Arm Cylinder Problem

This topic contains 10 replies and was last updated by lennox-jaipersad 8 years 7 months ago
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lennox-jaipersad
March 17th, 2013 11:56am
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Recently I had the seals of my Zaxis 200LC excavator changed. When the cylinder was reinstalled and correctly reconnected to the hydraulic lines I observed that for the first few minutes everything worked well. However after that the arm cylinder slows down. If the engine is placed on idel for a couple of minutes it works good again, but just for 2 - 3 times. I have replaced the cylinder and it same thing happends. What do you think is causing this? Please nofe that the hydraulic oil filled prior to reinstalling the cylinder is not the OEM recommended hydraulic oil. Do you think this could be part of the problem?
electronexciter
March 17th, 2013 2:51pm
Hi Lennox,



It sounds like you are on the right track by focusing on your oil. Cylinder speed problems indicate a flow issue. Keep in mind not all hydraulic oils are the same, since different OEMs have different additive packages to control oil aeration, oxidation, and viscosity index (rate of viscosity change as temp changes). Even if an oil has the same additives as OEM, it might have different quantities of additive which can cause problems. Additionally, keep in mind that the manufacture's recommended oil viscosity might be for a particular climate. If you are in a tropical or arctic climate and use a manufacture recommended oil that is intended to be used in a moderate climate, the manufactures recommended oil might be questionable. Consult a viscosity temperature chart and consult with your OEM to determine the correct oil. It would definitely be a good idea to make sure you have the correct oil. Using an incorrect oil can allow cavitation or aeration to occur which can cause pump failure-very expensive.



Did the original cylinder failure contaminate the oil? What specifically failed in the original cylinder? What did the failed seals in original cylinder look like? distorted? pitted? Eroded? What are your temperatures throughout the hydraulic system? If you don't already have one, an infrared thermometer is a very useful tool. What is the cylinder's temperature after idling for 2-3 minutes and what is the temp when the cylinder slows down. Is the arm cylinder hotter than the rest of the system? Are any of the other hydraulic functions affected with slow operation?
lennox-jaipersad
March 19th, 2013 1:38am
Thank you for responding!



Below are the answers to the questions asked earlier.

Did the original cylinder failure contaminate the oil? No! The cylinder rod was a slightly pitted in a couple of areas on the cylinder rod. The pits damaged the wiper end seals.



What specifically failed in the original cylinder? The seals on the wiper end began leaking.



What did the failed seals in original cylinder look like? distorted? pitted? Eroded? The seals on the wiper end had minor abrasion on areas where it passed over the pits on the cylinder rod.



What are your temperatures throughout the hydraulic system? I am not sure what the temperature is throughout the hydraulic system.



If you don't already have one, an infrared thermometer is a very useful tool. I will source an infrared thermometer.



What is the cylinder's temperature after idling for 2-3 minutes and what is the temp when the cylinder slows down. I am not sure



Is the arm cylinder hotter than the rest of the system? Yes! On holding the cylinder rod I could feel that it is hotter than the other cylinders.



Are any of the other hydraulic functions affected with slow operation? All other functions are working normal.
electronexciter
March 19th, 2013 10:49pm
It does in deed sound like a failed cylinder piston seal. Possible, but unlikely that the new cylinder was faulty though. What could have caused the new piston seal to fail? Could there be a flow restriction in a return line for that cylinder that is causing pressure intensification to occur in the rod end of the cylinder? A pressure intensification condition in the rod end would definitely slow down or stop the cylinder but would that cause the piston seal to fail. Both extend and retract are affected so we can probably rule out a return line restriction. Could the oil have gotten to hot? This is a completely new cylinder barrel, right? Did you reuse the old cylinder barrel?



I would get the right oil in the system and see what happens.
daylon-mosley
March 21st, 2013 5:33am
Definitely sounds like your piston seals have failed. Stall the cylinder all the way out, disconnect the hydraulic line at the control valve (follow the line back from the fitting thats closest to the rod end), have a bucket and put the disconnected hose in the bucket, continue stalling the machine and if any oil comes out your seals have failed or piston has come loose.



If it doesn't leak, try it retracted, had an issue once where the nut the holds the piston onto the rod had sheared off and would seal when the rod is all the way out but wouldn't when retracted.



Probably going to have to remove the cylinder and take it apart. Might be advisable to get an hydraulic oil sample taken as well.



(When stalling make sure you got boom and arm positioned so the weight would be pulling on the cylinder when stalling all the way out so the weight of the arm doesn't push the cylinder back in when you remove the line, and vice versa)
andy-stoecklin
March 23rd, 2013 2:41pm
Everything my fellow technicians write here is correct. If you have never done this before (removing hydraulic lines and stalling the function), be very careful. This is a dangerous procedure if not done correctly. Most machines have a procedure to remove system pressure before removing hydraulic lines. Never remove a line before releasing the pressure. If your machine uses flat face o-ring fitting, be sure to replace the O-rings before installing the hydraulic lines.
lennox-jaipersad
March 23rd, 2013 6:44pm
I have changed the hydraulic oil to the Hitachi OEM hydralic oil. The problem is the same as before.

When the rod is retracted and the cushion enters the cushion seat the rod extends slowly afterwards. Once the power is brought to low and the rod is retracted a few inches and then extended it works normal again on the low power.

We will test the new cylinder to see if the piston seals have failed as well.



Can you tell me if a solenoid could cause this problem too?
lennox-jaipersad
March 23rd, 2013 7:03pm
I have changed the hydraulic oil to the Hitachi OEM hydralic oil. The problem is the same as before.

When the rod is retracted and the cushion enters the cushion seat the rod extends slowly afterwards. Once the power is brought to low and the rod is retracted a few inches and then extended it works normal again on the low power.

We will test the new cylinder to see if the piston seals have failed as well.

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Can you tell me if a solenoid could cause this problem too?
lennox-jaipersad
March 23rd, 2013 7:05pm
Do you think that there is air in the system?
rodel-marata
March 24th, 2013 6:28am
i think u got it !! there is an internal leaking !! because when high pressure suddenly drops !! temperature rises !! !! in my opinion !! as leaking continues the viscosity of your fluid drops due to the rise of temperature, and check the viscosity of your fluid !! as the fluid viscosity drops the more the leaking the more the temperature until all of your system fluid becomes hot !! and maybe during idle the fluid will have much time to decipetate heat in the reservoir !! because of the buffle plate !! recheck your piston seals !!
mhub
June 21st, 2016 3:25pm
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