Section VIII: Unfired Pressure Vessels

This section has two división. Division 1 uses approximate calculation methods adequate for most services. Units built to these rules and inspected by an authorized inspector (AI) are stamped with ASME Code U symbol.

Under Div 1, pressure vessels meeting the following conditions may be exempted from inspection by an A1: (1) they are not required by Div 1 to be fully radiographed; (2) they do not have quick-actuacting closures; (3) volmes are 5 ft³ or less for a maximum design pressure of 250 psi or are 1 ½ ft³ for a maximum design pressure of 650 psi.

These units are stamped UM. If, despite exemption they are inspected by an AI, however, they may be stamped with the U symbol.

With some exceptions, equipment built to Div 1 may also be built to the alternative rules of Div 2 and stamped U-2. Units outside the scope of Sec VIII may be stamped with the code symbol if constructed according to all rules of the governing division.

What is Div 2? When should it be considered? Division 2 provides and alternative to the minimum construction requirements of Div 1. Bases on more precise calculatin methods. Div 2 rules are more restrictive. The do not permit use of some materials allowed by Div 1, the prohibit some common design details, and the specify which fabrication procedures may be used.

Engineering and manufacturing according to Div 2 are more costly, but when the stress intensity is controlled by ultimate or yield strength, Div 2 permits use of higher design stress-intensity values in the range of temperatures covered.

Consider using Div 2 rules under the following conditions: (1) service is severe enough to indicate the need for intensive analysis, (2) fatigue may affect safety and useful life, (3) shape changes may cause high discontinuity stresses, (4) pressure exceeds 3000 psi (20,670 kPa), (5) product of pressure times shell diameter exceeds 6000 lb/in (1,216 N/m), (6) ratio of shell diameter to thickness is less than 16, or shell thickness calculated under Div 1 rules exceed 3 in (76,2 mm), (7) costs of the necessary engineering analysis and more rigorous construction requirements are justified by savings in materials and labor, and (8) the unit will be installed in one location and used for one service its entire life.

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Solicitaciones

En el cálculo de un recipiente a presión, deberán tenerse en cuenta además de la presión interna o externa, las siguientes solicitaciones, si las hubiese:

a) Presión debida a la altura máxima estática de fluido contenido, más pesado, o en agua si la densidad es inferior a 1, tomada en las condiciones de cálculo.

b) El peso del recipiente con su contenido, más pesado, o en agua si la densidad es inferior a 1, tomada en las condiciones de cálculo.

c) El peso del recipiente con su contenido máximo especificado para la prueba hidráulica.d) La acción debida al viento.e) La acción debida a los efectos sísmicos f) Para las solicitaciones de acciones de vientos y sismos, se pueden admitid tensiones

superiores al 90% del limite elástico convencional al 0,2%, previo acuerdo de las partes interesadas.

g) Para solicitaciones de acciones de viento y sismos se deben seguir las normas oficiales.h) Las solicitaciones de viento y sismo se podrán considerar no simultaneas, eligiendo la más

desfavorable entre: Solo acción de viento Acción de sismo más un cuarto de viendo.

Se debe