How do you adjust a hydraulic valve?

Henro · Feb 21, 2005

Am I the only one starting to get a headache??? /forums/images/graemlins/grin.gif /forums/images/graemlins/shocked.gif

I suggest we focus on one small part of the puzzle. The hose going from the Tee on the pressure side of the loader valve to the input to the closed center valve.

It is apparent that this hose has pressure in it, because when Junk operates the closed-center valve, the cylinder connected to it moves.

Further, Junk has measured the pressure at the closed center valve as being about 1,500 psi when it is operated. Since the valve cannot make pressure itself, the pressure must be coming in via the line that we are looking at...

How can this be? /forums/images/graemlins/confused.gif Remember we are talking about when all the control valves in the open loop circuit are centered...

If we find the answer to this question, the rest will come easily...I bet!

(I will try to post a picture of the hydraulic schematic for the BX2200 when I get back to my other computer... /forums/images/graemlins/smile.gif )

Henro · Feb 21, 2005

BRAVO_WHISKEY,

Looks like you and I were typing at the same time and thinking about the same thing... /forums/images/graemlins/smile.gif

Junkman · Feb 21, 2005

( Am I the only one starting to get a headache??? /forums/images/graemlins/grin.gif /forums/images/graemlins/shocked.gif) NO

......................(I will try to post a picture of the hydraulic schematic for the BX2200 when I get back to my other computer... /forums/images/graemlins/smile.gif )

Could the BX22 be differant than the BX2200????? Inquiring minds "want or need" to know?????? /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

MadReferee · Feb 21, 2005

( The hydro fluid would want to follow the path of least resistance (which should be the open center valve) and not flow into the grapple valve. Does this make any sense? )

If that were the case then no spool would work. The spools in the loader valve are in parallel with the open center passage. In a typical parallel valve, opening any spool causes the open center passage to redirect flow to the spool parallel circuit where fluid is available to all spools on an as needed basis based on pressure requirements. This is clearly not the path of least reisistance.

MadReferee · Feb 21, 2005

( (I will try to post a picture of the hydraulic schematic for the BX2200 when I get back to my other computer... /forums/images/graemlins/smile.gif )
)

Don't waste your time. If the BX diagram is similar to the B series one then all it shows is a hydraulic block for the loader connection.

BRAVO_WHISKEY · Feb 21, 2005

( In a typical parallel valve, opening any spool causes the open center passage to redirect flow to the spool parallel circuit where fluid is available to all spools on an as needed basis based on pressure requirements. This is clearly not the path of least reisistance.)

Ah, well if the loader valve "redirects" then it is a sort of diverter which the grapple valve clearly is not. The grapple valve is only opened or closed. There still must be pressure on the system or the hydro fluid (given options) wouldn't take the "grapple route" circuit.

WhiteRock · Feb 21, 2005

Junkman, how many hoses are connected to your grapple valve?

WhiteRock · Feb 21, 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.

I am going to restate some assumptions to see if someone can identify it.

- The pump flows X GPM into the FEL valve, exhausting to the PB port.
- There is no pressure on this line (don't care if they call it the pressure line).
- Unscrew the gauge (leaving the tee in place), insert CC valve.
- The option PB port on the CC valve is not used (otherwise it would not be a CC valve).
- The outlet port on the CC valve is teed to the return line

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

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. You still haven't described how the pressure builds by pulling he lever when there is no pressure to start with and they are unrelated valves.

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. This could explain our confusion.

Junkman · Feb 21, 2005

( Junkman, how many hoses are connected to your grapple valve? )

Four...... two to the cylinder and the two that are tee'd into the lines that go to the loader valve.

Henro · Feb 21, 2005

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. You still haven't described how the pressure builds by pulling he lever when there is no pressure to start with and they are unrelated valves. 

WhiteRock,

While I am not MadRef, one assumption you made is that there is zero pressure at the line going into the FEL control valve. This is certainly not the case. Since there is flow through the valve itself, and tubing/hose, and the 3PH control valve in route back to the tank, there will be some pressure drop between the FEL input port point and the tank, and so there will certainly be some pressure felt at the FEL input port, with respect to tank pressure (or atmospheric pressure).

So in the real world one should expect to measure some pressure at the inlet port of the loader valve. How much is the question.

While no one has reported measuring it, I have come to believe the pressure at that point in a correctly operating system is likely to be between 100 and 200 psi. This is just speculation or an educated guess at this point though.

Let's say it was 150 lbs. And lets say a grapple cylinder was 2 inches in diameter. That 150 psi would be there and would be available to do work through a closed center control valve hooked to that point. There is no question in my mind about that. Not much work could be done by that 150 psi, compared to what 2,000 psi can do, but still, a little work could/would be done.

How much? Well, a 2" cylinder has a cross sectional area of 3.14 inches. 150 psi time 3.14 square inches is a little over 450 lbs of force. Enough to open and close a grapple I should expect.

So we should not be surprised that the circuit as we seem to understand it would work and operate the grapple. IT would not be able to supply much force to hold or crush anything, but the grapple would close and open.

I think we may be getting some wires crossed in the discussion so far. MadRef is saying that the grapple will work. Indeed it should work to the degree that it will likely open and close. But it will not work as strongly as it should and will not hold something heavy securely (although when the valve is centered again, the cylinder will lock in position to a great degree).

I still would not want to be between the grapple and bucket when it closed though... /forums/images/graemlins/shocked.gif

(more to follow... /forums/images/graemlins/grin.gif /forums/images/graemlins/blush.gif )