Hydraulic Fluid Temperature

High hydraulic fluid temperature - how it causes premature failures

I was asked recently to conduct failure analysis on two radial piston hydraulic motors that had failed well short of their expected service life. Inspection revealed that the motors had failed through inadequate lubrication, as a result of low fluid viscosity caused by excessive hydraulic fluid temperature.

How does this happen?

As the temperature of petroleum-based hydraulic fluid increases, its viscosity decreases. If fluid temperature increases to the point where viscosity falls below the level required to maintain a lubricating film between the internal parts of the component, damage will result.

The temperature at which this occurs depends on the viscosity grade of the fluid in the system. Hydraulic fluid temperatures above 180?F (82?C) damage seals and reduce the service life of the fluid. But depending on the grade of fluid, viscosity can fall to critical levels well below this temperature.

How can this type of failure be prevented?

The above example highlights the importance of not allowing fluid temperature to exceed the point at which viscosity falls below the optimum level for the system's components.

Continuing to operate a hydraulic system when the fluid is over-temperature is similar to operating an internal-combustion engine with high coolant temperature. Damage is pretty much guaranteed.

Therefore, whenever a hydraulic system starts to overheat, shut down the system, find the cause of the problem and fix it!

Editor's note: for more information on hydraulic failures and how to prevent them, read Preventing Hydraulic Failures.

If you enjoyed this article, you'll love Brendan Casey's Inside Hydraulics newsletter. It gives you real-life, how-to-do-it, nuts-and-bolts, hydraulics know-how ? information you can use today. Listen to what a few of his subscribers have to say:

Can't Put It Down
?I get magazines and e-mails like this all the time. I never find time to read them. I decided to read Issue #30 and I couldn't put it down. I'll make time from now on.?

Richard A. Shade, CFPS
Project Engineer (Hydraulic Design)
JLG Industries Inc.

So Valuable It Earned Me A Raise
?The knowledge I've gained from this newsletter has been so valuable it has earned me a raise!?

Jack Bergstrom
Heavy Equipment Mechanic
Sharpe Equipment Inc.

Love It - Keep Them Coming
?I just love this newsletter. As a Hydraulics Instructor for Eaton, I make copies and distribute them to my students as I address various topics... Keep 'em coming.?

Michael S Lawrence
Hydraulics Instructor
Eaton Hydraulics Inc.

Here's a sample of what's covered in this powerful newsletter: troubleshooting, contamination control, component repair and testing, preventative maintenance, failure analysis, and much, much more!

To get a FREE subscription to the Inside Hydraulics newsletter, fill out this form - don't forget to capitalize the first letter of your name - and hit 'SUBSCRIBE NOW!'

First Name *
Email *

This is a private mailing list that will never be sold or given away for any reason.
You can also unsubscribe at anytime.


Copyright © 2002 - 2013 Brendan Casey; Insider Secrets to Hydraulics