Hi guys A quick question, We have just bought a used Kobelco SK210-6e and the machine I would say is in great shape except for a very serious problem we noticed. We need to sell it but need to make sure the it's repaired properly before it goes. The problem is a 4" hairline crack on the top of the cylinder bore about 6" from the rod end cap. We ground it and found what appeared to be an inclusion during manufacture etc. However we welded with 7018 and found it just leaked again about an inch from where we'd welded. Just wanted to find out whether we are wasting time trying to weld this crack and if it just needs a new outer cylinder fitted or if indeed it can be welded successfully. We just wanna make sure the new owner won't have the same issue as we need to vouch for the repair. A guy I know suggested compete disassembly, grind out, dye test,weld with 6010, grind it out, peen it and then weld over using 7018 and more pending. I do have a good MIG and stick welder and the dye as well so could do it if in fact it would work. I found the same advise of some other forums but just wondering if it works on something this big. If anyone has any experience with something similar that would be great. Also just to mention the crack is for In side the cylinder. It looks like there's a bubble of slag or something and this cause the crack. Any advise would be appreciated!
Usually welding cylinders will get 'em out of round, sometimes bad enough that the piston seals either wont seal or get torn up in that area. Not saying it can't be done, but take into mind that it'll probably have to be honed afterwards. In most cases it's cheaper and faster to get a piece of honed tubing, cut the end off the old one and weld onto the new one and do any machining that needs done on the gland end. If holes have to be drilled for fittings, remember to pass a hone thru those areas after welding the fittings on.
Hey ol' Grump, Thanks for the advise. hmmm, looks like what you are suggesting would be the sure way to sort it.I have ready many blogs of people who've had cracks at the gland ends and managed to gring out the old weld and put a new one on ok. Gutted about this as we are gonna lose a lot of cash on this. And it had to be the biggest baddest cylinder on the machine as well! Anyways, will try and post some pics etc on what we finally do on this. Tempted to just weld it and see how long it holds, but theonly issue is we sell it so cant mess teh customer around, but tempted to try the weld as i wanna see how long it lasts! Just for the sake of some knowledge, otherwise try teh safe way and replace the barrel.
I won't say welding is a bad thing, but I have seen cases where after welding up a crack, during normal digging operations, the cylinder tube failed catastrophically with the tube cracking from the weld area the full length of the tube. YMMV
Hi thanks for the reply I have asked quite a few people as well and its a mixed response so far. Apparently JCB 3Cx rams split lengthwise as well and apparently no amount of welding will hold so they do what ok grump suggested and cut off the glands and reweld with a new barrel albeit a bit thicker in order to handle the pressures. I think I will have to go down the same route. Thanks for the advise and I really don't want a catastrophic failure like that on my head ifs case it injures someone!
I had the same thing on the dipper cylinder on a Komatsu PC200-6. I pulled the rod out, heated to show the crack, ground it out, and then mig welded. It lasted an hour of digging and split the length of the tube, and i ended up with a hydraulic oil bath. I think its safe to say we won't try that again.
Go looking for a replacement cylinder and don't waste any more time on that one would be my thoughts.
Thanks for the advise everyone, i am going to try and but a new barrel on this, if that fails then new cylinder!