Question regarding Power beyond configuration

[CalG]

With the plan to add a three circuit monoblock directional control valve to allow float function and an extra line when needed on an Allied loader fitted to my SL&H Prince 435, I have the need to understand what is going on inside the valve.

First, my suppositions:

A spool valve of open center configuration discharges all un-needed fluid to the return port and back to tank. Inlet flow is diverted only when the spool is activated, and pressure then builds.

The same valve configured for power beyond plugs the connection between the OC pressure supply and the return line, sending the unused supply fluid through the PB port, and allowing only "spent" discharge fluid to travel back to tank via the return port.

NOW the question.
IF the internal passage between the pressure supply and return chamber/port is plugged, (thus making a PB configuration) AND ALSO the PB outlet port is plugged rather than piped to down line service valves etc., that is then the CLOSED center configuration. (Nothing I need, but to be certain)

the three spool valve I have in hand has a pipe plug down inside the discharge chamber, accessible through an unmarked port ( none of the ports are marked (darned Italian machinery!;-) By comparison with published valve literature, this should be the PB configuration plug.

Some DCV makers supply a single fitting for field conversion from one configuration or another. I have not experienced the particulars of such modifications, but ...I can see a combination plug and cap if an alternate orientation port is to be used. (this valve offers both top and side inlet and discharge.)

Just looking for confirmation.


All comments appreciated

Cal

 

[RickB]

I just read your post twice and I believe you are correct on all points.

 

[whirly]

I just went thru this iteration. When configuring the valve with a PB port instead of the standard Open Center plug, you make the valve closed center. If you are using the PB for an Aux Svc port and do not have another open port valve attached, you will put back pressure on your fixed flow pump and can damage it.

In my configuration, I wanted the Aux Svc to allow me to attache implements that have their own valves - i.e. log splitter. post driver, etc. So I installed a crossover with a simple Open/Close valve so the unused flow could be dumped back to the tank when no implement was attached. You can also accomplish this by using a "jumper" hose but I could just see losing it AND you would have to turn the engine off to hook up the implements. So I went with a hard pipe crossover.

I've attached a diagram of the 3 different valve configurations. Not your valve but the functions are the same.

 

[CalG]

Hmmm

If my valve is arranged the same way as the diagrams, it is presently fitted to provide only "Closed Center" functionality. That is not what I want. I will need to check it out.

Thanks

Cal

 

[whirly]

Hmmm

If my valve is arranged the same way as the diagrams, it is presently fitted to provide only "Closed Center" functionality. That is not what I want. I will need to check it out.

Thanks

Cal

Just unscrew the "plug" you mentioned. If it does not extend much past the threads in the valve body then it is probably an open setup. The Closed plug extends well past the threads in the valve body.

One other point, which you may already know, is that you will still have to provide a return to the tank from the valve when you go to PB as that is where the cylinder return has to go. I just made a tee and plumbed the PB return into the valve return line.

 

[CalG]

The plug on this valve is in the location where the extended portion of the depicted Closed Center fitting. That is, stopping the Open Center passage.
I think I'll need to check things out carefully/

 

[whirly]

When looking at the control end of the valve with the work ports UP, there should be 2 ports on the RIGHT side. One is the normal return port and the other is where the Open/Closed/PB option is fitted.

Here is an example ... not necessarily yours but similar. I used it to plan my hoses & fittings: