Prince Stack Valve Relief Question

[Cocre]

If a Prince SV stack valve (or any brand I guess) is placed in a hydraulic system that already contains a system relief valve (I am talking about a JD 3320 tractor here) can or should the Prince relief valve plug be removed and replaced with the optional no-relief plug assembly or can the Prince relief valve just be set to relieve at its highest settings thus turning into a no-relief plug?

The Prince valve comes from the factory set to relieve at 2000 psi and the JD valve relieves at 2500. I would think you should have only one system relief valve in the system. Setting the Prince to relieve at 3000 psi should make it to where it would never relieve, effectively turning it into a no relief plug.

Any help in understanding this would be helpful.

 

[kennyd]

Multiple PRV's are common...the one on the valve should be set just below the main PRV setting so you are close.

Let's see what JJ says

 

[J_J]

The first RELIEF valve after the pump, should be set to protect the pump.

I would set the second or any sequential RELIEF valve the same or slightly lower. If you were trying to protect a 1500 psi motor, you would set the valve controlling that motor at around 1450 psi.

 

[Cocre]

I have not tested the factory relief valve pressure setting, but I assume it is OK. I was thinking that setting any other valve at a setting lower than the factory valve would "elevate" that valve to the primary one that controls the entire system pressure. That is why I was thinking either there should be no other relief valve or set all relief valves at a higher setting than the factory relief device. I've got a lot to learn.

Also, the way I currently have my toplink set up the Prince valve really can't relieve anyway. The relief may open, but the excess pressure is not reduced because it is dumping back into an oulet port that is being used as a power beyond port and is not dumping directly back into the tank. Once I get the valve setup with a real power beyond and the outlet connected to the tank return then I can see how the relief can work. But I could be way off here.

 

[Cocre]

On second thought, even relieving to the oulet on an open center system should lower the system pressure on all devices in front of the relief device. I am over thinking this thing again.

 

[Wayne County Hose]

If you could post a schematic of the valve and of your tractor's hydraulics, I could tell you exactly.

 

[AKKAMAAN]

The only problem I see with multiple RV's on the open center cirquit, is that if they all are on the same setting, before they are fully opened, they will start leaking a little at the same pressure. That will make some increase in leakage power losses. I like when the RV stay completely closed all the way up to the opening pressure, then I want it fully opened. Some of these valve I have used have even lowered the pressure a few psi after opening. They are flow compensated. They were common on mobile equipment where operator use throttle (rpm to increase pump flow).

I would, like J_J suggested, choose the one closest to the pump as the prime or main RV, to open first. The others will become extra safety, and I would set them on a slightly higher pressure, up to 150 psi higher at the most. That way the higher set RV should stay fully closed until the main start to open.

It is important that the RV is designed for the flow range it handling. If it is undersized, system pressure will increase if pump flow is increased.

I am probobly "waaaay overthinking" again, but this is my "theory" about it!!

Merry Xmas to you all!! I love this show!!

 

[RickB]

The only problem I see with multiple RV's on the open center cirquit, is that if they all are on the same setting, before they are fully opened, they will start leaking a little at the same pressure. That will make some increase in leakage power losses. I like when the RV stay completely closed all the way up to the opening pressure, then I want it fully opened. Some of these valve I have used have even lowered the pressure a few psi after opening. They are flow compensated. They were common on mobile equipment where operator use throttle (rpm to increase pump flow).

I would, like J_J suggested, choose the one closest to the pump as the prime or main RV, to open first. The others will become extra safety, and I would set them on a slightly higher pressure, up to 150 psi higher at the most. That way the higher set RV should stay fully closed until the main start to open.

It is important that the RV is designed for the flow range it handling. If it is undersized, system pressure will increase if pump flow is increased.

I am probobly "waaaay overthinking" again, but this is my "theory" about it!!

Merry Xmas to you all!! I love this show!!

Following this line of thinking will keep the system functioning up to its maximum design pressure. Good advise.

 

[Cocre]

My crude hydraulic schematics.

Pic 1 is of how it is now. Pic 2 is where I want it to be (Power Beyond feeding Rockshaft).

 

[AKKAMAAN]

If a Prince SV stack valve (or any brand I guess) is placed in a hydraulic system that already contains a system relief valve (I am talking about a JD 3320 tractor here) can or should the Prince relief valve plug be removed and replaced with the optional no-relief plug assembly or can the Prince relief valve just be set to relieve at its highest settings thus turning into a no-relief plug?

The Prince valve comes from the factory set to relieve at 2000 psi and the JD valve relieves at 2500. I would think you should have only one system relief valve in the system. Setting the Prince to relieve at 3000 psi should make it to where it would never relieve, effectively turning it into a no relief plug.

Any help in understanding this would be helpful.

Your new extra valve stack RV setting will basically not affect the RV (2500) in the selective valve because the new valve and rockshaft can not operate while operating the selective valve. For that case, the new valve stack RV can be set below 2500 psi like 2000psi. But then these 2000psi will limit pressure for the rockshaft to 2000psi. So best best is to set the new valve stack RV to like 2600-2700psi, and that way let it just be an extra safety RV.

I agree with you that pic #2 is the right way to plumb it. Pic #1, shows power beyond out from side outlet, which IMO is not good. I would not pressureize the return core of the valve.
Just make sure you have a "POWER BEYOND PLUG", in the power beyond port.