Help me with Control Valve question-Please

[George G]

I think you better go here to ask your ?Allis Chalmers Discussion Board. If I'm right, a WD-45 has an open center system. Runs between 3300 & 3700 psi, puts out a little less than 3 gpm, and the reservoir holds about 6 qt's of oil

 

[waldersha]

So one like this one would be correct? https://www.surpluscenter.com/item.asp?item=9-7862&catname=hydraulic

The system itself is pretty low flow (I think 4GPM or so) so Seems like this one would handle it, and I think 2000 psi is about right too. It says it has a plug to convert to closed center, is that sufficient?

Any opinion on Prince versus Cross versus??? I've only ever really been around Cross valves.

Thanks!

 

[waldersha]

Thanks George. I found the information that I was using on the "unofficial" Official Allis page. Different information on your link (7GPM, 3000 PSI) but no mention yet of open or closed center. I'll keep looking.

 

[George G]

The Service Manual refers to the pump as a Variable pump. The pump unloads when it reaches max psi(3300-3700 psi). So! I would say, you would treat it like a closed system.

 

[waldersha]

The Service Manual refers to the pump as a Variable pump. The pump unloads when it reaches max psi(3300-3700 psi). So! I would say, you would treat it like a closed system.

Arrrgh!!! :confused2: Thanks George. So then it would be like a closed center system needing closed center spool valves?

Is the one I linked to above correct then?

Thanks!

On Edit, asked the question over at YT as suggested. Got a response that I need open center, but nothing else as far as explanation. The valve linked above is open center with a plug for converting to closed. Is it as simple as hook it up one way and if it doesn't work try the other? Don't want to hurt anything, but there is so much conflicting information that I'm not sure what to believe.

 

[dcyrilc]

Perfect. Thank you for your help. So definately a 2 spool closed center valve.
Returning to neutral when not being activated. . . that doesn't mean that the lift gate would be able to float does it? It has to stay locked down so the bale doesn't get sloppy (pressure on from cylinders)

The fill tube for the hydraulic pump is plumbed for a return, so that shouldn't be an issue.

The twine control also has a 2-way cylinder, just btw.
Thanks again for your help. Gets me looking in the right direction.

No, it means that the control handle on the valve will return to the neutral/centered position if you let go of it. Otherwise, it would continue to move the ramp until you manually centered the valve handle. When the valve handle in is the neutral/centered position, the cylinder will be locked in its current position.

As for the twine cylinder, if it's a 2 way cyclinder, it also would use a DA spool. A Single Acting (SA) Cylinder will only have one hose for hydraulic fluid and a Double Acting (DA) Cylinder will have two hose connections (one on each end).

 

[dcyrilc]

Arrrgh!!! :confused2: Thanks George. So then it would be like a closed center system needing closed center spool valves?

Is the one I linked to above correct then?

Thanks!

On Edit, asked the question over at YT as suggested. Got a response that I need open center, but nothing else as far as explanation. The valve linked above is open center with a plug for converting to closed. Is it as simple as hook it up one way and if it doesn't work try the other? Don't want to hurt anything, but there is so much conflicting information that I'm not sure what to believe.

So far, it looks like your biggest chalange is going to be determining if you have an OC or CC system.

Here is the basic difference between the systems. On a Closed Center system, no fluid passes through the valve when it is in the centered/neutral position (the valve is closed between the input and return ports) and when the pump reaches operating pressure, it ceases to create pressure or pump fluid beyond what is needed to maintain pressure (this is why it is also known as a Constant Pressure (CP) system). On an Open Center system, fluid passes freely through the valve to the return line when it is in the centered/neutral position (the valve is open between the input and return ports) and the pump always pumps fluid (this is why it is also known as a Constant Flow (CF) system. Using a CC/CP valve on an OC/CF system will put the pump into relief (over-pressure state) because the fluid has no where to go. On the other hand, using an OC/CF valve on a CC/CP system will over work the pump as it is not designed for continous full operation as well as there may be issues from lack of pressure to operate the cylinders.

 

[dcyrilc]

On Edit, asked the question over at YT as suggested. Got a response that I need open center, but nothing else as far as explanation. The valve linked above is open center with a plug for converting to closed. Is it as simple as hook it up one way and if it doesn't work try the other? Don't want to hurt anything, but there is so much conflicting information that I'm not sure what to believe.

Almost all new tractors these days are OC/CF systems due to lower construction costs (unless you get into the larger tractors). Because of this, many people simply default to this if they are not familiar with the system.

Many of the older tractors had CC/CP systems which is why I expect to find it to be CC/CP.

 

[David Devuono]

Interesting discussion that has me real confused. In my case I am starting from scratch, building a small tracked ride on dumper. I am told I need an open centre valve for the drive motors. Looking at pumps, I have not heard information about whether there are open centre system pumps and closed centre system pumps. Now I am wondering if the pump I have will work for my installation. Don't answer here, I will start a new thread.

Dave

 

[waldersha]

Almost all new tractors these days are OC/CF systems due to lower construction costs (unless you get into the larger tractors). Because of this, many people simply default to this if they are not familiar with the system.

Many of the older tractors had CC/CP systems which is why I expect to find it to be CC/CP.

I asked dad and he said that it is a CP system. So that being said does the valve I linked to earlier make sense?

https://www.surpluscenter.com/item.a...name=hydraulic