Kubota B8200 - Valve/ hydraulic system question

[chase87]

Hi Guys. I am adding a Brand Hydraulics loader valve to my tractor to control a plow setup I am working on. While I am at it, I am going to add a 3 spool valve for additional remotes. My question is this:

Can I use a closed center valve for my remotes if I plumb it through the Power Beyond port on my loader valve? I found a 3 spool parker valve for really cheap... I bought it, but can I use it? A schematic is attached. I got it for $50.

Thanks for any help. This forum has been a life saver!

 

[J_J]

What system does your tractor have? Open center or closed center? If your tractor is open center, then you should use open center valves. Some valves can be converted by using a closed center plug.

 

[kennyd]

Hi Guys. I am adding a Brand Hydraulics loader valve to my tractor to control a plow setup I am working on. While I am at it, I am going to add a 3 spool valve for additional remotes. My question is this:

Can I use a closed center valve for my remotes if I plumb it through the Power Beyond port on my loader valve? I found a 3 spool parker valve for really cheap... I bought it, but can I use it? A schematic is attached. I got it for $50.

Thanks for any help. This forum has been a life saver!

Short answer: No

 

[chase87]

I believe that I have an open system... I understand that with an open system I should use open center valves, I am just not clear on how the power beyond works.

In my head, I see it working like this:
1. Fluid goes into pressure port of open center loader valve.
2. Fluid flows through open center of loader valve and back to tank.
3. Power beyond port Tee's off of P-T line inside loader valve, sending fluid to my closed center valve.
4. Closed center valve works like any other closed center valve (Fluid dead heads into valve until actuated, directing fluid into actuator and back to tank)
5. System remains open center because of the flow from P-T on loader valve.

Does my theory hold any water? I admit, I have been wrong before, that is why I asked the experts at TBN. This is my first tractor and I would hate to ruin something... but this is not my first time working with hydraulics and it seems like it would be Ok to me.

Thanks for any additional insight guys. If your answer is still no, can you explain why so I dont confuse myself again in the future?

 

[J_J]

A closed center blocks the flow of fluid, until it is needed. You should not mix valves. Open center valves circulate the fluid.

 

[cycle_gator]

Gotta agree on this one, KennyD said it best, NO.

Reason, with PB installed in the loader valve the only flow that really goes into the regular return lines is the backflow, or waste, from the workports. You may get a tiny bit of bypass flow, but not enough to keep the system cool. So all the system presure would make its way through the PB to the closed center valve and only be relieved when the work ports are open. Guarantee it, unless the valve was open all the time, the system will overheat.

The series of messages to AMPA are instructive in this case. WHen PB is utilized the PB port and return port are isolated from each other. Pressure all goes to the PB when it is not diverted to the workports by one, or more, of the spools, it is not an either or deal.

You might take a look at a Parker parts catalogue and see if they have a way to convert that valve to an open center valve. But the diagram you posted does not look real promising.

 

[Jay4200]

I believe that I have an open system... I understand that with an open system I should use open center valves, I am just not clear on how the power beyond works.

In my head, I see it working like this:
1. Fluid goes into pressure port of open center loader valve.
2. Fluid flows through open center of loader valve and back to tank.
3. Power beyond port Tee's off of P-T line inside loader valve, sending fluid to my closed center valve.
4. Closed center valve works like any other closed center valve (Fluid dead heads into valve until actuated, directing fluid into actuator and back to tank)
5. System remains open center because of the flow from P-T on loader valve.

Does my theory hold any water? I admit, I have been wrong before, that is why I asked the experts at TBN. This is my first tractor and I would hate to ruin something... but this is not my first time working with hydraulics and it seems like it would be Ok to me.

No, your theory does not hold water. The part you are missing is that an OC valve is open from either 'IN' to 'OUT', or 'IN to 'PB' if power beyond is used. All of the valves are in series, so fluid flows freely through all of the valves then returns back to tank. Pressure doesn't build until a valve is actuated and the flow is diverted into a cylinder. With no valves actuated, there is maximum flow but minimum pressure built in an OC system. You can't "Tee" the pressure side into a CC valve, as you suggested, since the unused side is open to tank and will short-circuit the CC valve (no pressure).

JayC

 

[kennyd]

Gotta agree on this one, KennyD said it best, NO.

Reason, with PB installed in the loader valve the only flow that really goes into the regular return lines is the backflow, or waste, from the workports. You may get a tiny bit of bypass flow, but not enough to keep the system cool. So all the system presure would make its way through the PB to the closed center valve and only be relieved when the work ports are open. Guarantee it, unless the valve was open all the time, the system will overheat.

The series of messages to AMPA are instructive in this case. WHen PB is utilized the PB port and return port are isolated from each other. Pressure all goes to the PB when it is not diverted to the workports by one, or more, of the spools, it is not an either or deal.

You might take a look at a Parker parts catalogue and see if they have a way to convert that valve to an open center valve. But the diagram you posted does not look real promising.

Well said:thumbsup:

You can only use CC valves on systems with a variable displacement pump, and you cannot mix CC and OC valves. Short answer remains in effect-NO.

 

[AKKAMAAN]

+5

I am following this thread with some minor interest....but....chase87 ...you are swimming in deep water here...

The valve you have showed in your post is made for a closed center load sensing system.....

An open center system can't be load sensing.
Only open center systems involves power beyond.

Both variable pumps and fixed displacement pumps can be used for closed center systems. They just need the different ways to control/govern pump flow. Your valve can eventually be used with fixed displacement pump, but system will then need a dump valve for flow. A dump valve is basically a very low pressure PRV, that is controlled by a signal from the actuator side of the CV. (dashed lines on you picture)......

chase87....Tractor data says you have an open center system on you B8200. Your valve is NO GOOD. End of story!

 

[chase87]

Well look at that, I'm wrong... Big surprise! Thats why I asked the question, I wasnt real confident that I understood everything involved.

Thanks for the info guys, now I understand why it will not work. I guess I missed that when utilizing the PB port the main flow does not continue to pass through the loader valve. I thought it was a type of flow-devider system vs. an either or thing.

Good thing the valve was cheap. I will put it on e-bay and try to get some money back out of it.

-Chase