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Internal bellows expansion joints inside FCC reactor

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This topic contains 3 replies, has 2 voices, and was last updated by  Anonymous 13 years, 4 months ago.

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  • #3982


    I just want to know about, other users experience of bellows expansion joint installed on top of duct riser between the VSS (vortex separation systems) chamber and FCC reactor cyclones.
    From my experience it seems to me that the behaviour of the referred expansion joint is very critical for the liability of the reactor.
    My expectations for the above expansion joint are coke build up on the convolutions, loss of flexibility, cracking of bellows plies, distortions on cyclones cross-overs and on top dome of VVS chamber. Please share.
    Luis Marques

  • #7221


    Dear Luis,
    The VSS disengager expansion joints have been a topic since they were introduced..  Coke build up was a major problem at a rectent turn around were the coke packed the joint and it “dimpled” the internal dome of the regenerator.  As a result of this “learning” experience, we no longer recommed internal/external insulation.  Also, the area between the bellows and internal liner has to be “cleaned” of coke every turn around.  The best solution is to install steam purging between the bellows and the liner.  However, this may be too costly and the alternative is to “clean” the bellows every turn around.  If you would like to discuss this matter further, please feel free to contatc me.
    Dan Edgar, PE
    Principal Engineer
    Senior-Flexoncis, Pathway Div

  • #7210


    That was my feeling, we will have a VVS internal disengager expansion joint without any insulation, with holes on top and with a blanketing steam, besides of this, I think that we will have coke build up inside and out side of convulsion bellows and along the time we will lost expansion bellows flexibility and we will force stress on top dome of riser chamber probably with crack ruptures and as result traffic hydrocarbon bypass.
    I think that in the near future the design concept will eliminate internal VVS disengager expansion joints. All the VVS system will be supported by the plenum/cyclones and the expansion of all the system will be freely done because the bottom of the riser chamber will be completely open.
    Thank you for the empathy and fell free to share other FCC matters
    Best regards
    Luis marques

  • #5978

    Patrick Bozanich

    We installed VSS in 1996. In 2001 we opened up and had no problems. In 2005 we had a failure (coke build up) and we had a 4″ dimple around the outlet of the dome. We discussed going to a slip joint design in 2009 but chose to delay until 2013. The EJ had some issues but the dome had not gotten any worse. Another idea is to go with a “seal deck” off the bottom of the cyclone. Maintain a dP across the vapor space of the outer can. Another of our units is trying this. Have not had the Reactor open to see how it is doing.

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