It's STUCK! Can We Get This BIG Cylinder Apart!? | Hitachi ZX470 Cylinder Rebuild | Part 1
how you going guys Kurtis from Cutting Edge engineering today we're going to get started on rebuilding a cylinder for our exchange fleet so this is offer Hitachi ZX470 Excavator it is actually the Dipper arm cylinder so it connects from the boom and then controls the dipper arm so we were really lucky to get our hands on this these are off a newer series excavator and there are still a lot of them around and these are quite a high turnover part so it will be good to get one of these refurbished and put on the shelf for one of our customers but rebuild components generally need a lot of work and this cylinder is no exception so what I know about this it has done about 8 000 hours on the machine the customer did take it off in order to get it resealed they tried to disassemble it they couldn't get the rod out of the barrel which generally says that there's been an internal failure something pretty serious so what I'm expecting has happened is the piston and the barrel have contacted each other they've started to make metal and they have jammed themselves together unfortunately our customer couldn't wait for us to rebuild this and we didn't have any in stock so they purchase it from another supplier we bought this cylinder off them to rebuild it and put it into our exchange fleet so we're going to be looking at re-barrel a new piston potentially repairing the gland and I don't believe the rod's going to be in bad shape but we're not going to know until we get this thing apart that's if we can get it apart because someone else tried to do it and they couldn't pull it apart they weren't tight righto so I have split the gland away from the head flange and I can see down inside there it does look pretty messy like things have been extremely hot so I don't want to pull the gland out with the rod just yet I need to keep it in place because it is the only thing holding the barrel and the rod in alignment if I was to pull it out it might the rod might sag down a little bit which would cause the piston to pinch in the barrel we'll give it the best chance we can to get it out by keeping everything in alignment what I'm going to do is put one bolt back through the gland into the head flange to hold it in place and then I'm going to attach the eye to the forklift and just pull it out a little bit and then I can attach the crane to it and try and pull the rod completely out of the barrel [Karen] woah you're moving the press righto so I did manage to get the rod to move about 500 mil but it has now stopped and the press doesn't have enough physical weight for me to pull on this any harder so I'm going to take it out of the press go and tie it to something really heavy and we're going to try and drag the rod the rest of the way out [Karen] oh no huh right so we managed to get the rod free of the barrel now that everything's open we can sort of see what's going on inside it looks like the seals are not genuine and they have been coming apart for quite a long time one of those seals is really deformed it looks like it would have taken pressure from the bottom side but none of the other seals behind it are damaged so I'd say that was during the assembly process they've pinched the seal and simply pushed the rod home and no one's caught it and I also found a few bits of material that is the barrel and the piston so we're going to get it put on a pallet take it inside and have a closer look at it so I've taken a quick look inside the barrel the scoring is from one end all the way to the other and it is extremely deep there is no way we're going to hone this back and be able to use it so this is going to need a rebarrel but we'll put this one aside and we'll get the rod apart so now we can see the extent of the damage on the piston we do have damage in two areas one is far worse than the other it looks to me that the seals have worn out and the Piston has contacted the barrel and then it just starts to make metal from there it is one of those things that is quite common for dipper arm cylinders because the cylinder spends the majority of its life horizontally there is a lot of weight pushing down on them and the seals do wear out quite quickly so I don't know when this was resealed last but genuine parts weren't put back in it these are aftermarket and they have started to break down cylinders aren't a forever thing like everything on a machine they do need servicing just because cylinders are not leaking doesn't mean they don't need to be rebuilt or need some attention this cylinder wasn't actually leaking the customer did notice a sound coming out of the cylinder while they were cycling the dipper arm one of the other big problems is a lot of customers don't go through the process of their oil sampling and sending that back to the manufacturer so they can then test the sample Hitachi would have known it was a hydraulic part that was failing obviously this customer doesn't do that otherwise they would have picked this up early and the cylinder wouldn't have got this bad so not only does it need a new barrel but it is going to need a new piston as well next thing I'm going to do is get the rest of this disassembled so the way the grub screw works it actually pushes a little ball into the rod and stops it from undoing itself once they do that up they generally center pop the side of the grub screw so it can't undo itself and fall out into the barrel so I do see my fair share of cases where people haven't undone the grub screw and remove the ball and they simply try to undo the nut and then it destroys the end of the rod and generally the nut at the same time now that we've got that undone we're gonna undo the nut this is just me being hopeful noooo righto so the stilsons didn't work that was sort of being a little bit hopeful I'm not going to go and push them because I will just end up breaking them I would usually use a flogging spanner but I did lend mine out to a guy I know and it never got returned I am going to chuck it in the ute take it over to a mate's place and he's just going to crack the nut for me then we can bring it back and finish the disassembly [snuffles] [squeeeak] [squeak SQUEAK] so now we've got the nut cracked we can continue to disassemble the rod so now with all those off we're going to get the bush pressed out of the eye degreaser so with the rod cleaned up I can see there are no scratches dents or even chips in the chrome it is in pretty good condition it is quite dull in the working area because that is pretty standard now I'm going to use a micrometer in four or five different locations just to make sure the rod is still in spec that's 129.99 0.02 undersized 0.02 130 on the button when I mic cylinder rods I always make sure that the rod is in the correct orientation as if it was mounted on the excavator or the dozer and that is because of the way the cylinder works it'll wear the top and the bottom of the rod out so miking it in that orientation is going to pick up if there's anywhere in the working zone of the cylinder so the rod should be 130 mil in diameter in the working area of the rod it is 129.98 so that is 0.02 of a mil undersized which is well within spec so overall this
