How to synchronize hydraulic cylinders|
Last week I got a call from a fluid power lecturer at a technical college in Sydney, Australia. One of the things we talked about is the apparent decline in interest in fluid power as a specialization among mechanical trades people and engineers. He told me that at his college they haven't had the necessary numbers to run an advanced hydraulics course for a couple of years. This year they managed to get the minimum requirement of 15 students, but due to a high drop-out rate, less than half that number will graduate.
I communicate with enough people around the world at various levels in this industry to know that this is not a unique situation. In fact, the story I hear is much the same everywhere.
This situation reminds me of a cartoon I saw recently. It pictures a man lying on a couch, telling his therapist: "Opportunity paged me, beeped me, linked me, mailed me and faxed me. But I was expecting it to knock!"
What's my point? KNOCK, KNOCK. If you're a mechanic, fitter, technician or engineer that's opportunity you can hear knocking. Pursue fluid power as a specialization and you'll always have as much work and as many job options as you can handle.
But don't take my word for it. Here's what Jack Bergstrom, a heavy equipment mechanic at Sharpe Equipment Inc. in Salida, Colorado wrote me recently:
"The information available from your web site and in your newsletter has
been so valuable to me it has earned me a raise!"
Anyway, rather than just sitting around and complaining about the shortage of skilled hydraulics people, I'm doing what little I can. In collaboration with my friend and colleague Marian Tumarkin, we are developing a new home-study course covering advanced hydraulics. It's designed for those who want to get skilled in this area, but don't have the time or opportunity to attend a vocational college or university.
My co-author, Dr Marian Tumarkin, has over 35 years of experience in the field of fluid power with a Ph.D. from the National Academy of Science in Moscow. He is an accomplished scholar in the field with over 50 published papers and 10 patents to his name. Marian has designed electro-hydraulic systems for Russian and Australian Air Forces and the automotive industry in Australia and America. Marian also has extensive teaching experience in Europe and Australia.
Our new self-study course and text book will be available around the middle of 2007.
In the meantime, we are publishing a series of electronic reports. These documents are
chunks of instant knowledge you can access when you need them.
The first of the series: How to Synchronize Hydraulic Cylinders is now available at:
13,000 hydraulics users can't be wrong...
Who else wants to get a LIFETIME of
hydraulics knowledge AND keep it?
Find out more...
Strange, VERY strange, but true|
In last month's newsletter, we set the scene for an unusual troubleshooting story.
If you missed it, or for a recap, it is available here.
The outcome of this story follows, as told by Doug Lien, founder and former owner of Cylinder City Inc.
"The squeal was present at all engine speeds - so flow rate / stroke speed was not an issue.
Through a process of elimination, I isolated or changed out all cylinder valves. No difference.
I then removed the cylinder from a machine and placed it on a bench. I connected the cylinder to the same new machine with quick disconnects. I removed the rod seal and under no load I stroked the cylinder and it still squealed. I then removed the piston seal and the squeal remained. So it continued to squeal with no seals installed.
I reinstalled the seals and connected the cylinder to an older machine, which was referred to as the "yard machine", while the cylinder was still on the bench. The squeal was gone! I drained the oil from the cylinder and reconnected it to the new machine -- the squeal was back! This eliminated the cylinder.
The General Manager at the OEM was still insisting that I contact my factory and get a crew of men to his plant and change out all 80 cylinders (he was what you might call a duck hunter). By now though I was confident that the cylinders were not the cause of the problem. I asked him to give me another day in order to determine the root cause.
Earlier that day I noticed two things that put me on the right trail. One was the color of the oil that was draining from the cylinder when I disassembled it. The oil looked like ivory soap. The other was a slight hissing sound when I removed the head gland from the cylinder. I knew at this point that aeration was causing the squeal.
But the challenge was trying to convince the customer's engineers. I had to prove where the air was coming from and why. So the big question was: What was different about the new model machine? Were the pumps changed? Was the design of the hydraulic tank changed in any way? How about the suction lines or suction strainer? The answer to all these questions was the same: NO.
When I had connected the cylinder to the new machine the cylinder squealed, when I connected it to the older machine it was quiet. When switching the cylinder from new machine to old machine I had made sure that the cylinder was completely drained of hydraulic fluid.
So now back to the questions. Have you changed oil viscosity, brand, supplier or formula? Again the answer was NO. I insisted that the oil was the source of air in the system and that air was causing the squeal. The oil vendor was called and he stated that to the best of his knowledge the oil was the same. I insisted that the oil vendor contact the blender to ask if the additive package had been changed. They agreed and the next morning a chemist from the oil blender was on site.
In the meantime I went to the nearest CAT dealer and got some of CAT's Anti-Chatter hydraulic oil additive. I added a quart to a machine that was squealing and within 5 minutes the squeal was gone.
Needless to say at this point all eyes turned to the oil blender and their chemist. It turned out that the formula of the oil had been changed and the amount of air-release additive had been reduced. All 80 machines had the hydraulic fluid replaced and their shipment to customers was back on schedule."
If you have a quirky or unusual hydraulics troubleshooting or maintenance-related story that you'd like to share with over 22,000 hydraulics users around the world, please send us your story at: firstname.lastname@example.org
"Brendan, Insider Secrets to Hydraulics
is a great book.
I made two mistakes:
1. Waiting so long to get it, and
2. Not having you autograph it!"
SMC Rig Repair, Casper WY
What are those couple of leaks really costing you?|
For the lowdown on the REAL cost of fluid power leaks,
read Brendan Casey's article in the July-August 2006 Issue of Machinery Lubrication magazine,
To receive a complimentary subscription to this informative magazine (US and Canada only) go to:
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