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.

 

[J_J]

I have never seen a relief valve on a PB port.

It should be close to or tied in to the IN port.

Can you show picture of the valve and point out the reliefs.

The valve is just an open center valve with a plug in the PB port.

If the PB port has the adapter, then it is setup for PB.

The valve could be converted to closed center valve by installing a plug in the PB port.

A closed center will have a no relief/pass through plug in the relief port.

Are you sure you want to use a 70 GPM valve?

 

[muddstopper]

JJ, pic will have to wait, I'm 350 miles from the valve now. I think the way I wrote my last reply, I misled you, the third relief is on the in side, not the PB. I am pretty sure the v70 valve can be made open or close center, just right now I am not sure which way it is set up, or what is needed to make the swap.. I am sure the pb plug is missing with just plastic caps in all the port holes. And yea, I think for what I am planning, the v70 valve will do the job. I plan on 60gpm of flow and the v70 is rated for 70gpm. I probably wont need the Pb as I only plan one circuit on this pump/valve.

 

[J_J]

If your valve is the last valve in the hyd circuit, then you need a plug in the PB port.

Then all flow will exit the OUT port.

You do realize you will need about 123 HP to pump 60 GPM at 3000 psi.

 

[muddstopper]

If your valve is the last valve in the hyd circuit, then you need a plug in the PB port.

Then all flow will exit the OUT port.

You do realize you will need about 123 HP to pump 60 GPM at 3000 psi.

Need more than that, I plan on a 30gpm and a 15gpm circuit as well. I have located a few engine sources. Right now leaning toward the 170hp, 7.3 international diesel, but have also located a 12valve 6bt cummins. The 7.3 is in the right price range and comes with the air compressor, rad, and electrical. The cummins, not so much. We'll see, still wheeling/dealing and sourceing parts.

 

[J_J]

105 GPM needs 180 HP. at 2500 psi.

If you go 3000 psi, you will need 216 HP

 

[muddstopper]

The 30gpm circuit is only going to be running around 700-1000psi