Cylinder Drift on a FEL

[SSdoxie]

Interesting stuff, guys! Is adding a dual pilot operated check valve between the valve and cylinders a good solution to loader drift? Is the dual pilot operated check valve the same thing as the "cross port checks" that you refer to? One scenario for which I would like to have zero drift is when using the loader as a scaffold support.

A "pilot operated check" and "cross port check" both serve the same purpose - to stop flow of oil from a cylinder to prevent drift. The cross port check is a more simple version, costs less to make but sacrifices some hydraulic efficiency. Some of the oil (flow @ pressure) going inot 1 end of the cylider is diverted to the bottom (valve) side of the other check valve to push the check open. This oil mixes with the oil coming out of the cylinder going back to return so some oil under pressure is getting sacrificed to open the check, resulting in a little loss of flow under pressure generating heat.
A pliot operated check works similar except instead off dupmig that pressure/flow to return, it shifts a spool that has a check valve in it and open passage. When the pressure pushes the spool it shifts to open the retrun passage but the pressured oil is stopped/deadheaded against the spool - no loss of oil or flow. The pilot operated cost more to build so its use depends on the application needed.

 

[npalen]

J-J
I'm confused by your first statement. The URL article states the opposite if I understand correctly. Can you clarify?

If you have down force and a leaking seal, the cyl will drift.

The Root Cause of Hydraulic Cylinder Drift

These mechanical cyl rod locks are about the only positive cyl locking device.

The load checks are for a good cyl.

 

[J_J]

Excerpt: The second exception involves a load hanging on a double-acting cylinder (Figure 2). In this arrangement, the volume of pressurized fluid on the rod side can easily be accommodated on the piston side. But as the cylinder drifts, a vacuum will develop on the piston side due to unequal volumes, and depending on the weight of the load, this vacuum may eventually result in equilibrium that arrests further drift.




If you have unequal pressure and leaking seals, what will happen.

The weight of the bucket and lift arms on a leaking lift cyl, will cause it to lower.

Just about every loader will drop the lift arms. A certain amount of leakage can be tolerated.

Leaking spools can also drop the lift arms.

To check for leaking spools, with known good cyl, raise the lift arms fully and shut off engine, then remove the OUT/return hose.

In the neutral position, the spools are supposed to block fluid flow. If the spools are leaking, the fluid from the cyl will flow out the OUT port as the weight of the load will force fluid past the spools to the OUT port.