Half skirt design for vertical vessel

[fizzy]

Hi guys,

I'm working on a vessel design which my client requires two half skirts welded on opposite sides of the dished head for its support. The vessel is a relatively small vessel (508mm OD) with two curved plates welded at opposite ends leaving the mid section open for access to the nozzles on the head. I've gone through some handbooks but didnt get much luck. I've also gone through previous threads to see if i could get the help i needed but the closest i saw was a large opening on the skirt which i assumed to be different. I guess someone might have had a similar experience and would appreciate if anyone could refer me to a book or an idea to go about this.

Thanks in advance.

Fizzy.

 

[TomBarsh]

I would think of these as "legs". For that matter, why not just use standard structural sections as legs, it will make the analysis so much easier. I would use 3 legs. You can use 2 legs but the vessel should then be laterally braced somehow.

 

[racookpe1978]

That small (about 1/2 meter dia) would be easiest (best access also) and cheapest to make with 4 angle iron (75 mm x 75, or 100x100) as legs, and a square pad (125x125 or so) with one bolt hole in the sq pad to mount it.

 

[MJCronin]

fizz..

Did you ask your client for the reason why he requires two half skirts ?

Time after time, I find that clients just seem to express bizzare "preferences" without any sort of reason or clear process need..

Again, I strongly advocate extensive drug testing of all clients at the earliest stages of a project.

Go with a multiple leg scheme.....like the rest of the world does.

-MJC

 

[fizzy]

Thanks guys for your feedback, i did consider the support leg option you've all adviced me to go with but wanted some insight if it was possible to have two half skirts. My understanding is the vessel is a replacement vessel, so i'm of the opinion that, it was possibly designed with two half skirts rather than support legs.

I'll have a chat with my client on your comments and see how things go from there.

Thanks once again.

fizzy.

 

[delray]

Another way of solving this problem is the put two access openings 180 degress apart in the skirt, such that it divides the skirt into two parts.

 

[SnTMan]

MJCronin, agreed and I would add apps and sales engineers also

Regards,

Mike

 

[roca]

The half skirt arrangement is a typical SHELL standard detail. I have used this several times in the past and I can't see what your problems are.
These are used on small vessels to allow you more access to the bottom head nozzle.
However these should not be used on vessels subject to fatigue or vibration (e.g. connected to a compressor system)and on vessels that need the skirt to be fireproofed.
I even have a calculation for a half skirt somewhere at home - if I knew I could find it easily I would offer you a copy

 

[fizzy]

Thanks roca,

I'll appreciate your calculation if you don't mind and maybe your referenced text. My problem is i can't find materials on half skirt design and i'm of the opinion that it's calculation is different from the calculation of an opening in a skirt which is explained in Bednar's handbook.

Regards,

fizzy