August 16, 2011 

'Inside Hydraulics' Newsletter

1. The elephant in the room
2. How is your heat-exchanger connected?
3. Considering pump and motor efficiency
4. Content for your web site or e-zine
5. Help us spread the word
6. Tell us what you think


The elephant in the room

I suppose I could just ignore the elephant in the room. But since it's plain for all to see we may as well grab it by the trunk and talk about it: more storm clouds have appeared on the economic horizon.

Which means now is the time you want to be SMARTER and more agile than the average bear. And hydraulics SMARTS is the best way I know of to stand out from the crowd.

If you're a hydraulics professional: mechanic, technician or engineer, it means adding more strings to your bow; delivering more value to your employer; making yourself more indispensable.

Good example: last week I had a conversation with a member who is a heavy-duty fitter. He can't read a hydraulic schematic and he knows it's a weakness. But after spending 1.25 minutes on the phone with him, I established he's not willing to invest in himself to fix it. When it comes time to downsize the workforce, all other things equal, who do you think will be out the gate first? The fitter who can read and interpret a hydraulic circuit diagram or the one who can't?

If on the other hand you're an equipment owner or caretaker (i.e. you don't own it but are responsible for it) it's now more important than ever that every dollar spent on operating and maintaining your equipment is a dollar well spent. This means getting your machines running reliably and lean and getting rid of the waste.

I recently re-read a sobering case study in which the pneumatic systems of two plants where surveyed for leaks using ultrasonic leak-detection equipment. In the first, a small plant, which took two hours to survey, 27 leaks were discovered. The calculated energy cost of these leaks was $9,000 per year. In the second, a much larger plant, which took two days to survey, 260 leaks where discovered. The calculated energy cost of these leaks was over $90,000 per year!

This amount of waste should never be allowed to occur. Ever. But especially not in the current economic climate. Don't let it happen on your watch (if you have a pneumatic installation at your plant, the procedure for quantifying your leakage losses is explained in detail on page 234 of Pneumatic Control for Industrial Automation Warning: if you do this exercise, the results may SHOCK you).

If the above numbers seem too outrageous to be relevant to your situation, consider that a relatively 'minor' hydraulic oil leak can easily cost upwards of $1,000 per year when all of the costs associated with make-up oil, clean-up and disposal are properly considered. This begs the question: how many of those annoying little leaks can you get fixed for a thousand bucks--and get pay back in the first year?

The reality is, in the current climate, too many people lose their stomach, retreat indoors and shutter the windows. When in fact, the exact opposite - BOLD ACTION is required. And on this note, the raw ingenuity of some of our members is inspiring:

"Brendan, your books motivated me to build a small kidney loop filter cart - a 145 micron screen, pump, water absorbing filter and final 3 micron filter (Donaldson P550275, P565062 and P551550 respectively). A second-hand 3 GPM pump and motor drive the system.

The limiting factor is inlet vacuum at the pump which I limit to less than 5 PSI via a pressure relief valve at the pump outlet which relieves back to the intake side of the inlet filter. That routing was chosen to provide rough filtration and more heat exchange surface for the oil being recirculated within the pump.

With cold hydraulic oil this gets me a throughput of around 1 GPM which I run for several hours to get several full "passes". All very modest, but a real money saver. The alternative - annual oil changes - would cost around $450 at today's $15/gallon prices. The total cost of my self-made cart was less than that so it paid for itself in the first year... I suppose I should still change the oil every three years or so to maintain the additives and all - at that rate the cart will have reduced my oil cost to one third of what they would have been - rather satisfactory."

Is this filter cart design technically perfect? Probably not. Is it effective at cleaning and drying his oil? Almost certainly. Sure, he needs to get a bit more sophisticated and do regular oil analysis - to know for sure when the oil's additives and/or oxidative life have been used up.

But the point is, this member identified a worthwhile project (measured by return on investment) and made it happen. He didn't wait until he got his PhD in hydraulic equipment maintenance - or for some other vague circumstance to eventuate. He gathered enough information and then acted.

Fortune always favors the bold.

The Nice Things People Say ...

"The knowledge I've gained from this information has been so valuable it has earned me a raise!" Find out more ...

Jack Bergstrom
Heavy Equipment Mechanic
Sharpe Equipment

2.   How is your heat-exchanger connected?

From the appropriately named Snowy Mountains where I am at the moment, I have to pinch myself to remind me of the sweltering summer our Northern Hemisphere members (and hydraulic equipment) have been sweating through.

And heat, or more precisely overheating, is public enemy #1 of hydraulic equipment. The component we most depend on to maintain acceptable and stable operating temperatures is the heat exchanger. Unfortunately, it's often considered an 'accessory' in the system - indeed most major manufacturers even catalogue them this way. As a result, the heat exchanger is often installed as an afterthought - wherever it will fit, and plumbed up in the most convenient, rather than the most efficient way.

For example, air blast heat exchangers should be situated so that they are at least half the fan diameter clear of any obstructions on both sides of the core. I recommend connecting the exchanger so that oil flows from bottom to top, or if the tanks are on the sides, from lower connection (inlet) to upper connection (outlet). The reason for this is to purge all air from the unit quickly and fill it completely for maximum efficiency.

The other connection issue for air-blast heat exchangers, which requires attention during initial installation, relates to whether it is single or double pass. These days, many exchanger cores are designed so that they can be configured as either single or double pass. This means they have at least 3 ports - two ports in one tank and one port in the other (see diagram below). A single pass exchanger is converted to double pass by the insertion of a fully welded baffle in the middle of one of the tanks at the factory. This makes the oil flow down one half of the exchanger core, and then back up the other half.

Heat exchanger with 3 port connections

Considering the above diagram, if the exchanger is single pass (no baffle in the top tank as shown), I would connect the exchanger so that port 1 is the inlet and either port 2 or port 3 (but preferably port 3) is the outlet. HOWEVER, if the exchanger is double pass (as shown above), the correct connection is port 2 inlet; port 3 outlet (or vice versa).

Note that if the unit is double pass and the technician doing the initial installation is not on the ball, he'll likely connect the unit in such a way that port 1 is used. Doing so means that only half the exchanger is effective. That is, if connection is made using ports 1 and 2, only the left-hand side of the cooler is effective. If connection is made using ports 1 and 3, only the right-hand half of the cooler is effective. And believe it or not, I've seen this happen more than once. But it's not hard to detect this mistake - due to the large temperature variation between the two sides of the exchanger.

So the next time you're working on a hydraulic machine, take note how the cooler is installed and connected. Could the installation have been improved? And even though the probability is low that the machine has a double pass exchanger which has been connected incorrectly, use your heat gun to confirm that the temperature drop across the cooler is even.

P.S. The above is an edited extract of an article that appeared in the April 2009 issue of Hydraulics Pro Club. And to be frank, I keep all my BEST, underground intel and advice for Hydraulics Pro Club members.

If you work with hydraulics, or depend on it to earn your living, you probably should be a Hydraulics Pro Club member (if you aren't already). And to help you decide one way or the other, you can take a $1 test-drive here.

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

Alexander (Sandy) Dunn
Plant Maintenance Resource Center

3.   Considering pump and motor efficiency

In a condition-based maintenance environment, the decision to change out a hydraulic pump or motor is usually based on remaining bearing life or deteriorating efficiency, whichever occurs first.

Despite recent advances in predictive maintenance technologies, a maintenance professionalís ability to determine the remaining bearing life of a pump or motor, with a high degree of accuracy, remains elusive... read the full article here.

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 20 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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