How do you know if the right lubricants are being used in your machinery? A lubricant specification survey, often called a lube chart, may have been performed, individual machine maintenance manuals may be used, or, you may use whatever lubricant has always been used. Regardless of the method used, assuming the original specification is correct, you might be surprised to find out what lubricant or lubricants are actually installed. I spend a lot of time auditing lubrication programs and I always find misapplications, even in quality lubrication programs. The point is, no matter who determines the correct lubricant for a machine, it is necessary to periodically review the specifications and re-survey the plant to determine the products in use are what is or should be specified. Additionally, a formal management of change process should be developed to govern any changes to existing specifications.
Change Process
Begin this process by surveying all lubricated components in the plant to obtain the necessary information to determine the correct lubricant specifications. At the same time, the existing product in use should be determined. During this process, it may be discovered that no one actually knows what the current product is for many applications. The information needed for a given component depends on the type of component and the application method. At a minimum, lubricating oil specifications should include base oil viscosity, base oil type, lubricant type (type of additive package), and specials considerations such as the use of solid additives. For grease, the thickener type and consistency (NLGI grade) must also be specified. The following provides brief descriptions of the necessary information for some common types of components.
Element Bearings
In most plants, a common lubricated component is element or antifriction bearings. Lubricant selection for these components is simple and usually requires only the following:
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Bearing dimensions
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Rotational speed
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Ambient and/or operating temperature
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Current lubricant type
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Oil or grease
Many bearings come from parts of manufactured components such as a blower or pump housing. For these applications, the make and model of the unit, operating temperature and operating speed will usually suffice. For grease-lubricated bearings, the user will also want to collect the necessary information for relubrication frequencies and volumes. This includes the bearing type, orientation and operating environment information, such as the degree of moisture or particle contamination the bearing is subjected to.
Enclosed Gearing
For most gearboxes, the appropriate lubricant type can be determined from the maintenance literature provided by the equipment manufacturer. However, there will likely be some applications where the engineering methods must be used to determine the appropriate viscosity and lubricant type. Some of the key requirements for lubricant specifications for gearing include:
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Make and model of the unit
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Type of gear (worm, helical, spur)
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Lubricant application method (bath or circulating system)
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Gear geometry (primarily, the pitch diameter of the slowest stage gear)
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Input and output speed
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Heavy loads or shock loading (yes/no)
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Ambient and/or operating temperature
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Does it have grease-lubricated bearings?
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Does it have grease-lubricated shaft seals?
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Operating environment conditions
Plain Bearings
For plain bearings, only the following is needed:
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Bearing geometry
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Shaft weight
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Shaft speed
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Ambient and/or operating temperature
Most plain bearings utilize hydrodynamic lubricating films, thus requiring only rust and oxidation inhibited (R&O)-type lubricants, although some applications may require the use of extreme pressure (EP) or other antiscuff additives.
Hydraulics
For hydraulic systems, most lubricant requirements are determined by the hydraulic pump and system pressure, but there are other considerations as well. The typical data needed consists of:
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Pump make and model
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Type of pump
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System operating pressure
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Operating temperature (high and low)
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Coldest likely startup temperature
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Requirements for fire resistance
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Type of valves and components (for fluid cleanliness requirements)
Vane pumps and piston pumps will typically require antiwear (AW) fluids while gear pumps can use AW or R&O fluids. Once again, there may be other pertinent information for a particular application, but these items should cover the majority.
Stay on Task
This is a brief introduction to the techniques of performing a lubrication survey. In addition to performing the survey and collecting the appropriate data, it is essential to obtain the knowledge necessary to utilize the data. This can be accomplished through training, self-directed studies, or with the assistance of a qualified consultant. Lubricant suppliers may provide assistance in this area as well. Remember that it is better to collect too much information rather than too little.
When surveying equipment, make sure to capture all of the available information that could be used to make not only specifications, but other lubrication or contamination control decisions as well. Finally, install a process to periodically re-survey equipment to determine whether or not the specifications are actually being observed or are being changed arbitrarily. By following these recommendations, it is possible to eliminate a number of unnecessary machine failures and achieve a greater degree of plant reliability.
