Membrane 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 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. 

This hypothetical problem serves to illustrate how categories and types of loadings are related to the stresses they produce. The stresses which are required for equilibrium of the vessel are primary stresses. The stresses due to pressure and wind are primary general membrane stresses since even if yielding occurred, redistribution of stresses would not be possible. These stresses should be limited to the Code allowable stress values, where increases for occasional loading may be allowed for certain sections of the Code. 

On the other hand, the stresses from the inward radial load could be either a primary stress or secondary stress. It is a primary stress if it is produced from an unrelenting load or a secondary stress if produced by a relenting load. A general primary membrane stress will not redistribute upon yielding, whereas a primary local membrane stress will, and for a secondary stress the load will relax once slight deformation occurs. 

Primary general membrane stress, This stress is the average primary stress across a solid section, is produced hy pressure or mechanical loads, and is remote from discontinuities such as head-shell intersections, cone-cylinder intersections, nozzles, and supports. Examples are ... 

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... 

There is no maximum hydrostatic test pressure specified by the Code. Good engineering practice limits the general primary membrane stress to. 9 Fy for carbon steel components and Fy for stainless steel components. 

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. 

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. 

Pm = primary general membrane stress as defined in Table 8.2... 

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

Hence, maximum stress = 14,300 psi. From Tables 8.1 and 8.2, the maximum stress for a general primary membrane stress is... 

ARemative Ratio = S E divided by the product of the maximum allowable stress value from Table UCS-23 times E. where S is the applied general primary membrane tensile stress and E and are as defined In General Note (3)... 

Load Combination Thickness Temperature General Primary Membrane Allowable Stress Description... 

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