Fig 2 Failed molasses tank, which fractured suddenly in New Jersey in March 1973. This catastrophic and sudden brittle fracture resulted in the release of the molasses in the tank similar to the boston molasses tank disaster in 1919 The next step in the design process is to identify the design parameters, such as configuration, design pressure, and so forth, Table 2 presents an example of a design parameter list applicable for a chemical process chamber(Ref 17). These design parameters are the same parameters considered when conducting a pressure vessel failure investigation and life Table 2 Pressure vessel design parameters Required design code) Penetration and location requirements Basic chamber configuration(Cylindrical or Contents and/or process within the pressure vessel spherical; flat, spherical, or elliptical end details, Internal volume capacity Estimated operational pressure and temperature cycle history (number of cycles at what pressures and temperatures over the Minimum inside diameter Piping, external and internal attachment requirements Minimum inside length Test chamber surroundings(enclosed in building or exposed to Chamber orientation(for cylindrical chambers, Test chamber physical geographical location longitudinal axis vertical or horizontal Support configuration(saddle supports, bottom Vessel special material requirements(vessel material other than cylindrical skirt, legs, etc Maximum internal operating pressure Vessel protection requirements(painted surfaces, stainless steel overlays at seals, cathodic protection, etc Maximum external operating pressure(vacuum,Fabrication requirements Design operating temperature range Material selection (a) AsMe Boiler and Pressure Vessel Code, Section VIl, Div. 1, 2, or 3; ABS; other Given the design parameters, the proper material(s)is selected for the structural component. Safety and economy are often the governing factors when selecting a material for pressure vessels. The material is selected based on its mechanical, corrosion, creep, toughness, and thermal properties as applicable. If necessary, the appropriate weld material is selected based on the chosen base material. Material is assigned an allowable stress value based on its ultimate and yield strengths and operating temperature range. This allowable stress value is then used in design equations or compared to results obtained from detailed analyses The design process then proceeds with the determination of the sizes and/or thickness of the various components. The design process is completed with the creation of the engineering and fabrication drawings. These drawings should include the dimensional information, but also specify materials, weld identification, weld procedures, and required weld inspections. Other helpful information to include on the drawings is basic parameters such as design pressure, design temperature range, design code, and other information deemed necessary for the particular structural component Structural Design Approaches. The criteria of failure are determined by the strength of materials, fracture toughness, creep resistance, fatigue behavior, and the corrosion resistance of materials. These are briefly discussed in this section Strength of Materials. In the strength-of-materials design approach one typically has a specific structural geometry (assumed to be defect free) for which the load-carrying capacity must be determined. To accomplish this, a calculation is first made to determine the relation between the load and the maximum stress that exists in the structure. The maximum stress so determined is then compared with the strength of the material. An acceptable design is achieved when the maximum stress is less than the strength of the material, suitably reduced by a factor of safety It can be assumed that failure will not occur unless omax exceeds the yield strength of the material, oY. To ensure this, a factor of safety (S) can be introduced to account for material variability and/or unanticipated greater service loading. The strength-of-materials approach is a good approach for materials with no defects and simple structures. Figure 3 shows the strength-of-materials approach and the engineering design regime based on a factor of safetyFig. 2 Failed molasses tank, which fractured suddenly in New Jersey in March 1973. This catastrophic and sudden brittle fracture resulted in the release of the molasses in the tank similar to the Boston Molasses tank disaster in 1919. The next step in the design process is to identify the design parameters, such as configuration, design pressure, and so forth. Table 2 presents an example of a design parameter list applicable for a chemical process chamber (Ref 17). These design parameters are the same parameters considered when conducting a pressure vessel failure investigation and life assessment. Table 2 Pressure vessel design parameters Required design code(a) Penetration and location requirements Basic chamber configuration. (Cylindrical or spherical; flat, spherical, or elliptical end details; etc.) Contents and/or process within the pressure vessel Internal volume capacity Estimated operational pressure and temperature cycle history (number of cycles at what pressures and temperatures over the vessel's lifetime) Minimum inside diameter Piping, external and internal attachment requirements Minimum inside length Test chamber surroundings (enclosed in building or exposed to elements) Chamber orientation (for cylindrical chambers, longitudinal axis vertical or horizontal) Test chamber physical geographical location Support configuration (saddle supports, bottom cylindrical skirt, legs, etc.) Vessel special material requirements (vessel material other than carbon steel, internal cladding, etc.) Maximum internal operating pressure Vessel protection requirements (painted surfaces, stainless steel overlays at seals, cathodic protection, etc.) Maximum external operating pressure (vacuum, etc.) Fabrication requirements Design operating temperature range Material selection (a) ASME Boiler and Pressure Vessel Code, Section VII, Div. 1, 2, or 3; ABS; other Given the design parameters, the proper material(s) is selected for the structural component. Safety and economy are often the governing factors when selecting a material for pressure vessels. The material is selected based on its mechanical, corrosion, creep, toughness, and thermal properties as applicable. If necessary, the appropriate weld material is selected based on the chosen base material. Material is assigned an allowable stress value based on its ultimate and yield strengths and operating temperature range. This allowable stress value is then used in design equations or compared to results obtained from detailed analyses. The design process then proceeds with the determination of the sizes and/or thickness of the various components. The design process is completed with the creation of the engineering and fabrication drawings. These drawings should include the dimensional information, but also specify materials, weld identification, weld procedures, and required weld inspections. Other helpful information to include on the drawings is basic parameters such as design pressure, design temperature range, design code, and other information deemed necessary for the particular structural component. Structural Design Approaches. The criteria of failure are determined by the strength of materials, fracture toughness, creep resistance, fatigue behavior, and the corrosion resistance of materials. These are briefly discussed in this section. Strength of Materials. In the strength-of-materials design approach one typically has a specific structural geometry (assumed to be defect free) for which the load-carrying capacity must be determined. To accomplish this, a calculation is first made to determine the relation between the load and the maximum stress that exists in the structure. The maximum stress so determined is then compared with the strength of the material. An acceptable design is achieved when the maximum stress is less than the strength of the material, suitably reduced by a factor of safety. It can be assumed that failure will not occur unless σmax exceeds the yield strength of the material, σY. To ensure this, a factor of safety (S) can be introduced to account for material variability and/or unanticipated greater service loading. The strength-of-materials approach is a good approach for materials with no defects and simple structures. Figure 3 shows the strength-of-materials approach and the engineering design regime based on a factor of safety