Lubricant: The “Blood” of a Bearing That Doubles Equipment Life

The Magic of Lubricants – How Do They Work?

Imagine going down a dry water slide. Your body would create a lot of friction with the slide’s surface. It would be slow and uncomfortable. But if there is a layer of flowing water, you can glide down smoothly.

Lubricants work in a similar way. They form a very thin but strong “oil film” between the rolling elements and the raceways. This film separates the fast-moving metal surfaces. It allows the rolling elements to “roll on oil” instead of “metal grinding on metal.”

A lubricant has four main jobs:

1. Reduce Friction and Wear: This is its most important task. The oil film prevents direct metal-to-metal contact, which greatly reduces friction and wear.
2. Remove Heat: Bearings generate heat from friction. A flowing lubricant (especially oil) acts like a coolant and carries this heat away.
3. Prevent Rust and Corrosion: The oil film protects the metal surfaces from moisture and oxygen in the air, preventing rust.
4. Assist in Sealing: Grease, in particular, can form a barrier in the gaps of a bearing, helping the seals to keep contaminants out.

The Two Main Types – Grease vs. Oil

Depending on the working conditions, bearing “blood” comes in two main types: grease and oil.

Grease – The Sticky Guardian

• What is it? You can think of it as a “sponge” filled with lubricating oil. It is made of three components: Base Oil (the part that lubricates), a Thickener (the sponge structure), and Additives (to improve performance).
• Simple Analogy: It’s like toothpaste or butter. It is thick and stays in place. It does not leak out easily.
• Suitable Applications:
  
  • Low to moderate speeds: Most common applications use grease.
  • Long-term maintenance: Grease can stay inside a bearing for a long time, so you don’t need to add it often.
  • Good sealing needed: It helps block contaminants and can be used on vertical or tilted equipment.
  • Moderate temperature ranges: Most general-purpose greases work well between -20°C and 120°C.

Oil – The Flowing Performer

• What is it? A pure liquid lubricant. Its most important property is “Viscosity,” which means how thick or thin the oil is.
• Simple Analogy: It’s like water or cooking oil. It flows very well and can reach every small space quickly.
• Suitable Applications:
  
  • Very high speeds: At high speeds, grease would create too much drag and heat. Flowing oil can lubricate and cool effectively.
  • High temperatures: Oil can be circulated through a system (like an oil bath or spray) and cooled externally. This is for jobs far too hot for grease.
  • Removing impurities: Circulating oil can wash away tiny wear particles from inside the bearing. These particles can then be removed by a filter.

Critical Mistakes – The Disastrous Results of Using the Wrong Lubricant

Choosing the wrong lubricant is not a small mistake. It can directly lead to equipment shutdown and bearing failure.

1. Using Grease in a High-Speed Bearing:

• • Consequence: The drag from the thick grease (called “churning”) will create a lot of heat. The bearing temperature will rise quickly. The grease will break down or “burn,” and the bearing will seize due to overheating. This is like trying to lubricate an F1 car’s engine with butter.

2. Choosing the Wrong Oil Viscosity:

• • Viscosity too low (too thin): The oil film will be too weak and break. The metal surfaces will touch, causing rapid wear and a much shorter bearing life.
  • Viscosity too high (too thick): The internal friction of the liquid will be too high. This also creates too much heat, wastes energy, and may prevent the oil from flowing to where it is needed in time.

3. Mixing Different Greases:

• • Consequence: The “thickeners” in different types of grease may not be compatible. When mixed, they can react. This can cause the grease to become too soft (and leak out) or too hard (and stop lubricating). This is one of the most common and fatal maintenance errors.

4. Too Much or Too Little Lubricant:

• • Too little: This causes lubricant starvation and dry friction, which is obvious.
  • Too much: For grease, filling the bearing too full (usually it should be 1/3 to 1/2 full) will cause severe churning and overheating, as mentioned before.