Re: How do you adjust a hydraulic valve? *DELETED*
I think I may have this thing figured out. Initially, and mostly, because of the fact that there is no hard schematic to go by, and it sort of goes against how we normally hook up an additional valve to operate an additional function. This is, granted, a bit confusing. Let me see if I can throw my theory in to the mix and see what comes of it. At first it would appear that the only way this system could operate is if the closed center valve is sucking the life out of the hyd system by constantly running over relief. However, if closer attention is paid to Junkmans second post it seems pretty clear that the flow from the hyd pump is still being permitted to continue, "eventually" back to tank through the loader control valve via power beyond through the open center system. From what I think I understand, viewing the picture, and from what was posted, I think I'm starting to get the picture. I am strictly going by the second picture with the "tee" fittings for this explanation: He has the "tee" picking up flow from the pump, which, with both valves (loader and grapple in the neutral position) allows flow from the pump to continue back to tank through the open center of the loader control valve via power beyond. If you look past the tee it continues to the closed center valve and stops (lets call it potential energy at this point) So hyd flow is continuing back to tank at this point through the fel valve. Now there must be some "parasitic" pressure built up prior to the fel valve (due to Henro's theory of restriction, and if this "kit" adds a restrictor in to the fel side this makes even more sense) It would cause even more "parasitic" pressure to be available as potential energy to the closed center valve. Now the added on grapple cylinder can operate off of this parasitic pressure to move, however, I don't see it building pressure to full relief do to the fact that prior to this flow it is returning to tank through power beyond of the fel circuit. He has the tank side of the fel "teed" in too, but keep in mind that the only time that cicuit is active is if the relief valve in the closed center circuit is activated or the relief valve in the fel circuit is activated/float position. But we don't really need to be concerned with those functions to see how this "may" be working. So Lets see, to move the added on grapple there is enough "parasitic" pressure to allow the grapple cyl to function and move to the desired position using the closed center valve. Once the closed center valve is released back to the neutral position that cylinder is locked in to position against the spool and should no longer move. Now if you curl the bucket function of the fel that is where you will build the pressure required to hold whatever it is you're trying to lift or grab. Do to the closed center valve not allowing flow back to tank, because flow at that point is "dead-Headed" at the closed center valve inlet. This is where I think the confusion is coming from (don't get me wrong, this thread was confusing because we never heard how it was operated) The only way I can see this system working is if the grapple portion (closed center valve) is used to position the cyl then the bucket portion of the fel being used to provide the real pressure neccesary to hold. Really hard to explain with words but does that make any sense to anyone? That's the only way I can figure this is working without running the system over constant reief to feed the closed center valve. Maybe the next question will be, why run this circuit the way it is when you could do the same thing by "teeing" in to power beyond and get full pressure from both valves?(assuming the new valve is converted to open center) I don't have a good answer for that one. If the additional valve has it's own relief, which it should, then it really shouldn't make any difference which way to go. Most grapple systems that I'm used to dealing with operate in this manner and they are set up so the bucket will "pop" the relief in the grapple circuit to prevent any damage.
