Snubbers for Cat Cracker catalyst lines

[StressGuy]

Time for me to learn something new. I'm working on a job where I have to spec out some replacements for worn out snubbers in an old FCCU. Thankfully, I've been able to find documenation on the current ones, so getting replacements will be pretty straightforward.


However, I don't know what I would do in this case if I were designing the snubbers for a new application. I've done designs with snubbers where the load sources were external, such as wind and seismic. However, in this case, the source is internal due to action of the catalyst. This is something I just have no experience with.

Can some of my more learned colleagues point me in direction of books or articles that address this topic? I'm betting I'm going to have to track down a copy of some 30 year old Hydrocarbon Processing article from somewhere

Thanks,

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.

 

[pennpiper]

Try this website

http://www.pipingtech.com/products/snubbers.htm

Rerards

 

[StressGuy]

Thanks, but that's not really what I'm looking for.

Given the parameters, I can size a snubber and have done so in the past. What I'm trying to get to is how to establish the parameters (particularly the force and frequency) for a reactor riser with catalyst flowing in it.

I'm wondering if there are some general guidelines that can be used if you know things like the flow rate and fluidized catalyst density, or if this is something that you send off to some PhD grad students for figure out for a semester project.

The original snubbers in my application were installed with the original 1952 FCCU construction and more were added in 1984, so I'm hopeful that there is some pretty long standing documentation out there. So far, Google has not been helpful in my quest for information.

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.

 

[NozzleTwister]

Hi Ed,

When I hear the term 'snubber', I think of hydraulic or mechanical snubbers, but I think that for your application, spring loaded sway braces would be more appropriate.

Your temperature may vary with the catalyst flow that is causing your vibration. It's possible that your snubbers will lock up at the time you need them to be free for thermal displacement. Sway braces can be sized to resist the forces causing the vibration while at the same time allow for thermal displacement.

I would think that your Process Engineer would be able to provide you with the frequency and forces due to the flow.

If you use the existing documentation to purchase the new snubbers or sway braces, I would review the original displacement data to see if it's still applicable today. I also have recently worked on an FCCU dinosaur and have found that in 50+ years of revamps, a lot of things change that could effect your thermal displacements.

Good luck,


NozzleTwister
Houston, Texas