Design of saddle support on shell flange

[Bmechz]

Can we design saddle support on shell flange of a heat exchanger?

One of the heat exchanger(DIV-2 & TEMA -R) currently I am designing is having fixed saddle support on its shell flange(Due to less space) and i am not able to design this saddle in PV elite software.So please suggest me how to prove the saddle design and kindly let me know any special load consideration required for that shell flange as it is welded to fixed saddle..

As mentioned in my previous thread while designing the bolted flange as per 4.16.2.2 of Div 2 we have to add the external loads also to determine the MAWP of flange. So i think in the above mentioned case we have to add an external load (total weight of equipment/2)on shell flange to determine the rating.

Baijuz

 

[fegenbush]

Baijuz,

You should read the following paper. Your application will require calculation by hand in order to analyze the stresses in the flange. It would be good practice, as well, since we should not rely solely on software to determine if the saddle design is acceptable.

"Stresses in Large Horizontal Cylindrical Pressure Vessels on Two Saddle Supports" by L. P. Zick

 

[SnTMan]

Baijuz, this is something that, every now and then, you just have to hold your nose and do it. Forget about the influence on the flange as the dead weight applied stress is generally negligable, compared to pressure stresses. Treat the support as a cantilever beam and design accordingly. See the attached for a simplified analysis.

Longitudinal load is generally taken as 1 1/2 times removable bundle weight. The moment arm is applied to the centroid of the arc of intersection with the cylindrical surface (R*sin alpha / alpha) term. Moment of inertia will be calculated on the section minimum depth, the support may be tapered to the flange thickness.

Forget about the flange.

Regards,

Mike

 

[SnTMan]

Oh yeah, and forget about Zick too, it is not about design of the supports themselves.