banana effect

[Anonymous]

Does anyone know about banana effect considerations in coke drum mechanichal design?? We are designing conical disc springs in the anchor bolts to permit a little desplacement due to the diferential thermal contraction. But, the problem is: how much we have to allow displacement? 2mm? 20mm?
Have anyone expirience on it??

[antonio saura Cebrian]

There are some numbers, that I do not Know are going to help you. During operating temperature the drum are going to grow between 7 to 9 inches, and the coke drums can deflect up to 12″ horizontally from the coke drum centerline in any direction during quenching (banana effect).Also this condition must be added to the stress analysis of the coke drum overhead
REgards

[Anonymous]

Thank you “españa2005”, o muchas gracias en este caso. It is exactly the data I had (12″=305mm). Considering the curvature due to this efect, the difference betwen the neutral axis length compared with the side length is around 80mm. The fact is, how much of this displacement is need to consider that is acting on the base, producing a force that can pull up the bolts?? We have to know this value to design the conical disc spring stacks. We know from our expirience data that consider 10 mm is enough, but the problem is how to justify it.

[Anonymous]

I think to consider a couple of milimeters is enough.

[Anonymous]

I don’t think anyone has measured the force applied to the base bolts while a drum is going through the “banana” condition. This is rather a slow happening. I feel there is more load applied to the base bolts when the drum is moving back and forth during a severe quench. I have seen drums actually rock back and forth during a severe quench. It would be interesting form someone to install strain gauges in this area.
 
 
 

[coker squirrel]

I have heard of a new “floating skirt” disign that allows for a little displacement.  I don’t know much about it.  Maybe someone could explain this new technology.

[Anonymous]

I have noticed the coke drums swaying while filling and quenching.

[Anonymous]

I have seen that bolts there are installed some conical discs springs in coke drum bolts. Could somebody tell me how many of these discs are installed tipically and how are they calculated??

[Anonymous]

Does anyone know how to calculate this top nozzle horizontal movement due to banana effect? Is thermal bowing formula will work the best considering detail analysis such as CFD and FEM will require unknown temperature profile of each element?

[Anonymous]

Banana effect is much similar to bowing in cryogenic piping for LNG loading/unloading line.
The temperature profile may not be clearly defined between coking and quenching.
As so it may well be estimated as linear temperature variation from maximim to minimum.
The reference is “Bowing of Cryogenic Pipelines”, W.G.FLIEDER, Transactions od ASME, Sep, 1961.
See http://sites.google.com/site/fareastpiper/reference in more information
 
Best Regards,
Far East Piper

[Author]

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