfluorinated Polyether (PFPE)

These types of oils and greases are widely used where stability at extremely high temperatures and/or chemical inertness is deemed necessary. This specialty lubricant possesses remarkable load carrying capacities. However, its inertness makes it less compatible to additives, and less corrosion resistant.