ASME Code Section VIII, Division

ASME Code Section VIII, Division 1 Most pressure vessels iisedin the process indiistiy in the United States are designed and constructed in accordance with Sec. TH, Division I (see Fig. 10-187). This division is divided into three subsections followed by appendixes. 

Many users have reported satisfactory performance of annealed or normalized and tempered steels produced before 1969, as shown in Figure 1. These steels have been used for pressure-retaining equipment at design stress levels allowed by the 1969 or earlier editions of commonly-accepted codes (such codes include the ASME Code, Section VIII, Division 1 the standards of the American National Standards Institute and, for the lower-strength materials, those of Deutsche Industrie-Normen). However, pressure vessels in hydrogen service have also been constructed using the higher allowable stresses permitted in either Section VIII, Division 2, or modifications of Section III of the ASME Code. Quenched and tempered or normalized and tempered steels have normally... 

Radiography Section V, Articles 2 and 22oftheASMECode Section VIII, Division 1, UW-51 (for 100 % radiography) and UW-52 (for spot radiography) of the ASME Code Section VIII, Division 1, Appendix 7 of the ASME Code... 

Design ASME Code Section VIII, Division, Edition and all Mandatory Addenda. ... 

Body flanges should be by preference of integral design. If flanges are attached by welding, they shall have the complete circumference of each attachment weld 100% X-rayed and submitted to the end-user for approval. The radiography and acceptance criteria shall be per ASME Code Section VIII, Division 1. 

Vessels for high-temperature service may be beyond the temperature limits of the stress tables in the ASME Codes. Section VIII, Division 1, makes provision for construction of pressure vessels up to 650°C (1200°F) for carbon and low-alloy steel and up to 815°C (1500°F) for stainless steels (300 series). If a vessel is required for temperatures above these values and above 103 kPa (15 Ibf/in ), it would be necessary in a code state, to get permission from the state authorities to build it as a special project. Above 815°C (1500°F), even the 300 series stainless steels are weak, and creep rates increase rapidly. If the metal which resists the pressure operates at these temperatures, the vessel pressure and size will be limited. The vessel must also be expendable because its life will be short. Long exposure to high temperature may cause the metal to deteriorate and become brittle. Sometimes, however, economics favor this type of operation. 

It should be noted that the ASME Code, Section VIII, Division 1, Para UCS-6 has the following restrictions on the use of SA-36 and SA-283 (Grades A, B, C and D) steels when used for pressure parts in pressure vessels ... 

It is recommended that the ASME Code, Section VIII, Division 1 be used for the construction of CRM lined metallic vessels. The use of Code construction is only required where the operating pressure exceeds 15 psig, but it should be remembered that a CRM lining can swell and exert high stresses. 

Maximum Allowable Stresses per ASME Code Section VIII, Division 1, (1980) Para UCS-23, for -20 to +650 F except SA-537 A-36 Modified is made to fine grain practice with manganese in range 0.80 to 1.20 percent by ladle analysis. 

The 1962 ASME Code Section VIII, Division 1 gives equation 4-4 for thin-walled (f <0.356r) spherical shells, which also applies to hemispherical heads. If the thick-wall correction factor (-0.6p and -0.2p for cylindrical shell and hemispheric head, respectively) is omitted, the thicknesses are 1 2, respectively. 

The ellipsoidal dished head with a major to minor axis ratio of 2 1 is popular for economic reasons, even though the theory for thin-walled vessels predicts that the head of this shape should have twice the thickness of a hemispherical head where the major and minor axes are equal. Such an ellipsoidal head used for vessels under internal pressure has the same thickness as the cylindrical shell if the same allowable stresses and joint efficiencies are applied to both parts. The 1962 ASME Code Section VIII, Division 1 gives the following equation for the thin-walled ellipsoidal dished heads with a 2 1 major to minor axis ratio ... 

Instead, the local building codes apply, and these usually give specifications for the maximum allowable tensile and compressive stresses for steel structures. Quite often the local codes specify 1/3 of the ultimate tensile strength for the allowable tensile stress, whereas the ASME Code Section VIII, Division 1 specifies 1/4 the ultimate tensile strength as the allowable tensile stress. 

This theory is the oldest, most widely used and simplest to apply. Both ASME Code, Section VIII, Division 1, and Section I use the maximum stress theory as a basis for design. This theory simply asserts that the breakdown of... 

ASME Code, Section VIII, Division 2, and Section III use the term stress intensity, which is defined as twice the maximum shear stress. Since the shear stress is compared to one-half the yield stress only, stress intensity is used for comparison to allowable stresses or ultimate stresses. To define it another way, yielding begins when the stress intensity exceeds the yield strength of tlie material. 

ASME Code, Section VIII, Division 1 vs. Division 2... 

On,=membrane stresses from sustained loads q , = membrane stresses from relenting, self-limiting loads S=allowable stress per ASME Code, Section VIII, Division 1, at design temperature... 

Since discontinuity stresses are self-limiting, allowable stresses can be very high. One example specifically addressed by the ASME Code, Section VIII, Division 1, is discontinuity stres.ses at cone-cylinder intersections where the included angle is greater than 60°. Para. l-5(e) recommends limiting combined stresses (membrane -t- discontinuity) in tile longitudinal direction to 4SE and in the circumferential direction to 1..5SE. 

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