Increasing lift capacity 3pt hitch of Kubota B3200

[aczlan]

I have a B3200 and a LA504.
The questions stays where do I find the second relief valve

Follow the 3 point lift control lever. It will connect to a valve that also contains the relief valve.

Aaron Z

 

[Dave M7040]

My question has to do with a comment by JJ which I do not understand as it pertains to my M7040 with FEL.
The Kubota manual shows connecting a pressure gauge to the outlet port of the factory installed remote to check and adjust the relief valve for the 3 pt hitch.
Instructions are to rev the tractor to 2,600 rpm once oil is warm and operate the remote valve while reading the pressure gauge.
My readings were initially around 2,000 psi down from the spec of approx 2,800.
I adjusted the relief valve located very close to the rear remotes on the main casting. The adjustments screws in or out with a lock nut to secure it.
The adjustment has bottomed out and the pressure is only 2,500 psi on a brand new gauge so I have no further adjustment at that location.
JJ mentioned adjusting the relief valve on the FEL first although the shop manual does not suggest this.
The dealership mechanic also suggested adjusting the FEL relief valve. This valve is a little harder to get to requiring the removal of some protective panels behind the foot rungs.
The shop manual does not make it clear to me why the FEL relief valve will affect the 3 pt hitch.
The dealer's mechanic stated to adjust the FEL relief valve with the pressure gauge inserted into the rear remote.
Can you please help me understand how this system works and what to do to get a bit more pressure to lift a very heavy blower.
Thank you.
Dave M7040

 

[J_J]

If you have one path for the fluid to flow, and you insert a gage in that line before any valve, then anything you do to block the fluid will be reflected on the gage.

Say your tractor is spec'd for 3000 psi and your FEL relief is set to 2500 psi. The most psi that you can get in pressure using the 3pt will be 2500 .

You can set it higher by some other means, but the FEL relief will control the pressure.

You should set them both the same, or even set the 3pt lower than the FEL relief. In that case, the 3pt relief will activate.

If you had remote valves and were using 2200 psi cyl, then you would want to protect the cyl by setting the remote relief valve to 2150 psi.

Final answer is to set all the relief the same.

Some people boost the FEL relief a bit to gain more pressure, and therefore more force.

If the 3pt had external cyls, you could go to larger cyl and gain more force.

The psi is thought out by engineers for the best match as to safety and longevity.

 

[Dave M7040]

Thanks JJ
I think my difficultly in understanding this system is because of my years with an old Nuffied with FEL where the hydraulic system was simple.
The relief valve on the FEL only seemed to activate when I asked too much of the loader. I had to be pulling or pushing on one of the levers and then could hear the FEL valve squeal.
On the Kubota, with its much more complex system, power beyond etc, it is obviously a different beast and I will have to adjust my thinking.
What does not help is that the shop manual does not have a diagram of the complete system including FEL and does not link the two but perhaps I need to study it much more.
I will get to the FEL relief valve and then post again.
Sharing your expertise on hydraulics is a big help to many of us!
Dave M7040

 

[skyhook]

This is what I've learned here....
Attached ( you can click on the pic for a larger image) is a sample of hydraulic lines.
I did not add the return lines for simplicity, the blue lines are the hydraulic "feed" lines and will "ALL" have pressure once they are used.
The Black boxs are your "relief" valves, remember, fluid is constantly going to "all" these relief valves, if the relief valves are not set "equally", the one with the "lowest set relief" will control the whole flow, it only makes sense.
This is why JJ states to have "all" your relief valves set at the same pressure.
But they should NOT be set higher than what your cylinder can handle....
Hope I'm right on this.

 

[J_J]

This is what I've learned here....
Attached ( you can click on the pic for a larger image) is a sample of hydraulic lines.
I did not add the return lines for simplicity, the blue lines are the hydraulic "feed" lines and will "ALL" have pressure once they are used.
The Black boxs are your "relief" valves, remember, fluid is constantly going to "all" these relief valves, if the relief valves are not set "equally", the one with the "lowest set relief" will control the whole flow, it only makes sense.
This is why JJ states to have "all" your relief valves set at the same pressure.
But they should NOT be set higher than what your cylinder can handle....
Hope I'm right on this.
View attachment 399370

There is only one path for the pump flow, as all valves are in series.

 

[skyhook]

There is only one path for the pump flow, as all valves are in series.

What about Power Beyond, is that not another path along with the path to the loader

 

[aczlan]

What about Power Beyond, is that not another path along with the path to the loader

Power beyond has 3 lines:
1. High pressure in
2. High pressure out
3. Low pressure out to tank
The object of power beyond is to not have back pressure on the "exhaust" line as could happen if (for example) you tried to raise the 3 point while lowering the loader.

Aaron Z

 

[J_J]

Power beyond has 3 lines:
1. High pressure in
2. High pressure out
3. Low pressure out to tank
The object of power beyond is to not have back pressure on the "exhaust" line as could happen if (for example) you tried to raise the 3 point while lowering the loader.

Aaron Z

PB is the flow path if the adapter is installed and is low pressure until a valve causes a cylinder or motor to operate.

You can have back pressure on the loader valve if a valve downstream is operated.

The relief valve is working in a one line flow path and will limit the pressure.

Each valve in an open center system has a relief and can regulate the pressure for that circuit.