Hi All I maintain a Case 688 wheeled excavator with road rail conversion which is owned and operated on our preserved railway. This has had an issue with the rotary joint which caused the brakes to be apllied when traveling and the travel to be applied when braking, not good! I have removed the joint (what a pig of a job!) and have split the unit open to clean and re-seal it. A seal set has been obtained from a local(ish) Case/Poclain dealer and this is where the question comes in. The new seals (which are constructed from what looks like a nylon inner and rubber outer and are two piece) are quite a loose fit over the inner liner, is this correct? Does the exposure to fluid cause them to shrink or does the fluid pressure force them against the central swivel? Many thanks Mark
i have had to make a clamp to go around the rings to compress them a few hours for them to size back to size. when you pull them over the shaft they tend to streach and stay that way till compressed.be sure to inspect the barrel for groves or wear.:drinkup
Are the grooves the seal rings fit into machined into the center shaft or are they machined into the outer housing of the swivel body?
hey atco i was assuming they were on the shaft. and by the way walts hittchen post went out of business no more good ribs.
Well darn, then I guess Montgomery Inn will have to do. :tong I've seen swivel seals both ways, fitted in grooves in center post, and others have the seal grooves in the body. Just not sure which way they are on this particular unit.
mljohn is right on with this one. quick tip for this or even piston seals in a cylinder....use an ole style piston ring compressor. On the swivel you will have to use about three of em or keep moving just one. Works like a charm!
Hi all, thanks for the replies Heres a few pics, first one shows the swivel, the seals fit into the outer casing. Second pic shows a pic of a damaged seal. The problem is that when the seal is offered upto the inner section as a trial fit, its loose and not the sort of tight fit I would expect.
Aye mate, I had a feeling that's what you were describing. I have a suspicion the seal rings alone would fit loosely if you were to simply slip them onto the center post. Likewise, I'd bet the grooves in the outer housing are slightly smaller diameter than the OD of the new seals. This would cause the seal ring to be slightly compressed, and smaller in diameter than it was when relaxed. Fit one of the seal rings in an outermost groove, lubricate it, and see how the center post fits when you slip it into the housing. I'd bet you'll be Ok.
Thanks I will give it a try. My concern was that the two part seal has a nylon inner which may not be compressable.
Could you post some pics of the new seals?
Ok, here is a pic of a seal which has been slid over the centre section. You can see the harder (nylon?) inner and the outer rubber part of the two part construction. You can also see my concern, there is a gap. Now of course this gap may be correct! Thanks for the help.
I should add that the gap is emphasised as I have ensured the seal is pressed against the rear of the centre section for the purpose of the pic.
I can see the gap that you're referring to, but I don't think that's excessive, can't say for certain though. I'd wager that hard seal ring is teflon, it will give and take a little, but not when it's cold. Place the swivel housing in front of some kind of heater to warm it a bit, don't really need it hot enough to burn you or a seal, just warmed up a bit. Put the inner (hard) seal ring in a pot of water on a hot plate and warm it fairly warm, boiling temp not necessary, but good and warm. Place the rubber loader ring in a groove of the warmed housing. Now gently work one of the warmed seal rings in the groove with the rubber loader. I think you'll find with everything warmed up, you can work that seal ring in the groove and it will make a nice snug fit when the center post is inserted. Here's to keeping my fingers crossed, I've done stepped out on the proverbial limb here.
Thanks, I will give it a go. I tried fitting one last night and it was having none of it. The inner plastic is Nylon 6 (managed to get the seal drawing from Case) and having fitted the rubber outer section in the groove, the nylon just would not go in at all, the old nylon insert from the original seals was fine though!
Yeah, there's not much give to nylon rings. You've asked your dealer and they assure you they are the correct seals?
Yes, there certainly the right part number (according to them and the case online parts tool). To me, it looks like a tolerancing issue on the part. I have taken the joint to my supplier and they are going to look at it and sort it for me (at no charge!) I will update on the outcome
Well now, that sounds like a good plan. Yes, do let us know how it worked out.
Well Mark, did ya ever get your swivel sorted out? I repaired one on a Case 9050B this week, one similar to yours, and this thread came to mind. I slipped one of the new seals over the swivel post, pushed it against the post surface on one side with my fingers, and sure enough, there's a gap on opposite side of the swivel post, just like you had with yours. The seals for this one are one piece seal rings, not two piece like yours was. They fit well in the grooves of the swivel body, and seal post fit nice and snug when it went together. Just curious how it worked out with yours.
Hi All Thought I would close this thread by giving feedback on the final result. We took the unit and seals to our local Case dealer who also had quite a few issues in fitting them (and they do this all the time!). Following numerous calls to Case USA they finaly came up with a working method which involved heating the joint to 60+ Deg C and also warming the seals in an over to 80 Deg C. This allowed said items to be inserted fairly easily (although because the joint is large the centre ones are tricky!). I have spent 1 night a week for the last 3 weeks (we are volunteers and the wife only allows me limited 'playing' time) fitting the joint back into place and having now connected it all up (and having finaly gotten all the hydraulic fluid out of my hair!) we are ready to test her this week. Initial start up went well with nothing to strange happening, rail wheels raise and lower, brakes work etc. This Thursday will see her taken outside for a full test and shake down.....fingers crossed!