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Hydraulic motor help

Flail

Cast Iron
Joined
Oct 29, 2013
Location
Bonsall, CA
I have installed a power forward electric hydraulic solenoid valve between my loader joystick and the backhoe swing circuit on a Kubota L-48 tractor. The purpose of the power forward valve is to run a grapple or a hydraulic motor driven trommel that replaces the loader bucket. Question I have is the motor has a line-in, line-out and a motor-drain. I need to figure where to connect the drain. I suspect I could plumb it all the way back to the tank. Would it work just as well to tee the motor-drain into the line-out of the motor? My thought is the line-out has minimal back pressure on it when the motor is running and doing work. would this setup protect from blowing seals or do I have this all wrong?

Thanks, and no Eskimo jokes.
 
IIRC surpluscenter.com has a block manifold device that switches the drain to which ever line is ported to tank at the moment.

some motors have this arrangement built inside.
 
Case drain needs to go back to tank
We have tried to join the return line and it always blows the seal on the motor shaft

Greg
 
The motor case drain should run back thru a filter and an oil cooler.....unless the filter is mounted on the pump body ,there is no other place to put one that isnt full pressure type.
 
I believe, IF the motor is incapable of reversing, the case drain can tie to the return line. Call it "less than 200psi"

That is a valving determination for the application. If the motor EVER would see fluid pressure on the drain line. Well, then there is no drain line.

Unless the device mentioned by digger doug is fitted.
 
the setup depends on what kind of motor and what pressure.....if you are using a simple gear motor,at low pressure,then the drain can go into the return line.......however if you are using any of the nongear motors....then the details may vary considerably motor to motor......for instance axial piston motors may need retained case pressure to limit cavitition ,or chattering....other kinds are vane motors,roller stator types,etc.,
 








 
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