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Hydraulic Experts

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    I have a question for you hydraulic experts David and Sandy or anyone else. I am going to upgrade my newly built press to electric controls with limit switches. I have pressed my first 20 parts and the press operated great but I want to get rid of the mechanical stops. David you told me which valve to order but I want to find one on ebay if I can and save a few bucks. Can someone explain what these diagrams mean. The manual valve I have now works great and I would like the electric one to work the same if possible. I have a log splitter type valve it returns to the center and holds in the up or return and kicks back to center when the cylinder is fully retracted. I have seen many valves on ebay for sale and they always have these diagrams but I don't know what they mean. I will post a picture I scanned from the Northern Tool catalog can someone explain what they mean and which type I would want. Is the valve I have now an open center?

    I plan on buying some limit switches 2 for the different stops I make 2 different bends in making my parts. I also plan on buying a foot switch to engage the electric valve and I will reuse my on and off switch that turns off the motor that runs the pump.
    Here is the diagrams that I want to learn what they mean.
    Thanks in advance.

  • #2
    Bump to the top and out of the past.


    • #3
      1 - this one is always moving the cylinder either in or out when the pump is running. ie, the pump is turned on only when the cylinder needs to be moved. It uses a single solenoid to move the valve to the other position, the spring moves it back to the normal position when the solenoid is deergized.

      The rest of the valves differ in what happens when they are deergized and are in the center position.

      2 - this type of valve is normally used on air systems since the center position blocks off all flow from the pump.

      3 - the cylinder and the pump are lined up to the tank. This way the cylinder can be moved by hand since it is not locked in place.

      4 - in the center position, the pressure from the pump is blocked, but both sides of the cylinder are sent to the tank. This way the cylinder can be moved by hand since it is not locked in place.

      5 - this is the most common, the hydraulic flow is directed back to the sump when the cylinder is not being moved in or out. The cylinder is locked in place.

      [This message has been edited by JPR (edited 03-06-2006).]


      • #4
        The surplus center latest flyer( has a fluid power book (item 9-1022) for $1.50 plus $0.80 shipping. Not sure how good it is or if it goes into the different valving or not, but the price is right.


        • #5
          Thanks JPR do these type valves no 5 usually have a relief valve built in like the manual valves?


          • #6
            I thought that number 2 was the more common type, with an exhaust valve returning fluid to the reservior, but then again I have done nothing with hydraulics.
            You never learn anything by doing it right.


            • #7
              <font face="Verdana, Arial" size="2">do these type valves no 5 usually have a relief valve built in like the manual valves?</font>
              A pressure relief or regulator is separate.

              <font face="Verdana, Arial" size="2">I thought that number 2 was the more common type</font>
              For air systems yes. Most of the hydraulic systems I have seen use #5. The reason I would avoid using #2 and let the regulator/relief return the fluid to the tank would be starting and stopping the motor under load, possible additional fluid heating, and possible extra wear on pump and components.

              Here is a basic drawing

              [This message has been edited by JPR (edited 03-07-2006).]