pressure relief question

[BigAl]

Can I just put a second pressure relief valve inline on my extra set of hyd hoses to my front loader add on attachnents ? Some need a very minimun pressure and others need all the pressure I can send . It would be nice just to turn a knob to regulate pressure . I don't want to bend any more parts !!! Big Al

 

[KiotiJohn]

I believe what you want is a flow regulator, but I'm no hydraulic expert. Maybe Mad will chime in with the answer. John

 

[MadReferee]

You mean you want to control the flow to the cylinders to slow them down? Then you need some type of flow control, either a line restrictor or a special flow control valve on the work port side of the spool valve.

Relief valves are used on the pressure side of the spool valve, not the work port side.

 

[BigAl]

Hi Mad ,
OK ,this is what I have going on . I have a custom built grapple added on to my existing loader bucket that has so much hyd. strength when the jaw's close that it can twist the mounting brackets for the ram and that is a solid 2" piece of steel tubing . I need to get less psi power but keep the same volume so it closes quickly . My other attachment that is in the "build works" now is a tree shear that needs all the psi and volume it can get . I was hoping I could just put something "in line" to work . /forums/images/graemlins/confused.gif Since I can't use the grapple at the same time as I use the shear ,I was hoping I could reuse the same hyd. lines for both duties . Thanks for your input .
Big Al

 

[RickB]

How about smaller diameter cylinder(s) to operate the grapple? If the existing cylinder(s) came with the grapple and the grapple's own frame won't hold up to the pressure the cylinder(s) exert, it sounds like a lousy design.

 

[jinman]

Al, you should look at the Prince RD1850H Prince Hydraulics adjustable pressure relief valve. Its range is 1000-2500 psi. If you mount it on your grapple's cylinder, when you remove the grapple, you remove the valve. That way your shear will have full pressure.

I'm not sure if this valve is a checkvalve in reverse, so you might have to add a checkvalve for opening your grapple.

 

[MadReferee]

Jinman,

The problem with putting a pressure relief valve, like the one you suggested, on a work port circuit is that you still have to have a return to tank hose since when the relief pops the fluid has to go somewhere, ie. to the tank.

If you look at the hydraulic circuit diagram of the RD-1850 you will see it needs a return to tank.

Pressure relief valves of this type are not designed to go in line. They simply monitor line pressure and provide the fluid a path to tank when the pressure exceeds the valve limits.

 

[BigAl]

Hi Rick ,
Yes ,I thought about that . I designed and built this grapple for extreme duty myself .So the only person I can go after is myself! /forums/images/graemlins/blush.gif Most of it is 3/4" T-1 steel . The ram is set up like the newer bucket ram on a Cat or JD . Only one ram in the center . This thing is also a ripper in the closed position and it is unbelievable at how well it works ,except for ram pressure problem . I have it off the tractor now and I am looking at all my options now . It seemed like a relief valve might be my answer . Thanks
Big Al

 

[MMM]

Do you have power beyond at loader valve and third valve for grapple? There are many control valves with adj relief that would work for grapple. A little simpler than plumbing inline relief. Single spool valves for $40 are abundant on E-bay and Surplus Center, etc.

 

[larso1]

It seems to me that you would want a pressure regulator...or pressure reducing valve (PRV) dedicated to your lower pressure cylinder, tapped off from the main pressure loop. Of course it would have to plumb back in to the return, back to the reservoir. But I could be wrong...I would need to see the circuit.

Bill