May 9, 2006 

'Inside Hydraulics' Newsletter

1. Fast response high-resolution water in oil monitor
2. Nailing logic element leakage
3. Supersize your fluid power knowledge
4. Content for your web site or e-zine
5. Help us spread the word
6. Tell us what you think


Fast response high-resolution water in oil monitor

Water in oil can cause rapid degradation and costly breakdowns. Damage can occur so fast that in many cases, water in oil can be a more serious threat than metal particle contamination. Water ingression can occur at any time, causing serious damage to bearings and other lubricated components without the user being aware it is happening. The EASZ-1 water in oil analyzer provides early warning of the problem so that corrective action can be taken.

EESIFLO's EASZ-1 water in oil analyzer

The EASZ-1 Water in oil monitor.

The EASZ-1 is a temperature compensated, microprocessor based, loop powered water in oil sensor that enables fast and reliable, drift fr'ee online detection and monitoring of moisture percentage or ppm. The EASZ-1 can be used for on-line moisture monitoring, as a control instrument allowing separators and oil purifiers to be started when required or as a diagnostic or preventative device protecting critical systems from premature failure.

The unit responds immediately to a change in the dielectric of the oil being monitored. The sensor is not destroyed by fr'ee water and it will continue to work in both high and low measurement ranges. Laboratory tests have shown stable measurements for moisture in oil under 100ppm (below saturation levels) with continued measurement in thousand ppm ranges - measuring fr'ee water content directly. The unit has been proven in hydraulic oil, ship fuel, diesel and aerospace applications.

Installation is simple and the EASZ-1 incorporates rugged sensor elements that stand the test of time. Accurate water in oil measurement has never been easier. For more information, or to locate your nearest EESIFLO representative, go to

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2.   Nailing logic element leakage

One of our readers wrote to me recently with the following question:

 "In one of our applications we are using NG 40 cartridge valves (sleeve, poppet and logic cover). With the valve closed and the inlet port pressurized to 315 bar, we are seeing a leakage from the outlet port in the order of half a liter per minute. Is this level of leakage acceptable?"

The first thing to consider is whether the logic element has been configured for leakless operation. If the direction of flow is from A to B this is referred to as base flow. If flow is from B to A this is know as annulus flow (see figure 1). A logic element can be configured for flow in either or both directions.

logic element flow paths

Figure 1. Logic element base and annulus flow configurations (Industrial Hydraulic Control).

To establish whether a logic element is configured for zero leakage, it is necessary to consider the direction of pressure drop across the poppet when it is closed. Consider a logic element configured for check valve function in both base and annulus flow directions. When configured as a check valve for base flow (A to B) see figure 2, the direction of pressure drop across the poppet when it is closed is from B to A. In this configuration the logic element is leakless.

logic check - base flow

Figure 2. Logic element; check valve function; base flow (Industrial Hydraulic Control).

When configured as a check valve for annulus flow (B to A) see figure 3, the direction of pressure drop across the poppet when it is closed is from A to B. In this configuration the clearance between the poppet and its sleeve results in leakage from A to B. The magnitude of this leakage may increase over time as a result of wear between the poppet and sleeve.

logic check - annulus flow

Figure 3. Logic element; check valve function; annulus flow (Industrial Hydraulic Control).

Assuming our reader's logic elements have been configured for leakless operation, other possible explanations for the leakage include:

  • damage to the poppet and/or its seat
  • degradation or damage to the elastomeric seal at the base of the sleeve
  • incorrect machining tolerance in the logic housing

In this, and all other troubleshooting situations, the first place to look for guidance is the machine's circuit diagram and your reference library. From there on, it is a logically process of elimination.

"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.   Supersize your fluid power knowledge

A really detailed understanding of fluid power components and circuits is something that few people master. But you don't have to spend a small fortune in time and money to gain this level of understanding. The Fluid Power Mother Lode effectively tackles the complex subjects of hydraulics and pneumatics, for all levels of understanding: design, operation, maintenance and troubleshooting. 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:

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