B2710 Swapping Kubota Power Blade for Aftermarket Loader - Power Beyond Question

[stryker]

I have a B2710 with a Kubota Power Angle front blade installled. It has the Kubota joystick currently installed. I purchased an new aftermarket (Mateng) loader I am in the process of installing. The loader came with its own joystick hydraulics and would like to use the new valve. The new valve has just two lines to connect to tractor, Pump and Tank. The existing Kubota joystick has three lines, Pump, Tank and Power Beyond.

MY question is can I just plug off the Power Beyond port on the hydraulic block on the tractor? Will this starve my 3ph?

Thanks, Paul

 

[eserv]

You can plug off the TANK line on your tractor and it will work. If you plug the POWER BEYOND line you won`t have any TPH.
Ed

 

[stryker]

So if I block off the tank line, do I connect the new valve like this?

Pump port on the tractor to P port on new valve?
Power Beyond Port on the tractor to T port on new valve?

Thanks

 

[eserv]

right, it`s the only thing you can do that will work if your new valve hasn`t got a PB port. There are lots of tractors operating in this configuration!

 

[stryker]

Great! Thanks,

So what is the advantage to the joystick having the power beyond port?

 

[eserv]

There are a few good reasons why Kubota ( and most other manufactures) use a power beyond system. When you use a valve that has power beyond the oil returning from the work ( cylinder, motor etc.) goes to the tank port which then dumps directly back into the reservoir. also, the oil that might go over the relief valve if you overload the system is able to escape through the same port with no restriction. Now imagine that all the oil returning from the work has to service another valve downstream! all is good until you use that other valve then you get pressure feeding back to the first valve which will limit the amount of work it can do but worse, it will pressure up the first valve and possibly cause it to leak. The backpressure on the first valve will act on the relief valve in it and cause it to not open untill a much higher pressure ( called amplification) Also, if you are operating a cylinder you would get a condition called intensification ( that is, if you apply oil to the base of a cylinder and measured the pressure at the rod end it would be considerably more! ( because the rod end cylinder area is the area of the rod less than the base end area).This higher pressure oil would then be applied to the next valve downstream and whatever it was operating! We ``get away`` with plumbing them without a power beyond because rarely do we use the TPH and the loader at the same time, but it could happen so all good hydraulic systems use a power beyond setup. ( the best ones use closed center but Kubota haven`t gone there yet!
Ed

 

[stryker]

Well I finished mounting the loader tonight, connected the new control valve. Started tractor, checked for leaks. No leaks. Tried to operate the loader, moved a bit, but the seemed to hydraulic lock. Both the lift and bucket cylinders. Figured I cross the lines between cylinders. Schematic for the loader seemed wrong to me, but re-plumbed to match schematic. Similar results. Put it back the way I first had it, and noticed the pump and tank lines were reversed. Oops! I corrected those. Restarted tractor. Now I have No Hydraulics at all! No loader, no 3ph, no power steering. I fear I have damaged the pump somehow. Fluid level is good. I tried reversing pump / tank lines back with no help. Any suggestions of what I can check?

 

[eserv]

Well I finished mounting the loader tonight, connected the new control valve. Started tractor, checked for leaks. No leaks. Tried to operate the loader, moved a bit, but the seemed to hydraulic lock. Both the lift and bucket cylinders. Figured I cross the lines between cylinders. Schematic for the loader seemed wrong to me, but re-plumbed to match schematic. Similar results. Put it back the way I first had it, and noticed the pump and tank lines were reversed. Oops! I corrected those. Restarted tractor. Now I have No Hydraulics at all! No loader, no 3ph, no power steering. I fear I have damaged the pump somehow. Fluid level is good. I tried reversing pump / tank lines back with no help. Any suggestions of what I can check?

If you put the tank and pump hoses on wrong you will deadhead the pump if you try to use any function. This will almost for sure damage the pump! On a "B" Kubota it usually breaks the drive tang off the pump shaft so the pump quites turning.
Ed

 

[stryker]

Good news! I pulled off the pump today. No Damage! Turned out I must have just forced air back into the pump, causing it to cavitate. The pickup / tank line on the pump is pretty high up. The dry pump must have no been able to draw the fluid uphill that far.

Anyway, the loader is working great! Thanks for all your help!