Interference between stiffener rings and saddles

[plantguyjj]

Can someone please offer guidance on the installation of external stiffening rings that would intersect with either nozzles or support saddles? Section UG (VIII-1) states that the rings shall extend completely around the circumference of the cylinder. But, as long as the required moment of intertia is satisfied at the gaps of the stiffener ring, why not allow gaps for external rings. Rules are given for gaps with internal rings.

 

[prex]

If a ring crosses a saddle it should be easy to provide an equivalent (or higher) moment of inertia in the saddle, thus satisfying code request.
In the case of a nozzle, I would personally avoid a ring crossing it: you can always put two rings in place of one.

prex

http://www.xcalcs.com

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[plantguyjj]

So is it acceptable for an external ring to cross a saddle? UG contains the statement that the ring shall extend completely around the cirumference. Allowances are given for internal rings. I would think the same should apply to external rings.

 

[SnTMan]

plantguyjj, I have in the past extended a stiffening ring around the vessel to the saddle back plate on each side, full penetration butt weld to the back plate. I don't see that there is anything wrong with the practice.

Echo prex on nozzle though. I wouldn't.

Regards,

Mike

 

[MJCronin]

plantguy..

Are you modifying an existing vessel in order to provide a "vacuum rating" ??

-MJC

 

[prex]

The statement that the ring shall extend completely around the circumference obviously means that you must provide the minimum required moment of inertia all around. You can get this from different pieces of metal, provided they line up correctly: think of a large vessel where the rings are built from many sectors welded together.

prex

http://www.xcalcs.com

: Online tools for structural design

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[plantguyjj]

MJC - yes I'm looking at options to modify an existing vessel.