how much loader drop is acceptable?

Willl · Dec 23, 2011

Troubleshooting hydraulic cylinder drift

J_J · Dec 23, 2011

This has been discussed many times, and even Mr Casey agrees that if a load is pulling or pushing on the cyl rod, that fluid will transfer. That is apparently happening with some loader and curl cyl.

Hydraulic lock is only when fluid can not escape.

You could also have both cyl seals, and valve leakage.

Although valves do leak, and even have a drops per minute rate for determining replacement, but it is up to you to say when.

If you hung a hyd cyl from a tree limb, filled the rod side with fluid and plugged that port, leave the base end port open and hung a 200 lbs weight on the rod, do you think that if the cyl has a leak that the fluid will transfer, and the cyl rod will extend.

Some might say you would have hyd lock, but if that were true, how come the loader arms descend and a lot of cyl seals replaced and when the seals are removed, you see the reason from torn o-rings, flatten o-rings, extruded o-rings, etc.

Both cyl and valves can be tested, with observation, physical evidence, and just common logic.

If you raise the loader arms, and shut off the engine, and remove the PB, and return hose, if the valve is leaking, the lift arms will descend, and the fluid from the cyl base end will flow out these ports.
If you collect the amount of fluid in the cyl, then you have your answer.

However if the loader arms descend and there is no or little fluid collected from these ports, then the cyl is bypassing, and the seals are bad.

Both you have the hyd shop have the ability to check out a lot of things.

Even a hand hyd pump will test cyl and valves for leakage. You can easily see the results. Even after rebuilding, you should check to see if replacing only the seals fixed the leak. The cyl wall might be worn down, or have a slight bulge.

oldnslo · Dec 23, 2011

J_J said:
This has been discussed many times, and even Mr Casey agrees that if a load is pulling or pushing on the cyl rod, that fluid will transfer. That is apparently happening with some loader and curl cyl.

Hydraulic lock is only when fluid can not escape.

You could also have both cyl seals, and valve leakage.

True statement

J_J said:
Although valves do leak, and even have a drops per minute rate for determining replacement.

Most spool type DCV manufactures don't even publish leakage rates. For reference, Company I used to work for that made D03 size DCV used 5 cubic inches/minute as there criteria for in-house pass/fail @ rated 3000 PSI. I do NOT know if this is any form on industry standard.

J_J said:
If you hung a hyd cyl from a tree limb, filled the rod side with fluid and plugged that port, leave the base end port open and hung a 200 lbs weight on the rod, do you think that if the cyl has a leak that the fluid will transfer, and the cyl rod will extend.

Yes it will extend since you have greater area in the cap end and it is also vented to atmosphere.

J_J said:
Some might say you would have hyd lock, but if that were true, how come the loader arms descend and a lot of cyl seals replaced and when the seals are removed, you see the reason from torn o-rings, flatten o-rings, extruded o-rings, etc.

This is true on curl cylinder where the load is trying to extend the cylinder. Not a true statement when the load is trying to retract the cylinder.

J_J said:
If you raise the loader arms, and shut off the engine, and remove the PB, and return hose, if the valve is leaking, the lift arms will descend, and the fluid from the cyl base end will flow out these ports.
If you collect the amount of fluid in the cyl, then you have your answer.

How do you know if the oil is leaking from the rod end of the cylinder through the seals or out the cap end?. You haven't isolated the two leak points.

J_J said:
if the loader arms descend and there is no or little fluid collected from these ports, then the cyl is bypassing, and the seals are bad.

If the valve isn't leaking the cylinder won't fall. This was pointed out in a previous post.

J_J said:
you have the hyd shop have the ability to check out a lot of things.

Even a hand hyd pump will test cyl and valves for leakage. You can easily see the results. Even after rebuilding, you should check to see if replacing only the seals fixed the leak. The cyl wall might be worn down, or have a slight bulge.

Agree, a good hydraulic shop can check cylinders, valves, etc..

Brad_Blazer · Dec 24, 2011

If a valve has a "load check" on each spool does that not prevent bypass due to spool tolerances?

"Features cast iron construction. Anti-drop load check on each spool. Adjustable relief up to 3625 PSI. Complete handle assembly. Power beyond or closed center available."

Directional Control Valves 220-957 Detailed Information

SSdoxie · Dec 24, 2011

Brad_Blazer said:
If a valve has a "load check" on each spool does that not prevent bypass due to spool tolerances?

"Features cast iron construction. Anti-drop load check on each spool. Adjustable relief up to 3625 PSI. Complete handle assembly. Power beyond or closed center available."

Directional Control Valves 220-957 Detailed Information

Anti-drop load check is located between the spool and the incoming oil form pump. When you fisrt start to move the spool the spool opens the cylinder circuit (with load on it) to the incoming oil, which at this time has very low pressure through the open center. Present load from the cylinder will push the load check closed until the incoming oil builds equal or greater pressure to open and allow oil into the work circuit. It has no affect on holding load in stationary position when the spool is neutral position.