closed& open center valves?

Hi Brent,

What is the definition of a closed center and open center valves?

Maybe I am using the wrong terms..so I'll try better:

I have a hydraulic valve with a valve spool in it..It is open center, which means that in the neutral position, the oil will flow from the "IN" port into the valve and then just go directly into the "out" port..so the oil is continuously flowing without holding pressure..

To make it a closed center valve, the valve spool needs to block the oil from the "IN" port in the neutral position. this would cause the system to hold pressure until the valve spool is moved out of neutral position..I think I understand this concept, but how can I make the valve run on both open and closed center pumps without modifying the valve.???

thank,s
Brent

Brent,

It sounds like you are describing a fail to open vs fail to close valve?

If this is the case, you can use the same valve, just switch the actuator (spring to open vs spring to close).

Am I on the right track here?

Ashereng:

I apoligize about not being specific. the valve spool is hooked to a trigger..So if you don't press the trigger then the hydraulic equipment will not operate. but when you do press the trigger, then this will send the oil to the piece of equipment to operate. This valve is between the hydraulic power unit and the piece of equipment..usually my customers will ask for an open center valve, some ask for a closed center valve..so this means that i have to have 2 different valves in my inventory..I would prefer to just have one valve that would operate on both closed and open systems..

Brent,

Oh, I see.

If you google "Norgren Nugget 500 spool valve", and take a look. Would something like this work?

Keep in mind, the Nugget 500 is for air, and you would need to find an equivalent one for hydraulic fluid, but, you get the idea.

Let me know if I get the idea yet.

You might look for 4-way spool valve designs. You may find four-way valves where you can select as a three-way valve with two-different travel directions, one open center, one closed center.

John

There's always forum1083 where the fluid power guys might be able to help. Make a note if you cross-post so the discussion is kept in one thread or the other.


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I don't suffer from insanity. I enjoy it...

brents:

About the only option I can think of is to stock one center configuration and spools for the second configuration.

You would also need to stock Name Plates for the different part numbers so the valve would have the correct identification.

Most manufacturers hydraulic directional control valves use spools that fit any body with a close tolerance so the spools are interchangeable and work well with minimal bypass.

When I was in sales we often changed spools and Name Tags to ship a valve quickly that was not a shelf item. Especially the odd ball center conditions that that were seldom requested.


Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com

Thanks for all of the replies..I guess I will continue offering 2 different models..Closed center, and open center..

thanks,
Brent