How do you adjust a hydraulic valve?

WhiteRock · Feb 21, 2005

No problem Henro.

A couple of points. One, my written delivery on a public forum is probably quite poor. I am trying to improve.

I understand that the pressure isn't going to be zero. Accelerating the fluid mass in a long pipe will create pressure. Once at the velocity of what ever inch/sec 5.5 GPM creates in its plumbing will have a slight pressure due to parasitic resistance. Your claiming it is almost 10% of the available pressure to the system. Quite a loss in my mind(3/4 hp). I think I will do some research and see I can determine the nominal value.

I like and agree with your logic though. Choosing a nominal pressure you have create sound support for the cylinder's activation.

Another good point you bring up is the cylinder locking. Once activated into position it should hold.

My claim earlier that I think was missed/ignored was very similar. Because Junkman said that he had used both at the same time explains a lot in my mind. If you activate the FEL valve, the pressure will go very high on the pump side. To further speculate, lets say from 200 psi to 1500 psi. Now that will activate the cylinder with a lot of force. MadReferee tells me that this makes absolutely no difference. I think that is incorrect.

I think your position on this has been correct all along. While you see me totally in the theoretical world, I think you are assigning a bit to much parasitic pressure in the system. I think your assumption is reasonable. I don't know either.

Thanks for your reply.

Henro · Feb 21, 2005

While you see me totally in the theoretical world, I think you are assigning a bit to much parasitic pressure in the system. I think your assumption is reasonable. I don't know either 

Sorry. My head frequently resides in the theoretical world...did not mean to accuse you of living there too! But you did say some like "no pressure..." /forums/images/graemlins/grin.gif

Seems like TBN is experiencing some problems at the moment. Hope this posts. I lost one a few minutes ago... /forums/images/graemlins/frown.gif

Henro · Feb 21, 2005

Like WhiteRock said, pick you own numbers...unless you can make or find a measurement! /forums/images/graemlins/smile.gif

In a post above, WhiteRock calculated that at 1,500 PSI about 1 HP is used for each GPM of flow in a hydraulic circuit. This power could be used to accomplish useful work, or to generate heat. An example of a heat generator would by an activated PRV in a system operating at 1,500 PSI.

Getting past the “can it work or not” aspect of the discussion, we need to ask “should it worry me or not.”

If we were to take a tractor that had an open center hydraulic control scheme, and measure 1,500 PSI at the input port of the loader control valve, Should we be concerned, or just stand there feeling happy?

The BX actually sends about 4 GPM to the OC circuit, at full pump output, since the first 1.5 GPM is dedicated to the power steering. Still, that would mean that about 4 hp, according to WhiteRock’s calculations, would be developed as heat, since no useful work is being done.

4 HP = 3 KW (or pretty close). That is a pretty big heater to have in the hydraulic system!

A measurement like that would sure worry me.

Would anyone not worry about this? If not, why not?

If there is reason to worry, then the next step would be to ask what the cause of the 1,500 PSI being there might be.

MadReferee · Feb 22, 2005

( If you remove the pressure guage and connect the CC valve's inlet there and tee the outlet into the return line it will work fine. Same if you tee the CC inlet anywhere in what they call the pressure line between the 2 valves (the line that goes from the bottom PB port to the upper valve's inlet).

No, that will not work. One of us is missing something.)

WhiteRock,
It must be you since I am standing strong on my comments. Also, since we know for a fact that this works just fine (Junk has proven that), I believe it is up to you to prove me wrong.

One more time, there is absolutely no difference if the CC valve is connected before or after the FEL valve.

( The CC Valve WILL NOT work. It will have the same 0 pressure as the gauge in the picture. )

But is DOES work. Junkman proved that. As soon as the CC valve spool is actuated pressure will be generated against the cylinder connected to its work ports, same as any other valve.

( The area where I disagree with you is your claim that there is pressure at the gauge. Since the valves are NOT in series, the FEL valve dumps all pressure to the PB, and there is nothing to block flow. )

I never claimed that. You obviously still do not understand power beyond because you make the statement that "the FEL valve dumps all pressure to the PB". The FEL valve passes fluid from the inlet port to the PB port. Exhaust from work ports is dumped to the tank. (Let's leave the regen function out of this as it is the exception) /forums/images/graemlins/laugh.gif

The power beyond sleeve in an open center valve simply blocks the outlet port from the PB port and creates a clear path from the inlet port to the PB port. This is a straight thru unrestricted passage. The outlet port is then used for work port exhaust fluid and is tied to tank.

