Power Beyond Port?

[MadReferee]

OK, now moving back to confused. Let me try this. When I installed the loader, I ran three lines (in, out, PB) from the hydro block (above left rear tire) under the tractor and into the gismo (tech term) that the loader control joystick comes out of. All three lines go into this thing. In that joystick gism there are 3 valves (correct?). These control the flow of hydro fluid depending on how I move the stick. There are four lines that come from the gismo that go to the loader. I am assuming that two (in & out) for each arm cylinder. What about the dump cylinder (only one)?

What you are calling a gismo is in fact the loader spool valve.

Your loader valve has 2 spools, in other words it has 2 functions. One spool controls the raise/lower cylinders and the other spool controls the bucket curl/dump cylinders. If there are 2 cylinders for that spool function, which most tractors have, then those 2 cylinders will be connected in parallel. The cylinders connected to one spool are independent of the cylinders connected to the other spool.

Each spool has 2 work ports These work ports connect to the cylinders for that function. Depending on the direction of the lever, one work port will be applying pressure to the cylinders and the other work port will be exhausting fluid from the cylinders.

The loader valve itself has 3 ports, inlet, outlet (aka return to tank), and power beyond. The loader valve is connected in series with the hydraulic pump, 3pt and tank. The series circuit flow enters the valve at the inlet and exits via the power beyond port. The return to tank port is used for exhaust fluid from the work ports.

 

[kwolfe]

Mad,
Thanks a lot. That is what I needed to hear. The PB port is actually and outlet (so to say). Now I see that if I were to connect a hydro top link, I would have to be teed into both the inlet and PB.

The pictures on this link helped me out, although I don't know if they accurately depict my scenario. It appears from the drawings that the only difference is that my loader would be using the PB port as on outlet as approsed to sharing the fluid exhaust outlet from the work cylinders.

Technical help

 

[MadReferee]

The PB port is actually and outlet (so to say). Now I see that if I were to connect a hydro top link, I would have to be teed into both the inlet and PB.

The PB port is the main flow outlet and it goes to the next valve in line (usually the 3pt).

You cannot TEE into either the inlet or power beyond ports. All valves must be in series. This means you must break the line and insert your valve. However, you can tee into any return to tank line.

The link you posted has good pictures and I have referred people to it many times. Your tractor is the picture that is titled Open Center Circuit with Power Beyond.

 

[kwolfe]

Got it now. Thanks a lot for the information.

 

[tenderman]

So if I understand correctly, the 'outlet' port dumps to the tank and the 'power beyond' port is used for series connecting valves in an open center system. For yearas I have been using the inexpensive Prince four-way valve and just connecting the outlet of one to the inlet of the next, ad nauseum. The systems have been working correctly, and I'm not even sure if there is a 'power beyond' port on these particular valves. I assume a device plumbed out of the regular 'outlet' port would still function, but is there a difference in the way the flow is handled with 'power beyond"?

 

[jinman]

I believe your valve should have a "P" tap for pressure, "T" tap for tank, and a "PB" tap for power beyond. The outlets to the working cylinders are separate from these. The "P" tap of the first valve should be connected to the pump pressure. All the "T" taps can be tied together in parallel. The "PB" tab of the first valve then attaches to the next valve's "P" tap and this process continues to the last valve where the PB tap is tied back into the system or into the "T" line if it is the last valve in the open center system.

The only time the PB port has full pressure is when the particular valve is centered. The T ports serve to vacate the fluid from the non-pressure side of the working cylinder via the spool in the working valve.

I'm sure someone will correct me if I've stated this wrong, but I believe my description is the proper way to connect the valves.

 

[tenderman]

Thanks for the response. I don't recall seeing those labels. The tractor has two quick disconnects on hoses coming off the main valve. I tested the hoses and they each have pressure;one when the hydraulic control lever is pushed in one direction, the other when it is pushed the other way. That leads me to believe that the main control valve on the MM is basically a four-way valve. I figured I would hook my loader valve up and plan on only using the lever in one direction and it should function as an open center system. My question is more what port do I hook pressure to when I add a second, third, etc... valve for other things. Also I am curious how Power Beyond differs from a standard outlet on a regular four-way valve.

 

[jinman]

Thanks for the response. I don't recall seeing those labels. The tractor has two quick disconnects on hoses coming off the main valve. I tested the hoses and they each have pressure;one when the hydraulic control lever is pushed in one direction, the other when it is pushed the other way.

That's the way remote hydraulic taps work. The lever reverses flow so that you could hook those lines to a Double-acting hydraulic cylinder and power it in both directions. When you want to use the remote to power another open center valve, you move it to one position or the other and leave it while you are using your open center control valve. Many of us hook up log splitters that way.

The 4-way valve you are talking about is just a two-spool self-centering valve isn't it? Like a joystick valve?

 

[J_J]

On your valve, you may also see I for IN port, T for TANK port, PB for POWER BEYOND. A or B for work ports. A1 B1, A2 B2, etc.

Non PB valves are usually designed for one valve operation and the OUT/T fluid goes to tank.

Tractors without PB ports also use the T port to connect to the 3pt port, and then to tank. 3pt valves always has a relief valve, for basic operation. Pump to 3pt to tank.

If your valve has PB port, it is best to use it. Valves in a open center system, are connected in series. The first valve upstream has priority.

There is also a back pressure limit on the tank port. Most all tank ports should go to tank.
Most times you will only see fluid coming out the T port, is when the cyl is extending or retracting.

The last valve in an open center hyd circuit is usually the 3pt valve.