How do you adjust a hydraulic valve?

Junkman · Feb 20, 2005

That posted added another dimension to the equasion.... a auxiliary valve mounted on the ROPS. The auxiliary valve mounted on the ROPS is plumbed with 3 hoses, but that is not the valve in this discussion. I have no idea of why someone would bring into this discussion my auxiliary valve mounted on the ROPS, but they did. I merely confirmed that what they posted is how my auxiliary ROPS mounted valve is plumbed.

As for the valve in this discussion, it is the valve furnished with the grapple by the manufacturer. It is a closed center valve with two hoses as shown in the picture that I posted.

This is a Parker single spool mono-block valve with option #3, which says ..........
( CLOSED CENTER PLUG OPTION 3
This option provides for closed center operation. This is typically used with a variable displacement pressure compensated pump or in a system with an unloading valve. When the spools are in neutral the inlet port is blocked. The power beyond plugs can be used for closed center conversion by plugging the power beyond port. PLEASE NOTE it may be necessary to increase relief pressure above pump compensator setting.)
What all this means, I have no idea and at this point, I really don't care. I asked a simple question about how pressure is regulated and it evolved into a discussion of why and how this should or shouldn't work. All that I know is that it does work and that is good enough for me. Why it works is irrelevant to my question.
I look at the diagram that is supplied by Parker and it shows this valve being plumbed the way that I have it plumbed. There is a pressure line that is common to the loader line. I have a valve outlet line that is tied into the return line of the loader valve, which is marked "return line" on the diagram supplied by Parker. I have two lines from the valve to a cylinder, just like in the diagram supplied by Parker.
There is also a note that says: "Please note this relief is optional and can not be set higher than the RELIEF in the loader valve assembly, but can be set lower". How to adjust this relief valve was my original question. Now that I have found the original paper work that came with the valve, I have that information.

PineRidge · Feb 21, 2005

In other words I think Junk might be saying, "Get off my case, I don't need your additional advice." /forums/images/graemlins/grin.gif /forums/images/graemlins/smile.gif /forums/images/graemlins/laugh.gif

MadReferee · Feb 21, 2005

Junkman's plumbing of a closed center valve in an open center configuration is correct and will work with no problems. Since he has no need to have anything connected after the closed center valve, and that he connected it in parallel with the open center flow, he is ok.

There are several references on the internet and in readily obtainable text books that show this exact configuration. I mentioned one in a previous post. Mixing open and closed center valves in the same system is quite common in industrial applications.

Also, his aux valve on the ROPS is an open center valve connected in series and is plumbed correctly.

Junkman · Feb 21, 2005

Yesterday was a really bad day, hopefully today will be problem........ If you would like to see the diagram, please try this...... go to http://www.princehyd.com/ and click on valves....... then go to Mono Block Control Valves and go down the page to valve RD41..... click on Parts manual..... then go to the diagram in that manual on page 10. The only difference between my application is that instead of the line going from the power beyond port on the loader valve, it is tied into the pressure line on the other side of the valve. This is the way that my paper instruction sheet shows it also. Hope that this is clear now. Thanks Junkman... /forums/images/graemlins/smile.gif

Henro · Feb 21, 2005

What all this means, I have no idea and at this point, I really don't care. I asked a simple question about how pressure is regulated and it evolved into a discussion of why and how this should or shouldn't work. All that I know is that it does work and that is good enough for me. Why it works is irrelevant to my question.


Junkman, I think I may be the guilty one! /forums/images/graemlins/blush.gif Sorry about that.

But I think you should consider WHY the "Why it works" may actually be relevant to your question.

I'll tell you why it would be to me. You can dispose of my thoughts any way you like... /forums/images/graemlins/shocked.gif /forums/images/graemlins/grin.gif

For whatever is connected to your "closed center" valve to work, there must be some pressure available to the valve.

Your valve is connected to a point in the open center loop where normally there "apparently" should be very little pressure available when all the other valves are centered.

So something may have been changed to cause the hydraulic pump to be working differently (harder) than it would in the stock BX hydraulic loop configuration.

What might cause this to happen? A restriction in one of those Tees that came with your control valve is one possibility.

In my view, the question is not that your setup works. It obviously does. The question as to WHY it works relates to whether something has been changed on your tractor which causes your tractors hydraulic pump to be pushing against a high pressure a lot of the time (1,500 psi maybe) when in the non-modified state it might expect to see about 100 or 200 psi on its output side, when nothing is being operated.

