Hydraulics Help Needed

[Dave M7040]

Pardon the interruption. But can each of you describe what you mean in detail? I am in the process of installing a new spool valve on a L3700 Kubota and I am now confused!

Suggest you start your own thread with your specific questions.

You need to describe what you are trying to accomplish and how.

Where do you plan on getting hydraulic pressure, do you have a loader, how many hoses on the loader valve 6 or 7.

The issue being discussed in this thread has to do with a valve's TANK port. Many mistakenly use the TANK port to feed another valve instead of providing Power Beyond from the prior valve in the chain.

TANK ports are limited in the pressure they are designed to withstand. Usually 500 psi. If you call on the valve being fed from the TANK port of a prior valve to provide pressure say for a top and tilt, the pressure in the prior valve's TANK port will spike up to the relief valve setting and will damage the valve.

I have included instructions found on the internet that describe how, in the wrong way, to add additional hydraulics.

Also valve specs showing the limited pressure rating of TANK ports.

Dave M7040

 

[ericm979]

There are many valves with only an in, out and two work ports. If you use the out (AKA tank) port of a valve to feed another valve, the tank port has to be rated for full system pressure or above. That's because all the valves in the chain ahead of the valve you are using will see full pressure on both in and out ports if you're operating the valve at max capacity. Valves that are made for this usually have the tank port rated to about 3000 psi which is well above tractor system pressure. For example the subplate type solenoid valves commonly used for 3rd functions have full pressure tank ports. None are available with separate PB and tank ports (the subplate format does not support that). An example: D3 SOLENOID OPERATED DIRECTIONAL CONTROL VALVES | Trausch Dynamics.

There are many tractors using valves like this from the factory, aftermarket suppliers and dealers.

If you have a valve that does not support greater than full system pressure on the tank port, it does need to set up with separate PB and tank ports if you're feeding another valve from it. Or use a valve that supports full pressure on the tank port.