Hello Fellow Stressers!!

Have anyone encountered this banana effect in Coke Drum? How do we obtain this information to be considered as a boundary condition.

During the quench the cold drum will be cold compared to the vapor line. Is this the same case to banana effect?

Please share your experience.

Warm Regards,

It's referred to as "thermal bowing" in CAESAR, and is in the special execution parameters. Though I've never had to deal with it, personally.

Offhandedly, I'd say if you know the temperature difference and OD, you can estimate what radius R would be the resulting bow.

You could then turn the curvature into a displacement and rotation of the end, though if it's something you can physically see in the field, there's a chance you're outside of CAESAR's "small displacement" applicability.

Thanks Michael for the information.

I will also try to discuss with our Mechanical Engineer if it's part of Vendor's deliverable.

Any other experience is greatly appreciated.

Cheers!!!

For a first pass analysis the typical bowing displacements can be taken as 6" (150 mm) in 4 directions (N, S, E, W) similar to the wind direction logic. Obviously the bowing can occur in any horizontal direction but the logic above should be adequate. The vessel, mechanical, vendor or specialty group may be able to do an FEA on the actual vessel geometry.

FEPipe (and maybe now Nozzlepro) can apply temperatures to separate sections of the shell model to perform this analysis but you have to know your way around the software.

Personally I would like to do this but can never find the time. When I was at Foster Wheeler in the specialty group, Ryan P. stated he did these types of bowing evaluations "regularly" using Algor or Ansys and the results would not exceed 8" (200 mm) and were typically 6" (150 mm). Similar results from our Lummus group.

Field folks have observed 4" (100mm) in one plant.

Thanks Bob for sharing your experience.

Is it possible to model the equipment (Coke) while considering also the displacement at the top nozzle/coke drum junction to capture both the wind effects on the coke drum and displacement effects due to banana movement of coke drum. Have anyone tried this? Is it via cnode with displacement (due to banana effect)?

Warm Regards,

You need to put the translational banana displacements at the coke drum skirt anchor point in the Caesar II model. In reality there will be some rotations the upper nozzles but I have not seen people going into that kind of detail.

The above allows you to model the coke drum just like any other vessel with OD, Thickness and temperature for the various cases so wind and seismic loads can be applied to the drum.

Thanks Bob for that practical approach. Since the drum is rigid enough vertically, the top portion will move together horizontally with the skirt at the bottom. If it's possible to assign thermal bowing by "element", it would be nice to assign it for coke drum only and not globally to the whole system.

Any other experience is greatly appreciated!!

Cheers!!

Note that Thermal Bowing is acting in Caesar only for horizontal elements.

The thermal bowing option in PCL-Gold (FEPipe beam element pipe stress program) allows bowing input on an element by element basis and an orientation vector but only one set of bowing data per run/model.

PCL-Gold allows different bowing data anywhere in the model and no bowing (off). You CANNOT have have multiple bowing cases on each element analogous to multiple thermal cases.

Thanks Bob and Danb for sharing that info.

It would be convenient if it can be done in other beam element softwares also, considering both horizontal/vertical and on an element by element basis.

Cheers!!!