I just pulled the rod and piston out of a dipper cylinder to reseal a leaking gland. I was surprised to see the piston rings are failing. What would cause that ? It was resealed about ten years ago. Quite a few hours are on it since then.
Looks like leakage past the seal ring. It usually creates heat and melts that stuff over time. Could just be weak material also.
Can we discuss “dieseling” again..? IIRC it caused a bit of a stir last time.
Hell yeah give it another whirl!!
I need to find my tin hat first...!
Looks like old style chevron packing to me. That stuff will shred like that when you are getting spiking in the system. What machine and which function is that particular normal disaster from?
It is out of the dipper (crowd) cylinder of a Case T/L/B. The gland seal was leaking quite badly. I have a OEM (CNH) seal kit for the entire assembly. Should I use a different brand ? The PO had the wrong bushing in the rod eye and incorrectly installed the barrel eye bushings resulting in a situation that prevented them from being greased. It seems both bushings were installed from the same side of the barrel resulting in no space in the center for the grease. The rod eye had one wide bushing instead of two narrow ones. It was not a tight fit. It has grinder marks around the outside of it.
I am seeing seals geting gume an soft an looking like that, my thought is the oil has changed, or maybe i just see more than i used to. guess just cost of my toys. mother always said the only thing between boy and men were price of toys.
Actually the pistons rings are quite brittle. Extreme heat likely as posted above. Or an inferior aftermarket seal kit is the other possibility, I would suspect.
When I started in the business, nearly all cylinder packing was of the chevron type. I believe that type was derived from hand valve and water pump packing. A lot of it was basically like rope fiber that was formed into the V pattern. The end pieces were flat on one side so that something could press against the flat and force the V sections to push out. Lots of cylinders had a nut on the outside that could be tightened to stop the leakage for a bit. That stuff is affected by heat and also be age. System pressures that it was used in were typically no more the 2,100 PSI and less. A dipper stick is subject to plenty of hydraulic spikes and that type of packing won't take much of that. We changed some of those over to poly pack type packing in the eighties. It was just a single ring then and you had to have spacers to make up for the extra room you had left. There use to be a company in the area that just sold packing and they would put together what you needed from the old samples and some measurements. Nobody does that anymore. If you have the new packing from Case, it should be fine. That stuff didn't last long when everything was right. Unless you use the machine everyday making house payments and payroll, it works fine.
Good day Tinkerer I recall the cylinder repair shop was most busy with Arm or dipper cylinders maybe these are more stressed than others, one explanation is that if the bucket strikes the ground when travelling the shock can be beyond any safety valve, there are I am sure many other similar situations that the cylinder will be stressed. Attached a document that may help you explore some of the possible cause's and some suggested corrective action. Kind regards Uffex
I had the seals in my skid steer bucket cylinders do something similar and they are the newer type of seals. Changed the seals and they've been good for quite a few years. I don't know if a leaking seal can start chunking pieces after a while or does cause dieseling.
Uffex ; Thanks for taking the time to find and post that .pdf file. Interesting information. I am guilty of abusing the cylinder I guess. I have taken out a lot of standing trees with the backhoe. Two feet in diameter is the biggest. Bigger than that I saw them off and then deal with the stump. I dig deep trenches close to and around the root ball. After doing that I use the backhoe to push them over. It is (was) a good way to pop the root-ball out when the tree goes over. After reading about dieseling I think I will abandon that procedure.
All you need is a few bubbles of air entrained in the wrong place in the hydraulic oil. Added compression and the effect is broadly similar to that of boiling coolant with resultant cavitation on the outside of a cylinder liner. The difference is that while the first one is caused by a bursting bubble of steam on steel, the other is to all intents and purposes caused by an explosion and the piston seals are a lot less resistant to shocks of that magnitude than the material of a liner.
Nige ; I understand completely what you just explained. I wasn't aware of dieseling in a hydraulic cylinder before. The file Uffex kindly posted made me aware of a situation (dieseling) I really knew nothing about in a hydraulic cylinder. I am convinced my use of the backhoe to push over trees created the problem with those brittle piston seals.
If pushing trees over with a backhoe or excavator were to be the cause of dieseling, in general, I'd be putting seals in every machine here, every 6 months. 10 years since reseal, and leaking gland causing teardown, leads one to believe that some other force was/ is at work here. Dipper cylinder on my 322bl would eat Bulldog piston seals within 2 months, regardless of how meticulous I was at removing air at installation. Only reason for removal was electrocution of rod. After 3rd set of Bulldog seals, put Caterpillar seals in...never touched that cylinder again.
Seals are blown because they are old and old technology. How are you going to get air in a cylinder that has been running for years? Do whatever you want to do and stop worrying about something that wore out on its own.
Absolutely John C. I'm going to reseal the cylinder and put new bushings in the rod and barrel mount.
Turn a new piston for newer style seal and 2 wear bands... fixed lol