Can you trust a grease compatibility chart?

Have you ever had the experience of working on a piece of machinery and getting some grease on your hands? It can be pretty hard to remove. Unlike oil and other lubricant products, grease lubricants are more of a long-term lubrication solution. They are meant to stay on equipment for longer, and they are intended to be challenging to come off.

Grease products are a type of lubricant, but they are more solid or semi-solid. They can be handy for lubricating machinery and components that need long term protection or cannot contain a liquid lubricant. Grease lubricants are usually smeared on equipment components until they wear off. The American Society of Testing and Materials (ASTM) defines lubricating grease as “a solid to a semi-fluid product of dispersion of a thickening agent in a liquid lubricant.” Many different types of machinery require grease lubricants, from heavy equipment to bicycle chains. Grease lubricants can be an essential part of maintaining the mechanical process.

Grease lubricants are made up of three components: base oil, thickener, and additives. Together these products create a lubrication solution that can help engines and machinery perform better. These types of lubricants are easy to contain, can act as a sealant against spillage, are more resistant to contamination, and don’t need to be regularly monitored. Types of machinery that benefit from grease lubricants may:

 Run intermittently or remain in storage for periods. Grease lubricants stay in place to provide long term protection.
 Machinery that is difficult to lubricate consistently.
 Machinery used in extreme temperature conditions, at high or low speeds, or under pressure.
 Older mechanisms with worn-out parts.

Grease lubricants are a great way to protect your equipment. The problem occurs when it’s time to change the type of grease you are using or remove it altogether. It gets stuck in nooks and crannies in machinery and adding another grease product can cause a reaction. Unless you remove each component and clean it to remove the old grease, there will almost always be some mixture of the old grease and the new grease. You want to choose a chemically similar product to the previous one used. Manufacturers have created grease compatibility charts to help users choose the right types of products, especially when switching lubricants.

A significant issue of grease compatibility charts is that they are often unreliable or directly contradict one another. Most tables are based on thickener types and don’t take into account additives, base oils, and other factors. Grease charts rank compatibility as one of three classifications:

 Compatible: The mixture is chemically similar.
 Borderline: The combination is significantly different.
 Incompatible: The mixture is entirely different and may cause an adverse reaction.

These three risk factors are not enough to make an educated choice. They don’t consider many other factors that could affect performance. In a recent article from Lubes ‘n’ Greases magazine, it was reported that “a review of 21 grease compatibility charts found online show[ed] major inconsistencies.” The report concluded that “it was obvious that trusting these compatibility charts is unreasonable and potentially dangerous to grease-lubricated machinery.”

Compatibility testing must be completed to ensure the product is right for the equipment and the conditions. To determine if a grease mixture is compatible with your circumstances, it must meet a few characteristics:

 Maintain a comparable dropping point to the individual greases.
 Maintain mechanical stability with the range of the individual greases.
 Maintain a consistent constituency even after a temperature change.

Most charts contradict one another or even completely disagree with each other. When incompatible greases mix problems can occur. In a recent article in Machine Lubrication it is was found that “many mixtures will initially soften, often to the point of migration through seals or away from lubricated surfaces. Some mixtures will cause the thickener to release the oil, and the separated phase will run freely from the bearing, gear, or housing. Other mixtures will harden initially and cause component load issues and poor grease motility.” These are just a few of the concerns of a grease mixture. That’s why it’s so important to be careful.

Using the wrong products together can damage your equipment, leading to lost time and costly repairs. It can be complicated to remove grease lubricants once placed on machinery. That’s why you always need to check first before applying. We consider how our clients use their machinery and the conditions they use it in. We tailor our client’s orders to help keep their equipment running and in good order. If you have questions about grease lubricants, ask us. We can’t help you get the grease off your hands, or even off your equipment, but we can make sure that the new products you put on wouldn’t cause a reaction!