Dirt Moving Rear hydraulic remote .

[SSdoxie]

The DPOC will only open with a certain pressure from the valve, it will open both check valves. So unless the air is being introduced through the cylinder, there is no way for air to get into the cylinder, after it gets cycled a couple of times after install of course.

And if the weight takes over, like it's happening here, the way the DPCV work, won't let that happen because it will then lose pressure on the remote side and will close the check valves.

This is correct. Pilot Operated Check Valve requires incoming oil to the cylinder to be at higher pressure than exiting oil to open the exiting oil check valve.

 

[K5lwq]

I don't disagree. My theory is with the OP's seemingly worse situation than most, the DPOC will snap closed repeatedly as he extends the cylinder creating a jerking action in the extension. Each time it snaps, a small amount of air can be introduced. Each time he does that more air and more spongy cylinder. A poppet style counterbalance valve might work better as it will smooth the action of the cylinder and extend under a load in a more controlled manor. Not an expert by any means but my old brain just sees this as a better solution.

 

[ptsg]

I don't disagree. My theory is with the OP's seemingly worse situation than most, the DPOC will snap closed repeatedly as he extends the cylinder creating a jerking action in the extension. Each time it snaps, a small amount of air can be introduced. Each time he does that more air and more spongy cylinder. A poppet style counterbalance valve might work better as it will smooth the action of the cylinder and extend under a load in a more controlled manor. Not an expert by any means but my old brain just sees this as a better solution.

It's always a smooth operation when the DPCV is installed.

Here is a little demonstration with a heavy implement:

Tractor 3 point Hydraulic Top Link Installation PART 2. It's complete! - YouTube

 

[K5lwq]

This probably explains what I was trying to say better.

Distinguish Between the Operation of a Counterbalance Valve and a Pilot-operated Check Valve - Fluid Power Journal

 

[DK35vince]

My top and tilt cylinders with the Piloted check valves are smooth. And have always been smooth for the past 18 years the have been on my tractor.

 

[countrybumpkin]

Yes mine works fine too.

 

[K5lwq]

My top and tilt cylinders with the Piloted check valves are smooth. And have always been smooth for the past 18 years the have been on my tractor.

I have piloted check valves on my side links and they are smooth as well. But I also do not have a problem with the cylinder extending faster than the flow like the OP is experiencing.

In that case the pilot will loose pressure and snap closed. Then pressure builds again allowing the valve to open. That is what will create the jerky motion. Now it may not be an issue at all due to the short stroke of the cylinder in question but I see the potential for this scenario. It is hard for me to compare because I don't have an issue to begin with.

 

[countrybumpkin]

Your trying to make a mountain out of a mole hill.

 

[K5lwq]

Your trying to make a mountain out of a mole hill.

Understood. Was not my intent.

 

[Threepoint]

I have piloted check valves on my side links and they are smooth as well. But I also do not have a problem with the cylinder extending faster than the flow like the OP is experiencing.

In that case the pilot will loose pressure and snap closed. Then pressure builds again allowing the valve to open. That is what will create the jerky motion. Now it may not be an issue at all due to the short stroke of the cylinder in question but I see the potential for this scenario. It is hard for me to compare because I don't have an issue to begin with.

K5lwq, thanks for posting the link to the Fluid Power Journal article. Distinguish Between the Operation of a Counterbalance Valve and a Pilot-operated Check Valve - Fluid Power Journal. It seems to explain what I just witnessed this week with a friend's 18-month old, good-quality hydraulic top link with DPOCV on his CK3510SE HST. He showed me how it stutters/jerks a bit when he asks for quick full extension with a 500 lb box blade. By contrast, if he actuates it slowly, the operation is very smooth.

I have an identical top link (bought at the same time from the same well-regarded vendor) on my own CK3510SE HST. However, I cannot replicate the stutter/jerk with a slightly lighter box blade.

Both of us have restrictor-orifice fittings installed in both the cylinder-end and rod-end hoses. In fact, we put them at both ends of the cylinder precisely to reduce the risk of disequilibrium in outflow vs. inflow due to weight of the implement during extension.

Not a big deal, perhaps even a mole hill as CB says but surely a curiosity.