There seems to be a lot of pent-up frustration lately about fluid power’s future and how we should be training our people. We’ve had a pretty serious discussion on all of this at our Fluid Power Forums. I’ve also received some emails on the topic and seen similar threads elsewhere on the Internet.

One of the basic questions is: Will we ever truly have “Fluid Power Engineers?” Is it enough to simply give someone a week-long class or two and proclaim them the company’s fluid power expert? We can’t continue this way and keep fluid power growing.
A recent quick poll conducted on our website asked the question, “What’s the primary way that you learned about fluid power?” The responses were as follows:

* On the job/from co-workers: 34%
* Reading up on it myself: 27%
* Short courses/seminars: 11%
* In college: 28%

Do you find it a concern that so little of our technology is really taught at the university level? I certainly do. Some sort of industrial fluid power degree is really the only sensible solution. In this age of increased electrical control and integrated systems that encompass fluid power, mechanical systems, and electrical devices, fluid power stands a chance of getting lost in the mix. How can we continue to treat fluid power as an add-on to a mechanical engineering degree, or something that can simply be picked up on the job?

A concerned reader recently pointed me to a post on a fluid power site. There, someone had asked how they could learn more about fluid power. The majority of the response was that the person should contact their component supplier, basically passing the buck. Is that sound advice, letting someone else worry about the technical details of your system? It’s the ultimate in outsourcing, and a sorry habit that far too many companies have fallen into.

So, what should be done? I’d like to see the Fluid Power Society, NFPA, and the universities from the new NSF-funded Engineering Research Center form a study group to push for a new fluid power degree at the university level — I’ll certainly volunteer my time to the cause, too.

We have a starting point in the one-week classes that some universities and manufacturers provide, not to mention the fluid power certification classes and exams already offered. I think we need users, OEMs, component manufacturers, and educators all to get together and figure out a solution that best serves our industry.

Do you agree? Disagree? Is there a better solution, or is all of this impossible to achieve? Let me know what you think, so we can start a dialogue on the future direction of fluid power.

Paul J. Heney
senior editor
pheney@penton.com

Would this be a degree in guessing or engineering?

There doesn't need to be a separate degree. for engineers. There should be a 1 term 4 hour course though as part of a mechanical engineering or mechatronics degree. This class should be taught the junior year after the student has had differential equations.

If you think about there is only few equations that govern how an actuator will move.

To calculate position one integrates velocity.
To calculate velocity one integrates acceleration.
To calculate the acceleration one calculates the net force on the actuator and divides by the mass.
To calculate the net force one needs to to calculate any force necessary to over come gravity and frictional forces. One all needs to calculate the differential force across the piston.
To calculate the differential force across the piston one needs to calculate the pressure on each side of the piston.
The pressure on either side of the piston will change using the general formula

delta P = Bulk Modulus of Oil * delta volume/volume.

delta volume is determine by flow and how fast the piston is moving. The volume is also changing as the piston moves.

Flow is given by a how far the spool is open times flow constant times the square root of the pressure drop across the spool land. What makes this tricky is that the supply pressure and the pressure in the cylinder is alway changing.

The spool position is controlled by the controller but the spool position doesn't respond instantly. The response is different from valve to valve. This information is difficult if not impossible to obtain unless one has their own lab.

The valve flow constant isn't alway linear either. Again this information is difficult or impossible to obtain.

Going back to the pressure drop across the valve. It is easy enough to calculate the supply pressure if one knows the pre-charge pressure and the steady state system pressure. Then one can calculate the net flow into and out of the accumulator to adjust the gas volume and the pressure.

What about the pressure drop across the poppet valve in a bladder accumulator. Where do I find that information?

To calculate the net flow into and out of the accumulator one needs to know the flow from the pump. This is easy if the pump is a fixed displacement pump but one still needs to know how the flow changes on a millisecond to millisecond basis or finer. One should be able to know about the flow ripple from the pump. This instantaneous flow information is also not available. It is harder yet when the pump is a variable displacement pump and one doesn't know how the swash plate will move as a function of the pressure changes.

