Relief valve

[lumberjack1986]

[QUOTE="Greg9504;3856557"...lumberjack1986, FWIW every install document that I've read from manufacturers of hydraulic thumbs recommend that the bucket over powers the thumb. I think probably in most cases this keeps the pressure below the max rating of the cylinder used for the thumb. Also regardless of what the relief on the side used to extend the thumb is set to, you need to set the relief on the side used to retract the thumb as well. Otherwise you could be over the max rating of the cylinder when you retract the thumb. <img src="http://www.tractorbynet.com/forums/files/construction-equipment/385334-relief-valve-takeuchi_tb135_valve_marked-jpg"/>[/QUOTE]

The bucket cylinder overpowering the thumb cylinder is a lazy, simpleton method of accomplishing what we understand. Assuming the system is limited by pressure and not structural strength, all that matters is the pressures in the cylinders can't exceed their design factor.

You're right, thumbs need work reliefs on both sides of the circuit. I use my thumb occasionally to pull, and the work relief protects it for that. All fluid in a system needs to be controlled by a pressure relief. Thumbs and the bucket cylinder need work reliefs as well.

 

[StPat]

Does the auxiliary hydraulic circuit have a shutoff valve? I am trying to set the pressure for the thumb cylinder as per manufactures instructions, but have no pressure at the boom stop valve. Could the auxiliary circuit be turned off or is it active all the time? This is an Takeuchi TB135

 

[StPat]

Does the auxiliary hydraulic circuit have a shutoff valve? I am trying to set the pressure for the thumb cylinder as per manufactures instructions, but have no pressure at the boom stop valve. Could the auxiliary circuit be turned off or is it active all the time? This is an Takeuchi TB135

I got the auxiliary circuit operating and the relief valves set, (I set them to 2K) now I need to find a stop valve, Takeuchi P/N 1901719800. No dealer around here, any suggestions as to a substitute part or source for a used valve? Thanks, Patrick

 

[mike69440]

I got the auxiliary circuit operating and the relief valves set, (I set them to 2K) now I need to find a stop valve, Takeuchi P/N 1901719800. No dealer around here, any suggestions as to a substitute part or source for a used valve? Thanks, Patrick

I use a Prince 1/2 NPT 3 GPM 15-3 PSI Hydraulic Cushion Valve | Relief & Cushion Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com

Buy a few extra as if you are clumsy and really push te bucket too fast against the thumb this cheap cast iron valve will crack. Best to set relief about 2100- 2200 Psi

 

[PNW1020D]

Hello there TBN team.

I am resurrecting this thread because it seems to have the subject matter that I am interested in, and has a diagram posted that I was able to relate to my scenario.

Thing is I don't really know what my diagram is showing vs. the one posted in this thread.

Here is my scenario:

I am working on a mid 90s Kobelco SK35-2. The machine came from the factory with three ports at the front of the machine. One is a return to take port, and the other two ports are for hooking up a breaker (1 way) or a thumb (2 way).

I have helped run the plumbing, friend built the thumb, etc. etc. but of course I am an idiot and didn't know about pressure relief valves and therefore bent the thumb cylinder rod... :-(

Now here is my question. Does my machine come with pressure reliefs built in to the "aux circuit valve stack"? Where the **** is my aux. circuit in this diagram? Can someone please educate me?






---ADDED PHOTOS FROM LAST NIGHT---

So it seems to me that my machine has the proper 2 way valving built in to therefore use a thumb, but I don't believe that I have the proper port relief cartridge(s) in the "aux. section" aka my service spool to be able to safely run a thumb?

Looking at my machine, it seems I could only install one port relief cartridge in my "aux. section" vs. two? One top and bottom?

I am thinking of just putting in a in-line pressure relief valve on the butt end of the thumb cylinder, and just teeing off that and running another section of hose to the tank return? What do you all think?

 

[PNW1020D]

Any suggestions or input?

I would rather not run another line to the front tank return port if I don't have to, etc.

Please, any help would be greatly appreciated.

 

[ptsg]

So you only need a Work port relief valve on the extending side of the cylinder, so when the bucket hits the thumb, it just lets go. Since your auxiliary valve has one relief valve, just change the hoses around so the extending port of the cylinder has the relief valve. Then you can also adjust the pressure on this relief valve to a lower setting, since usually work port relief valves are set at a much higher pressure than the system.

 

[PNW1020D]

Thank you so much for the reply!!!

Not to sound as if I am questioning you, but how can you tell I have one work port relief valve in my aux. circuit? It doesn't show one in the control valve block diagram that I posed above?



Here is a picture of just the "service section=aux. section" from my manual. Where does it show a port relief valve in this circuit?

 

[ptsg]

Oh crap. Sorry! I might have confused things on my brain. That's what happens when you reply before dinner.

Anyway, after a closer look, the auxiliary circuit don't have a relief valve, so you will need to add one.

To make things easier for yourself and actually a bit cheaper, since you have a tank port along with the aux ports that you showed on the picture I attached. That tank port is used for case drains when you run attachments like flail mowers and things with hydraulic motors that use case drains.

You can add the relief valve right there, which would be really easy to connect to the tank line with a short piece of hose.

I drew on the picture a good place for the relief. I would install it on one of those ports and just run a hose to that tank line. Hopefully you can understand what I'm saying. Something I might lack on some terms since English is not my main language.