Oilers/Plant Tenders (HHC) Civil Service Practice Exam

Bearings operating at high shaft speeds and low pressure generally require what type of lubricant?

1. High viscosity lubricant

2. Low viscosity lubricant

3. Solid lubricant

4. No lubricant

The correct answer is: Low viscosity lubricant

Bearings that operate at high shaft speeds and low pressure are best suited to low viscosity lubricants. Low viscosity lubricants have a thinner consistency, which allows them to flow easily and reach all parts of the bearing rapidly. This is crucial in high-speed applications as it reduces friction and heat buildup, ensuring smoother operation and preventing premature wear on the bearing surfaces. In addition, using low viscosity lubricants at high speeds helps to create an effective hydrodynamic film between the moving surfaces, which supports the load and enhances the performance of the bearings. This is particularly important in maintaining efficiency and extending the life of the equipment. On the other hand, high viscosity lubricants would not be appropriate in this scenario because they are thicker and can create excessive resistance to motion at high speeds, possibly leading to overheating and increased wear. Solid lubricants may provide some benefits in specific circumstances but are generally not used in high-speed applications as they can fail to provide adequate coverage. Lastly, using no lubricant at all would lead to severe friction and damage to the bearings, making it an impractical option in any operational scenario.