HELP IDENTIFY PORTS ON 3PT POSITION CONTROL VALVE (PICTURE INCLUDED)

[npalen]

In the process of adding rear remote valve and needing to know where to tee the return line into the system. Since the 3PT position control valve (shown in pic) will be close by, I'm looking to tee in somewhere in this vicinity. Looking at the hydraulic parts list (courtesy of Messicks), the two smaller lines (1/2") attached to the valve are labeled "pressure" and "return". The large line (3/4") is labeled "charge pump" and it goes to the large replaceable filter element and from there into the top of the hydrostat. I had planned on teeing the return line from the remote valve into this 3/4" line. Then I got to wondering why the three lines into and out of the 3PT valve. Can someone familiar with the usual plumbing to the 3PT valve clue me in here, please?
Edit: The two 1/2" lines are both connected to the hydraulic distribution block that feeds the power steering, FEL valve etc.

 

[J_J]

Only use the return line for teeing.

Do not mess with the charge pump line.

 

[npalen]

JJ, I appreciate your advice and understand that the charge pump is critical to the operation of the hydrostat and won't mess with that line. Help me understand why the three lines are connected to the 3PH position valve. The large 3/4" line coming out of the valve and going thru the filter and then back to the charge pump would seem to be a drain line that all of the flow from the pump is passed thru to filter the system and make sure the charge pump has a good supply. If that's the case, then why the need for the return line to the distribution block mentioned in post #1 above. It seems counter- intuitive to me but I'm sure there's a logical explanation.

Edit: This is one my Kubota B9200 with FEL

 

[J_J]

There are a lot of hyd blocks return ports on tractors that go directly to tank.

If your hydrostat is using a charge pump, then it is probably sucking fluid from the tank through a filter, because the hydrostat needs extra clean fluid.

My charge pump draws directly through a 10 micron filter for the closed loop variable speed pump.

I really don't think you would want to suck tank fluid directly with out a filter.

Just drain your tank and look at the crud.

If your hydrostat used tank fluid, it would not last very long, and replacement would be very expensive.

 

[npalen]

JJ, I'm thinking now that what the parts book calls the charge line (in the Japanese to English translation) is actually the RETURN LINE that goes thru the main hydraulic filter before returning to "tank". The tank in this case is the transmission housing which includes the hydrostat. There is no separate hydraulic tank as such and the transmission fluid also serves as the hydrostat/hydraulic fluid. There is a strainer in the suction line going from the bottom of the transmission to the pump on the motor. The erroneously named "charge line" mentioned above is a much larger diameter which is similar to the return line to avoid any back pressure as in many hydraulic systems. The main filter is plumbed into this return line so only clean oil goes back into the "tank". The serviceable strainer in the suction line keeps transmission shavings/debris from being sucked into the pump. This is the way I'm seeing it but could be wrong. I think that I gave you bad information in the first post giving the impression that the large line went to the charge pump.

 

[J_J]

If you are talking about the B9200, pipe #200 is the return pipe.

Pipe #100 feeds the 3pt.

It comes from the bottom of the hyd block and goes to the tank.

 

[npalen]

That makes perfect sense now that I get the picture! My mind was trying to make the fluid go in the wrong direction in that return pipe #200. Thanks for bearing with me on this one, JJ!