October 19, 2004 

'Inside Hydraulics' Newsletter
http://www.hydraulicsupermarket.com


IN THIS ISSUE
1. What's your biggest hydraulics problem?
2. Dealing with water in hydraulic fluid
3. Advanced hydraulics troubleshooting
4. Content for your web site or e-zine
5. Help us spread the word
6. Tell us what you think

1.

What's your biggest hydraulics problem?

Readers who tell us about their hydraulic problems inspire many of the articles published in our Inside Hydraulics newsletter. So that we can continue to deliver editorial that is informative and interesting to you, our readers, we are asking for your help.

To assist us in providing you with future Newsletters that are relevant to your interests, please go to this page and answer one question: What is your biggest hydraulics problem?


2.   Dealing with water in hydraulic fluid

If you have worked with hydraulic equipment for any length of time, it's likely that you've come across a hydraulic system with cloudy oil. Oil becomes cloudy when it is contaminated with water above its saturation level. The saturation level is the amount of water that can dissolve in the oil's molecular chemistry and is typically 200 - 300 ppm at 68°F (20°C) for mineral hydraulic oil. Note that if hydraulic oil is cloudy it indicates that a minimum of 200 - 300 ppm of water is present. I recently audited a hydraulic system with cloudy oil that was found to contain greater than 1% (10,000 ppm) water.

Why is water in hydraulic fluid bad?

Water in hydraulic fluid:

  • Depletes some additives and reacts with others to form corrosive by-products which attack some metals.
  • Reduces lubricant film-strength, which leaves critical surfaces vulnerable to wear and corrosion.
  • Reduces filterability and clogs filters.
  • Increases air entrainment ability.
  • Increases the likelihood of cavitation occurring.

How much water is too much?

A number of factors need to be considered when selecting water contamination targets, including the type of hydraulic system and reliability objectives for the equipment. It's always wise to control water contamination at the lowest levels that can reasonably be achieved, ideally below the oil's saturation point at operating temperature.

Water removal methods

Methods for removing free (unstable suspension) and emulsified (stable suspension) water include:

  • polymeric filters;
  • vacuum distillation; and
  • headspace dehumidification.
Vacuum distillation and headspace dehumidification also remove dissolved water.

Polymeric filters - These look like conventional particulate filters, however the media is impregnated with a super-absorbent polymer. Water causes the polymer to swell, which traps the water within the media. Polymeric filters are best suited for removing small volumes of water and/or maintaining water contamination within pre-determined limits.

Vacuum distillation - This technique employs a combination of heat and vacuum. At 25 inches Hg, water boils at 133°F (56°C). This enables water to be removed at a temperature that does not damage the oil or its additives.

Headspace dehumidification - This method involves circulating and dehumidifying air from the reservoir headspace. Water in the oil migrates to the dry air in the headspace and is eventually removed by the dehumidifier.

In the case of small systems with high levels of water contamination, changing the oil may be more cost-effective than using any of the above methods of water removal.

Prevention is better than cure

Like all other forms of contamination, preventing water ingress is cheaper than removing it from the oil. A major point of water ingression is through the reservoir headspace. Many hydraulic system reservoirs are fitted with breather caps that allow moisture (and particles) to enter the reservoir as the fluid volume changes through either thermal expansion and contraction, or the actuation of cylinders.

Replacing the standard breather cap with a hygroscopic breather will eliminate the ingression of moisture and particles through the reservoir's vent. These breathers combine a woven-polyester media that filters particles as small as 3 microns, with silica gel desiccant to remove water vapor from incoming air. The result is relative humidity levels within the reservoir headspace that make condensation unlikely, therefore reducing water contamination of the oil. For a demonstration of how a hygroscopic breather works go to: http://www.hydraulicsupermarket.com/hygroscopic


"Thanks for the great work on the two publications, Insider Secrets to Hydraulics and Preventing Hydraulic Failures. I have been in the hydraulics business for the past 20 years and it is very difficult to find any decent material on hydraulic maintenance, troubleshooting and failure analysis. These two books cover it all in easy to understand language... I conduct hydraulic training courses and plan to purchase copies to distribute to my students to share your practical approach to understanding a not so understandable subject."

Paul W. Craven, Certified Fluid Power Specialist
Motion Industries, Inc.


3.   Advanced hydraulics troubleshooting

'Advanced Hydraulics Troubleshooting' covers four case studies representing the most common types of hydraulic service calls technicians encounter on hydraulically powered equipment. The viewer is challenged to develop their own diagnosis before the cause of each problem is explained. Common mistakes technicians make when diagnosing hydraulic problems are illustrated along with procedures for avoiding these costly errors. Find out more


4. Content for your web site or e-zine

Need some fresh content for your web site or e-zine? You now have permission to reprint these 'Inside Hydraulics' articles on your web site or in your e-zine, provided:

1. Each article is printed in its full form with no changes.

2. You send an e-mail to editor@hydraulicsupermarket.com to advise us where you'll be publishing them.

3. You include the following acknowledgement at the end of each article:
About the Author: Brendan Casey has more than 16 years experience in the maintenance, repair and overhaul of mobile and industrial hydraulic equipment. For more information on reducing the operating cost and increasing the uptime of your hydraulic equipment, visit his web site: http://www.InsiderSecretsToHydraulics.com


5. Help us spread the word

If you've found our 'Inside Hydraulics' newsletter interesting and informative, then chances are you have a colleague who would too. Help spread the word about 'Inside Hydraulics' by forwarding this issue to a colleague. If they share your interest in hydraulics, then they will surely appreciate being told about this newsletter.

New subscribers can get the newsletter by completing the form at http://www.insidersecretstohydraulics.com


6. Tell us what you think

We would love to hear what you think of this issue of our 'Inside Hydraulics' newsletter. And of course, if you have any suggestions for future issues, please send us those too.

Just e-mail the editor at: newslettersuggestions@hydraulicsupermarket.com

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