Bending stress primary general

The Code establishes allowable stresses by stating in Para. UG-23(c) that the maximum general primary membrane stress must be less than allowable stresses outlined in material sections. Further, it states that the maximum primary membrane stress plus primary bending stress may not exceed 1.5 times the allowable stress of the material sections. In other sections, specifically Paras. l-5(e) and 2-8, higher allowable stresses are permitted if appropriate analysis is made. These higher allowable stresses clearly indicate that different stress levels for different stress categories are acceptable. 

Primary general bending stress, P/,. Primary bending stresses are due to sustained loads and are capable of causing collapse of the vessel. There are relatively few areas where primary bending occurs ... 

Primary local membrane stresses are a combination of membrane stresses only. Thus only the membrane stresses from a local load are combined with primary general membrane stresses, not the bending stresses. The bending stresses associated with a local loading are secondary stresses. Therefore, the membrane stresses from a WRC-lOT-ri pe analysis must be broken out separately and combined with primary general stresses. The same is true for discontinuity membrane stresses at head-shell junctures, cone-cylinder junctures, and nozzle-shell junctures. The bending stresses would be secondary stresses. 

The bending stresses associated with a local loading are almost always classified as secondary stresses. Therefore, the membrane stresses from a WRC-107-type analysis must be broken out separately and combined with general primary stresses due to internal pressure, for example. 

General primary membrane. Pm Primary membrane stress plus primary bending stress across the SE... 

Guideline 4 establishes the global locations for assessment of stresses, and states that the general primary membrane stress intensity, should be evaluated remote from a discontinuity whereas the primary membrane plus bending stress intensity, Pl + Pb, and primary plus secondary stress intensity, P + Q, should be evaluated at a discontinuity. 

Primary stresses, including general primary membrane stress, local primary membrane stress, and primary bending stress Secondary stresses Peak stresses... 

However, it is a general practice to provide detailed stress analysis for the vessel components outside the Code approved details using either the maximum-stress or the maximum-shear theory of failure and to select allowable stresses for design conditions other than normal operations or for computed stresses other than direct membrane or direct membrane plus primary bending Code stresses. CEGB R6 method based on fracture mechanics is highly recommended. This method later on has been thoroughly discussed in this chapter. 

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