According to Granger, "The thickener holds the oil so that it doesn't leak out of the bearing. For on-highway and off-highway applications, the predominant thickener is Lithium or Lithium Complex. Generally, they are pretty compatible with other Lithium and Lithium Complex thickeners. For compatibility reasons, I would suggest to stay with the Lithium or Lithium Complex thickener unless there is a special need for one of the other thickeners."
Two greases with the same NLGI grade aren't necessarily compatible. "Many greases utilize different thickener systems, which can be incompatible with each other," says Smallwood. "When mixed, these thickeners can soften or possibly run out of the bearing or bushing. If you do switch between different thickener systems, your maintenance program should allow for thorough purging of all the old grease with the new grease."
Pay Attention to Distribution
When using a manual grease pump system, such as a grease gun, always consider safety first. While these devices appear simple, there is an injection hazard if you don't understand proper technique. "Grease guns generate extremely high pressures," says Snyder.
Then make sure the system can effectively deliver the grease where it's needed. "Sometimes grease distribution systems are so bad, they can hardly get the grease to the end of the gun let alone into the equipment," says Granger. "So a good pumping system is key." This is especially important when you are trying to pump grease in cold weather.
"We have worked with companies to ensure their grease distribution systems could flow enough grease," says Granger. "Some shops measured the amount of grease and the amount of pressure each system put out. It was really surprising to find the differences in the amount of output between the various systems. I cannot emphasize enough that if you use a system to pump the grease, then it needs to be able to pump that grease through the zerk fittings and be able to flow inside the joint."
Autolube and central greasing systems also need frequent inspection to make sure proper lubrication reaches critical joints and bearings. "Ensure central system integrity at the onset of the shift and thereafter to maintain proper lubrication at remote locations," says Snyder. "The most common issue with central systems is a broken line from operation, yielding insufficient or no lubrication at specific remote applications.
"However, this is not the only failure that may occur and prevent proper operation and lubrication," he continues. "Soap residue buildup, cold temperature application without proper product selection and contamination (like dirt, welding dust, etc.) in the product could generate blockages that yield high-pressure faults and ineffective system operation."
Not All Grease Points Are Alike
"You need to understand each grease application and each grease point," says Granger. "Some joints hold grease better than others. You definitely want to get grease in there in the proper interval."
One of the most common mistakes is not greasing enough. Don't try to save costs by cutting intervals. "Many choices are being made to cut costs and usually the maintenance program will suffer the most," says Smallwood. "When determining the point at which to re-grease, a costly mistake is to wait until you hear the sound of metal grinding on metal. This creates metal flakes in the bearing or bushing that eventually lead to failure."
You can't treat all grease points the same. Consider large pin-and-bushing joints. "You probably want to grease until you see new grease purging out. Purging of the new grease helps remove contaminants," says Granger. "But there are also cases where you do not want to purge grease through a joint." If it has a tight seal that is not made for purging grease, you may damage it. You also don't want to purge grease through bearings.
"Excessive product application may rupture protective seals and allow contamination ingression," says Snyder. "Excessive application may also pack bearing applications, yielding high operating temperature."
Keep It Clean
"Clean grease zerks are a must in your preventive maintenance practice," says Smallwood. "Grease attracts dirt and becomes caked up on the fittings. When you re-grease before cleaning off the grease zerks, you will push dirt inside the bushing or bearing, which will act as an abrasive and can lead to premature failure."