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  1. #1
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    Default "Priority valve" Vs. "Power Beyond"

    Sorry for the dumb questions... I have a bunch these days

    What is the difference between a "Priority Valve" vs. a "Power Beyond" port?

    I'm putting both a FEL & Power Steering on my Yanny. The person where I'm getting my PS parts from says I need a Priority Valve to "split" the circuit. He said that 1 side would be the "priority" side (the PS), and the other side would get the non-priority.

    But, what would be the difference between doing that and using a Power Beyond port?

  2. #2
    Elite Member RonMar's Avatar
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    Default Re: "Priority valve" Vs. "Power Beyond"

    A priority valve is basically like a "T" in the line that only flows fluid down that branch line when there is a demand down that branch.

    An open center circuit has to have a open center from which fluid is diverted, usually by a spool valve to perform work. A power beyond port is just a high pressure extension of this main open center line that can feed another device/valve downstream, provided that device has an open center flow thru it.

    A power steering valve is not configured with an open center. It is basically a vane pump that will pump fluid out it's outlet ports to move it's cylinder a particular way when the wheel is turned a particular direction. Because of this, it will function(as long as it has fluid in it) without the engine or hydraulic pump running/supplying pressurized fluid, it will just require more muscle to turn the wheel.

    If you feed the inlet with pressurized fluid, this action becomes powered and you can turn the wheel with 2 fingers. If you are not turning the wheel, there is no hydraulic flow thru it(no open center) so it can't be placed in series with the main open center circuit like the loader or 3PH control valve can. By supplying the steering valve with a priority valve(automatic "T") it will only draw/divert fluid from the main open center line when you turn the wheel. As soon as you stop turning the wheel, the priority valve restores flow back to the main open center line. If the priority valve is placed early in the system, it will place power steering over all other hydraulics, such that you will not be able to lift the loader, or 3PH while you are turning the wheel.

    You will also need a separate low restriction return line from the steering valve/pump outlet to the resovoir to return the diverted fluid back to the system.
    Ron

  3. #3
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    Default Re: "Priority valve" Vs. "Power Beyond"

    That's awesome. So, if I read this correct, the return line from the PS pump will go into a plug port in the side if my trans, not back into the "series".

    THANK YOU VERY VERY MUCH!

    Here is what I think I need. Please trash as appropriate


    Quote Originally Posted by RonMar
    A priority valve is basically like a "T" in the line that only flows fluid down that branch line when there is a demand down that branch.

    An open center circuit has to have a open center from which fluid is diverted, usually by a spool valve to perform work. A power beyond port is just a high pressure extension of this main open center line that can feed another device/valve downstream, provided that device has an open center flow thru it.

    A power steering valve is not configured with an open center. It is basically a vane pump that will pump fluid out it's outlet ports to move it's cylinder a particular way when the wheel is turned a particular direction. Because of this, it will function(as long as it has fluid in it) without the engine or hydraulic pump running/supplying pressurized fluid, it will just require more muscle to turn the wheel.

    If you feed the inlet with pressurized fluid, this action becomes powered and you can turn the wheel with 2 fingers. If you are not turning the wheel, there is no hydraulic flow thru it(no open center) so it can't be placed in series with the main open center circuit like the loader or 3PH control valve can. By supplying the steering valve with a priority valve(automatic "T") it will only draw/divert fluid from the main open center line when you turn the wheel. As soon as you stop turning the wheel, the priority valve restores flow back to the main open center line. If the priority valve is placed early in the system, it will place power steering over all other hydraulics, such that you will not be able to lift the loader, or 3PH while you are turning the wheel.

    You will also need a separate low restriction return line from the steering valve/pump outlet to the resovoir to return the diverted fluid back to the system.

