Learn hydraulic fluid fundamentals

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Service truck professionals are no strangers to hydraulic fluids – they’re vital elements of the industry’s varied pumping and lifting applications. So it’s an advantage to truly understand hydraulic fluid and its properties on a deep level, beyond just memorizing handling and maintenance instructions.

Attendees at ConExpo-Con/Agg 2020 in Las Vegas this March will have an opportunity to learn from an authority on the topic when Paul Michael, research chemist at the Milwaukee School of Engineering Fluid Power Institute, presents “Hydraulic Fluid Properties, Efficiency and Contamination Control.” The session is among the educational programs of the International Fluid Power Expo taking place in conjunction with ConExpo at the Las Vegas Convention Center.

Michael has spent over 40 years formulating and testing lubricants. He is also active on

standards committees with the American Society for Testing Materials (ASTM), International Organization for Standardization (ISO), and National Fire Protection Association (NFPA). And he has been a principle investigator for energy efficient hydraulic fluids at the Center for Compact and Efficient Fluid Power.

In an interview with Service Truck Magazine, Michael said attendees at the ConExpo session will gain a fundamental understanding of the characteristics and functions of hydraulic fluids, how to evaluate the condition of the fluid, how to make decisions regarding maintenance intervals and what maintenance strategies should be implemented to prevent and combat oxidation, contamination and other forms of fluid degradation.

Cost-savings potential

One key factor that Michael identifies is the longer lifetime and performance of oils and fluids today. Technology has allowed for a longer life and an extended drain interval.

“There’s a potential for savings for those people that either are trying to maintain the equipment or if they’re trying to sell the equipment to their customers as a product that has a low total cost of operation,” Michael said. “If you can reduce the amount of oil changes required over the life of your machine, your total cost of operation goes down significantly.”

The session will also delve into the different types of hydraulic fluid out there, including multi-grade, synthetic, biologic, bio-degradable and even fire-resistant fluids, as well as their ideal applications. Each fluid type is best suited to certain types of operations. Fire-resistant fluid, for example, is used where ignition is possible because of high-pressure oil being ejected from a system and creating a mist with a large surface-area-to-volume ratio.

“It’s kind of like fuel injectors,” Michael said. “They’re basically trying to inject high pressure gasoline or diesel and make very tiny droplets so that when they encounter oxygen and either compression or spark, they instantaneously ignite. The same thing can happen with hydraulic fluids.”

Similarly, there are a variety of different filter options, which are also best suited to specific applications. As Michael noted, it’s very important to have the right application in mind for the filter.

“There’s technology for filter selection that describes the efficiency of the filter elements in removing particles of a given size,” Michael said.

About the beta ratio

The term usually used to describe that is the beta ratio — the ratio of the number of particles going into a part of a filter at a given size compared with the numbers passing through in a multipath filter test, he said. This beta ratio provides the consumer with a methodology for comparing filter performance and making decisions about the appropriate filter for an application.

“So we’ll talk about beta ratios, the multipath filter tests, as well as what types of filters are appropriate for different applications, be they kidney loop, high pressure, return line filters or suction filters,” Michael said.

At the 2017 ConExpo-Con/Agg, Mike Vorster of CEMP Central, argued that every fleet should have a “fluid czar,” who would be the supreme authority at the company for all oil and fluid related issues. In the absence of such an authority, Michael said, it can be very difficult for those who are on the floor, implementing maintenance practices and working as mechanics, to get an in-depth understanding of hydraulic fluids that go beyond the conventional wisdom and common sense.

“My background, I’m kind of a scientist here,” Michael said. “My experience is that common sense can actually lead you to the wrong conclusion many times if you make a lot of assumptions. One of them would be the desire to have better performance by changing the oil more frequently. That seems like it’s common sense but actually that’s not true. I think that understanding more of the science behind lubrication is helpful when making decisions about your lubricant maintenance plans and investments.”

A newer avenue that Michael finds extremely interesting is the development of energy efficient hydraulic fluids. These fluids can cause the pump to create more flow with less leakage and less input energy requirements, which improves productivity and reduces battery drain.

Fluids and EVs

“So in the electric vehicle segment, while the battery is used for operating propulsion and many of the other features in the truck, the lift system is still hydraulic because of the inherent benefits of hydraulic to linear actuation,” Michael said. “If you want to get the most hours out of your battery as possible before recharging, it’s beneficial to have a highly efficient hydraulic system and hydraulic fluid that complements it.”

Michael hopes attendees will take away from his presentation a deeper understanding of the fundamentals of hydraulic fluid as well as an appreciation that not all lubricants are alike.

“Engine oils and automatic transmission fluid make very poor hydraulic fluids,” Michael said. “There’s a reason for that. I would like them to understand the differences between fluids, why all lubricants are not alike and why it’s beneficial to have hydraulic fluid that is optimized for their specific application.”

Michael noted, however, that he will speak extensively about engine oils, as they are a valuable comparison point for the audience in attendance. He will also provide background on engine oils and how they are formulated, and then explain how hydraulic fluids are different.

All about accessibility

“Most people that are going to be in this audience are interested in engine oils, whereas I think the general public just doesn’t want that light to come on (the dashboard),” Michael said. “I’ll be talking about engine oils and using that as a basis for explaining how hydraulic fluids will function. I try to make the whole presentation really accessible to the audience participants. I’m not going to be talking about molecules very much.”

“Hydraulic Fluid Properties, Efficiency and Contamination Control” will be presented on March 10, 8 a.m.-noon, at the Las Vegas Convention Center’s Westgate Ballroom E-F.

For more information, visit www.ifpe.com.

—Matt Jones

Matt Jones is a freelance writer based in Fredericton, N.B.