Oil Recirculation in closed loop system

[J_J]

I always thought the joystick valve had a return to the tank and you would be getting the cylinders purged with use. Shows what I know.

Ken

The FEL valve does have a tank port and dumps the total flow, both expended steering cyl fluid and pump flow.

I an not sure you are replacing all the fluid when you steer, maybe a little at a time as you use the steering.

You would have to go left full steer and then right full steer to use all the fluid.

 

[SpringHollow]

I meant purged over time, not 100% each time the steering was used.

Ken

 

[MossRoad]

opposite ends of the cylinders are tied together instead of the same ends.

That's the key.

In the FEL lift circuit, when both cylinder bottoms fill, both cylinder tops empty towards the tank. When both cylinder tops fill, both cylinder bottoms empty towards the tank.

In the steering circuit, when the left cylinder bottom fills, the left cylinder top empties towards the right cylinder bottom, not towards the tank. When the right cylinder bottom fills, the right cylinder top empties towards the left cylinder bottom, not towards the tank. Since both the left steer and right steer circuits are of equal volume, there is no need for the fluid to go back towards the tank, as it has to fill the opposite cylinder end.

 

[MossRoad]

I don't agree.

The steering is available at all times, and has priority.

The FEL get the PB fluid from the steering valve.

The fluid is flowing through the steering valve through the FEL, then to tank.

You always have volume in GPM, the hyd components develop the pressure.

I think you are correct on that. That's why the FEL locks up when the steering is at full turn.

 

[MossRoad]

The FEL valve does have a tank port and dumps the total flow, both expended steering cyl fluid and pump flow.

I an not sure you are replacing all the fluid when you steer, maybe a little at a time as you use the steering.

You would have to go left full steer and then right full steer to use all the fluid.

Yes, you lose a little fluid back to the tank when steering, but it has to be an extremely small amount. Going full left and then full right moves most of the fluid between the cylinders, not back to the tank. Look at the schematic. If fluid leaves the bottom of one of the steering cylinders it has to be made up in the top of the opposite steering cylinder. Very little fluid will pass through the post of the TEE back to the steering valve. It has to go through the cross of the TEE to fill the other cylinder.

I'm saying the steering valve is pressurizing one side of the steering circuit while relieving pressure on the other, not flowing tons of GPM, just tons of pressure.

:confused3:

 

[MossRoad]

I meant purged over time, not 100% each time the steering was used.

Ken

I don't see how it can ever be purged even over time. That's why the oil is darker in the steering rams. Perhaps a call to Terry at PT is in order for clarification.

 

[MossRoad]

My guess is they'll tell you to crack a fitting to purge any air from the steering cylinders.....

 

[SpringHollow]

Hi Moss,

I would agree with you if there was a mechanical force pushing and pulling on the steering cylinders but it is a hydraulic pump. There is significant flow required. If I ever think to do it, I will ask Terry what he thinks about that circuit.

Ken

 

[J_J]

Maybe I am not seeing things the way some of you do.

Every time a cyl moves, the expended fluid try's to go to tank.

New fluid from the valve is going to the cyl pushing and the other cyl pulling.

Turn the steering, and the fluid moves the other way.

I believe you are putting fluid in a line and then adding to it, with fluid going to tank.

You don't pull from one cyl and add to another.

So when you are turning full lock, the fluid is filling the base side on one cyl and the rod side on the other cyl.

I believe the hoses are short enough to exchange fluid

You have the hose from the steering valve to the cyl and then you have the hose from the cyl to tank.

The steering valve is sending fluid to the cyl or to the lift circuit or both at the same time.

You only have full flow from the steering when the steering wheel is at full lock, and there must be a relief valve there somewhere.

Put several drops of fluorescent hyd dye in one cyl and see if it ever gets to tank. Use black light and look in tank.

 

[SpringHollow]

That is the way I see it.

Ken