Difference between OC and power beyond

[jsranman]

I am in the process of schooling myself on hydrualics to add a plow set up to my kubota.

I have learned about directional control valves. I think open center type valves allows fluid to flow back freely to the reservoir when the spool is in the neutral position and, I think, to other directional control valves downstream.

The kubota loader control valve has a power beyond port. Is power beyond type valve just another name for open center valve and if not, what is the difference?

 

[kennyd]

I think open center type valves allows fluid to flow back freely to the reservoir when the spool is in the neutral position and, I think, to other directional control valves downstream.

That is 100% correct. The pumps on our tractors are of the fixed displacement type, so they pump full flow all the time and that flow cannot be stopped, so all valves must be open center so as not to block that flow in neutral.

The kubota loader control valve has a power beyond port. Is power beyond type valve just another name for open center valve and if not, what is the difference?

Correct, your FEL valve has a PB port. PB is used to carry any excess flow of oil not used by the spool to the next valve in-line, and the exhausted fluid from the spool goes to the OUT port and then back to the tank. The PB just provides a more efficient way of feeding multiple valves in a open center system and also helps keep the downstream valves from starving for oil.

Most open center valves have the option for PB by a plug that is insterted into the valve.

Clear as mud right

 

[J_J]

Open-Center-Power-Beyond - Same as Open-Center valve except oil flows to downstream circuit in the neutral position instead of returning to the tank.

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http://www.surpluscenter.com/item.asp?UID=2008121214373564&catname=hydraulic&item=9-4895-B

 

[john_bud]

If you are getting a new control valve, you also need to be aware of tandem center vs straight open center. A control valve for motors is open center, but not tandem. If used on a cylinder, it will allow the cylinder to move in response to a load, a tandem center valve won't. Often the advertisement will say OC motor valve or OC cylinder valve.

Just one more thing to confuse you!

jb

 

[jsranman]

Thanks for the good info.

Stay tuned. I am sure to ask some more dumb questions in the near future.

 

[J_J]

There are hydraulic manuals on cd's on Ebay and other sources. Go on Ebay and type hydraulic cd. It should come up with several .versions.

.hydraulic cd, Books, Business Industrial items on eBay.com

Some of the data you may learn.

How the forces in liquids work.
How to manage fluid lines and fittings.
Everything there is to know about valves.
Basic hydraulics.
Hydraulic plumbing.
Management of hydraulic directional devices.
Pump management and maintenance.
How to use actuating devices
Everything there is to know about hydraulic seals.
Much, much more!

 

[Knight]

If you are getting a new control valve, you also need to be aware of tandem center vs straight open center. A control valve for motors is open center, but not tandem. If used on a cylinder, it will allow the cylinder to move in response to a load, a tandem center valve won't. Often the advertisement will say OC motor valve or OC cylinder valve.

Just one more thing to confuse you!

jb

John's response nails it! I bought an open center valve, because of hearing "open center" term used around here. The cylinder was flopping around like a dead fish. I had to return it for a tandem center valve for my cylinder.

Open Center= All ports open in neutral position
Tandem Center= A,B work ports closed, P,T open in neutral position