Grease is crucial to heavy construction equipment.
"Many times, grease is not only the lubricant, but it is the barrier to contamination," says Stede Granger, OEM technical manager, Shell Lubricants.
"Make sure you review the requirements of your equipment," says Granger. "Then work with a grease supplier and make sure everybody agrees that this is the right grease for the application."
Start by reviewing any information provided by the equipment manufacturer. "Proper grease selection begins with OEM specifications and recommendations regarding product type and lubrication interval," says Jeff Snyder, industrial brand specialist, Chevron Lubricants. "Then adjust selection and frequency based on operating conditions."
Snyder stresses the importance of using the right product in the right place at the right time and in the right amount. Considerations include base fluid viscosity, pumpability, load carrying capabilities (extreme pressure/antiwear properties), water ingression and operating conditions.
Select for Conditions
"In some heavy equipment maintenance manuals, you will find very vague descriptions for a grease recommendation such as 'bearing grease' and 'multi-purpose type grease," says Kim Smallwood, grease product manager for Citgo Lubricants. "The information does not give you much help in selecting the right grease."
It's important to understand your equipment's working environment. Conditions affect the way grease behaves.
"Compare the various grease tests as shown on the product information sheet to select the best grease for the application," Smallwood advises.
Make sure the product is up to the task. A "one-grease-fits-all" approach to minimize inventory is not always the correct solution.
For example, extreme pressure characteristics or viscosity that is too low can cause metal to metal contact, which leads to welding. Water tolerance that is too low can lead to rusting.
Pick the Right NLGI Grade
"The stiffness of the grease tells you how well it stays in the joint," says Granger. "For off-highway [applications], you probably want to stay with a NLGI #2."
An exception would be when working in cold weather. You may need to drop down to a NLGI #1 to ensure pumpability.
"Under a wide variation of temperatures (hot to cold), the case can be made to use an NLGI #2 grade during the warmer summer months, and when the temperature falls below 60° F, switch to a NLGI #1 grade grease," says Smallwood. "If you continue use of a NLGI #2 grade grease [during colder weather], the operator may think the equipment is a little harder to operate."
Another option is to use a synthetic grease year round. "Synthetic grease provides similar or better performance qualities," says Smallwood. "As the temperatures fall, synthetic grease will provide the added benefit of continuing to work, giving the operator a sense that the equipment is operating the way it should."
Autolube systems have unique NLGI requirements.
"Autolube systems generally use smaller lines," Granger notes. "To pump heavier grease through the smaller lines would be difficult. But you don't need a grease that is going to stay in the joint a longer time, because you are going to have an interval that is fairly short. You are going to pump a little bit of grease fairly frequently. The grease that is spec'd for an autolube system may be a NLGI #0. In some cases, it might even be a NLGI #00, depending upon the system and the application."
Of course, you also have to consider additives, such as moly, and the weight of the base oil when selecting grease.
"[NLGI] only measures one physical property of the grease," says Granger. "Predominately, what performs the lubrication is the oil that we put into the grease. The general rule for oils is the slower it turns, the heavier oil you use."