Hydraulic valve: Which one?
- Thread starter MicroRacer
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goeduck
Super Member
If you insert a valve and do not pipe a tank line, just in and power beyond, what happens? Does it not work? Seems the fluid when the new valve is not in use would still go to the power beyond and the next valve would have all the pressure. Just checking to see if I can save a few fittings on the tank line.
bigdeano
Platinum Member
It will work until you operate the new valve to move a cylinder etc, then the oil that's supposed to go to the tank has nowhere to go, and the cylinder won't move.
goeduck
Super Member
How come the last valve can do it without a tank line? :confused3: or is the last valve not considered power beyond or not piped power beyond?
farm boy00
Veteran Member
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The last valve in a series does not need a power beyond port because it is the last one, hence not needing to feed power beyond that point. So all it needs is a line In (feed) and line out (return to tank)
CincyFlyer
Veteran Member
Note that on the Mahindra 25 series (and other Mahindra/TYM/Mitusbishi tractors) the backhoe has only one in, and one out; the out, which is a Power Beyond, goes to the 3-point lift. So it doesn't need a drain, even though it's not last in line! The backhoe is frame mounted, so the 3-point will never be used when it's attached. The two hoses on the tractor are simply attached together when the backhoe is removed.
That being said, as I have a similar tractor, I replaced the FEL valve with a new unit having a joystick (with the proper float) and a third valve for a grapple or tree grabber. I'm attaching the old FEL joystick to the back of the tractor to operate Top'n'Tilt or other gadgets.
That being said, as I have a similar tractor, I replaced the FEL valve with a new unit having a joystick (with the proper float) and a third valve for a grapple or tree grabber. I'm attaching the old FEL joystick to the back of the tractor to operate Top'n'Tilt or other gadgets.
goeduck
Super Member
Are your 3 point arms active when the backhoe is attached? Most are not. If they are than I am back to being confused. What farm boy00 and bigdeano said is what I have always heard and done (never made sense but is what I have always heard).
On my B21 I have to switch a valve besides loop the backhoe hose back to the tractor. On my Bradco 611 I have to switch power beyond from the backhoe to the 3 point. On both the 3 point is not active with the backhoe active.
I may need to pull apart a spool and see how the fluid porting differs between power beyond and tank. :muttering: :muttering:
bigdeano
Platinum Member
On a valve which has both power beyond and tank ports, the oil returning to a work port is directed to the TANK port, not the PB port. When the valve is centered, the oil from the IN port goes to the PB port instead of the TANK port, so the next valve can use it. It's actually quite simple, no need to take a valve apart.
CincyFlyer
Veteran Member
It will certainly work: that oil going through the valve is essentially going through a straight pipe if a valve isn't actuated! The only difference is that it's dumping waste into the PB line, which would fail to work if,
and only if, the 3-pt lift was engaged when trying to use the backhoe. No need for that, it's a subframe-mounted BH, so no worries.
Theoretically, if you would only operate one valve at a time, you can stack PB valves with no drains. It's a really bad idea, because you could "backwash" some pressure and cause unintended and potentially dangerous consequences, so it's rarely done, beyond the instance I've described.
goeduck
Super Member
Good descriptions. Thanks