Open Center or Closed

[1S1K]

Hi All,

Can someone tell me how to tell the difference between an open center and closed center hydraulic system, My D4 Cat has an aftermarket pump and valve that are pretty old and I can't easily tell what the pump is. The problem is that the float position on the valve is worn out and its leaking. Also it only has 2 remotes to control the blade and I would like a third so I can run my disc at the rear without unhooking my blade controls. Also, is there a way to figure out how many GPM the system is so I can properly size the new valve? Thanks for the help.

1S1k

 

[J_J]

Open center pumps runs when the engine runs.

With all the valves in neutral, there is flow but very little pressure.

Open center valves usually have a relief valve built in to the valve.

Your CAT dealer shop supervisor should be able to tell you,

Someone could so a flow and pressure test.

 

[bigdeano]

You could disconnect the return hose that goes from the valve back to the tank. If oil squirts out when you start it up it's open center. You could time how long it takes to pump a few gallons into a bucket to measure the flow rate.

 

[Tx Jim]

Closed center pump turns with engine but only pumps oil when pressure falls below a specified(pre-set) pressure. Closed center control valve should have no oil exit out port when all control levers are in neutral while open center control valve will have oil exit out post with control levers in neutral.

 

[muddstopper]

Since we are on the open center/closed center topic, Whats the best way to tell if a valve, without disassembling the valve, and its not hooked to anything, just setting on a bench, if it is a open center valve or a closed center valve. I have parker v70 that i thought was open center, but now I am being told its a closed center. Its a new valve, but without the box

 

[J_J]

If you blow air through the IN port, with the lever in neutral, no air should exit the valve.

The valve might be a convertible valve where you add plugs to modify the valve to open or closed center.

http://www.lifcohydraulics.com/cata...)-Directional-Control-Valves,-Open-Center.pdf

 

[MinnesotaEric]

Hi All,

Can someone tell me how to tell the difference between an open center and closed center hydraulic system….

1S1k

Closed center is like the water system in your house: always under pressure and fluid does not move till the valve is opened. Open center is like a spray pump where the water goes round and round the system till it is needed, then diverted off in another direction by a valve.

 

[RickB]

If you blow air through the IN port, with the lever in neutral, no air should exit the valve.

The valve might be a convertible valve where you add plugs to modify the valve to open or closed center.

http://www.lifcohydraulics.com/cata...)-Directional-Control-Valves,-Open-Center.pdf

Correct, but to clarify, this result means the valve is closed center. An open center valve would allow air to flow from the 'P' port to R', 'T', or 'PB" unimpeded when all spools are centered.

 

[muddstopper]

I figured the air trick would tell, but I am not at home to give it a try. This is a specialty valve of some sort. It has a lever handle for operation, but also has a aircylinder for air operation of the spools. I am planning on using it on my wood processor to operate the splitter cylinders, (60gpm), using a air foot pedal to keep my hands free for other functions. This valve also has three reliefs, one one each directional port and a PB port, but plug for PB port is missing.

 

[Tx Jim]

This valve also has three reliefs, one one each directional port and a PB port, but plug for PB port is missing.

I'll bet with the valve having 3 relief valves that it's open center.