kubota back hoe issues

[peavey]

I am a new member, however I have reviewed post on this forum many times when searching for information. You guy,s and Gals know your business and have helped me several times from previous post. I have recently purchased a used kubota back hoe attachment (BT 750) and I am trying to get it to operate from a 11 gpm 2500psi hydraulic pump. Not sure what went wrong, but I blew one of the hydraulic sections on the main valve chest apart. Any help would be great.

 

[Muhammad]

Welcome to TBN.

 

[peavey]

Thanks, This is a great source of information for us not so handy folks. Hope I will be able to contribute from my limited experience of mechanic skills and fabricating.

 

[Briana03]

Hello & WELCOME to TBN!

I moved your thread to the Hydraulics Forum.

 

[peavey]

Thanks Bri, really new to this stuff.

 

[wdchyd]

Peavey, Welcome to TBN.....

Wow, blown apart..?? ....That's a serious issue.....

Maybe the in/out ports are reversed......is there anything downstream plumbed into this circuit (ie: 3ph, other control valves)....

We may need some pics and a brief description of the existing plumbing already on the tractor......

 

[Egon]

Welcome!:thumbsup:

Best be looking for an instruction manual.

 

[J_J]

What was connected to the valve section that cracked opened. Input, output,which cyl, etc.

Did you change any hoses on the valve?

Were you using QD's to connect the BH?

 

[peavey]

Nothing downstream, just a regular kubota backhoe hydraulic valve consisting of 6 sections. I am trying to get it to be powered with a 13hp gas engine and a 11 gpm hydralic valve (log splitter type). I don't think my old Gravely 9000 can handle working the hydraulics, so I thought an external power source would be needed. A poor mans version of a back hoe.

 

[peavey]

I was using quick couplings to connect to the valve. when I first started it up the hydraulics did not function right, so in all my wisdom I held down the right stabilizer jack handle and bang, sounded like a really loud pop, and cool little spray of hyd. oil shout out between the first and second section. Took the valve off and found a seriously damaged valve, metal busted on the back side.Kubota wants about $500.00 just for the parts.

 

[J_J]

You do realize that the pump is only putting out 1.8 GPM's at 2500 psi under load, and 11 GPM's at 650 psi with no load.

Is the BH valve possibly set up for closed center hyd system?

In neutral, does the fluid flow through the valve?

 

[J_J]

You do realize that the pump is only putting out 1.8 GPM's at 2500 psi under load, and 11 GPM's at 650 psi with no load.

Is the BH valve possibly set up for closed center hyd system?

In neutral, does the fluid flow through the valve?

 

[tommu56]

Are you sure you didn't hook it up backwards?
If you dead headed it some way it might have caused it.
There checks in the logic on each valve in the bank the BT600 on the 23.

The system should be open centered again if it is like the BT600

tom

 

[peavey]

Your probably right about hooking the hoses up backwards. I immediately switched the hoses after it happened, thinking I only blew an O'ring between the sections, wrong again. Now I am just trying to make sure I can salvage the rest of the valve chest and have enough pump to make the thing work decent. Can I leave the busted section out and shorten the bolts and just add another single somewhere else to work the stabilizers, and do I need a better hydraulic pump? And No J J I did not know that about the pump, what do I need to do? Thanks for your help.

 

[J_J]

Now we have the rest of the story.

That pump will operate the BH, but real slow. Your 13 HP engine can power a 7.5 GPM hyd pump at 2500 psi.

A .5 cu in pump at 3600 rpm will deliver 7.7 GPM. Something like this.

https://www.surpluscenter.com/item.asp?item=9-7769-B&catname=hydraulic

 

[J_J]

That pump will operate the BH, but real slow. Your 13 HP engine can power a 7.5 GPM hyd pump at 2500 psi.

A .5 cu in pump at 3600 rpm will deliver 7.7 GPM. Something like this.

https://www.surpluscenter.com/item.asp?item=9-7769-B&catname=hydraulic

 

[J_J]

I was using quick couplings to connect to the valve. when I first started it up the hydraulics did not function right, so in all my wisdom I held down the right stabilizer jack handle and bang, sounded like a really loud pop, and cool little spray of hyd. oil shout out between the first and second section. Took the valve off and found a seriously damaged valve, metal busted on the back side.Kubota wants about $500.00 just for the parts.

You can fix that part if you know the manufacture of the valve, by adding another section, or moving some hoses around.

I believe you can get a new 4 lever valve from Baileys for the BH, for about $495

http://baileynet.com/index.php?dnfwd=1&page=ProductDetails&line=CVTJ&baileyno=220-951

 

[peavey]

Sounds like I need a better pump then. Thanks for the help. I know just enough about this stuff to, well bust a $500.00 hydraulic valve. I have a lot of ditching to do around the house and need to get this project going, already got the gravely working decent with a scraper blade, just need get the hydraulics right, then make a sub frame and mount the thing.

 

[peavey]

Thought I would drop the bad valve section out, shorten the three bolts or make spacer, then T the pressure side of the pump to a single spool valve with a built in relief and run the other side of the pressure line (T) to the main valve chest. Thanks for the quick link for the .5 cu pump, ordering one tonight.

 

[wdchyd]

Maybe the in/out ports are reversed...........

Hence the "No-working relief valve".........BANG...!!!!!!


Many years ago while attending a basic hydraulics seminar....the instructer said "All hydraulic systems have a relief.....True or False".....

The answer was true.......the relief is not always the relief "valve"....sometimes the relief is a hose, fitting, cyl, control valve, as anything on the machine can relieve the stress ........BANG......

His main purpose to the question was to make sure the relief valve relieves before the rest of the machine......