Keller-Heartt Blog: January 2017
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The Benefits of Comprehensive Hydraulic Fluid Testing

No steadfast rule exists that can tell you when it is time to change your hydraulic oil. This depends solely on the quality of your oil, as it would be costly and wasteful to prematurely change fluid or filters that have very little contamination. A comprehensive fluid analysis, however, can give you an accurate picture.
Conventional wisdom dictates that your hydraulic oil should be tested, at the very least, quarterly. For systems that are exposed to other elements, including marine hydraulic systems, testing may be more frequent. Some operations that own their own testing kits will have an even better handle on preventative maintenance by finding contamination well before the oil needs changing, or worse, once a failure analysis is needed. While DIY testing is an excellent line of defense for your hydraulic system, additional lab testing offers an in-depth analysis of more than just contamination severity, but also the type and source of contamination.
A lab analysis can give you information on three things: degradation, wear, and contamination. This information is deduced by testing the following:

  • Additive depletion: Are anti-foaming or anti-wear additives degraded?
  • Viscosity: Have particles increased viscosity, making the oil more difficult to pump? Has the pour point changed significantly?
  • Metal wear and contamination
  • Water contamination: Is water present, causing a decrease in fluid viscosity?
  • Changes in acidity
  • Particle Count: How clean is the oil?

Spectrometric analysis for additive and trace metal content, particle isolation for particle identification, and Energy Dispersive X-Ray (EDX) analysis for exceptional contamination, are all common tests performed by laboratories that provide much more information than an in-house, portable particle counter. Though some available technology offers elemental analysis of contaminants, portable particle counters often give information limited to the number of particles and their size.

Furthermore, the analytical techniques in a lab have the added benefit of expert knowledge, and that knowledge frees up the ability to skirt costly and time-consuming employee training in your operation. The process is as simple as taking a sample while the system is operating, either from a valve on the system’s return line just before the filter, or in the midpoint of a reservoir, away from its walls and base. Once the lab receives and analyzes the sample, a thorough report will be sent back with helpful guidance and warning signs for your hydraulic system.

If the time is right to change the fluid in your hydraulic system, Keller-Heartt can help. Use the code HYD5 by January 31st to save 5% on all hydraulic fluid.

The Many Uses of Hydraulic Oil

Whether your hydraulic system is in a car, a lift, a plane, or cruise ship, there is a magical elixir of mineral oils, glycols, esters, and additives to fit the situation. Hydraulic oils are used for many mechanical purposes that include high pressure, extreme temperature, and heavy-duty applications.


Braking systems rely on hydraulic fluid to smoothly bring your car to a stop. Brake fluid, a specialized type of hydraulic fluid, has a high boiling point, which makes it more appropriate for the heat-producing function of braking a car, motorcycle, truck, and even some bikes. These hydraulic fluids are mostly made of glycol ethers or refined mineral oils.

Heavy Machinery

Bulldozers, excavators, cranes, tractors, and lifts, use hydraulic systems to create enough force to move materials and equipment. Many of these systems employ hydraulic cylinders that transfer power through the hydraulic oil between cylinders, often with the assistance of motors. When high-pressure, heavy load conditions are present, a fluid with a higher viscosity grade and anti-wear additives work the best. For plows and applications that operate in extremely cold temperatures, anti-freeze additives are also considered.


Hydraulic oils used in aviation or aerospace applications must fulfill a host of different demands, because they come into contact with a wider range of environments. A high viscosity index, low-temperature properties for high altitudes, and oxidation resistant additives make the oil more reliable for such a demanding industry. Aviation-specific oils are used for flight controls, landing gear, brakes, wing movement, and other aircraft hydraulic motors and pumps.


Boats and ships require hydraulic oils for maneuvering, and these hydraulic applications include steering systems, bow and stern thrusters, anchor windlasses, and shell doors, among others. Hydraulic oils in the marine industry are often biodegradable due to regulations and the fragile environment in which they operate. It is also necessary that these fluids are long-lasting and efficient in cold temperatures.


Non-mineral oil hydraulic fluids, especially water-glycol or phosphate ester synthetics, are suitable for moderate operations where it is dangerous to generate too much heat. Military and metal industry applications, die casting machines, and furnace hydraulic systems commonly use these oils to prevent fires.

Environmentally Friendly

In addition to the maritime industry, biodegradable oils are used in off-shore drilling, forestry, and other applications where leakage can damage the environment. These hydraulic fluids are made from vegetable oil, synthetic esters, and poly glycols. Vegetable and animal oils are nontoxic, but can be less effective and easily oxidize compared to the other water non-soluble hydraulic oils.

For all of your hydraulic needs, Keller-Heartt’s diverse catalogue of hydraulic oils will keep your system efficient and lubricated. Use the code HYD5 by January 31st for a 5% discount on Keller-Heartt hydraulic

Three Questions to Ask Before Choosing Hydraulic Fluid

Lubrication. Anti-wear. Heat transfer. Sealing. Pump efficiency. Hydraulic fluid wears many hats, but unfortunately, that hat is not one size fits all. When choosing the proper hydraulic fluid, the requirements are based on a multitude of factors including the fluid’s components and the hydraulic system itself. The first place to start is with an in-depth analysis of your hydraulic system.

What are the characteristics of my hydraulic system?

The type of hydraulic fluid that you need is dependent upon the type of hydraulic system you operate: vane, gear, or piston pumps. Unlike piston pumps, which run along an oil film, vane and gear pumps involve metal-to-metal contact. According to Hydraulics and Pneumatics, vane or gear pumps require a fluid with strong anti-wear (AW) capabilities over rust and oxidation (R & O) capabilities. Paying attention to the additives and components of the hydraulic fluid can make a great difference fulfilling these needs. 

Furthermore, take into consideration the following:
  • System speed
  • System operating temperature
  • System’s age
  • Load size
These characteristics will come in handy later when choosing a specific ISO grade.

What hydraulic fluid options do you have?

The answer to this question lies in the base stock. Is a common mineral oil-based fluid sufficient for your pump? Or, is there a possible fire hazard that makes a petroleum or mineral oil-based fluid dangerous at high operating temperatures? In this case, a flame retardant hydraulic fluid would be best. This may include a water-glycol or ester-based fluid.

Or, perhaps a biodegradable hydraulic fluid is more aligned with your environmentally-conscious operation. Hydraulic fluids that use rapeseed (canola) oil have a lesser impact on the environment, best for a setting with strong environmental restrictions.

What is the most effective viscosity index for my operation?

Remember the first question? This is where your system’s characteristics make all the difference. Start with your system’s operating temperature. Typical ISO viscosity grades include ISO 32, 46, 68, and 100 or above for particularly heavy-duty fluids. As these numbers increase, the fluid’s ability to maintain its viscosity at higher operating temperatures increases as well. Therefore, a high operating temperature may require a grade of 68 or higher. Consider, however, if a very thick lubricant is fluid enough for your system’s speed.

Don’t forget to also look at the system’s age and condition. Does your system run the same as it did five years ago? Is a certain viscosity still appropriate? Is there any contamination that may compromise viscosity, or that first requires maintenance? Your system may be more nuanced than what it would theoretically be in a new model, so it is important to choose hydraulic fluids on a case-by-case basis.

Now test it!

Of course, the best way to determine if you are correct is to test the hydraulic fluid, and this month Keller-Heart is offering a 5% discount on all hydraulic fluids. Use the code HYD5 through January 31st to take advantage of this deal.