Electro-Hydraulic vs Hydraulic Component Reliability

[horsefeather]

The units I have operating (3000 psi/120 gpm) use hydraulic valves (proportion & directional)that are remotely piloted. I was going to build new equipment using the same configuration because I was not convinced that electrically controlled hydraulic valves were not as reliable. After talking with a respected Gulf Coast hydraulic expert, he assured me that the electro-hydraulic valves were every bit, if not more so, reliable as the remote hydraulically piloted type.

I'm reasonably familiar with the differences in cost and weight.

I'm reasoning that the added hydraulic circuits (remote pilot and valve pilot) increases my chances for contamination opportunity. The risk may be offset by an electrical actuator requiring an external interface seal and operation in a hostile environment.

Are there any opinions regarding reliabilty of the two designs in practical use?

 

[IceStationZebra]

I didn't want to give the impression that I am against change or electro-hydraulic valves. I spent the last 3 yrs perfecting both the hardware and software of a custom electro-hydraulic valve. You can get better control, you should have better diagnostics, and you can do things that are impossible or very difficult with hydro-mechanical systems. If it were my money that's what I would buy. And by the very fact that you are reading this means that you probably agree.

My issue is with people who do not accept change because it is change. Yes, absolutely, a multimeter is an easy tool to use. But we all know how often torque wrenches get used...

It sounds like you are determined to use electro-hydraulics. By all means go forward, after all the only constant is change . The only real issue I had was that the electro-hydraulic valves were not as tolerant of dirt compared to spool valves, so we switched to 10 micron filters.

If you have the time and some money you might consider a technology prototype. The things you learn will be invaluable as you will be dealing with a whole new set of "challenges" such as milli-amp vs. gpm non-linearity, jump-to current, tuning for valve-to-valve variance, etc. A thorough set of diagrams and diagnostic routines will go a long way to minimizing the transition.

ISZ

 

[ScottyUK]

Horsefeather,

Have a look at this little gadget:

http://us.fluke.com/usen/products/Fluke+771.htm

Not cheap but accurate and well made. I am planning to get one soon because of the obvious benefits of not breaking in to a signal loop on live plant.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[IDesignHyd]

Regarding reliability - Modern day aircraft use fly by wire which translates industrially to electro-hydraulic. Having come from the aerospace side of the hydraulic field I must say I have not heard the term debooster used in years since leaving the aerospace side. A debooster was typically used in brake systems to reduce high system utility hydraulic pressure to lower pressure higher volume to apply the multiple rotor brakes on large aircraft. Clearly as a system becomes more complex there are more things to eventually fail, however the reliability of proportional hydraulic valves and servo valves has been quite good providing you maintain an oil cleanliness that meets or exceeds the manufacturer specification.