Need some answers hydraulics 101

[super55]

I today went and did some parts pricing to hopefully eventually set up secondary hydraulic to both the loader and and rear of a tractor (It will be one hydraulic run with a selector valve to front or rear). I have a few questions that hopefully you guys can chime in and answer for me. I am hoping to set up a solenoid system operated by a toggle switch that is push button dual directional.

1. If the system on the tractor is already a open hydraulic system is it still necessary to have a return line from the sol. valve even though the main valve body to the loader and power beyond port already has a relief valve? I would think I could just cap the return port on the sol. valve and be good since the syst. is already relief valved.

2. Is 1/2 NPT hose/fitting/ports etc. adequate dia. for running implements such as a grapple or a directional cylinder in the back. The tractor's flow rate is about 5 gpm with about 9 gpm max. I am assuming I could go 3/8 if I wished but it would just be slower.

3. Since this is going to be a solenoid operated system I figured I would need a flow control valve to help regulate the speed of the cylinders. The one I was looking at was a flow control/relief valve but they also sell them with out the relief valve. If the tractor already has a relief valve in the system do I still need one and if I do install one won't the whole system on the tractor pretty much function of the one valve with the lowest setting anyway.

As you can see I don't have a whole lot of experience with hydraulics other than rebuilding a valve body on a meyer snowplow once but after doing the research it looks like something I can tackle on my own and save some serious $$$ as compared to having it professionally done.

 

[J_J]

No, you can not cap the tank port as that port feeds the next valve, and is high pressure rated.

Look at this drawing, even though it is a double DO3 sub plate for the solenoid valve.

http://www.surpluscenter.com/Drawing/DR9-5883-2.pdf

You have a pressure port , a tank port, and work ports.

A solenoid valve is full and quick action, no feathering.

It can be located anywhere between the FEL valve and the 3pt valve.

If all valves have reliefs, you should set then all the same.

The solenoid valve has no relief, and will rely on the FEL relief valve.

As far as which relief valve will relieve, it will depend on if a particular valve relief setting is lower, then that valve will relieve when the cyl or motor in that circuit develops the pressure to cause relief.

Say you had the FEL relief at 2500 psi and the 3pt set at 2200 psi. Wen using the FEL, the 2500 psi can be developed, and when the 3pt is in operation, and the load develops the 2200, then the 3pt relief valve will relieve