Hydraulic fluid is the lifeblood of your hydraulic system, whether it's in your skid steer loader or a massive hydraulic shovel. In this Shop Talk Blog post, we are going to look at some interesting facts about hydraulic fluid, including its origins and the importance of proper disposal.

Here are some other blog posts on the subject of hydraulic fluid ...

• Hydraulic Fluid: Just the Facts
• Should I Change or Flush My Hydraulic Fluid?
• Common Hydraulic Fluid Issues

Hydraulic Fluid in Space

The NASA space shuttle has a powerful hydraulic system that handles various aspects of the shuttle’s flight control, including positioning of aerosurfaces, landing gear deployment, nose wheel steering. This system uses MIL-H-83283 synthetic hydrocarbon fluid, chosen primarily because of its ability to reduce fire hazards. (Extra bit of trivia: the main hydraulic pump on the shuttle operates at 3,900 rpm).

From Water to Mineral Oil

The use of hydraulic fluid dates back to the time of ancient Egypt and it probably won’t surprise you that water was the first type of hydraulic fluid. Water continued to be used through the Industrial Age. It was not until the 1920s that mineral oil began to replace water, and this occurred for three major reasons: mineral oil boils at a higher temperature than water, which greatly extended its usefulness; it is not corrosive to iron and steel parts; and it serves as a lubricant, which water is not good at. Mineral oil is also denser than water, which meant it can handle heavier loads. However, water-based hydraulic fluids for certain applications.

Origins of Petroleum-based Oils

Mineral oil as a hydraulic fluid evolved into our modern petroleum-based oils. The term “petroleum-based” signifies that the base stock of the hydraulic fluid is petroleum. As the science and engineering behind hydraulic fluids advanced, additives were added to the base stocks to create various specialized hydraulic fluids.

Biodegradable Hydraulic Fluids

One of the problems with hydraulic fluid is the damage that it can do to the environment if it is spilled. This can be a major problem when it comes to hydraulic powered equipment working in environmentally sensitive applications such as marine dredging or agriculture.

To mitigate damage from an oil spill in equipment used for such applications, manufacturers have begun designing the hydraulic systems that use biodegradable hydraulic fluids. These include vegetable or animal oils that are water-insoluble, such as rapeseed, sunflower, and soybean oils.

The Duke Hydraulic Fluid Incident

In 2005, an incident at two community hospitals in the Duke University Health System occurred: surgical tools were inadvertently washed in hydraulic fluid instead of detergent. As it turned out, the mixup occurred because elevator company workers had drained hydraulic fluid from the elevator system into some empty detergent containers. There were an estimated 3,800 patients affected. This is a good example of the importance of proper disposal procedures for hydraulic fluids.

Conclusion

Hydraulic fluid -- both its history and the science behind it -- can be utterly fascinating. Are there any interesting facts that you’ve discovered? Share them in the comments!