The dipper cylinder developed a leak on my EC330. We reasoned that this machine with 5500 hours on it simply had tired seals and we made efforts to buy seals. We bought a seal kit for $500 from Volvo. Our Volvo doesn't do cylinders so we lined up a cylinder shop to do the repair. The leak was between the head the the tube (see a drawing at the link attached-the head is #6). After the repair the cylinder still leaks there. We have not put oil to the new seal but have tested with 150 psi air. It leaks a lot air. The cylinder shop guy thinks that the tolerance between the head and the gland is excessive. He feels that the tube or gland has stretch or cracked. We feel like we have eliminated a cracked as the air is leaking out between the tube and the head. He did not torque the bolts (#21) to the 380 ft-lbs Volvo suggested; however, he claims that these don't seat against anything so for testing purpose this torque shouldn't matter. Could the tube or gland stretch? Could the factory o-ring be too small? Could the tube or gland be out of round? Could there be a crack? Comments and suggestions please. https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0BwZwbhREGIseNTFmY2EyYjgtMGViMi00NGEzLWFiNWMtZGEzYzc2ZmI0M2Vk&hl=en
The tube where the o-ring seats is 6.960" id and about 18" into the cylinder the tube is 6.890" id.
First thing id do is pull the gland out again and check the o-ring didnt nip going back together!
it didn't tear going in. we think it is out tolerance and has stretched. do you believe this could happen?
You're saying the cylinder ID is 6.960 out near the end, and is 6.890 farther down in the barrel. That's only a difference of .070. That's just a hair more than 1/16", which is .0625. Split that difference on each side for tollerance, that's only about 1/32" clearance all the way around the diameter. I really don't think that sounds excessive, but I can't say that for certain. The diameter difference could have been cause by a previous rebuild when someone honed the very end of the barrel to remove rough spots or wear rings. I really don't think that gland or cylinder barrel has stretched, not with all those bolts locking it together. I'm with cps, take it back apart and give it a closer inspection. If it's leaking that bad, it shouldn't be that hard to see the problem.
it has been apart and back together. we are sure that the o-ring is in good shape. at 150 psi air pressure it leaks a lot. this is very minor pressure compared to hydraulic pump pressure. the 20+ year guy at the cylinder shop says that this is too much for him to make up with a big o-ring or seal. keep in mind this isn't just 1/32" around the circumference this is an EXTRA 1/32". maybe i am getting taken?
I understand, not disagreeing with you. I'm only saying this 1/32" could be caused by a previous "shade tree" repair job where someone honed the crap out of the end of the barrel. Assuming that's the case, seems you have few choices; 1) buy a new cylinder, 2) weld the end of the bore and re-machine to spec or, 3) try a slightly larger o-ring and backup ring. Seems to me you have little to lose trying a slightly larger o-ring, possibly even a Viton o-ring. Might just get you going again.
How long have you had the machine? Has it always had a bit of a leak there & suddenly got worse? What did the old oring & backup look like? If pressure had been getting past it, the oring & bu would be chewed out... Is there enough protusion of the new oring on the gland? Can a bigger oring fit in the groove? Has the gland nut been crack tested? It's hard for anyone of us to say without looking at it - but like ATCO, I wouldn't think the barrel would stretch any..... If it did, it would have a bit of a belly in it & not be parrallel down to the smaller measurement
I would think the clearance should only be around seven to ten thousands between the barrel and gland. I'm wondering it the measurement is being made in the right place in the barrel. I have also seen where people have taken one of the piston O rings and put it in the gland packing. You might also check with the Volvo people and see if there are any serial number breaks on that cylinder and any factory updates. Just some thoughts.
This has not been an on going leak as far as i know. I have had the machine fr almost a year. Old ring and backup were chewed up and it was obvious that oil was going past. no crack test or x-ray on the gland nut. I don't know if a larger o-ring would work. None have been tried. I have spoken with Volvo technical service--not the local dealer. They were closed after we got the measurements so I will speak to them to see what the specs are tomorrow. The 20+ year cylinder man thinks that a larger o-ring will wash out right away.
BTW--it isn't really a gland "nut". The gland head #6 on the drawing is held on by many bolts. I would guess on a smaller cylinder this would be a nut??? Also i would be ecstatic if i could get away with using a larger o-ring. That would be great.
And he is right. If the clearance, gap, whatever you choose to call it, is too large, it will cram the o-ring through that gap and wash it out. For o-rings to operate properly, they require the proper gap tollerance. In your case, you're up the proverbial creek without a paddle, note the choices I presented above, that's what you have to work with. I'm only saying, if your wallet is thin, like mine, try a larger o-ring, use a Viton o-ring and backup ring. You may have to machine the groove in the head to accept the increased width of the o-ring, but do not cut the groove deeper, only wider to accecpt the o-ring. That increased width won't hurt a thing if you end up having rework the barrel and use proper o-ring. You have very little cost in trying a larger o-ring, and it just may get you by. But if it doesn't work out, not a lot of money out of your pocket for the failed effort.
is it possible one of the seals inside the head of the cylinder was installed backwards?