cylinder Rod's in pretty good shape the eye is still in really good condition it hasn't got any cracks inside it and there is no excessive wear from the bush turning the threads on the end are in good shape the silicon bronze are still within spec the chrome does look a little bit dull so all I'm going to need to do is polish the chrome and we can reuse this rod in our cylinder so the next thing I need to do I need to do an inspection on the cylinder gland righto so I'm going to start by removing the O-ring and its backup ring that seals the gland to the barrel then I'm going to remove the little locking wire that holds the bearing in place then I can turn the gland back over and do the rest of the work from the top so that's the wiper seal removed what this does is wipe all the dirt and the dust off the rod before it gets sucked back into the cylinder so this is its only layer of protection from the outside elements so there are a few ways that rods can be protected there are shields that go over the cylinder rod and they are sort of like an accordion they do work quite well but they do trap a lot of dirt and debris inside them and then you can't tell that the cylinder is leaking oil unless you actually pull it off and check it out so they're generally more trouble than they're worth because they do stretch and they close up and they start to tear and then they fall apart anyway so this is the backup ring for the u-cup this sits on top of the u-cup seal and basically as it says it backs it up so it can't invert itself or roll itself inside out see that it's smeared so that's the rod rubbing against the gland so that is the u-cup seal that is the main pressure seal from inside the cylinder these will hold back about 3000 psi while the machine is in operation as the hydraulic pressure goes this way when it's cycling the ram it oil gets forced into that groove and squeezes that against the rod so it can't bypass oil so that's the buffer seal you can see inside the buffer seal it also has a bit of wear on it where the rod has been sitting on it these are a two-part seal so you have a rubber outer ring that goes in first and then the plastic ring or polymer ring that goes in over the top this is also used to help hold back pressure so that there is the bearing which stops the rod from contacting the gland while it is in operation a lot of different excavators out there will run a polymer or a plastic style wear band hitachi's run these metal cage wear bands there is a polymer on top and then underneath that is a much softer material so if they do end up wearing through it it doesn't contact the cylinder gland and damage the rod so it's actually done its job and stopped the rod from colliding with the gland the gland is actually in really good condition the seals were in really good condition so we can reuse this all I'm going to do is give it a good cleanup and sand blast it to remove the paint so the other parts I removed off the rod was an expansion ring and that goes underneath the cushion bearing and that is designed so when hydraulic oil gets in underneath them it expands and holds the choke in the center of the rod so it can then go inside the head and slow down the cylinder so the expansion ring is in really good condition there is no reason for that to be damaged so I will reuse that because I don't believe the seal kits come with a new one and over the top of that is the choke also known as a cushion bearing and the cushion bearings in good condition there is no reason to replace that and then there's the piston I am just going to take those seals off so you can sort of see the extent of the damage on the piston look at the metal in it so that's our cylinder completely disassembled I need to make a new piston make a new barrel before I can fit the new seals and the bushings and reassemble it but you'll have to stay tuned for the next video thanks for watching So today we're going to get started on rebuilding a cylinder for our exchange fleet [Karen] yep right ready [Karen] yeah oh it's pretty munted but it's it's not [ __ ] munted the next thing we need to do is get this fully assem mmm [train going past] righto [air compressor] so I have [compressor again] hmmm [compressor AGAIN] ughmmm hhhmmmm [Karen] why is this being so painful I don't know so all I'll need to do is give the rod a polish that sounds bad [giggle] so all I'm going to need to do is polish up the rod [Karen] just stop saying rod right right so all I'm gonna [Karen] just and stop saying right right [giggles] [Karen] just not right so any other starting but right so no but how did you start it after that right so that's ugh right so [pfffttt] right so that's our cylinder [Laughter] oh [ __ ] come on put the camera back up stop laughing you make it take too long [Laughter] mmmmm uh oh [Karen] oh my God can you go turn the power point on the wall [Karen] there's just bits falling off everywhere [Karen] [giggle] I'm so distracted right now ahhh goodbye birds no they're not leaving [Karen] ah far out they're having fun they won't be [bang clang] [ __ ] off [Karen] they're not there's a new one [Laughter] [staffy grunts] drop it Homey hey get it let's go [Karen] and then when you're finished just walk off and I'll pan down but you'll have to stay tuned for the next video thanks for watching but you'll have to stay tuned for the next video thanks for watching [Laughter] I can't
2023-09-14 09:15
