Bearings lubed-for-life

Traditionally, greases and oils have been used to lubricate ball and roller bearings. These lubricants can be messy, causing significant housekeeping problems and requiring periodic maintenance to replenish the lubricant. Solid lubricants, such as microporous polymeric lubricants (MPLs), can significantly reduce or eliminate these problems.

03/10/2004


Key Concepts
 
  • Microporous polymers can incorporate oils tailored to the application.

  • Sponge-like construction releases and absorbs lubricant as required.

  • Oil-filled polymers can be incorporated in all types of bearings during manufacture.

Sections:
Characteristics of MPLs
Applications
Limitations
Sidebars:
Advantages of MPLs vs. grease or oil


Traditionally, greases and oils have been used to lubricate ball and roller bearings. These lubricants can be messy, causing significant housekeeping problems and requiring periodic maintenance to replenish the lubricant. Solid lubricants, such as microporous polymeric lubricants (MPLs), can significantly reduce or eliminate these problems.

Characteristics of MPLs

MPLs are made up of two major components, a polymer containing a continuous microporous network and oil that is contained within these pores. The type of oil incorporated into the polymer can be tailored to the requirements of the application. For example, the oil can be an FDA/USDA-approved food-grade lubricant to eliminate product contamination and improve housekeeping and safety, or an oil with an extreme pressure (EP) additive for high load applications.

Other additives can be used to alter the lubricant's properties and include oil property enhancers such as corrosion and oxidation inhibitors, coefficient of friction modifiers, and lubricating solids such as molybdenum disulfide, graphite, and Teflon. The oil content in the polymer can be controlled during processing and the MPL can contain over 50% oil by weight.

The microporous polymer acts much like a sponge, releasing and absorbing oil. Oil is released from the polymer to its surface through capillary action. It is then transferred to any surface it contacts to provide the necessary lubrication. As the quantity of oil on the surface decreases, the MPL releases more oil. If excess oil becomes present, it is re-absorbed by the porous polymer.

As the temperature of the MPL-filled bearingincreases, more oil is typically released by the MPL. This oil is reabsorbed by the MPL as the bearing temperature decreases. Because of this, MPLs reduce or eliminate the need for relubrication, minimizing or eliminating maintenance and housekeeping.

Applications

A major application of MPLs is the lubrication of ball and roller bearings, providing an extended source of lubrication. It is molded into the space between rolling elements and the races of the bearing (Fig. 1). The MPL provides a continuous source of lubrication.



Because it is solid, the MPL helps shield the bearing and reduce contamination. This is useful in applications where bearings are exposed to dust or dirt. Reducing the incursion of debris into a bearing can significantly extend its life.

MPLs can also be produced in various solid profiles by casting, extruding, and injection molding (Fig. 2). While they are not designed as load-bearing materials, these solid profiles offer a unique method of delivering lubrication, especially for difficult-to-reach locations.




Solid profiles have been used to lubricate crane wheel flanges, ball screws, and linear bearing rails, and as lubricating plugs in bushings and sleeves. One application is an MPL sprocket (Fig. 3) being used as an idler to lubricate chains.



MPLs are made by mixing proprietary polymers, oils, and additives. The mixture is packed into the bearing and thermally processed. Because MPLs require this treatment, the bearings must be processed in the manufacturer's facility, where the MPL is incorporated into the bearing.

It is not possible to put oil-filled polymer lubricants into a bearing in the field. Bearings must be purchased MPL-filled or sent to the manufacturer to be filled. Nearly any type of bearing can be lubricated with MPLs, including ball, roller, needle, tapered, spherical, and cam followers.

Limitations

Various formulations of MPLs provide operating temperature ranges from -40 F to 350 F. If the high-temperature limit is exceeded, the polymer softens and can be ejected from the bearing. MPLs do not dissipate heat rapidly, and as a result, there are rotational speed limitations based on bearing type and size. Maximum rotational speeds (rpm) at room temperature have been determined for each type of bearing and can be calculated by using the Ndm Value from the table in the following formula. The Ndm value is a factor relating maximum rotational speed to bearing size. Ndm values for various bearing designs are shown in the table.

Ndm Value

_____________

Maximum rpm =

While MPLs generally resist contamination better than greased bearings, this does not make the bearing waterproof and will not prevent corrosion of the bearing. Direct contact with solvents, cleaners, or acids is not recommended. Repeated exposure will deplete the oil from MPLs, making them less effective.

