Building A High Performance Hydraulic Oil

Building A High Performance Hydraulic Oil

• Do you know what the VI is for SWEPCO 703?
• Do you know why such a high VI gives our products an advantage?
• What percentage increase does 703 offer in efficiency of the equipment?

After you read this Technical bulletin you will be able to answer these questions and know why we are building A High Performance Hydraulic Oil for you (or actually 2…)

More demanding, tighter tolerances and wider operating temperatures

Hydraulic systems are widely used in a variety of applications in industry, transportation, and many other uses. Over the years applications and operating conditions have become more demanding with tighter tolerances and wider operating temperatures. To keep up with these increasing demands on the hydraulic fluids, SWEPCO 703 and 704 have been improved to meet and exceed today’s fluid requirements. First we will look at some of the issues facing hydraulic systems today.

The initial demand on a hydraulic pump is the oil viscosity during a low temperature start up. If the viscosity is too high at a low temperature start, it may result in poor efficiency, difficulty starting, lubricant starvation, cavitation, and wear. Most pump manufacturers will provide recommendations for:

1. Maximum start up viscosity under load
2. Optimum operating temperature range and viscosities
3. Maximum and minimum operating viscosities.
4. Optimum operating pressures.

Fluid Viscosity

Next is pump efficiency which measures the amount and degree of work accomplished. Hydro- mechanical efficiency relates to the amount of energy to produce fluid flow or pressure and internal frictional losses. Volumetric efficiency relates to internal leakage and flow losses. Both of these items are affected by the fluid viscosity. These properties are inversely proportional of each other and must be balanced by proper fluid viscosity selection. As Hydro-mechanical efficiency increases, volumetric efficiency decreases and vice-versa.

High fluid viscosity at start up can result in poor system performance, lubricant starvation, and cavitation. All of this can lead to pump and system failure. Once normal operating temperatures are reached, the fluid will thin (lower viscosity) and start to leak around pump vanes and valves, reducing pressure and performance.

This really becomes evident when the ambient temperature rises above 90°F (32°C) and the fluid thins to the point it doesn’t hold pressure and the system has to shut down and cool before more work can continue, commonly known as “afternoon fade”.

Why high VI oils?

Fluids with VI (Viscosity Index) higher than 100 will thin less with temperature change and reduce leakage problems. For example:

• an ISO 46 fluid with a VI of 99 would be 46 cST at 104°F (40°C), and 25 cSt at 140°F (60°C).
• Whereas a ISO 46 fluid with a 115 VI would be 46 cSt at 104°F, it would be 35 cSt at 140° F, a significant improvement in viscosity at operating temperatures. This allows for more work to be accomplished, less down time and improved performance.

Another benefit of high VI oils

Another benefit of high VI oils is that they usually have better low temperature properties. Again taking our ISO 46 fluids:

• the low VI would have a viscosity of > 10.000 cST at 0°F (-18°C),
• whereas the high VI has a viscosity of 43000 cST at 0°F. This is a significant improvement over the lower VI fluid.

Leakage issues

One of the issues facing hydraulic systems is leakage. Federal and local environmental agencies are cracking down on leaks and spills so the need for cheap short life fluids are diminishing. Fluids are expected to last much longer under higher stress before change out. Older fluids had an oxidative life of 1000 to 3000 hours, today’s fluids are expected to last more than 6000 hours before a change out is required. A high performance fluid would contain a seal conditioner or seal swell agent to help keep hoses and seals pliable and last longer without leaks.

30% increase in efficiency

The bottom line is that a better fluid will help save time, energy, equipment, and lower overall cost of operation. Here’s where SWEPCO 703 and 704 come onto the scene, both of these products have been improved to provide premium performance and fluid life. 703 has a VI of 182 with a reduced shear for better productivity. A controlled study showed a 30% increase in efficiency. All of the 704 viscosities have a VI over 100 and a superior performance package. Both products have a UV dye for easy leak detection and tracing. The oxidative life has been extended to 8000 hours plus with LOA (Oil Analysis), and have excellent low temperature properties. Because of all this we have been building A High Performance Hydraulic Oil.

SWEPCO continues to provide products that will meet or exceed OEM requirements and provide superior performance for your equipment.

Source: SWEPCO