In other words, why bother with an engineering degree when one must guesstimate about how the components work? The math and the physics are easy IF one had accurate data on flow constants, pump response, losses through tubing etc. The OEMs don't know how their own equipment works and they wonder why the industry is leaking applications. An engineer can't design without the having some accurate data about the valve, pumps, cylinders and piping he is using. Servo motor manufacturer are very good about supplying information about rotational inertia, torque/amp etc. One can design servo motor systems because one has accurate data on how the motor will work.

So now you tell me how there can be a hydraulics degree when even if you could do the math there are no valid numbers to stick in the formulas.
This also requires more math than just adding a gear box or drive shaft to get energy from on point to another.

BTW, one sticks all these equations in a loop and solves the system of non-linear differential equations in small 100 microsecond or even 10 microsecond increments. It takes only a few seconds to run a simulation.

Ask me again when the OEMs start providing specifications that mean something.

Then there is the other 98% of Fluid Power to be considered also Peter.

The mundane everyday circuits that cause so much trouble because halfway works so why worry about doing it right.

The circuits that are being replaced by any and every other way of doing the job by TRAINED persons who understand the discipline they are TRAINED to implement.

In your primary field of Proportional and Servo valve applications, How would youu like to see an M.E. be responsible for designing these circuits once every two to three years???? Do you think they would be proficient????

And, once every two to three years is not unusual in my part of the country it is the norm. Even Bang-Bang circuits do'nt come up real often at most companies.

However, as you point out, most companies cannot afford to hire a full time Fluid Power expert so what is the next best approach?

Depending on he Fluid Power Distributor works most of the time but can be far from best in a lot of applications. Who trains them to design Fluid Power circuits? Who checks their design and choice of components?

Did you notice the answers to the poll on where people learned about how to implement Fluid Power? Pretty scary to me for one and probably s to many.

At last these forums are pointing out some problem areas, so there might be an answer to what I call a Dilemna in the future.

quote:

Originally posted by Bud T:
Then there is the other 98% of Fluid Power to be considered also Peter.

But you don't need a engineering degree to do that. A trade school or apprenticeship program will do.

Peter wrote;

quote:

But you don't need a engineering degree to do that. (Design Bang-Bang Circuits?) A trade school or apprenticeship program will do

That is exactly how Fluid Power has been handled for all its life and you can see where that has led!!!!!

Bud, I think you have too dim a view of hydraulic knowledge in general. You know I sell hydraulic motion controllers. We have seen our business grow a lot over that last 10 years. You just don't see it because you don't get involved with hydraulic servo control. I will soon be going to Ireland to help setup and tune 63 hydraulic actuators and 6 servo motors. That is a lot of motion control. Someone had to design those systems and some hydraulic distributor got a nice order. The company that is installing these actuators has at least three people that are dedicated to the design and installation of the hydraulics. Just because you don't see them doesn't mean they don't exist. They are out there. There isn't enough but there are more than you think.

Like you, I have been trying spread the word too but my message is about how one can move more mass faster and more accurately. It is about
servo valves, cylinder sizing and accumulator sizing. It doesn't include counter balance, bang-bang or sequence valves etc.

Earlier in January we got an order for 30 controllers. These can control 60 actuators with differential pressure feedback as well as position feedback. This system is going to test wooden frames for load bearing and earth quake properties. One isn't going to use bang-bang valves for that so you will not see it. Also, a major hydraulic OEM is doing all the design.

To be honest, I think that the major OEMs ( Parker, Bosch, Vicker, Atos, HR Textron etc ) could get by with just one hydraulic engineer that can design the really difficult systems and support the distributors. This one engineer would be able to model the system using the math techniques I described above. There are hydraulic simulation packages that do this already. We use 20Sim. It cost us about $3500.
We also have a few engineers that can use this software. There may be better hydraulic simulation packages out there.

Bud, I think the hydraulic world is getting more hi tech and you don't see it. You just see the log splitter and back hoe posts by the individuals that are clueless.

If permitted I would like to have start thread r even an new section called success stories. These would be show off successful hydraulic installations. They should include pictures, movies and and customer testimonials and be like application notes. The current forums is dreary. The only people that post have problems. I have lots of success stories. Otherwise I/we would have been out of business long ago instead of growing.

Now how do I post pictures and movies here?

Peter, I can tell you how to do pictures, like I did on one of my threads, first thing to do is get a free account at a image hosting site I use photobucket.com they claim to have free video hosting also, haven't done that yet.
The success stories forum sounds like a good idea, get a hold of the forum owner and ask if they will set it up.

