Hydraulic solenoid valve issue
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  1. #1
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    Default Hydraulic solenoid valve issue

    Hello all,

    I'm having a weird issue with some solenoid valves in a simple hydraulic circuit, let me try and describe the situation as best as I could..

    So coming out of a 2 station manifold, I have 2, 4 way, spring return, center drain valves. 120VAC, controlled through relay outputs by a PLC. Each valve controls a set of cylinders, A position down, B position up. Wired up such that 1 leg of each coil jumped together to my 120VAC control, the other 4 legs to their corresponding PLC output.

    Initially, I had valves with a center position, A&B drain to T, P blocked. Everything worked correctly from a controls standpoint, only problem was when both valves were "off", I was holding at full pressure (~1700 psi)and building up alot of heat.

    So I swapped out the valves for center position, A to B blocked, P drain to T. Wired up exactly the same as before. Now when I actuate, lets say, valve 1, side A, nothing happens...until I actuate valve 2 side A, then cylinder on valve 1 actuates, as well as the cylinder on valve 2. Electrically everything is right when I check with a meter, program is running as it should as well. So that leads me to believe that somethings going on hydraulically.

    This is the manifold im using....
    McMaster-Carr

    And my Motor/tank/pump......
    McMaster-Carr

    Original valves
    McMaster-Carr

    And the ones I changed out for
    http://www.eatonpowersource.com/products/configure/industrial-valves/details/02-145150/#/h:80694/s[1]G4V/s[2]:-3/s[3]:S/s[4]:-8/s[5]:C/s[9]:-VM/s[11]:-FW/s[14]:-B/s[15]:5/s[16]:-61/s[22]:_

    Anyone have any idea whats going on? It seems like when I have one valve, P going to A and the other "off" (P to T) that I might have to much pressure going to tank, preventing B to T thus keeping my cylinder from moving?

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    in a word, yes, I think that is what you have. If you wanted to reduce the system pressure when all valves are closed, I would suggest a separate drain valve to tank you can turn on with the plc whenever the valves are closed to center.

    NOTE: This may cause pressure spikes in the system and you may need an accumulator or surge suppressor to deal with that if it proves to be a problem.

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    If your using 2 drain - centre to tank valves then yeah, nothing will happen when you activate just one because it drains the full flow to tank still from the other centred valve.

    Other easy way to achieve what you want is to only have the pump run when the valves are actuated like your old valve arangment.

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    Ahh I see...Thanks for your replies guys. What do you guys think about this... Separate the two valves to two, independent station bases with check valves on the tank lines? Do you think that would help me out, or would I still have a problem getting the oil over that check valve to tank?

    This is on an automated assembly machine that cycles between sides very quickly ( < 1 Sec) and there is very little time where both valves are closed. This is my first hydraulic system design so please forgive the ignorance...

    Tonytn36,

    If im reading you right, then go back to the P blocked in center valves with a drain valve up stream of the manifold?

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    ^ Yep as per tonyt36's sugestion, you still want that max pressure relief though, a properly sized accumulator as per his suggestion will also increase your cycle speed too as it can store pressurized volume to be used at a moments notice.

    Basically, i would have something like this,

    Tank, with suction strainer,

    Pump + pressure relief set to your needed operating pressure,

    Tonyt36's relief - drain valve, probaly run a spin on cartridge filter on that return to tank leg as the systems filtering.

    Then a check valve

    Accumulator, either small or slightly larger to supply - speed up the cycle,

    Then your original dead heading valve block,

    Then what ever those valves control.

    Done right with a suitable accumulator you should be able to have a lot faster cycle time, you simply pump it up when the pump outputs not being used. if your designing it from scratch you can even get away with dropping the pump size a fair bit in a lot of tasks like this by using one.

    Theres a fair bit to good hydraulic design though, max fluid velocities, temp considerations + reservoir sizing. Its just as involved as doing electrical circuit design if you want good cool running and reliable. With modern energy efficiency requirements - power costs theres also real savings to be had getting that side of the design good too.

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    If you need help, call in your Parker-Hannifin rep. At least here in the southeast, they are more than excellent at helping you design and set up a system properly.

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    Quote Originally Posted by adama View Post
    ^ Yep as per tonyt36's sugestion, you still want that max pressure relief though, a properly sized accumulator as per his suggestion will also increase your cycle speed too as it can store pressurized volume to be used at a moments notice.

    Basically, i would have something like this,

    Tank, with suction strainer,

    Pump + pressure relief set to your needed operating pressure,

    Tonyt36's relief - drain valve, probaly run a spin on cartridge filter on that return to tank leg as the systems filtering.

    Then a check valve

    Accumulator, either small or slightly larger to supply - speed up the cycle,

    Then your original dead heading valve block,

    Then what ever those valves control.

    Done right with a suitable accumulator you should be able to have a lot faster cycle time, you simply pump it up when the pump outputs not being used. if your designing it from scratch you can even get away with dropping the pump size a fair bit in a lot of tasks like this by using one.

    Theres a fair bit to good hydraulic design though, max fluid velocities, temp considerations + reservoir sizing. Its just as involved as doing electrical circuit design if you want good cool running and reliable. With modern energy efficiency requirements - power costs theres also real savings to be had getting that side of the design good too.
    Thanks Adama!

    So in the short instances where both my valves are closed, my drain valve is dumping to tank to prevent heat build up while my accumulator is there to smooth things out and provide enough back up that everything runs right due to all the fast valve switching that'll be going on.

    Im not familiar at all with accumulators...I assume that using a gas charged unit, its charge pressure should be equal to or greater than my max system pressure and bladder/capacity size should be able to handle the flow rate of the system? My required flow rate is so low its almost negligible, but my pressure requirement is up there.

    Other than that, I think I have a much better handle on the situation, much appreciated!

    Corey

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    Quote Originally Posted by Tonytn36 View Post
    If you need help, call in your Parker-Hannifin rep. At least here in the southeast, they are more than excellent at helping you design and set up a system properly.
    Ill just have to make sure I don't tell them Im using Vickers and Eaton

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    Quote Originally Posted by capocoreyollo View Post
    Ill just have to make sure I don't tell them Im using Vickers and Eaton
    They won't care if you buy the accumulator and dump valve from them...
    The Vickers guys are pretty good too.


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