Design engineers know that manufacturers are continually challenged to minimize operating costs by reducing maintenance expenses and service time, as well as improving efficiency of equipment.
One immediate and cost-effective way to do so is by using high-quality lubricants in machinery and their components, such as gearboxes. Horizontal grinding mills with large open gears are using multi-megawatt gearboxes to drive the pinion. These multi stage planetary gearboxes are often filled with 500 liters or more of traditional mineral gear oils, which cost a few hundred dollars. Let’s make a simple calculation:
By switching from a mineral oil to synthetic oil, the efficiency improvement of only 2 percent on a mill drive gearbox can result in a savings of more than $42,000 of energy costs in a given year. How can such savings be explained?
The coefficient of friction
PAO or polyglycol based synthetic oils have lower values compared to mineral oils; for example 0.06µ for mineral oils versus 0.03µ for polyglycols. By minimizing the friction between the tooth flanks and inside the bearings, the oil contributes to the overall effectiveness of the gearbox.
Additionally, friction losses are resulting in elevated oil bath temperatures. These higher oil temperatures have a negative impact on the oil service lifetime. According to the Arrhenius equation, few Kelvin less oil temperature can double the lifetime of the gear oil, which results in reduced disposal and maintenance costs.
In fact, the energy saving calculation isn’t that simple, load factors, churning losses, gear design, and surrounding factors have to be considered, as well as process influencing causes eliminated. This results in a factor, which shows energy consumption per produced good. In the case of grinding mills, it is kWh/ton ore milled. This makes it possible to compare “apples to apples.” Klüber Lubrication uses power and energy analyzers, thermography analysis, and torque measurement devices to make the energy savings visible, as well as statistical methods according to international standards to eliminate influencing factors.
Klüber Lubrication started its energy efficiency program several years ago. Now with more than 100 energy efficiency projects conducted in different industries, we are confident to say: Energy saving projects are among those investments which pay-off within a few months, they generate quick savings and are not tied to large expenses in new equipment.