Machinery Chatter

Incompatible Greases Could Lead to Costly Repairs

Dan Miller
By  Dan Miller , Progressive Farmer Senior Editor
Greasing an implement is one of those jobs that, while at times requiring gymnastic ability, is a task not to be neglected. (DTN/Progressive Farmer file photo)

I'd like to be able to say that I knew a lot about grease -- you know, stick the grease tube in the grease gun, connect the grease coupler to the grease fitting and you're golden. Andrew Hamilton, director of technical services and quality energy for Cenex, offered a bit more expertise on the matter.

Greasing an implement is one of those jobs that, while at times requiring gymnastic ability, is a task not to be neglected, Hamilton said.

Equipment is put to the test during planting and harvest seasons. To avoid downtime, farmers routinely perform basic, in-the-field maintenance, such as reapplying grease lubrication to pins, bushings, bearings and into vertical joints. Grease also resists the intrusion of water and dirt into parts where they should not be found.

The function of grease, according to the publication Machinery Lubrication, "is to remain in contact with and lubricate moving surfaces without leaking out under the force of gravity, centrifugal action or being squeezed out under pressure."

"Greases will last much longer than 15 or 20 years ago. But they are also more sophisticated and specific," Hamilton added. But not all greases are the same. Mixing incompatible greases can cause results as bad as not greasing joints, bearings, pins and bushings in the first place, Hamilton said.

Having the same price and color doesn't necessarily mean two tubes of grease are compatible. One tube of red grease may not have similar properties as the next tube of red grease. "If you put two greases together that were not meant to be put together, you can have issues that you were not expecting. The result can be catastrophic," Hamilton explained.

It is important, then, to understand the compatibility -- or incompatibility -- of different greases, Hamilton said. Mixing incompatible products may cause thickener components to react with one another, leading to the loss, or the release, of the base oil. The base oil is the largest component of grease and performs the actual lubrication.

This might be a good place to explain the three components of grease: base oil, thickener and additives.

-- Base Oil: Mineral oil-based greases perform well in most industrial applications. In temperature extremes, a synthetic base oil is better.

-- Thickener: The thickener is often referred to as a sponge that holds the lubricant (base oil plus additives), reports Machinery Lubrication. The primary type of thickener used in current grease is metallic soap. These soaps include lithium, aluminum, clay, polyurea, sodium and calcium. Non-soap thickeners are also gaining popularity in special applications such as high-temperature environments. Bentonite and silica aerogel are two examples of thickeners that do not melt at high temperatures.

-- Additives: Additives improve desirable properties of grease, suppress undesirable properties, and impart new properties. The most common additives are oxidation and rust inhibitors, extreme pressure, antiwear, and friction-reducing agents.

Proper care must be taken to ensure compatibility when changing from one grease product to another. That exchange may even require you to clean out all the old grease. Any reputable supplier will have at hand a grease compatibility chart, Hamilton said.

Here's an example:

Grease No. 1 is Cenex's ML 365 (Multi-purpose All Season Grease), which works well under extreme pressure. It has excellent cold-weather performance, resists water washout, provides protection from rust and corrosion, and reduces the risk of oil separation during long periods of storage.

It is useful in high-temperature applications, moist environments, heavy shock load conditions, for chassis lubrication and wheel bearings.

ML 365 contains a lithium thickener.

Grease No. 2 is Cenex's Poly-Xtreme, a high-temperature polyurea grease.

Poly-Xtreme has advantages over conventional soap-thickened greases in terms of longer life, high-temperature and wet applications. This grease also has the ability to migrate where lubrication is required.

It has similar applications at ML 365 -- general machine lubrication, high-temperature applications, wet environments, shock and heavy load conditions, chassis and wheel bearing lubrication.

But the two greases are incompatible. Lithium and polyurea greases cannot be mixed.

"They can cause each one to lose their oil and dry out," said Hamilton. The product loses the ability to lubricate. A kind of dry, husky material is left behind. That result is bad enough. In other instances, the interaction between incompatible greases creates a rock-salt-like material.

"It's highly abrasive," Hamilton said.

The takeaway is this:

-- Take a photo of the grease product to the retail outlet for comparison.

-- Compare it to the product on the shelf for compatibility.

-- Most outlets have someone who is an expert in lubrication production. Ask them for assistance when in doubt.

"Incompatible greases essentially attack one another," Hamilton said. "When you hear that grinding sound coming out of a piece of equipment because you've used the incorrect grease, you're going to have to clean out everything."

**

If you have a machinery or technology idea, please call Dan at 205-414-4736 or send an email.

Dan Miller can be reached at dan.miller@dtn.com

Follow Dan Miller on Twitter @DMillerPF

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Dan Miller