The allowable stresses for blast load for vessel saddle support/skirt design

[mechengineer]

Hi All,
Any one have experience with using the allowable stresses (tensile, bending, shear) for th saddle support design under blast load (0.5 barg)? Whateaver it is from client specifications or engineering book/references.
Thanks in advance.

 

[MJCronin]

I do not believe or recall that there is a seperate category for pressure vessel support loadings entitled "blast loadings"

I believe that there is an overall category called "transient" or "emergency loadings" which would include earthquake, tornado etc. etc. where your blast loadings should be evaluated as a seperate load case.

As I recall, it would be a common practice to evaluate your PV saddles to 0.9Sy for this type of loading .... but there may be other criteria required by your contract documents.

All of this is based on my opinion ...and recollection

What did you find when you searched eng-tips for "blast loadings" ???

MJCronin
Sr. Process Engineer

 

[mechengineer]

Hi MJCronin,

Thanks for shearing your view.
I found that there are mostly steel structure design by searching Eng-tips. They use the Load and Resistance Factor Design (LRFD) method for is called the slenderness ratio (KL/r) is larger. It may not be applicable for the saddle support, KL/r is very small.
Yes, I also remembered that it was just simply say that the allowable stress shall be 0.9 yield stress in the specification my previous project. This may be the point for the allowable stresses of the blast load. Based on the tensile strength=0.9yield and 0.6yield in Allowable Strength Design (ASD), the ratio is 1.5. So that we can get other's allowable stresses, bending & shearing by using the allowable ratio accordingly as per ASD. The discussion broadened my mind.

Thanks.