Adding Valve to Closed Center Post Pounder

[RickB]

RickB
Would you please explain how to connect an open center valve on a closed center hyd system so CC hyd pump won't cavitate.
Thanks,Jim

Exactly as described in the OP. Accepting flow from the tractor and using the PB flow from the O C valve to power the original CC pounder valve. The CC valve would stop the flow through the OC valve except when any valve spool was stroked.

 

[Tx Jim]

Aaron & Rick
Thanks for your reply. I'm not from the "show me state" BUT I'D HAVE TO WITNESS THIS FEAT to believe CC hyd pump won't cavitate with an OC valve with or without PBY attached to it. I've witnessed CC hyd system hyd pump cavitate when CC plug blew seal which is similar to valve with PBY plug. I guess I can't see the forest for the trees but I've spent many,many diagnosing CC hyd failures.

 

[RickB]

Aaron & Rick
Thanks for your reply. I'm not from the "show me state" BUT I'D HAVE TO WITNESS THIS FEAT to believe CC hyd pump won't cavitate with an OC valve with or without PBY attached to it. I've witnessed CC hyd system hyd pump cavitate when CC plug blew seal which is similar to valve with PBY plug. I guess I can't see the forest for the trees but I've spent many,many diagnosing CC hyd failures.

The downstream closed center valve blocks the flow from the Power Beyond port of the open center valve. That makes it function exactly as if that same OC valve had a closed center plug installed. Not ideal, but it would be fully functional and not compromise the CC system.

 

[aczlan]

The downstream closed center valve blocks the flow from the Power Beyond port of the open center valve. That makes it function exactly as if that same OC valve had a closed center plug installed. Not ideal, but it would be fully functional and not compromise the CC system.

Here is a flow diagram:

A and B are work ports
T is low pressure return to tank
P is high pressure in from the pump
PB is high pressure Power Beyond

Aaron Z

 

[WranglerX]

Here is a flow diagram:

A and B are work ports
T is low pressure return to tank
P is high pressure in from the pump
PB is high pressure Power Beyond

Aaron Z

This is my understanding how it should work....

Dale

 

[Tx Jim]

Although I've never seen or heard of this method of attaching open center control valve to closed center hyd system I can envision that returning oil to ""ported hyd filter cover"" could help keep CC pump from caviatating BUT returning simply to TANK I'd have to see it operate correctly to believe it. Can someone explain how returning oil to tank via the posted schematic is any different than blowing seal on CC plug on FEL valve which will return oil to tank will cause frt pump to cavitate??

IMHO JD engineers failed to install a high enough GPM trans pump from the beginning then when an internal leak to sump occurs frt pump runs out of oil too fast.

Has anyone witnessed 1st hand the system outlined in schematic operating on a JD CC hyd system??
Thanks,Jim

 

[Tx Jim]

The downstream closed center valve blocks the flow from the Power Beyond port of the open center valve.

Please explain this part of schematic because I can't determine how a CC valve is blocking the OC valve. Plus I'm not buying into the return oil(green line) will be low pressure. I've never measured it but when one sends 2250 psi to return line I think it won't be low pressure in return line.

Another fallacy to that schematic not functioning on a JD closed center hyd system is the blue arrow(suction) because JD piston pumps are incapable of sucking oil & requires oil to be supplied to them via a charge pump. The blue suction might be fine IF large hyd reservoir was mounted above CC pump but it won't operate correctly with smaller reservoir because many JD tractors have a smaller reservoir & had hyd problems

 

[RickB]

It will work. The flow characteristics will not differ from the original CC valve only installation. The diagram is functionally accurate except the detail of the missing charge pump and does not account for the woefully inadequate charge pumps used by Deere for decades.
If we cannot make you believe or understand that is OK.

 

[Tx Jim]

It will work.
If we cannot make you believe or understand that is OK.

Rick
I'm just attempting to determine how it's designed to work. I'm still attempting to understand how CC valve can block oil to the added OC valve. I suppose from what you stated that you have actually seen this type of setup utilized on a JD CC hyd system.
Thanks,Jim

 

[ptsg]

Rick
I'm just attempting to determine how it's designed to work. I'm still attempting to understand how CC valve can block oil to the added OC valve. I suppose from what you stated that you have actually seen this type of setup utilized on a JD CC hyd system.
Thanks,Jim

First valve will have a PB plug feeding the second valve. The second valve will then have a Closed center plug, therefore making both valves closed center. The pressure side will be blocked no matter how many valves are behind the last one (fitted with a CC plug).