May 6, 2008 

'Inside Hydraulics' Newsletter

1. Why a little hydraulics knowledge is dangerous
2. Are you sure it's broken? Then don't fix it
3. Four diagnostic tests you should know
4. Content for your web site or e-zine
5. Help us spread the word
6. Tell us what you think


Why a little hydraulics knowledge is dangerous

This comment from a concerned member arrived in my inbox a few weeks ago:

"I read your comments with morbid interest and feel that you trivialise the hydraulics profession by indicating to interested party's that they should "get involved" in dealing with their hydraulics themselves. You wouldn't get away with it in a legislated business such as electrics."

Hmmm…. to set the record straight and so the 1500 new members reading this newsletter every month don't pick up the wrong end of the stick, I've decide to address this here and clarify what I'm about.

Contrary to this new member's inference, I'm NOT in the business of encouraging people to fiddle with hydraulics when they don't know what they're doing. In fact at the beginning of Insider Secrets to Hydraulics, I warn loud and clear:

Do not make modifications, repairs or adjustments to any hydraulic system unless you are competent or working under competent supervision. If in doubt, consult a qualified technician or engineer.

Further, as I've stated in this newsletter before, I think regulation of the hydraulics profession in a similar way to electricians - to prevent people without adequate knowledge from fiddlin' would, overall, be a good thing.

No, the main reason I publish this newsletter and write articles for half a dozen or so industry magazines is to move people from the first stage of learning to (at least) the second. The first stage of learning about any subject is often referred to as unconscious incompetence (or uninformed ignorance) - meaning we aren't even aware of what we don't know. The second stage is conscious incompetence (informed ignorance) - we're at least aware of what we don't know.

For example, in nanotechnology I fall into the uninformed ignorance category. I haven't the foggiest idea what I don't know about the subject. But if I were to surf websites, subscribe to an industry newsletter and begin reading articles and books on the subject, I would quickly gain awareness of the body of knowledge about which I know very little. At that point I've moved from uninformed ignorance to informed ignorance.

If I were to become fascinated by nanotechnology or aware of the economic benefits of acquiring more knowledge in the field, further concentrated learning would lead eventually to unconscious competence - the final stage of learning. Once at this point, I could very likely design or modify a nano-device in my head while driving to work.

But whether your thing is nanotechnology, hydraulics or anything else, I'm a big advocate of life-long learning. When I visit friends in their home, I can generally tell the ones who've reach their vertical limit of success by the size of their library relative to their TV. A big TV and small library is a good indication they've stopped learning. And if you stop learning you stop earning. Most people who visit me at home remark on the amount of books we have - in just about every room of the house.

Only last week I read about William Gladstone, a British politician who was reputed to have read 20,000 books during his lifetime. He was elected Prime Minister four times. Reading is definitely a valuable habit to cultivate. And it's a cheap and effective form of self-education.

But self-education requires self-reliance and independence - two character traits which are rarer than you might think. You should see some of the questions I receive from members.

It's not the asking of a question that annoys me, it's the type of questions some members ask. Questions they could easily answer themselves by doing a bit of research - often less than 10 minutes worth, with the help of google. Others may require investment in a book, DVD or other resource to get the answer. But the quality of the information you get is generally proportional to what you pay for it.

Asking dumb questions or expecting solutions on a platter only demonstrates a lack of independence. My six-year-old CAN wipe his own ass, though he PREFERS to have his mother do it for him. But he's smart enough not to ask me to do it. Maybe it's a pride thing. I would never ask a mentor or peer a question without trying real hard to figure out the answer for myself first.

I see the apparent growth of thumb-sucking dependency in the developed world as good news for us self-reliant, independent types. It means more options, more opportunities and makes it much easier to stand out from the crowd.

The Nice Things People Say …

"If more hydraulics users had this information - us manufacturers would have less problems!" Find out more ...

Phil Serre
International Director of Training

2.   Are you sure it's broken? Then don't fix it

Speaking about questions I get from members, there's a very valuable lesson in this one:

"We have some problems with a Denison transmission pump P24S 2R1C 9A2. Oil temperature rises from 20 to 50 Celsius within 15-20 minutes of only light operation (65 bar working pressure). The pump was sent to a local workshop for repair and cost us US10,000 dollars and yet the problem remains. The repair shop sent an engineer to investigate but he couldn't solve it?"

So the pump wasn't the cause of the problem. Ouch! An expensive mistake. And one I've seen made all too often by hydraulic equipment users. But is there really a problem here at all?

Oil temperature is rising to 50 Celsius within 20 minutes of operation. No big deal. Since this member is from Singapore, I would expect him to be using a VG68 hydraulic oil. Depending on the viscosity index of the particular oil he's using, optimum operating viscosity is achieved between 55 and 78 Celsius. So after 20 minutes, the system isn't even at operating temperature. Of itself, no cause for alarm.

But why does this system heat up so fast? Well this is a big transmission pump - 24 cubic inches or 400 cubic centimeters per rev. So it will have a big charge pump. As big as 4.8 cubic inches or 80 cubic centimeters per rev. If these pumps are turning at 1500 rpm and charge pressure is set at 23 bar, the charge pump is generating 4600 watts of pure heat load. That's equivalent to the power of two electric kettles.

And being a hydrostatic transmission, it won't have a large reservoir - perhaps as small as half the available charge pump flow per minute. Which in this case, could be as little as 16 gallons or 60 liters. So the transmission's inbuilt heating element, a.k.a charge pump, will soon warm up this volume of oil - even with the transmission in neutral.

Based on my long experience in the hydraulics biz, the whole issue of efficiency, heat-load and cooling - and its inter-relationship with viscosity and lubrication, is grossly misunderstood by hydraulic equipment users. And as the above example illustrates, it can get them into a heap of trouble.

Which is why during the Breakdown Prevention seminars I presented last year, I spent nearly half a day dealing with this whole issue. You can watch a short video clip of it, where I explain why the charge pump in a hydrostatic transmission is pure heat load - and the reason why this member blew 10,000 dollars on an unnecessary pump overhaul. Watch the video here.

"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's 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.   Four diagnostic tests you should know

Fundamentals of Hydraulics and Troubleshooting explains when and how to use diagnostic tests, including the direct pump test, system T test, spool valve leakage test and cylinder piston seal leakage test - all from the convenience of your lap top or desk top computer. 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 19 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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