Reduce pressure to thumb (bends pivot pin)

[muddstopper]

You need a 3-port valve as others have stated, SODO. Ideally on the valve stack. To provide
work-port relief inline, you need something like this, a "crossover" RV. An RV must dump
to a low-pressure line to the tank.

I had these made up for my hydraulic chainsaw projects, which needed to be limited to
2000 psi. Definitely less than $100, but you have to find a place to mount them. This
is about as small as you are going to get with an inline setup.

Im missing something here, it looks like all your lines are tee'd together.

 

[BertZegers]

The left image shows how I plumbed the pressure relief valve. It works when the thumb cylinder is extended, and it works when the bucket pushes the thumb cylinder back, protecting bushings and pins. The valve is adjustable.

P=pressure
P=pressure
T=return to tank

The second picture shows how good the valve works. :laughing: :laughing::laughing:

 

[wdchyd]

Im missing something here, it looks like all your lines are tee'd together.

x2......

 

[BertZegers]

x2......

Pressure ( P ) to pressure ( P ) is always open. The return to tank ( T ) is the pressure relief valve, and opens only when the pressure exceeds the pre-set maximum pressure.

 

[Sodo]

OK back to the task at hand. I think I will use the SurplusCenter 3-holer. I found what the difference is betw. 2-holer and 3-holer relief valves - the 3-holer includes the "Tee".

Here's the RV.

I'm going to put it betw the fittings on the right "on the extension line".

I called SurplusCenter and they could not help me with the fittings. I need to get a list together, of the fittings to Tee the RV into the extension line. And then the push-on size to Tee into the return (probably 3/4" barbed). Does anybody know the name of the "fitting style" that is used by Kubota? The fitting size is appx same as 3/8NPT.

 

[Luke'sScreenName]

Im missing something here, it looks like all your lines are tee'd together.

It's an optical illusion. There is 90deg fitting superimposed on top of the other line so it looks like is plummed in a circle. Look at the picture again and you can just make out the lower line on the right.

 

[TMGT]

From what you've said I believe this is the valve you're looking for.

1/2 NPT 3 GPM 15-3 PSI HYD CUSHION VALVE

 

[Ron50]

I used the relief valve that Ken at Boltonhooks sells. Gives relief for both directions of cylinder pressure. $100 seemed worth it to prevent damage down the road. I used excavators that I could tell had a relief valves installed on the thumb.

 

[dfkrug]

Im missing something here, it looks like all your lines are tee'd together.

My photo does not show the connections well. Look at BERT's first diagram with the dashed circle; that shows the
3 ports for a cylinder RV application.

 

[BukitCase]

Sodo, from looking at the inset in your hose pic you might be looking at japanese JIS fittings - if you don't already have DHH's pdf on fitting dimensions, dnl it here

http://www.discounthydraulichose.com/v/vspfiles/downloadables/thread_guide.pdf

page down to the Japanese JIS 30ï½° flare fittings and check the actual thread diameter on YOUR fittings to compare - from the outside, the japanese versions look a LOT like JIC, and from my experience you have either one or the other. Getting EXACT measurements across the threads will likely tell you yours are either 06 JIC or o6 JIS - while the mating faces might actually seal with either type, the threads are off by 1 tpi and thread diameters are off too, best you could hope for if you get it wrong is some destroyed fittings.

Sooo, look at the drawings of both, measure yours with digital calipers, and you should have your answer... Steve

Downside - if yours ARE JIS, you may have a harder time finding a solution; DHH doesn't have much of a selection of the Japanese version

Japanese Cone Seat (JIS 30°) Hydraulic Fittings