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580SK DIPPER CYLINDER blowing out the end

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CARL COSSIN

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My dipper cylinder end was blowing out so I removed both hoses and see that there is fluid coming out of both in and out at the same time. I think its in the valve for the dipper. maybe the check valve is sticking or there is a blockage. I took it apart and don't see any apparent damage to the seals or the valve. im ordering a new seal kit but not sure if it will fix it. apparently there is pressure on both hoses when I am extending or retracting which causes buildup of pressure in the cylinder and the threaded end pops out. I drilled two shallow holes and placed pins in to prevent the end from coming out but it still blew out. so I started investigating the valve. could it be the check valve or should I look into something else. all other cylinders work properly. we had recently repacked this cylinder and it has functioned good for about a month.
 
alrman

alrman

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I have seen this a number of times, as @Tinkerer says, the problem will simply be the threads at the gland & barrel. They are under immense load.
Unfortunately, once a gland has been spat out of a barrel, BOTH are a throwaway :rolleyes:

When the cylinder was repacked, did you have trouble undoing the gland?
Had the gland worked itself loose? & had the machine continued to be used?
Were the threads rusty?

- All these things can affect the holding strength of those threads.
 
JL Sargent

JL Sargent

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alrman said:
once a gland has been spat out of a barrel, BOTH are a throwaway
Click to expand...
I'm sure this is true. Since they are trash now, why not repack the gland one last time and retread and very carefully weld it to the barrel over a day or two keeping it from getting too hot. Might buy you another 10 years. :)
 
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TVA

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JL Sargent said:
I'm sure this is true. Since they are trash now, why not repack the gland one last time and retread and very carefully weld it to the barrel over a day or two keeping it from getting too hot. Might buy you another 10 years. :)
Click to expand...
Will probably balloon the welded end and then will blow piston seal!

And i didn’t know you were a comedian!:)
 
C

CARL COSSIN

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When i disconnect hoses to the dipper cylinder and activate the control while running both hoses from the valve to cylinder shoot out hydraulic fluid when i extend the cylinder control. This tells me something is not right in the valve body causing cylinder to over pressurize since one of the hoses should be a return rather than bothvsending pressure.
 
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CARL COSSIN

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If both hoses are sending then something has gotta give. In this case the gland blew out of the cylinder tube. I think welding it on after replacing seal kit in valve body should fix it.
 
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TVA

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Well! just FYI: unless your cylinder stoped by something else that it connects to, the gland stops your piston, putting same pressure on both sides of the piston will have equal force as a piston pushing on the gland from blind end. Because force is your affective area of the piston times pressure! As your rod end have less of effective area it’s force is smaller, but the oil in rod end side is a media which pushes on the gland.
So you don’t have multiplication of the force, but the force is equal to when piston pushes on the gland directly!
 
JL Sargent

JL Sargent

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Having welded crazy things in the past such as tractor trailer chassis bolsters, backhoe subframes, power hammers, 30 ton log splitter frames, spindles to axles, etc, I have no doubt that I can weld that gland to that cylinder for a sound repair one time if all is steel. I would take extra time to get it all very clean before welding though. Weld very slowly over a few days keeping the work reasonably cool. Here is a video of a guy welding on a cylinder end cap for example.
 
JL Sargent

JL Sargent

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Here is a video of a guy weld repairing a gland end of a hydraulic cylinder. It's done all the time.

 
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T

TVA

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JL Sargent said:
Having welded crazy things in the past such as tractor trailer chassis bolsters, backhoe subframes, power hammers, 30 ton log splitter frames, spindles to axles, etc, I have no doubt that I can weld that gland to that cylinder for a sound repair one time if all is steel. I would take extra time to get it all very clean before welding though. Weld very slowly over a few days keeping the work reasonably cool. Here is a video of a guy welding on a cylinder end cap for example.
Click to expand...
I didn’t say it will happen for sure. I used word “might”. Cylinders balloon on their own even without welding! Welding will distort the barrel and put it out of round that’s for sure, but if the distortion will happened at the place where piston not reaching to - you might get away with it!
With your method it might just work, but it will take couple of days to finish!
 
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CARL COSSIN

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TVA said:
Well! just FYI: unless your cylinder stoped by something else that it connects to, the gland stops your piston, putting same pressure on both sides of the piston will have equal force as a piston pushing on the gland from blind end. Because force is your affective area of the piston times pressure! As your rod end have less of effective area it’s force is smaller, but the oil in rod end side is a media which pushes on the gland.
So you don’t have multiplication of the force, but the force is equal to when piston pushes on the gland directly!
Click to expand...
If you put extreme pressure on both the inlet and what should be the return then theres no place for the pressure to go but to blow out the gland or blow a hose. Backhoe was pulling up a stump at the time so there was stress on the cylinder. When i disassembled the dipper valve i found that one of the poppets in the valve assy load check was sticking. Im not sure if that would be the cause. Since we repacked the cylinder recently is there any seal that could fail and cause the gland to blow out of the cylinder??
 
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CARL COSSIN

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one other event that happened before the failure: the metal pipe that goes to bottom hose of the cylinder was not tied down in its bracket and wore a hole in it. A friend welded up the pipe and shortky afterwards (couple hrs of work) the cylinder failed. This led me to believe that a piece of the weld may have become lodged some where in the valve control or cylinder to cause a blockage. But with both send and receive hoses disconnected and both putting out pressure i thought the problem to be on the valve assy
 
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TVA

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If you have regen on that cylinder you will have flow on both ends! But one will have pressure and the other just connects to the other one to speed up process!

Your problem with the threads is mechanical not hydraulic! If you welded on the end where the threads are and only in one spot - it oval out the barrel this being open end and not blind one made it easier and weakened the treeads!
 
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TVA

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Have you ever noticed that stick out is stick in? And stick out having flow to the piston end supposed to be slower! That’s your regen! It’s add flow from rod end to piston end to go faster, and it does it inside your control valve. If you see flow from both hoses while hitting stick out - it’s normal.
 
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TVA

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Well! I messed up on ends! I admit! Your stick out is a rod end! But you get the picture on regen!
The loaders curl up is a rod ends!
 
T

TVA

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And another thing: if you had equal pressures on both ends of the piston
- you couldn’t have worked with it! The cylinder would move slow and would be weak!
And it would only move one way - arm in!
 
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TVA

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Yes, and to conclude my “smart ass babbling and yapping” - yeah you right! Looks like you got check valve not holding pressure on regen! And it probably can wear out your gland threads, because it puts load on the gland all the time and not half of the times - but not that fast!!!
 
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