( I have now found a circuit configuration like you suggest, but it uses a variable displacement pump. Is this what we are missing? I thought the BX had a fixed displacement gear pump. )

In a circuit that only has closed center valves, you better have a variable displacement pump that can go to zero flow since the circuit is not a complete open loop. However, a closed center valve can be used in an open center system if it is connected in parallel to the open circuit loop.

A similar description of Junk's circuit can be found HERE. The last description (closed center with power beyond) is just about what we have only Junk's pump is fixed displacement.

Another resource for hydraulic info can be found HERE. It doesn't give our exact example but it does contain useful information.

In conclusion, Junk's system works and until any of you can prove otherwise, I think we are wasting valuable bandwidth beating this to death any more. What we really need is a college mechanical engineering professor who specializes in hydraulics.

Henro · Feb 22, 2005

In conclusion, Junk's system works and until any of you can prove otherwise, I think we are wasting valuable bandwidth beating this to death any more. What we really need is a college mechanical engineering professor who specializes in hydraulics.

MadRef,

With all due repect, how about backing up you statements with some fact that directly applies to this discussion.

In a post above I have put some numbers on the paper to show how a setup like we think Junkman has, would possibly "work," but not as strongly as it might.

Why not expand on that and illustrate with more than just general statements why a setup like we are discussing would work better than just marginally ?

These are simple circuits really, and should not take a mechanical engineering professor to discuss them or to figure them out, or even to show with some simple numbers how they work.

The most difficult part is probably being 100% certain what someone has put in place without being there to examine it. But we have passed that point by assuming what the circuit is and talking about that assumption.

Frankly, I thnk my example above did "prove" how Junkman's setup could work half-baked well. Why not carry that thought a little farther, and explain why (with numbers) it should be expected to operate better than my evaluation?

Discussion like ths can be a learning process. It can evolve from a "can't work" / "can work" difference, to a "can work to some degree" conclusion, or even into absolute proof one way or the other.

Reasonable discussion between interested parties is not a waste of time or bandwidth.

MadReferee · Feb 22, 2005

Henro,

As I have said on several previous occasions, I am not an expert and I am not into the actual formulas and theory behind how something works. I can tell you how to connect stuff and why and how the connection is correct from a physical standpoint but the theory end is not my bag. Plenty of times what looks good on paper just doesn't hack it in the real world.

The discussion here has drifted into the theory of how hydraulics actually work and when we start arguing over a few psi (as an example) I think it's time to give it a rest. None of us are obviously versed enough in this subject to give technically correct answers and I see no need to continue to give (in your own words) "half-baked" answers and suppositions.

WhiteRock · Feb 22, 2005

Re: How do you adjust a hydraulic valve? *DELETED*

Post deleted by WhiteRock

Junkman · Feb 22, 2005

( Starts to make me suspicious as to why Junkman was looking for more pressure. Cranking it to the max will not fix it in that circuit. )

Your suspicions are all wrong. I purchased a gauge to check the pressure after another BX user posted about having less pressure than factory specifications when his was checked with a gauge. I did the same and found that my tractor hydraulics was at full specification pressure. Then I also checked the valve for the grapple, even though the grapple is not installed at present. I found that to be at 1500 PSI, so I wanted to raise it. Plain and simple. There is no nefariousness to my post or the situation at hand. A simple request for a simple answer to how to make an adjustment. Nothing more..........

As for ( Cranking it to the max will not fix it in that circuit.) your for assumption that something is wrong, you are gravely mistaken. There is nothing wrong with this circuit and changing the relief valve will allow the circuit to take full advantage of the 2300 PSI that is available to the valve. I rest my case..... it is now up to you the jury to decide if what I have done violates the laws of physics and if I am to spend the rest of my tractoring life confined within the boundary's of heaven or ****. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

WhiteRock · Feb 22, 2005

If your happy, I'm happy. /forums/images/graemlins/smile.gif

It doesn't appear that our questions are helping anyone. Not even us. I will cleanup what I can.

MadReferee · Feb 22, 2005

( I think I see the problem. This is what Henro and I were concerned about. If this system is being plumbed like your first link, that is wrong for this system. That is for a variable displacement pump. That is an incompatible system and works quite differently. Will it work? Yes, barely.)

For a totally closed center system to work properly you need to have a variable displacement pump or some other method to deal with the constant flow from a fixed pump or variable pump that cannot be turned off, like an accumulator or additional parallel circuit. One of the links I posted earlier shows some examples of this.

In Junk's system, he has simply connected a closed center valve in parallel to the open center circuit. Fluid still flows continuously throughout the circuit. The last picture in one of the links show something similar.

( You can go with what works, I just hope you don't get hurt or damage your equipment. )

Have no fear. Junk's system will work/is working fine and will not harm his system at all.