The most of screw compressors are running on a fixed drive speed. The capacity is controlled by a slide valve which creates an internal leak. How this effect influences the efficiency of the compressor unit?

Can a Variable Speed Drive (VSD) compressor lower the operation cost or create higher costs in fields other than energy?

Reducing energy costs is becoming a top priority, so it's no wonder that VSD compressor units are increasing in popularity. There is a common belief that VSD compressors are the most efficient part-load rotary screw compressors. As much as I agree with the high quality of VSD compressors, I cannot stress more the importance of fine tuning and adjusting the compressor unit to the field working conditions.

For example, at full load, a VSD compressor increases power draw by 2%. The way to compensate for this loss is by using a permanent magnetic E-motor, which saves 4% of power.

Viscosity is generally considered the most important property of a lubricant. What is it? And why should it matter to you?

Simply put, the viscosity of a lubricant (or any fluid) is a measurement of its resistance to flow. This example illustrates the concept: Suppose you have two glasses, one filled with water and the other with honey. If you were to tip the glasses over, the water would spill out of its glass faster than the honey. The honey has a higher resistance to flow, a higher viscosity, than water.