How do you adjust a hydraulic valve?

PineRidge · Feb 18, 2005

When Junkman and I talked on the phone he indicated to me that once his grapple was set with a load and the grapple valve was released that he was concerned that he might drop the item in the grapple traveling as pressure bled off the cylinder of the grapple.He also said that as long as he held the control valve in the closed position that pressure remained on the grapple/item itself.

I couldn't understand for the life of me how his system was working correctly not being connected directly to a power beyond port on the loader valve for pressure. And I must admit that even after reading this thread I'm still confused. /forums/images/graemlins/frown.gif

Henro · Feb 18, 2005

I posted a question related to minimum hydraulic system pressure here , asking if anyone has actually measured (or knows) what typical system minimum pressures are...

Steve_Miller · Feb 19, 2005

Well its morning and at least I didn't dream hydraulics.
 The final chapter in the discussion would be what happens to the pressure at the grapple control valve when the loader goes into a stall situation, like full up or down, or end of movement of the bucket, when the system pressure goes up to the pressure relief valve trip point? 
Henro,
It would just go up to the relief setting of the loader valve I would assume. (1500 psi.) Now if the 3PH was connected to the PB which I think is the way my Kioti is set up, then, if the 3PH came up to its maximun load then you would probably get system relief. (2XXX psi.) Just my assumptions, right or wrong. I'm glad its not just me that is somewhat puzzled about all of this.

Steve

SPIKER · Feb 19, 2005

HI GENTS /forums/images/graemlins/ooo.gif
nice post so far lots of good ?s to answer. /forums/images/graemlins/smile.gif

ok here is more than likely what is happening the loader valve is probably 1st in line for junks application and fom there it probably goes to a powersteering diverter valve? then on to the 3pt. the power steering diverter valve will keep just about 1500 psi on the system up stream of it at all time to make sure the power steering cylinder an maintain its postion. (this is exactly how my import tractor works and is pretty normal on CUTs especially with ones with power steering.)

the garden hose analigy is sort of correct but also misleading. as the open center pumps are constant volume pumps which do nothing more than move XX CC's of fluid per revolution from the intake side of the pump to the outlet side of the pump. the pressure is produced EXACTLY as described above. pressure builds to the point of it blowing a hose or pump or relife valve if the engine is running and the FLOW has no where to go.

Varrialbe volume pumps are a different as they put out XXXX pressure with full flow all way back to very little flow. BUT if flow is uncontrolled (blown hose say) then the pressure will decrease untill pump max flow volume is reached. (probably several GPM)

OK now if the LOADER VALVE (or any other valve down stream flow of the grapple valve) is displaced then the snow chute/grapple pressure available will increase to the same pressure as the loader is seeing on the control spools/relife pressure.

so anyhow hope this helps.

MarkM /forums/images/graemlins/wink.gif /forums/images/graemlins/crazy.gif /forums/images/graemlins/grin.gif

mopacman · Feb 19, 2005

If you are using a pressure relief valve to regulate the pressure it will cause over heating of the oil. this would be hard on the pump also. A pressure relief valve should only be used to limit the max pressure. I would not want something in my system that would cause a constant pressure of 1500 psi.

TractorTodd · Feb 20, 2005

Junkman, You own a Kubota so why use a closed center valve on an open center system? Checkout the attachment for how two open center valves should plumbed.

Junkman · Feb 20, 2005

That is exactly how my auxiliary valve is plumbed and mounted on my ROPS. /forums/images/graemlins/grin.gif

PineRidge · Feb 20, 2005

Junkman, You own a Kubota so why use a closed center valve on an open center system? Checkout the attachment for how two open center valves should plumbed.


That's what was supplied to Junk as part of his grapple package if I'm not mistaken.

I'm thinking if it were me I might just call the manufacturer of the grapple for some answers. Junk where did you purchase that grapple, were you eBay shopping again when the wife was working hard?

PineRidge · Feb 20, 2005

That is exactly how my auxiliary valve is plumbed and mounted on my ROPS.


Junk I lightened your picture and I'm only seeing two hoses off your valve are you sure that you are connected the same as the diagram?

JerryG · Feb 20, 2005

It might have just two hoses off of the last valve in the group. There is only two hoses needed for the last valve in a open center system, a PBY is not required.