Producing Maximum Efficiency with Mechanical Lubricants
Over time, systems used throughout various industries have been growing in complexity in order to meet the demands of customers. In order to meet this demand, mechanical lubricants have become a crucial part of achieving maximum efficiency from the system. In order to choose the right lubricant, a number of factors must be considered.
Choosing a Fluid
The viscosity of the oil will be your biggest concern. At low temperatures, excessive viscosity will result in poor mechanical efficiency, difficulty in starting, and wear. As the oil temperature increases, viscosity decreases. This results in lower volumetric efficiency (inefficiency in converting hydraulic energy back to mechanical energy), overheating, and wear. In order to decide on the proper viscosity level, consider the following:
- Maximum startup viscosity under load.
- Range of optimum operating viscosity.
- Maximum and minimum operating viscosity.
Selecting the optimum viscosity will produce the most efficient pump performance at standard operation temperatures. In other words, you will minimize lost time, energy, and fuel costs for your operator.
You should consider Maximum Efficiency Hydraulic Fluid (MEHF), which has become the new performance standard for hydraulic fluids. They will enable any hydraulic pump to deliver increased power at much lower energy levels.
Pump Efficiency
The overall reliability of your system will depend on two measures of your system’s efficiency: volumetric efficiency, and hydromechanical efficiency. The latter refers to the frictional losses of a hydraulic component and how much energy is required to generate fluid flow. It is related to flow losses and the degree to which internal leakage occurs.
These two properties will be highly dependent on the viscosity of your lubricant. As hydromechanical efficiency decreases, fluid viscosity increases since there will be a much higher resistance to flow. Conversely, volumetric efficiency increases as fluid viscosity increases since there will be less internal leakage. Both volumetric efficiency and hydromechanical efficiency must be considered simultaneously.
Cavitation, Wear, and Overheating
At low temperatures, a high viscosity will negatively affect the mechanical efficiency of a hydraulic system, resulting in reduced system performance, lubricant starvation, and cavitation. Cavitation is particularly dangerous, since it can cause metal fatigue and spalling (breaking into smaller pieces), which will leave abrasive metal particles in your system’s fluid. This is why pump manufacturers specify the maximum viscosity for your system.
A lubricant is meant leave a lubricating film to reduce wear on moving pump parts. Its effectiveness will depend on the viscosity, sliding speeds and loads, and fluid stability. Once the temperature increases to a certain level, the film will thin and rupture, exposing the system to metal-on-metal contact. As a result, there will be wear within the pump and heat within the fluid will increase. Since the wear will be centered on areas essential to volumetric efficiency, the pump will need to work much harder to achieve the proper flow. Inadequate viscosity will result in higher temperatures within the fluid, accelerating wear and increasing internal leakage.
Fluid Selection
The NFPA has a viscosity grade selection system which is based on recommendations from leading hydraulic pump manufacturers. The most common viscosity grades are ISO 32, 46, and 68. Machinery Lubrication came to the following conclusions after comparing the performance of these three ISO grades:
“The high VI oils that meet the MEHF performance level definition contributed to significantly lower hydromechanical losses at temperatures lower than 40°C. The gain in hydromechanical efficiency can exceed 50 percent at start-up temperature, resulting in lower energy consumption, shorter warm-up times and reduced wear.
At temperatures of 80°C and 100°C, calculations made for a series of vane pumps showed that the high VI oils deliver a higher flow rate and a better overall efficiency. This translates into higher equipment productivity, as well as significantly lower operating costs for the equipment user due to lower fuel consumption. Energy and fuel savings up to 20 percent can be expected under standard operating conditions when MEHF-type oils are used. Higher productivity gains and savings can be achieved at peak operating temperatures.
The cost savings associated with the use of maximum efficiency hydraulic fluids in a single vane pump are approximately $400 per year per pump. This advantage could be expected to result in approximately $50,000 savings annually for a medium-sized equipment fleet.”
Please take a look at the full article for more information on choosing lubricants for your system.
Seals for Maximum Efficiency
If you want to get the most out of your hydraulic system, you will need a custom-built seal that will meet every requirement your application demands. Real Seal can help you produce that perfect seal with the expertise of our full-time chemist, and our experience producing thousands and thousands of seals every year. Give us a call and we’ll help you get started.
