Power Beyond Qestion?

[timbertime]

Hey Guys, my question in simple form is...

Can a power beyond port off a spool valve be both dead headed and run an open circuit valve?

A little more back round; Here's what I'm attempting to do. I want to run two double acting rams (for down riggers on my truck) using a two spool valve with a power beyond port. From the power beyond port I'm planning on putting putting aux hydraulic ports on the back of the truck to run an existing open center two spool valve on my dump trailer. So when the trailer isn't hooked the power beyond will be dead headed. Can the first valve be both open center with a power beyond or is it one or the other? Is this ok to do, or can someone offer a better way to set this up? Or do I need a pressure relief valve somewhere?

Will a valve similar to this one work? Prince Manufacturing Wolverine 2 Two Spool Hydraulic Valve MB21BB5C1 8 GPM 4W3P | eBay

 

[J_J]

No, An open center hyd valve needs fluid flowing at all times.

If you deadhead it, it will try and relieve, and it may not be able to, and either a valve, hose, or pump may be damage.

What kind of hyd system is on your truck.

What you may be able to do is install a male and female QD on the hoses, and when not using the trailer, just connect the two QD's together and that will complete the path if the system is open center hyd.

 

[JCByrd24]

Well the valve probably doesn't care too much, but your pump is what you have to worry about, and the answer is likely that your pump should not be dead headed. It is likely designed for open circuit vice closed as it is much more common. This means that with no valves activated flow just runs out of the pump through all the valves and back to the tank at low pressure. Each valve when activated will send the flow out one of the work ports and return it through the other and build pressure as necessary to move the load. When not activated though, you need to supply this path for your pump to flow from it's outlet to the tank at all times. Even if your pump has a relief valve, you want to set your system up properly for open circuit. You seem to know that aux hydraulics involves two ports: in this case one out to your trailer valve and one coming back. With the trailer valve connected and not activated flow simply goes in to it and out and back to the tank. Thus, when you remove the valve (unhook the trailer) all you need to do is install a short jumper hose between the two aux hydraulic ports to give the pump a flow path back to tank. This can be done with a separate hose or by strategic arrangement of the quick disconnect fittings on your aux ports.

For example, if you want two hard mounted female quick disconnects as your aux hydraulic connections, you will need a separately short hose with male quick disconnects on each end as your jumper (and also males on each side of your trailer valve hoses).

Alternatively your aux out has a hard mount female and your aux in is a length of hose with a male that will reach the aux out when the aux is not in use, and your trailer will have corresponding male in and female out. Thus no need to carry around a separate hose. This is how my buddys Kubota backhoe is set up.

Note that standard tractor aux connections are two females on the tractor with no jumper required, because the valve is on the tractor not the implement, the work ports have the quick connects not the supply and return.

Finally, with either jumper arrangement, you will want to verify there is some sort of relief on the pump before the quick disconnects in the event that the jumper doesn't seat properly you don't want to dead head the pump.

 

[timbertime]

Yes I know the pump itself cant be dead headed. I have a PTO driven pump. I found a diagram nearly exactly the same as the setup I am intending on doing (with the execption of the second valve a two spool). I know I cant have two standard open center valves in my system. Now if I have a setup like the diagram and I deadhead the power beyond will the first valve flow like an open center? I don't want to have to loop the hydraulic hoses on the aux lines, as I dont want to run back and forth tuning on and off the pto from the cab when I'm unhooking the trailer (the second spool on the trailer operates a hydraulic dolly leg).

http://www.baumhydraulics.com/files/infobuild/basic_hydraulic.pdf

 

[timbertime]

I forgot to mention in my last reply that it is an open center system. I will be replacing my existing two spool valve for the down riggers because I'm getting some seepage from the spools. Really just need a good explanation on the oil path on the return line and power beyond line coming from the first valve in the diagram from my previous post. And thanks for the previous responses.

 

[J_J]

In an open center hyd system, the path is very simple.

The fluid is moving at all times, and flows from pump to tank through all valves.

All the valves are in series.

If the trailer valve is on the truck, then just uncouple the QD hoses from the trailer.

If the trailer valve is on the trailer, then just connect the pressure hose with the PB hose from the truck together, and disconnect the return hose and cap.

 

[BHD]

put a third valve in the bank and then use that to run the line to back of the truck,

I like the stack valves, my self, as if you need a different type of vale you can use it, and if for some time in the future you want more you can add and only change the tie bolts,

the other option is to use a power beyond and then run the return to the back of the truck and when you want to add more there is the pressure line and return line, and in the mean time it will work like a crude cooler, I other words just run a loop to the rear of the truck, with the last valve using a power beyond,. or hooking to the return line with adding a power beyond plug later,

 

[J_J]

If he is operating the trailer lift from the back of truck or at the trailer, he would want a valve there at the trailer.

Two or three lines from the truck to the trailer.

The PB line from the front valve would have a QD at the back to connect to the PB line or OUT hose from the trailer valve.

The last valve in the open center system flow path does not need PB, so if the trailer valve is the last valve in the series path, just plug the PB port on the trailer valve and use the OUT/return port to feed cyl fluid to tank.

 

[oldnslo]

Word of caution or advice.

Any time you have to loop a "PB" port to tank with a hose ALL the flow must be stopped before attempting to connect or remove this hose. If flow is not stopped the pump is basically dead headed and pressure builds to system relief setting.

 

[J_J]

Just to back up here.

What kind of pump is in your truck.

Is it one of those DC pumps that only run when powered on?

Is the pump driven by the fan belt and running all the time. Even those have 12v clutches for on/off.

You say open center, but is the fluid flowing all the time?