Hydraulic Cylinder Leak Down on Box Blade???

[ovrszd]

Hydraulic Cylinder Myth - Exploded!

This is some good info on what happens when the piston seal leaks. I realize that a leaking piston seal was not the culprit in this thread but thought some might be interested nonetheless.

Well,, in a way it was,, the leaking bypass valves were acting the same as a leaking piston seal would.

 

[npalen]

True that.

 

[LD1]

Leaking bypass valves were not causing the cylinder to drift. Just the same as leaking piston seals wont cause it either

 

[ovrszd]

Leaking bypass valves were not causing the cylinder to drift. Just the same as leaking piston seals wont cause it either

Just pointing out that the result would be the same. Never laid claim to what that result would be.

I guess we really don't know what that is yet.

 

[muddstopper]

I started to not jump into this, but what the heck. a cyl can drift because of bad seals. I dont care what the video showed. the guy didnt take into account the possible variables. While it is true, that the cyl cant retract because of the rod adding volume to the cyl. The rod can extend, creating a vacuum. Water boils at 212F at sea level. increase altitude decreases pressure. At 10in mercury, water will boil at 192 f and at 29in mercury, water will boil at 32degrees. The same is true for oils, altho the mercury numbers might be different. Now with that said, a cyl carrying a suspended load, should be able to hold that load up to the point of mechanical failure. If there is no way for the oil to escape the cyl, there is no room for movement of the rod. If the seals are bad on the piston, (mechanical failure) it is possible for the oil to bypass from one side of the piston to the opposite side of the piston. While this wouldnt allow the rod to retract, it would allow the rod to extend. If the weight being suspended is great enough, the extending rod would create a vacuum inside the cyl. This vacuum would increase the mercury readings and the oil would boil. The boiling oil would release gas which would expand allowing the cyl to drift, outward. If this occurs often enough, the cyl could create a cushion of air (foaming oil),and allow the cy to extend and retract as the air is compressed and decompressed. This would be a extreme set of circumstances, but to say a cyl cant drift if the oil cant leave the barrel is just wrong.

 

[ovrszd]

What's interesting to me in this particular case is the speed at which the cylinder retracted. If it retracted because of an abundance of air in the system wouldn't it have been "bouncy" like sitting on a large rubber air filled ball?? In this case it retracted at an even steady pace until the scarifier was resting on the ground. Then after the bypass holes were plugged it no longer retracted. Still can't quite figure that part out???

 

[Luke'sScreenName]

What's interesting to me in this particular case is the speed at which the cylinder retracted. If it retracted because of an abundance of air in the system wouldn't it have been "bouncy" like sitting on a large rubber air filled ball?? In this case it retracted at an even steady pace until the scarifier was resting on the ground. Then after the bypass holes were plugged it no longer retracted. Still can't quite figure that part out???

Yup.
Seems clear that either volume (air or fluid) left the system fairly rapidly OR there was one heck of a vacuum in the system to start OR the syatem is very compliant like a water balloon.

My money is on the first option. :2cents:

 

[LD1]

Just pointing out that the result would be the same. Never laid claim to what that result would be.

I guess we really don't know what that is yet.

Some of us know what the result will be.

If there is no way for the oil to escape the cyl, there is no room for movement of the rod. If the seals are bad on the piston, (mechanical failure) it is possible for the oil to bypass from one side of the piston to the opposite side of the piston. While this wouldnt allow the rod to retract, it would allow the rod to extend.

^^^^ This

 

[ovrszd]

Some of us know what the result will be.

Is there a reason you won't share that information??

 

[jenkinsph]

What's interesting to me in this particular case is the speed at which the cylinder retracted. If it retracted because of an abundance of air in the system wouldn't it have been "bouncy" like sitting on a large rubber air filled ball?? In this case it retracted at an even steady pace until the scarifier was resting on the ground. Then after the bypass holes were plugged it no longer retracted. Still can't quite figure that part out???

Since a small shaving was stuck in the piston valve it is feasible that the shaving was holding the valve "cracked open" so the fluid exited through this valve slowly. Air space on the back side of the system allowed this fluid to escape. That is my opinion or gut feeling as to why the cylinder retracted slowly along with simple friction.