I know you always do your best to treat your machines as well as your dogs ( Well above gold, more like platinum treatment) and my past life experience (tuning/troubleshooting/upgrading industrial control systems) is telling me something doesn't sound normal (correct, right) here.

The 1,500 psi that seems to be available at the closed center control valve is the flag.

 Why it works is irrelevant to my question.


I have to agree with this specific point. But I also have to add again, WHY it works could (maybe, possibly, just might) have a negative long term affect on the tractor's hydraulic pumps longevity. Or maybe the pump, by design, doesn't care what pressure it is pumping against...but extra heat would be developed in the hydraulic fluid too...

Something to consider, anyway... /forums/images/graemlins/crazy.gif

PS Sorry also for extending this tread... /forums/images/graemlins/blush.gif However I do think there is some value here...beyond satisfaction of intellectual curiosity... /forums/images/graemlins/grin.gif

Junkman · Feb 21, 2005

The system has to have at least the 1500 PSI all the time or even the 2300 PSI design pressure flowing through it at all times, otherwise the power steering and the hydro wouldn't work. I have had this on for almost 6 months and have never experienced any heat problems on the tractor. The only time that the hydro ever got hot enough to expand the fluid and push it out the vent, was when working the tractor this past summer and at that time, the valve wasn't even installed. I have also used both the loader valve and the grapple valve simultaneously. Have you looked at the diagram that I have posted the directions to and the link above? Possibly that will help you to understand what is going on with the system. Yes, I do realize that I could pipe this from the power beyond port to the valve and then add a return line so the valve would then be an open center valve, but what would be the advantages of doing that. It works properly the way it is and the valve manufacturer suggests plumbing this way also. The reason that I have 1500 PSI on the valve is that is where the pressure is set by design of the valve. It also says in the directions that the setting can be increased up to 3000 PSI. It further states not to exceed the pressure limit of the relief valve in the loader circuit. Assuming that the system pressure is 2300 PSI and the loader valve relief is set at 2500 PSI, then I can safely increase this valves pressure limiting valve to 2000 PSI. It if were an open center valve, it would still have the same characteristics, but just have one more line for oil to return to the tank.

WhiteRock · Feb 21, 2005

Not that it matters, but I am in the camp that doesn't understand how this scenario works. But, I don't think we have seen a full schematic.

My calculation show that on the BX 22 with 5.5 GPM of flow, if you are pumping against 1500 psi, you are using 5.7 hp to do it. Sure seems like a lot of wasted power for no activity.

I don't think the hydro is power by this pump....

Junkman · Feb 21, 2005

Since the new valve is tee'd into the system that controls the loader valve, there can be no additional resistance. Think of it as having a dead hose line where each hose terminates at the valve when the valve is closed. There is no wasted activity since this is EXACTLY the way that Kubota designed the tractor. On a BX, there is only one pump and it powers everything hydraulic.

WhiteRock · Feb 21, 2005

I agree that there should be no additional resistance. If your tee connection is on the pump side of the FEL control valve, no pressure should appear there until the FEL is activated. This is what has some folks (including me) baffled. A cylinder can not be actuated with no pressure. So I think this leads folks (that are studying how this works) to say, where is the pressure coming from to give you such good results /forums/images/graemlins/confused.gif.

If there is pressure there, then there is a restriction that is loading the system down stream.

I thought the claim was that you had a pressure gauge at this same location (tee equivalent) and was measuring 1500 psi with no activity. Perhaps this is not the case, because you can't have flow and pressure with 0 work.

I realize that this one pump runs everything, except the HST.

MadReferee · Feb 21, 2005

( If your tee connection is on the pump side of the FEL control valve, no pressure should appear there until the FEL is activated. )

Whether or not the closed center valve is connected before the FEL inlet or after the FEL power beyond outlet will make absolutely no difference. The FEL valve has absolutely and positively nothing to do with the correct operation of Junkman's valve. The power beyond feature of the FEL valve insures that any flow not used by the loader valve spools will be transferred thru the valve and back into the circuit. That's why it's called power beyond.

The closed center valve in this configuration is acting almost like an additional spool. No flow will go thru it until the valve is actuated.