How to repair a hydraulic cylinder with leak problem:
Consider this hydraulic cylinder :
This cylinder is about 6 ft. in height and 10 in. in diameter. Our problem now is how to replace all the cylinder seals inside it. Here are the things we have to do to fix the problem.
1.] First you have to remove the cylinder to it’s mounting. In some cases you do not have to do that if the space for doing the job is sufficient or for some other purposes like to save some time.
2.] You have to drain the oil inside the barrel or cylinder. To do that you have to suspend it vertically, so that the gravitational force will force the rod downward and the oil that is trap in the barrel will be forced to go out in the passage where the fittings of the hydraulic hose is attached. One of the things why we have to remove the oil is that we can not remove the lock ring if it is filled with oil because we have to push back the hub to get an access to the lock ring.
3.] After removing the oil, we are now to back out the hub. We may have to rotate and push down the hub until we see the ring lock. We have to remove it in order to totally remove the hub out of the cylinder. Just use a small screw driver to remove the ring.
4.] Pull the hub outside. This may be the hardest part for this job. You may use some kind of special tools to remove it or in my case, I just used a hydraulic jack. I put the jack to the top of the piston rod vertically. I have a chain and connected it to the two bolts that I provided. I did put a wood on the top of the jack so it will hold while I pump the jack. And so we are able to removed the hub from the barrel. The hub holds the seals inside.
5.] You can now remove the seals and the ” O ” ring in the hub. There is a seal in the bottom of the piston rod too. Replace all the seal and ” O” ring with new and good quality materials.
6.] Put back the piston rod and the hub to its place. You may have to use a piece of wood and a hammer to push down the hub.
7.] Insert the lock ” ring ” to it’s groove and put cover.
8.] Install it back to it’s original mounting.
Note : Some cylinder may have a locking device or design such as in the figure A. In this case, you will just have to rotate upper covering and use some kind of small screw driver to force the strip outward to remove the metal strip that they used to lock the hub cover in placed.