December 7, 2004 

'Inside Hydraulics' Newsletter

1. Survey results - What's your biggest hydraulics problem?
2. Hydraulic troubleshooting 101
3. Hydraulic oil cleanliness
4. Content for your web site or e-zine
5. Help us spread the word
6. Tell us what you think


Survey results - What's your biggest hydraulics problem?

In the October Issue of Inside Hydraulics we asked you to tell us about your biggest hydraulics problem. Thank you to all our readers who completed the survey. Many of the problems raised have been covered in previous issues of our Newsletter.

Perhaps not suprisingly, external leaks featured strongly in the survey results. While the nuisance-value of leaks is well understood, their real cost is often overlooked. Those leaks you have been meaning to fix could be costing you a small fortune, this article explains why. This article explains how to achieve leak-free port, tube-end and hose-end connections, and this article presents a method for eliminating drips from 37-degree flared connections.

Overheating was another problem high on the list. This article offers some guidance on understanding and solving heat issues. Noise and vibration also featured prominently and is addressed in this article, as did water contamination of hydraulic fluid, which was covered recently in this article.

Internal leakage (wear) was another major concern. While all hydraulic components will wear out eventually, an effective maintenance program is the key to maximizing component life and minimizing operating costs. This article examines the issue of proper equipment maintenance.

In 2005, you can look forward to 'Inside Hydraulics' articles dealing with many more of the problems submitted by respondents to our survey. In the meantime, a complete list of articles from past Newsletters is available at:

2.   Hydraulic troubleshooting 101

One of our readers wrote to me recently regarding the following problem:
"We have a hydraulic system that operates two cylinders. The maintenance staff recently reported that the pump (piston-type) had failed - for reasons unknown at this time. The tank, valves and cylinders were cleaned and a replacement pump installed. The new pump is delivering a maximum pressure of 1,000 PSI and appears to be creating heat. Can you suggest some tips to find a solution to this problem?"

In any troubleshooting situation, no matter how simple or complex the hydraulic system, always start with the basics. This ensures that the obvious is never overlooked. In order for the 'obvious' to be obvious, the fundamental laws of hydraulics must be kept in mind:

  • Hydraulic pumps create flow - not pressure.
  • Resistance to flow creates pressure.
  • Flow determines actuator speed.
  • Pressure determines actuator force.
  • Fluid under pressure takes the path of least resistance.
  • When fluid moves from an area of high pressure to an area of low pressure (pressure drop) without performing useful work, heat is generated.

Theory is great, but it always makes more sense when put into practice. So let's apply these fundamentals to the above situation in a way that ensures the obvious things are not overlooked.

"The new pump is delivering a maximum pressure of 1,000 PSI..."

We know that a hydraulic pump can only produce flow, not pressure. It follows that if the pump can't get oil it can't produce flow. So check that the reservoir is filled to the correct level, the suction strainer or filter (if fitted) is not clogged, the pump intake isolation valve is fully open and the pump intake line is otherwise unrestricted.

If the pump is producing flow, then an absence of pressure indicates an absence of resistance to flow. Knowing this, and that fluid under pressure always takes the path of least resistance, the task now is to find the point at which pump flow is escaping from the circuit. If you're skilled in reading and interpreting hydraulic symbols, the system's schematic diagram (if available) can be useful in identifying possible locations.

"The new pump... appears to be creating heat."

Because heat is generated when there is a pressure drop, using an infrared thermometer to check the temperature of individual components will quickly lead us to the hottest part of the system - and the probable location of the internal leakage. Note that in a properly functioning system fitted with a piston pump, it is not unusual for the pump case to be the hottest part of the circuit.

The above checks should have taken less than 10 minutes. If nothing conclusive was revealed, I would continue the process of elimination using a flow-tester to conduct a direct pump test.


The type and variation of problems a hydraulic system can encounter are infinite. But as you can see from this example, a solid understanding of the fundamental laws of hydraulics can be applied in any situation, and is the foundation of effective troubleshooting. To learn more about hydraulic troubleshooting and develop your troubleshooting skills, click here.

"This book has the potential to save many organizations lots of m0ney. It should be on the bookshelf of every engineer, supervisor, planner and technician that deals with hydraulic equipment... it's worth its weight in gold." Find out more

Alexander (Sandy) Dunn
Plant Maintenance Resource Center

3.   Hydraulic oil cleanliness

The findings of a three-year study of 117 mobile and industrial hydraulic machines to determine the correlation between fluid cleanliness and breakdown frequency, has shown that maintaining fluid cleanliness at ISO 4406 14/11 will result in a tenfold gain in the average time between breakdowns when compared with a fluid cleanliness level of 22/19. Hydraulic Oil Cleanliness explains how hydraulic fluid contamination damages hydraulic components and outlines methods for its effective control. 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 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:

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.

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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:

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