Tw-5 Hydraulic pressure.

[RodinNS]

There is no value in disconnecting the
loader lines. The supply and returns are
just open tees. The load sense line (pilot)
will have a shuttle check tee at each
junction... ie it's got a floating ball
check inside the tee.
To further the theory, each remote section
has a primary and secondary shuttle (ball
check) and a couple o-rings on each
shuttle.
When you activate a remote or loader valve
the bypass oil that is present in the
supply circuit passes over the spool and
into the load sense circuit. The pressure
rise shifts the combining/sequencing valve
simultaneously with the flow control spool
in the remote. If any of the o-rings on the
shuttles leak or the ball doesn't seal, oil
is lost to sump. Any oil that is lost
effectively limits the maximum pressure to
be developed in the circuit. The way the
shuttles work, the circuit demanding the
highest pressure will close the shuttle to
provide maximum load sense to the combining
valve. This provides pressure compensation
in the circuit. So if you have one that is
dead, the shuttle is leaking. If you dead
head another and the dead one works that
confirms the diagnosis. Likewise if you
have a leaker and you deadhead the one
providing the highest pressure on the gauge
and you get more lift from the loader...
that would tend to suggest that the
shuttles or at least the load sense circuit
for the loader is leaking.
You could also have an inlet relief on the
loader valve depending on what's
installed...
It's a complicated system.
I'm not saying that a main spool in a Rex
valve will not leak after 15k hours but I'd
be skeptical. The shuttles are known
trouble in the MP series valves and
probably to a lesser extent in these
monoblock valves.
If you have a dead or under performing
remote and all others work the first place
I'd look is the shuttles.

Rod

 

[Daniel in PA]

Rod, I m am learning a lot about this system with your help, I take what you and other post, review the diagrams and thing start to fall together. To clarify two things, you said "main spool in a Rex valve" are you referring to main control spool in each remote or something else, maybe a typo. Also you referred to a primary and secondary shuttle valve, I see in the diagram each remote stack has an internal shuttle and then they is an external one that ties the two stacks together, is that what you were referring to. I was thinking maybe I could disconnect the pilot line from the remotes and plug then pressure check at the loader to determine if I have a leaking shuttle in one of the remotes, of course this would disable the remotes. Thanks for taking time out of your day to help.

 

[RodinNS]

The valves remade by Rexroth (Bosch) today.
When I refer to the main spool I'm talking
about the control spool that is activated
by the control lever. These valves are all
closed center load sensing (CCLS).
The primary shuttle is internal to a single
valve section. It acts as a ball check for
load sense between the raise and lower side
s of the spool. The secondary shuttle
provides isolation between the other valves
in the block as well as making passage to
the flow control spool so that flow is
managed according to load.
The external pilot lines have additional
shuttles at each tee so that the highest
pressure load sense has priority.
As far as disconnecting the pilot lines...
that would only help if you tee the gauge
into the loader circuit somewhere or the
pilot. Line itself in an open tee.
The easiest way to determine if you have a
weak section in the loader is to dead head
a section you know has full pressure and
see if the loader will lift more with the
other one dead headed. Since supply oil
will equalise pressure, if you have a
lesser load sense pressure on the loader,
the increased load sense pressure from the
dead head section should provide more
pressure to the loader.
You should also look at the loader valve in
the event that it has port relief valves.
Who knows what is actually fitted there.

Rod

 

[Daniel in PA]

Rod, got my fitting and did a test today. Setup: Removed male QC (quick connect) off my gauge and replaced with female, took the male QC and plugged the end and put it in the remote that gave me the highest reading, wasn t sure if the remote would deadhead without anything in it. Disconnected QC to lift cylinders and installed gauge. Tests: (1) Tested pressure with just the joystick pulled to lift (2) Tested pressure with remote deadheaded and joystick pulled to lift. Results: Test (1) little over 2400 psi. Test (2) little over 2300 psi. Tractor run for maybe 5 minutes, 60 degrees today, RPM s @ 1400 per manual. Previous test at remote was 2400. Gauge is 5000 psi so 100 psi incumbents and small when setting in tractor. Not sure if I mentioned but loader moves slow unless I rev it up a little, and the cable seems somewhat stiff (remote joystick with control cable) so I thing I will check to see that the spools are achieving full travel. Thoughts?
Thanks
Dan