Peter, I think the success stories idea is a great one. Why don't we start it off as a topic in the System Design subforum ... if there is enough interest/posting there, we can certainly create a whole new subforum for that, a little bit down the proverbial road.

To post pictures, when you're typing in the window that pops up for new posts or replies, there is a hotlink that says, "Add Attachment?" right below the window for your text. I believe you can only add PDFs, jpegs, and maybe word files. For videos, you'd need to put them on your own site and put a link in your message.

Also, for some odd reason, this forum program only allows you to post one image per post. So, if you've got 5 pictures, you'll need to add the first picture, and then do 4 replies to yourself, each with a photo. Annoying, I know, but they tell me that's just the way this is set up!

Peter and Paul, there is also a image link button in the reply window toolbar, first from the left it is right next to the envelope (email address) button.

Peter wrote;

quote:

The company that is installing these actuators has at least three people that are dedicated to the design and installation of the hydraulics.

Well and good for the installer, how about the end user? Who in the end user company will maintain or if necessary upgrade the controllers and what they control????

"The company that is installing these actuators has at least three people that are dedicated to the design and installation of the hydraulics. They are out there. There isn't enough but there are more than you think."

I undestand the OEM's often have Fluid Power Engineers but they are busy with new equipment not taki=king care of problems in the End Users plant. However several OEM's in my area do not have on staff Fluid Power persons.

"To be honest, I think that the major OEMs ( Parker, Bosch, Vicker, Atos, HR Textron etc ) could get by with just one hydraulic engineer that can design the really difficult systems and support the distributors. This one engineer would be able to model the system using the math techniques I described above. There are hydraulic simulation packages that do this already. We use 20Sim. It cost us about $3500."

They have engineers on staff already but that is a poor fix for the real problem. owever, I don't think the manufacturers will be pushing for End User Fluid Power Engineers either.

"Bud, I think the hydraulic world is getting more hi tech and you don't see it. You just see the log splitter and back hoe posts by the individuals that are clueless."

I agree some are but the vast majority are "clueless" as you say. That is evident by the post' you mention and the lack of post's from End Users of Fluid Power equipment.

On the "Suess Story" thing, MAKE SURE TH COMPANY YOU DESIGNED THe CIrCUIT FOR IS AWARE AND WILLING TO HAVE THEIR PROPRIETARY EQUIPMENT SPREAD OVER THE INTERET. I have found many companies to be less than excited about their grand ideas being touted for their competitors to see. Even if it is your design I believe you can get into hot water if the End User wants to take you on. I have been given an OK on only a few of these type circuits for articles in the past.

Someone in Japan is taking hydraulics seriously. What the blogger is representing is a linear version of a system of differential equations.

Just click on the links and look at the diagrams unless you can read Japanese.

http://servomaster.sblo.jp/

Interesting site Peter. I know it means a lot to you, However, on 99.9% of the circuits I'm involved with it will never be of use.

If or when I get into one of these circuits you or someone with your expertise will be the second one to know about. I am not the least bit bothered when I have to tell a customer I don't know but I know someone who can do the work.

On another note check out my next post that follows along the way this thread started.

Would you believe a PHD In Fluid Power??????

I received an email from a person in Italy who noted he has one.

Maybe the EU has realized something the States are behind on.

I've asked him to weigh in on this forum if he was willing, and to offer feedback on the programs there.

quote:

Originally posted by Bud T:
Interesting site Peter. I know it means a lot to you, However, on 99.9% of the circuits I'm involved with it will never be of use.

That maybe so but I can't say that about mine. Obviously others think it is important. I know the physics approach to hydraulics is a lot different from what you are familiar with.

Hello Paul,

My opinion is that accredited engineering colleges and universities should offer a fluid power engineering option to their mechanical and aeronautical engineering,bacheior of science degrees. The option should include fluid power system design and application along with electrical control system design commonly used in fluid power circuits. The courses should be more hardware orientated rather than theorical.

Most engineering colleges and universities offer their mechanical engineerung students specialty options in the senior year such
as machine or mechanical design, process piping design, vibration/noise engineering to name but a few. Fluid power design and application should be offered as one the engineering options.

Eugene F. Lucas
glucas16@sbcglobal.nnet