FCCU Expansion Joint Bellows 1

[StressGuy]

Gentlemen,

I've posted this question in the piping design forum to get input from my fellow piping design and stress engineers. But I'm also curious to hear the experiences of you who have to live with and maintain cat crackers, so I am posting this question here as well:

I'm in the process of specing out an expansion joint for an FCCU regenerator flue gas duct. I'm talking with vendors, but I'm curious to get the views on the group on the current "state of the art" regarding protection of the bellows from the build-up of catalyst.

The two main methods are packing the bellows with insulating material to block catalyst buildup and purging the bellows with air/steam/inert gas to sweep catalyst out.

Any tips, preferences, horror stories, etc regarding the use of one method vs. the other are appreciated.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

 

[0707]

Edward

In my opinion the best method is good packing insulating material as well as a good braid fixing condition to minimize catalyst ingress into the convulsion plies. Air or steam injection should be avoided because of dew point formation and acid corrosion of bellows plies. If you suspect that catalyst build-up is obstructing plies expansion movement it is better to sweep it with inert gas to minimize bellows corrosion.

Because of plies corrosion it is also good practice to have a good external insulation of bellows plies to avoid internal condensation and dew point drops.

During shut downs is important to inspect the condition o the wire braid remove catalyst and any damaged insulation

It is also good to have a 2 ply bellows with a vacuum pressure manometer which will alert you when the inner bellow is corroded and gives you time to purchase another bellow maybe till the next shut down.

Best regards

Luis Marques

 

[0707]

Edward

In my reply I forgot to tell you that if you have 2 ply bellows is also important that your expansion bellows be mounted with a clamshell to be quickly tightened when you have the indication that the inner ply failed.

Regards

Luis Marques