FEL wont stay up

[muddstopper]

Mudstopper: wrong on all accounts. The cylinder cannot collapse.

The cylinder is full of oil and capped so oil cannot exit the cylinder correct?

For the cylinder to collapse, the rod has to enter the cylinder. So I ask, where does the oil go that the rod displaces?

The rod side of the cylinder is capable of holding LESS oil than the piston side. In order to go from full extend to full collapse you are saying all the oil from the base end has to transfer to the rod end. But there is more fluid than the rod end can hold due to the rod taking up space.

Ease explain where this extra oil goes?

Explain to me then please how a hydraulic shock absorber works, its filled with fluid, the fluid is sealed inside the shock. The shock has a rod and piston, yet the rod can completely extend and retract without the oil leaving the cylinder. Now I know a shock is equipped with internal valveing to allow the oil to flow at a restricted rate from one end of cyl to the other. I also know that a double acting cylinder doesnt have that valveing. But i will bet you a dollar to a donut that if you drilled a hole thru the piston on a new cylinder, filled it with oil and capped the ports, that cylinder would collaspe under load. The rate of collaspe would be determined by the size of the hole drilled in the piston, but none the less that clynder would collaspe. Bad seals are no dfferent than drilling a hole in the piston. If oil can get by the piston, then the cyl can collaspe and speed of which is just determned by the amount of bypass of the piston. Where does the oil go, it doesnt go anywhere, it doesnt have to, just because the piston is moving from up to down or in to out, the volume of the cyl does not change and zero oil would have to leave the cyl to allow the cyl to collaspe. The oil only moves from one side of the piston to the other side. The volume of the cylinder does not change simply because the piston relocates inside that volume.

*waves a white flag* it finally clicked in me mind.

View attachment 381812

when i started to draw, and just about to open excel sheet to rough calc volume... for total hyd oil volume in A and B diagrams.
B = more hyd oil in the cylinder vs A diagram, that has less total volume of hyd oil in it.

thanks for keeping at me. was in the old fart mood, stuck in me ways and not about to budge.

White flagged raised, I wasnt considering the volume displacement of the rod as more rod volume is added to the total volume inside the cylinder. I give!

 

[muddstopper]

After further review, it now looks to me that if the piston seals in a cyl where bad, in order for the lift to creep, then oil would either have to be leaking around the rod gland and dripping down the outside of the cyl body, have a leaking hose or fitting, Or Leaking back thru the control valve and returning to tank. Does this sound right?

 

[Tx Jim]

YEA team.

 

[muddstopper]

die:die:die::ashamed: By the way, I looked up how a shock absorber works, a tube in a tube with check valves. the outer tube acts as a reservoir to hold excess fluid from rod as it fills up the inner tube.

 

[LD1]

Sorry, been sleeping all day. (Nightshift)

After further review, it now looks to me that if the piston seals in a cyl where bad, in order for the lift to creep, then oil would either have to be leaking around the rod gland and dripping down the outside of the cyl body, have a leaking hose or fitting, Or Leaking back thru the control valve and returning to tank. Does this sound right?

100% correct

die:die:die::ashamed: By the way, I looked up how a shock absorber works, a tube in a tube with check valves. the outer tube acts as a reservoir to hold excess fluid from rod as it fills up the inner tube.

Yep, totally different system.

Glad everything finally clicked for you. It seems everytime we have one of these threads, we get a few more people that have that "eureka" moment.

Now if only JJ would....

 

[muddstopper]

Next time this subject comes up, just go ahead and quote that link you posted first thing. As much as you try to say something, sometimes a picture, or in this case a drawing, is worth a 1000 words.

 

[stan33]

Update.
Metal shavings 'n flakes in dished plate below sump/below hydraulic screen (about a teaspoon full) and a few in screen but not blocked.
Guess this means pump cavitation with air causing wear in pump.

The hydraulic lines for the FEL come off the left, PTO cover plate. Have been told that they probably would have installed an additional valve in there for the FEL. Reckon I need to take off the lift cover to see what is going on in there.

Any ideas on where to look for cause of air problem?. Will the pump likely need to be overhauled?

 

[Egon]

You may want to check out the pump after screens etc. were cleaned. See if it has volume and pressure.

 

[stan33]

Update.
Got the cylinders and valve checked out at a hydraulics repair shop. Cylinder seals were toast, valve checked out ok. Had the cylinders re-built and got all new hoses and a gauge.
Will put it all back together after re-painting the fel then test the pump pressure.

I think this was a combination of factors. Thick mucky oil, water in system from condensation, leaking cylinder seals, air in system, a screen which was getting blocked during operation (sucking all the metal and thick stuff from below the screen on to the screen) leading to cavitation of the pump and more air and pump wear.
It's amazing that the fel went up at all with all that going on.
Will post the pressure test results later.

 

[Tx Jim]

Update.
Got the cylinders and valve checked out at a hydraulics repair shop. Cylinder seals were toast, valve checked out ok.

I'm curious how hyd repair shop tested hyd valve. Did they have a hyd test stand with an operating hyd pump to test valve?