Adding power steering & power beyond plumbing question

[etpm]

I have a Yanmar YM2310. Last year I bought a hydraulic cylinder/valve combo made for adding power steering to this tractor. I got or made all the parts necessary to do the job except for the hose and some fittings. The project got put on hold for a while but now I once again have time to finish it. Before I order the hose and the rest of the fittings I would like some advice on plumbing.
The tractor has an aftermarket FEL and the valve for the FEL has power beyond. The hydraulic line that used to go directly to the 3PH was cut and now goes to the FEL valve. From the power beyond port on the valve a hose goes to the line that goes to the 3PH.
I have a flow divider and from that divider the fluid will flow to the power steering cylinder and to something else. The divider can be plumbed before the FEL valve. If plumbed that way the FEL and 3PH will be affected by the reduced flow. If the divider is plumbed after the FEL valve then only the 3PH will be affected. I think the latter scenario is the best way to plumb everything. I could be wrong though.
To maybe make things more clear I will restate things. The output from the hydraulic pump can go to the divider first. Then from the divider the pressurized fluid will go to the power steering cylinder and the FEL valve. Then from the FEL valve power beyond port the fluid will go to the 3PH. OR, the output from the pump can go to the FEL valve first, then from the power beyond port to the divider. Then fluid from the divider will go to the power steering cylinder and the 3PH.
If I plumb the diverter before the FEL it will mean less fluid to the FEL so it will move slower but the steering will work even if I am using the FEL. If I plumb the divider after the FEL the steering won't work if I am moving the FEL but the FEL will move as fast as it does now.
I can raise the engine RPM to compensate for the decrease in fluid if the divider is plumbed before the FEL. I don't usually use the FEL at top engine RPM anyway. Another way to compensate for reduced flow would be to buy and install a hydraulic pump with a larger displacement. However, I have not been able to find one that will fit my tractor.
Opinions?
Thanks,
Eric

 

[Rich B1]

I would install the priority flow divider between the pump and FEL valve. Your steering should have hydraulic priority over anything else. The sacrifice in FEL speed is minor compared to loss of steering when you inadvertently activate the FEL while moving and steering. And it will happen.

 

[oldnslo]

You must have the system relief as the first valve in the pressure line. I agree steering should have priority so you may need to add a relief to the system before the the flow control.

 

[etpm]

I would install the priority flow divider between the pump and FEL valve. Your steering should have hydraulic priority over anything else. The sacrifice in FEL speed is minor compared to loss of steering when you inadvertently activate the FEL while moving and steering. And it will happen.

You are correct. I do need to have the steering at all times, it does need to have priority. I will plumb the divider before the FEL valve.
Thanks,
Eric

 

[MossRoad]

Our machine has a power beyond port on the steering valve. That feeds the FEL, then returns to tank. That makes the steering have priority.

 

[etpm]

You must have the system relief as the first valve in the pressure line. I agree steering should have priority so you may need to add a relief to the system before the the flow control.

I didn't consider that a pressure relief valve might be needed. There appears to be two already on my tractor, one somewhere in the 3PH hydraulic system and one in the FEL valve. Since the divider splits flow at all times even if the power steering cylinder is dead headed won't the two other relief valves still do their job? I don't see how the pressure could get too high if the divider is always venting fluid to the FEL and the 3PH. Now I am wondering how the divider works. It must capable of be delivering high pressure fluid to the power steering cylinder valve even if the other port dumping directly into the hydraulic fluid sump. So it must already have some sort of pressure relief inside.
Thanks,
Eric

 

[oldnslo]

Most priority flow controls block all excess or bypass flow if priority flow is blocked so if something blocks flow in steering circuit what happens? Hose break, steering unit crack, pump housing crack? Not trying to scare just provide some insight on how the valves work.

 

[Rich B1]

Check your tractor for the relief location. Many have a relief at the pump. If it does, then you don’t need to add a relief. If it located somewhere else on the tractor, then you need a relief between the pump and flow divider.

 

[etpm]

Most priority flow controls block all excess or bypass flow if priority flow is blocked so if something blocks flow in steering circuit what happens? Hose break, steering unit crack, pump housing crack? Not trying to scare just provide some insight on how the valves work.

I guess I don't understand how a flow divider works. I thought that inside the diverted is a pressure relief valve that is constantly operating. The relief valve keeps the regulated flow at high pressure and dumps any high pressure fluid not needed out of the port that goes to the FEL or 3PH or whatever or the sump. It sounds like you are saying that if the regulated flow is dead headed then all flow from the divider stops, both ports will have no flow. Am I wrong?
Eric

 

[oldnslo]

A flow divider and priority flow control are two totally different valves and operate in a different manner.

Priority flow control directs a predetermined flow to the controlled flow port and all excess flow is directed to the excess flow port. This is most common valve used for steering since it provides a constant priority flow rate to steering.

A flow divider splits the flow at some predetermined ratio. This ratio does not change so with 4 GPM inlet and 50:50 split you get 2 GPM to each circuit. With 6 GPM inlet you get 3 to each circuit. With most flow dividers blocking flow in one leg blocks flow to both legs. Most common use is trying to keep two circuits operating at the same speed.