Tandem center vs Open center valves

[Eric_Phillips]

Tandem center is a new term I came across when looking at valves on Baileynet. Knight and Kennyd had some discussion on the subject in THIS thread. Doing some more research I the attached diagram on Brand's site. In this the first spool is open center and the last two are tandem center. The second attachment gives some description to open and tandem center.

So all these loader valves we have been using that places like Surplus Center call open center are really tandem center. Take a look at this from Surplus Center. In the description it says open center. If you go to Brand's web site and build the product code number listed it says both spools are tandem center. If it was truly open center the loader would come crashing down when in neutral.

I hope this information helps others when looking at valves and would like to hear any comments others have on this subject. I think this also might raise a lot of uncertainty when ordering a valve. When looking at Surplus Center stack valves they only say open center but I am betting they are really tandem center.

 

[john_bud]

In common usage a tandem center (open center) valve is simply called "open center". A simple open center valve is called a "Motor valve" as they don't hold the hydraulic pressure in the load lines when in neutral. That allows a motor to continue to spin down and not blow out the line should there not be a cushion valve in the circuit.

jb

 

[MichiganIron]

I believe the completed description would be "open center / 4-way" valve. A closed center valve blocks pump to tank flow in nuetral, an open center allows pump flow to the tank in nuetral.

"Tandem and Parralel" usually refers to the relationship of flow between the spools in a stacked or multiple spool configuration. "Open Center" and "Closed Center" refer to the pump-to-tank flow in the spool nuetral position.