Removing a stuck pneumatic cylinder

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  #1  
Old 11-07-09, 12:45 PM
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Unhappy Removing a stuck pneumatic cylinder

I have an office chair where the pneumatic cylinder was losing pressure when I sat on it. The chair is over 7 years old. I called the manufacturer for advice and they sent me a new pneumatic cylinder at no charge to install. Instructions were pretty simple: remove the base (easy to do); tap the seat mechanism with a hammer while pulling on the existing cylinder - the hammer taps were to create a vibration that would allow the seal to break so the cylinder could be pulled out. Well, it didn't budge. I pounded harder and tried to pull harder. Still no luck. I removed the seat mechanism from the chair and proceeded to see if I could get the cylinder to turn using a pipe wrench. I sprayed WD40 on both ends in the hope that would help loosen it up. No luck with that either. I was able to get a steel rod on the base end of the cylinder and pounded on it with a mini sledge. It seemed to move a fraction but still wouldn't submit to pulling, the pipe wrench, and yet more pounding. I then proceeded to drill a 1/4" hole thru the cylinder (which let all the air or whatever out along with some black gooey stuff). I then put a steel rod thru the cylinder and tried to exert pulling force using that. No luck.

I thought an extractor of some sort might work, but I don't have one. Given all that I've tried, does anyone out there have any suggestions on how I might get this thing out so I can install the new one? Thanks in advance for any and all advice.
 
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Old 11-07-09, 03:08 PM
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Are you trying to remove the entire cylinder or the piston itself? I believe removing the piston will prove unproductive. Can you see where the piston is fastened on the other end? what brand and model chair is it?
 
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Old 11-07-09, 08:22 PM
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I'm attempting to remove the entire cylinder. The pneumatic cylinder that will replace the one in the chair is a complete cylinder. The chair is a High Back Tilter made by Global Industries. It appears to be a fairly standard type of pneumatic cylinder for office chairs that can be raised and lowered using a rod on one side of the chair. When you're not in the chair and you lift the rod, the seat goes up. To lower it, you sit in it and lift the rod and the seat goes down. The problem is the cylinder is pretty much frozen (it is 7 1/2 years old) in the seat mechanism and simply won't budge. With chairs in the past, I've been able to pull the cylinder out and insert a new one... or I've purchased a new chair. I am hoping not to have to resort to the latter as I really like this chair.
 
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Old 11-08-09, 10:02 AM
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Time to look at heat I would suspect. Watch out for igniting the hydraulic fluid though. DO it outside and keep an extinguiser handy.
 
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Old 11-11-09, 09:48 AM
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Thanks for all the suggestions. I was finally able to get the cylinder to release using suggestions from an engineer at the manufacturer's facility. I soaked the seal with WD40 and let it sit for 2 days, then at his suggestion, instead of pulling on the cylinder, I held it tightly up off the workbench and hit the mechanism (not the cylinder) 5 or 6 times with a heavy hammer and voila!, out popped the cylinder. I guess patience was more the key here than brute stength. Thanks again to all who replied.
 
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