Sorry about that - I'm in a habit of having to screw most glands in & the term just comes as a second nature to me......... Certainly seems a strange situation. Wouldn't be the first time a genuine part has been wrongly supplied or packaged - but you would think the repair man would pick that up. I can't even imagine the gland being cracked, but a dy-check test would be happening for sure.
I have actually done that. Had the barrel welded up and machined. To fix the exact same problem. Not so much on OEM cylinders but on thumb cylinders. The cylinder shop has a formula for what clearances/crush there should be to seal the o-ring. We have also had the o-ring groove enlarged on the gland and a bigger o-ring and back up ring installed for a quick fix.
i don't need a quick fix, i need a repair. does this mean that i should go the weld and machine route?
factory specs are 175 mm (6.890") to 175.1 mm (6.893") for id of tube. o-ring is a 8.4mm (0.331") +/- 0.15 mm (0.006)
what about trying to trap an o-ring between the head and the tube? like a flange gasket?
cylinder barrel A good cylinder shop should be able to make you a barrel. Tom
It is possiable that the glan is cracked, i have seen it before! How are your specs to the factory specs!
We've had barrel ends go ovalshaped right at the end. What's the diameter of the gland and depth of groove?
The way that cylinder can is built, I'm thinking it would be less expensive to weld the bore at the end and machine to spec than to build a whole new can. Just my opinion.
something doesn't sound right with this problem, the rod guide bolts to the barrel, so how could anything have wore in the area described. The rod guide and part of the barrel described as being to big should not be a wear point. I would investigate thoroughly the problem before making a hasty repair. Only explanation I can fathom is that someone has either replaced the rod guide or barrel in the past with wrong part. Good luck this seems like a doosy of an issue.
Time to find a dealer that will support the equipment you buy from them. Years ago I took a thumb cylinder in to a local repair shop and they assured me they could fix it ( Boss had to have it done as soon as possible and since I broke it he told me to get it fixed). Well after three "repairs" we took it to the local JD dealer 1 hr away. First thing they call and let use know that the barrel is bent and we need a new one. They fixed it once and it worked fine after that.
I'm with SRE on this one. I have found i never save any money trying to save money. It just never works out for me. ( i should say almost never, cuz for the really simple stuff i can have some success) But anyway, my thoughts would be the rebuild kit had wrong parts in it. I would think the shop could find a bent or oval tube. That is fairly easy to diagnose with a straight edge and a mic. The best money might be to take the unit to a volvo shop that has the skill to diagnose it. They will tell you quickly if its a factory tube, or the wrong parts, or whatever. The first loss is the smallest. Good luck
the nearest volvo shop that does cylinders might be 1200 miles away. the shop i use is good at the uniquely volvo stuff but they don't do things others are experts in---like cylinders. i am not saying i have a bad shop, but they don't do cylinders. even if they did my nearest volvo shop is 250 miles away. it has not been sense our recent economic boom that i had any dealers closer than 120 miles, other than Cat. now i have Cat, John Deere, and Case withing a couple of miles. RDO and Titan just opened their shops within the last twelve months.
I've resently discused i case like this with the local Volvo importer. They state that its important to change your seals, and do a overhaul as soon as it starts leaking/sweating.(They have made it a check point in their service plan) Its a so long and heavy sylinder, that the rod and sylinder hangs easily. If the seals starts to wear, there is so little clearanse between the steel piston and the sylinder inside, that the piston will scrape/shave the inside quickly. Same goes with the rod, wear of the seals, quickly makes steel contact and shawing. And this is a common problem for any make of equipment....
make sure #30 and #24 aren't swapped at assembly. Oring goes to pressure side- back up ring closest to rod end of cylinder
Hi rshackleford, was just wondering if you ever got this ram sorted and what the cause was? Aiden
The ram ended up egg shaped at the end. We installed the seals and still had a leak under 200 psi air. We took the cylinder to a machine shop and had the ID measured and found that we were out of round by quite a bit. We were okay at the piston but not at the end cap. We ended up squishing an o-ring between the end cap and the end plate of the cylinder and have reduced the leak to a drip once a week.
We spent $3500 on seal kits and cylinder shop labor and ended up using a $100 o-ring to make the repair.
Hope you meant to tell us a $1.00 oring to make the repair!
Nope. I meant $100. I guessit's a pretty special o ring.