  4. #4
    Elite Member RonMar's Avatar
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    Default Re: "Priority valve" Vs. "Power Beyond"

    From your question I thought you were refering to a stand-alone priority flow divider. Not knowing the exact makup of the ports on your 3PH valve, if that is what those ports you are tapping in and out of are for, then your drawing looks OK, with one exception. IF that is your FEL valve in the lower left of the drawing, you may have the out and PB ports backwards. "IN" is a high pressure inlet. PB is a high pressure outlet that feeds the "IN" port of another device. "OUT" may be the low pressure return line out of the valve. It only has flow when the spools are being operated and the fluid returning from the cylinders that are moving goes here. It also has flow when the safety opens. IF the fluid you are feeding back to the 3PH valve block has to perform any work, then you will probably want the PB outlet to go there. The return line from the FEL, like the return line from the steering, has to have a low restriction path to the reservoir. No more restriction than would be provided by a return line filter...
    Ron

  5. #5
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    Default Re: "Priority valve" Vs. "Power Beyond"

    Ron,

    Yes, actually, I was specifically talking about a seperate priority valve. However, it looks like I may have one on the tractor spool already (per my other thread named "what port is what". Sorry - didn't mean to confuse anyone.

    Thanks on the catch on the drawing. Yes, that is a FEL spool (would have been nice if I would have labeled it, huh). I was confused then about where the PB & "Out" had to go.

    I have updated the drawing. If you refresh the page, it should be modified per your comments.

    THANK YOU! THANK YOU! THANK YOU!

  6. #6
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    Default Re: "Priority valve" Vs. "Power Beyond"

    Jimmer:

    Paul in VT indicated in the other thread that your three point hitch valve has both a priority flow divider and proportional flow divider. The valve body seems small to contain both, but I hope he is correct since that will save you both the cost of the priority flow divider and associated plumbing. Since you are going to have to remove the plugs in these ports anyway when you connect the power steering and FEL, perhaps you should do so now to confirm what is inside. The nature of priority flow dividers is that when the priority flow is blocked completely (say by the plugs in the valve now) the excess flow is also completely blocked. In your valve, if the built-in priority flow divider output is blocked by the plug, then the excess flow would also be blocked and the valve would pass no fluid. Therefore, it seems that you are going to have to do something to "activate" the priority flow divider in addition to removing the plug. Installing some kind of sleeve or plug inside the port may be required.

  7. #7
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    Default Re: "Priority valve" Vs. "Power Beyond"

    Farmer, et all....

    I was under the understanding (which, probably make it wrong, I seem to be batting 1000 lately ) that I would have to install a small plug internal to the spool (something like a 1/4" plug) inside of the "O" port (non-PowerSteering Priority port) in order to make the fluid flow from the banjo fitting, out the "O" port so it could feed the rest of the spool by coming back in through the "I" port.

    My question is, what would happen if I didn't install such a plug to "Force" the fluid into the FEL valve body? The way I see it, if the FEL spool is open, and nothing is requiring fluid, then wouldn't the FEL get the fluid? If the 3pt was open, then it would get it. If both the FEL & 3pt were being used, then they would have to share. Is that accurate? Obviously in this instance there wouldn't be a way to "prioritize" either the FEL, or the 3pt. (Hopefully the PS "priority" port would still have priority above all, but I'm doubting that).

    What that buys me, is the ability to remove the FEL & it's spool without having to plumb the 2 hoses into each other & risk burning up the hydraulic pump when (not if) I forget.

  8. #8
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    Default Re: "Priority valve" Vs. "Power Beyond"

    Well, after reading some clips from a Yanmar Shop manual for a different model, with a different spool, I have found this out:

    1) I MUST insert a 1/4 - 18 Headless plug inside of port 4)

    2) The spool has a "Main Relief Valve" and a "Safety Relief Valve". (Not a priority valve like I was hoping )

    3) Port number 4) feeds the double acting valve spool

    4) Port number 1) is the return from the double-acting cylinder valve spool "Power Beyond Port"

    5) Port number 3) is for single acting cylinders

    So, it looks like I will need an aux priority valve after all (as well as changing the layout of how things are plumbed).

    I will update the drawing asap to show what I think I need now

    thank everyone again & again for all your good information!



    Here are some pictures of my spool from the "what port is what" thread.




  9. #9
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    Default Re: "Priority valve" Vs. "Power Beyond"

    Diagram updated.

    I added a pressure releaf valve so that when I forget to couple the in & Power Beyond hoses together, I won't kill the pump

    what do you think?

  10. #10
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    Default Re: "Priority valve" Vs. "Power Beyond"

    Updated the diagram again.
    '05 Kubota 1830
    HST, FEL, 54" MMM, Canopy,
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