Removing Double Ferrule Fittings from tubing

[Tuckabag]

Hi All,

We've got a device (3 actually) that have been shipped to us that incorporates some 5/8" heavy wall Duplex tubing fitted with a Swagelok double ferrule compression fitting (already pre-swaged).
The factory in their infinite wisdom, shipped the units with 316SS ferrules and nuts despite the request for Duplex items to be supplied, so we need to swap them out for Duplex.
Normally we'd just cut the tubework, fit new ferrules and be done, but in this case we need to retain the tubework length as it is part of a pipeline insertion device and any tubing removed is going to reduce the amount of insertion we have available.
So, does anyone have any experience in cutting ferrules off tubework and the re-swaging new fittings in the same location?
Were you able to get the ferrules to re-seal in the same location?
I suspect that we are going to have sealing issues but would like some feedback from anyone that's tried this.
Swagelok naturally says we can't do this, but I understand that they need to take this point of view to cover arse.
A hydro to 9,000psi needs to be performed once we've done the swap as well.
Appreciate any feedback.
Cheers.

Cam.

 

[Oldhydroman]

No, it can't be done and, for the sake or safety, don't even try. The tube material work hardens under the ferrule and, even if you could get the old ferrule off without making a single mark on the tube surface, the second-time-round joint will not be secure. No-one can/will trust it and your insurers will simply love it (because you paid them the premium and they won't have to pay you anything back when it all goes wrong).

You can cut the tube back and fit a "reducer" which happens to be the same size both ends. I can't see it in my catalogue for the 5/8" size but that doesn't mean it isn't available. Ask Swagelok for a **-1010-R-10 fitting. [In place of ** put the code for the material you want the fitting made of.]

You haven't said what the fitting is. If, for example it is a male connector then you might be able to replace it with a tube adaptor and a straight union. Or you might be able to fit a male-male adaptor into the body of your device and then fit a female connector on to that. The idea is to space the Swagelok ferrule position further away from the device than it is currently so you can cut back your tubing and remake with the correct ferrule.

DOL

 

[Tuckabag]

Thanks Hydro.
That was pretty much what I was expecting to hear, just needed to confirm it.
The fitting in question is a 5/8" tube to 3/4"MNPT, the problem we have is that we require all of the current exposed tube length for insertion as it slides through an end cap on the atmospheric side of the insertion device. Therefore if we shorten this length, whatever fitting we swage onto the tube will butt up against the end cap prematurely and reduce the amount of insertion length we have available.
We might just have to live with this as there appears to be no other option unles anyone else has any bright ideas?

 

[Compositepro]

I would not say it is impossible but you won't find any body who will give you any guarantees. The ferrules will spring back a little when the nut is loosened. You can push the nut and ferrules off with an arbor press using an arbor the same diameter as the tube. The new ferrules must be seated in the grooves left by the original ferrules and the fitting should do that automatically as the nut is tightened. If it passes hydro you should be good to go. The risk benefit analysis is up to you.

 

[Oldhydroman]

I would advise you in the strongest possible terms NOT to push the ferrule off the tube. The ferrule does spring a bit when the fitting is undone and you can rotate the ferrule on the tube but you can't displace it axially.

This is the process you need to follow:

1) Take a look at the picture attached - this shows the ferrule in its made-off position.

2) Now engage your professional engineering judgement: do you think you can push the ferrule off without deforming the tube end in any way?

If the tube end is deformed (by pushing off the ferrule) then it will be well out of spec on OD and surface finish. If you were able to get a new ferrule over the mangled remnant of the tube end then, when you make off the joint ,it will certainly no longer look like the picture. The new ferrule will not be as secure in its axial position and the pressure rating will be reduced. Even if you do pass the hydro test (which I doubt) you can say nothing about the new fatigue and vibration resistance of that joint.

Just don't do it.

DOL

 

[moltenmetal]

Yes, it can be done, but NOT for a system subject to a 9,000 psig hydrotest. Don't waste your time trying. It is not just the ferrule which is deformed during the swaging process.

Cut off the ferrules and orbitally weld a piece of tubing onto the cut ends to make up the required length, being sure that the heat affected zone of the welding is not underneath the new ferrule location. Being close enough to the end, you can paste pickle the welds on both the ID and OD after welding if required for your corrosion service.