Why 3 lines for the backhoe attachment?

[BuggyMasters]

Is what I have circled below the “return line”? In the valve picture above, the bottom-most line goes directly to this place at the back of the machine. Is this what supplies hydraulic pressure so the 3-point hitch can function? My current 2638 runs through the backhoe and then through the 3rd function valve, and then to this same place as circled below.

 

[BuggyMasters]

And lastly, here is what’s on my 2638 now. The input/supply line they have T’d off to feed the backhoe. The very bottom line is what I believe needs to go to the port at very back of tractor as circled in pic above. Very different setup to what’s on the latest 2638’s.

 

[ptsg]

Is what I have circled below the “return line”? In the valve picture above, the bottom-most line goes directly to this place at the back of the machine. Is this what supplies hydraulic pressure so the 3-point hitch can function? My current 2638 runs through the backhoe and then through the 3rd function valve, and then to this same place as circled below.

That lines comes from the Power Beyond on the loader valve and feeds that plate. Since that tractor doesn't have remotes, it then feeds the 3 pt hitch. That plate also has a relief valve.

 

[BuggyMasters]

So it is the last in line on the series then, correct? Aka the return.

 

[BuggyMasters]

And on the new loader valves, this is the power beyond?

 

[newbury]

Who changed the title from "limes" to "lines"?

 

[BuggyMasters]

Ha ha…I did. Fat fingers…

 

[Bentrim]

Maybe if the open center system is explained the answer will appear.

In an open center system the pump moves oil, it does not make pressure, in an open center system oil MUST move constantly with the least resistance possible or something is gonna break. I once broke the center section of a pump when the couplers did not connect properly!

Pressure is generated when a load is placed on the system ie the loader is lifting a load. the pressure generated is only enough to overcome the load. More load, more pressure required. A relief valve prevents excessive pressure in the system

Speed of lift is controlled by the volume of oil produced by the pump usually rated by GPM or gallons per minute. GPM of pump or speed of pump.

Power beyond. A hydraulic valve usually has a supply and a return. When oil is to be "sent" to another valve a Power Beyond plug is installed. This serves two functions.. One it takes the load off the seals in the valve. 2 the oil in directed thru the valve with full flow and will not interfere with the function of the valve. Example if a 2nd valve is plumbed into the return port the valve can do weird things when the second valve is activated. Such as the loader may raise or the bucket dump. This is the reason for three hoses.

The power beyond can hook up many valves For example the loader valve to the backhoe valve to the three point valve.

When a valve uses a power beyond fitting it must have a separate return to tank, so 3 hoses or lines. BUT if the 2nd valve is taken out of the system such as taking the backhoe off two of the lines MUST be hooked together. Why? remember open center MUST flow oil. If you hook the supply hose to the tank hose you eliminate the three point hitch and oil just returns to the tank.. If you hook the correct hoses you have your three point hitch back.

Your original question was "Why are three lines needed?" I hope I have explained why. But remember each valve needs its supply, power beyond (except the last valve) and the return to tank to handle the return from the cylinder or motor.

I tried to find a diagram of power beyond but only could find super technical explanations that took a well trained Xpert to understand.

By the way an Xpert = In math you solved for the unknown or X in science class you learned a spert was a drip under pressure. So an Xpert is an unknown drip under pressure.

Have a great day.

 

[CalG]

If the valve leaks internally,...in any way,... (they all do)

that fluid MUST be allowed to return to tank.

Even if it is leakage from the return to tank circuit.

go figure!

 

[goeduck]

I look at it this way on an open center system. If you take food off of the sushi train (In line) in a Japanese restaurant, once you are done with the dish it goes in the trash (the tank). If you don't think you want the dish you leave it on the sushi train and it goes to the next guy (power beyond). If no one wants it, the last guy in line sends the whole thing to the trash (the tank). Each spool valve is like a guy sitting at the sushi train.