Basis for 0.2L Saddle Location 1

[kixter]

Does anybody know what is the basis for limiting the distance between a head tangent line and the center of a saddle to a maximum of 20% of a vessels length? I have read through Zicks paper, Bednar, Megyesy, Harvey and (I think) all likely threads here, and can find no specific engineering basis for this.

Currently I have a project to build a 120” ID x 20 ft. t/t, 175 psi carbon steel vessel with unsymmetrical locations of saddles. The saddle locations are dictated by existing site conditions and would require one saddle to be located past the accepted guideline of 0.2L.

Thanks in advance for any insight!

JC

 

[codeeng]

0.2L is a guideline as is symmetrical saddles (refer PV Design Manual by Moss). Just make sure that you take into account the higher bending stress at the long end.

 

[kixter]

codeeng: thanks for the quick response. As I anticipated, it is only a rule of thumb and provides some guidance to help reduce the chance of exceeding allowable stresses. I will keep a close eye on all the stresses produced. Thanks again!

JC