Because the bearing cavity is filled with MPL, rotational torque is increased compared to grease-filled bearings, especially on startup. This is usually not a problem in most industrial applications.

More Info:

If you have any questions about microporous polymeric lubricants contact the author at 937-743-8061. Article edited by Joseph L. Foszcz, Senior Editor, 630-288-8776, jfoszcz@reedbusiness.com .

Comparison of bearing lubricating methods

Hand greasing Automatic greasing Automatic oiling MPL
Lower preventative maintenance costNoIgnoring significant capital costsIgnoring significant capital costsYes
Particulate exclusionNoNoNoSome
Application to hard-to-reach areasNoYesYesYes
Lubrication applied as neededNot automaticYesYesYes
Reduced housekeepingNoNoNoYes
No external application equipmentNeed grease gunNoNoYes


Bearing Ndm values

Bearing Type Ndm Value
Single row, deep groove ball300,000
Ball with plastic cage40,000
Double row, deep groove ball150,000
Angular contact ball150,000
Self-aligning ball150,000
Cylindrical roller150,000
Spherical roller85,000
Tapered roller and roller thrust45,000


Advantages of MPLs vs. grease or oil

Cost savings due to the reduction of maintenance

Protection of bearings from dust and dirt

Extended bearing life

The ability to provide lubrication at difficult-to-reach locations

Release of oil to bearing surfaces on demand

Improved plant housekeeping and safety conditions.



Top Plant
The Top Plant program honors outstanding manufacturing facilities in North America.
Product of the Year
The Product of the Year program recognizes products newly released in the manufacturing industries.
System Integrator of the Year
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
October 2018
Tools vs. sensors, functional safety, compressor rental, an operational network of maintenance and safety
September 2018
2018 Engineering Leaders under 40, Women in Engineering, Six ways to reduce waste in manufacturing, and Four robot implementation challenges.
July/Aug
GAMS preview, 2018 Mid-Year Report, EAM and Safety
October 2018
2018 Product of the Year; Subsurface data methodologies; Digital twins; Well lifecycle data
August 2018
SCADA standardization, capital expenditures, data-driven drilling and execution
June 2018
Machine learning, produced water benefits, programming cavity pumps
Spring 2018
Burners for heat-treating furnaces, CHP, dryers, gas humidification, and more
October 2018
Complex upgrades for system integrators; Process control safety and compliance
September 2018
Effective process analytics; Four reasons why LTE networks are not IIoT ready

Annual Salary Survey

After two years of economic concerns, manufacturing leaders once again have homed in on the single biggest issue facing their operations:

It's the workers—or more specifically, the lack of workers.

The 2017 Plant Engineering Salary Survey looks at not just what plant managers make, but what they think. As they look across their plants today, plant managers say they don’t have the operational depth to take on the new technologies and new challenges of global manufacturing.

Read more: 2017 Salary Survey

The Maintenance and Reliability Coach's blog
Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
One Voice for Manufacturing
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Maintenance and Reliability Professionals Blog
The Society for Maintenance and Reliability Professionals an organization devoted...
Machine Safety
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
Research Analyst Blog
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Marshall on Maintenance
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
Lachance on CMMS
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
Material Handling
This digital report explains how everything from conveyors and robots to automatic picking systems and digital orders have evolved to keep pace with the speed of change in the supply chain.
Electrical Safety Update
This digital report explains how plant engineers need to take greater care when it comes to electrical safety incidents on the plant floor.
IIoT: Machines, Equipment, & Asset Management
Articles in this digital report highlight technologies that enable Industrial Internet of Things, IIoT-related products and strategies.
Randy Steele
Maintenance Manager; California Oils Corp.
Matthew J. Woo, PE, RCDD, LEED AP BD+C
Associate, Electrical Engineering; Wood Harbinger
Randy Oliver
Control Systems Engineer; Robert Bosch Corp.
Data Centers: Impacts of Climate and Cooling Technology
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
Safety First: Arc Flash 101
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
Critical Power: Hospital Electrical Systems
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
Design of Safe and Reliable Hydraulic Systems for Subsea Applications
This eGuide explains how the operation of hydraulic systems for subsea applications requires the user to consider additional aspects because of the unique conditions that apply to the setting
click me