Difference in performance and reliability between AC and DC hydraulics valves

I would think there is little diiference in reliability & performance.

There was a thread a while back about AC vs DC relays and how they work which may be of interest (It taught me something!)

The (electrical) control generally depends upon the environmet in which you are using the valves e.g a fixed machine tool may use 220/100v ac coils but a vehicle mounted system will use the battery output typically 12/24v dc

There is no difference in the performance of the valves.

The (electrical) control generally depends upon the environmet in which you are using the valves e.g a fixed machine tool may use 220/100v ac coils but a vehicle mounted system will use the battery output typically 12/24v dc

reply:

I am trying to locate a couple of companies that make the 12/24V hydraulic valves for a pet project, any help with some names would be appreciated.

thanks, zweistein

We use a company called Betavalve ...most companies shoild be able to provde coils for a variety of voltages. We use 230V AC and 12vDC. They can supply cheap plastic valves as used in washing machines, even do a nice one with 4 individually controlled outlets from 1 inlet...even these have replaceable coils, so we get 'em in 12vDc flavour!

Del

thanks for the info Hydroscot and Del the Cat.

I will research their products.

zweistein

Just about about any valve manufacturer who makes solenoid controlled valves will supply them in any voltage.

It depends upon the the application: for machine tools etc you could try Rexroth, Parker etc but for mobile you might try Valvoil or any of the Italian manufacturers. basically just put the name of the industry in front of the word "hydraulics" and Google e.g mobile hydraulics.

I'l give you a case study that may illuminate the differences.

The application is a Fairmont Tamper shoulder jacking tamping machine used for railway track maintenance. The original control of these machines (nicknamed Pigs for good reason) is very simple. The use boards that interrupt a light beam and immediately turn off power to the jacking solenoids which ceases the lift operation. The original solenoids ar 110vac direct acting and work adequately. The solenoids have become hard to source so some of the mechanical types retrofitted a machine with modern 24vdc pilot operated valves. The result was unpredictable overlift as the turnoff response was too slow for the application. The control system would have needed upgrading to use the new valves so the machine was parked up. I inherited a sister machine and had the advantage of seeing the converted machine on the dead line, so I had the original valves refurbished along with any spares I could beg, borrow or steal.

The bottom line is AC full power coils are very quick to respond (in simple on off applications) but in modern systems are not usually needed because modern control regimes usually contain PID or other forward looking elements that utilise low voltage low current DC coils extremely well. Additionally proportional valves and servos are DC and both lend themselves well to PID.