Understanding power beyond circuit

[Builder]

Mine has 3 lines. Why not just 2? (One supply, one return?) 2 of them have quick connects, one does not. The one that does not is looped to one of the remaining 2 with the quick connects. What's the deal? The tractor once had a backhoe on it. Are 2 feeds necessary to run a subframe mounted backhoe?

 

[kennyd]

On most CUT's when the backhoe is mounted the 3PH is bypassed, so there is a extra return that goes directly to the tank.

 

[Builder]

My 3ph is not bypassed and functioning normally. The rockshaft has its' own hydraulic line running to it.

 

[kennyd]

My 3ph is not bypassed and functioning normally. The rockshaft has its' own hydraulic line running to it.

It's only bypassed when the backhoe is mounted.

 

[Builder]

It's only bypassed when the backhoe is mounted.

Is that the reason for 3 circuits? When the backhoe is installed one is backhoe supply, one is backhoe return and the 3rd is the one is the 3pt hitch return?

 

[kennyd]

Is that the reason for 3 circuits? When the backhoe is installed one is backhoe supply, one is backhoe return and the 3rd is the one is the 3pt hitch return?

Yes, I kind of eluded to that in my first reply...there are TWO returns, one feeds the 3PH (what your "loop" is connected to now) and the other bypasses the 3PH and goes directly to the tank. Not positive your machine is this way-but a lot of CUT's are.

 

[deepNdirt]

On most CUT's when the backhoe is mounted the 3PH is bypassed, so there is a extra return that goes directly to the tank.

Yup! What -->kennyd Said<--,

 

[Builder]

Any uses for this loop of flowing hydraulic fluid other than a backhoe?

 

[Scotty370]

deepNdirt- About KennyD, I was the first to say : "Even when he thinks he's wrong, he's right!" ~Scotty

 

[kennyd]

Any uses for this loop of flowing hydraulic fluid other than a backhoe?

Logsplitter...

 

[kennyd]

deepNdirt- About KennyD, I was the first to say : "Even when he thinks he's wrong, he's right!" ~Scotty

Thanks

 

[kenstrac]

You probably have a closed hyd.system and it's not a power beyond just a return.

 

[aczlan]

You probably have a closed hyd.system and it's not a power beyond just a return.

Assuming that we are talking about Builders Agco/Challenger, TractorData.com says that the hydrualics are open center which would make these three hoses highly likely to be: PB in, PB out (the two that are coupled together, normal warnings of not running without these being hooked together at the risk of cooking a hyd pump) and waste return (lone hose) they can be used for a BH or anything else that you want to add separate hydraulics for.

Aaron Z

 

[J_J]

Closed center systems.

You can tell if you have a closed center system, because they usually have an accumulator in the system, and all the valves are in parallel. The pumps are usually smaller. Closed centers system are not used for attachments that require large volumes of fluid. If you think you have a closed center system, put a pressure gage in the input line to the valve, and you will have max pressure as long as the tractor is running. The out flow from all the valves can dump into a single line, and back to tank. When you shut down a closed center system, there is pressure in the accumulator, and has potential for moving cylinders and such until the fluid bleeds off. There may be an accumulator dump valve somewhere that can be operated for safety. There may also be a problem with heat buildup, as the gear pump is running constantly, and after the pressure is satisfied, the fluid is relieved/unloaded back to tank.

The danger in not knowing about the closed center system is that some unknowing person might use a wrench to loosen a fitting, and get hyd spray in his eyes, or elsewhere.

One good advantage I can see is you can use any or all valves at the same time, but will have reduced operation at any one valve. If say, all three valves were the same, and you had 12 GPM. Then all valves would have to support 12 GPM. Now as you operate two valves, the volume is split 6 and 6, and if you operated all three, the volume would be split 4-4-4 GPM

 

[Builder]

Assuming that we are talking about Builders Agco/Challenger, TractorData.com says that the hydrualics are open center which would make these three hoses highly likely to be: PB in, PB out (the two that are coupled together, normal warnings of not running without these being hooked together at the risk of cooking a hyd pump) and waste return (lone hose) they can be used for a BH or anything else that you want to add separate hydraulics for.

Aaron Z

I think it's the "waste hose" as you call it that has me baffled. I can understand PB in and PB out. What's up with the waste hose??

Specs on Challenger:
System type: Open center
Total Pump Flow: 14.9 GPM.
Flow to Remtoes: 10.5 GPM
Power Steering: 4.4 GPM

 

[Builder]

Logsplitter...

Ahh yes, flow can be controlled with a lever.

The reason I ask all this is because some of the utility companies around me use hydraulic tools like pruning saws, hydraulic breaker hammers, concrete saws, etc. They run them off the bumper of the utility trucks. Must be a PTO pump or something like that with a hydraulic tank.

My LB115 backhoe actually has a hand tool circuit that I can hook up.

However, it would be easier with my Challenger smaller tractor since it's lighter on its' feet and, well...smaller.

Just wondered what the possibility of running smaller hydraulic tools of my tractor was. Would be great for limb pruning saw

I think the problem is going to be flow control.

 

[J_J]

Well, how much flow do you have. Some of the external hyd chain saws, and cement cutters, require 3 - 5 GPM. @1500 psi. Also, a lot of those attachments are closed center. Some have a switch to switch between open center, and closed center. I have about 6 of those limb cutters, and several hyd chain saws.

One of these will give you flow control.

https://www.surpluscenter.com/item.asp?UID=2009100607330670&item=9-4169-8&catname=hydraulic

 

[keyman1808]

Ok here a question for everyone. I'm running a BX24 and want to be able to use a grapple on my bucket. Not really looking forward to messing with the Hydro system. Could I just remove my BH and hook the grapple lines in there and control it that way. I know I would need a vavle to control the open close of the grapple. Seeing I have this type of set upAny thoughts would be great.

 

[J_J]

Yes, you should be able to do that, with another set of hoses and valves for the grapple.

 

[aczlan]

I think it's the "waste hose" as you call it that has me baffled. I can understand PB in and PB out. What's up with the waste hose?

Being as you could be using something downstream of the PB out (ie: if your loader is before the backhoe your fluid flow could look like (Red is high pressure): PB In on Loader > Loader > PB Out on Loader > PB In on BH > BH > PB Out on BH > Three Point Hitch > Tank)
Thus you might be trying to lower the loader while the curl circuit on the backhoe is engaged, then the fluid trying to exit the loader would have to get to a high enough pressure to make the BH pressure relief go into bypass before it could get to the tank. That would be suboptimal and would make doing anything difficult, as such there is a "Waste" hose that is guaranteed to go directly into the tank without any blockages or significant backpressure no matter what.
This way your fluid flow in the same situation would look like (Red is High Pressure, Blue is Low pressure): PB In on Loader > Loader > Low pressure waste line > Tank less complicated and easier on the equipment
Here is an system fluid flow diagram as it would probably be for your tractor with the BH installed. Blue is low pressure, Red is high pressure


Clear as mud?

Aaron Z