Splitting Hydraulics

[GrandFX]

I'm new to hydraulics and it seemed straight forward enough I went on a recent endeavor to split my lines which ended in failure. I'm stumped as to why it didn't work and was hoping someone might give me some advice.

I have a Kubota B3300 and we recently had a 3 lever spool added. When they added the spool it was setup that each time I wanted to use my backhoe, I had to disconnect the spool and connect the backhoe and visa versa. I figured I could put a Tee on the lines and have everything connected at once.

It seems when I did this, nothing works; however, I have multiple quick disconnects setup and if I disconnect any single disconnect going to one of the implements (spool or backhoe) the implement still connected will work.

What is the issue? I have provided some illustrations of the before and after setup. Hopefully someone has some advice.

Thanks
Tim

Lines are color coded by direction of fluid (in/out) and the Yellow/Green rectangles represent my quick disconnects.

 

[Jim L.]

You might want to look at this recent thread: books on tractor hydraulics?

The usual tractor setup is in series with power-beyond. Your diagram shows tees, which is a parallel setup.

 

[OldeEnglish]

I don't know much about your tractor, but tractor data says you have an open center system. It need to be one continuous loop, that's why you have to unhook the 3 spool to use the hoe. It needs to supply from the tractor, to the 3 spool, out to hoe supply, return that back to the tractor. No T's. To use T's a ball valve would have to be installed to divert flow.

If your have power bond, sorry I can't help you there.

 

[ShaunBlake]

You might want to look at this recent thread: books on tractor hydraulics?

The usual tractor setup is in series with power-beyond. Your diagram shows tees, which is a parallel setup.

Unfortunately, that search item (books on tractor hydraulics?) did not include a link. Check it out here:
http://www.orangetractortalks.com/forums/showthread.php?t=17904

 

[Kennyd4110]

You cannot Tee in to the hydraulic lines, all valves MUST be added in series or the fluid (like electricity) will take the path of least resistance back to the tank, and that will be through the other valve that's in parallel.

Here is a good diagram showing how to do this with a "power beyond" equipped valve: http://www.baumhydraulics.com/files/infobuild/basic_hydraulic.pdf

If you give the specifics on the new valve you have, we can advise better on how to hook it up.

 

[GrandFX]

Thanks to all for the quick response and the links.

I suspected there wasn't going to be a simple solution. I will likely put ball valves on 2 of the lines so I can make quick adjustments.

The thing I don't get is... is the spool, backhoe, and other attachments an open system that always allows fluid to circulate in a full loop even when you are not operating the controls. If that's the case, I get it, if not, I guess I need to do some reading to better understand why the tees don't work.

Thanks again!!

 

[OldeEnglish]

This is one way it can be done if you remove your hoe often. It can be risky if the hoe was disconnected and you had the ball valve shut, that would cook the pump.

If done this way, I highly suggest turning tractor off before connecting or turning the valve. Connect the hoe with valve Open, start tractor, Slowly shut valve to divert flow and I mean slow to make sure everything is connected properly. I would also place the valve in a way it can never be accidentally turned and always have a small loop of hose looping the TS together when hoe is not attached,

Only one ball valve and 2 T's needed. Closing the valve will divert flow through the hoe, into the spool. Back to tractor.

If the hoe stays on all the time, I would just hook it up as a continuous loop and forget the T's and valve. It is much safer that way and no room for errors.... Errors in this case would be costly. Or better yet, get a PTO hydraulic pump for the hoe.

 

[North Idaho Wolfman]

GrandFX,
Yes the fluid flows through the valves all the time.
Another way to do it is too have a loop line to put in place when you disconnect the Backhoe.

 

[Kennyd4110]

The thing I don't get is... is the spool, backhoe, and other attachments an open system that always allows fluid to circulate in a full loop even when you are not operating the controls. If that's the case, I get it, if not, I guess I need to do some reading to better understand why the tees don't work.

Thanks again!!

OK I'll try if different way...
Yes, in an OC (open center) system like you have the fluid is continually flowing from the pump, through all the valve and then returning to the tank to get cooled and picked up by the pump again. When all valves are in neutral there is very very low parasitic pressure in the system, usually about 500psi or so. The pressure doesn't rise until something blocks/redirects the flow to do some work.

As I stated above, the fluid will "take the path of least resistance" back to the tank, so when you move a valve off-neutral and the fluid meets resistance, it will seek an easier way back to the tank which would be through the other valve that's in parallel.

All valves in an OC system MUST be plumbed in series, generally using the PB lines to do so like in the drawing I linked to above.

 

[philztoy]

I think if you just put the 3 lever in line on either line between the hoe and the tractor it would work. Although, I am really new to hydraulics myself. I changed your view below to reflect this way of doing it. If it isn't correct maybe someone will give me a comment as I am planning on plumbing this type of setup on one of my tractors.

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[OldeEnglish]

You can't use T's in an open center system. Fluid can only go one way, the path of least resistance. With a T, if you operate the spool, the fluid will bypass the spool your working and will continue flowing through the loop and not the branch because it's open center.

This is the way it should be. Like Wolfman said, after disconnecting the hoe, a piece of hose has to be installed to complete the loop. T's can only be used with a ball valve to direct the flow, like my drawing a few posts ago.

The way it works.... Fluid is always circulating, starting from the pump on the tractor, through all spools, back to the tractor. When you operate the spool, it directs that flow to what ever your operating. Once spool is released to neutral, the fluid is now running its normal path. When the spool is operated it will either supply fluid to a cylinder/motor, or suck the fluid out and return it back to the tractor.

Hope this helps understand it. Once you figure it out, it's really simple. Power beyond is cool but can be complicated to understand if your new to hydraulics or piping systems. That was an excellent diagram for PB KennyD posted a link to.

 

[OldeEnglish]

Here is some better diagrams of using T's, a ball valve, and a pressure relief valve. I wouldn't do it this way without one, it could save the tractors life . If something goes bad it will just dump oil all over the place. I would put it somewhere to notice if it blows off but pointing down so it doesn't spray ya in the face . Always use the same pipe size as the PRV outlet, never reduce in size, and try keep the vent pipe fittings to a minimum. Soft roll copper would work well for it.

Some day I'm going to hard pipe some hydraulic lines to get rid of the medusa looking mess I have now. If you take your time think about how/where to pipe everything, there is a way to do this and have it come out like a factory option for a fraction of the price .