Selection of materials fabrication

Engineering specification and purchasing procedures are essential to ensure that all items are to the design specification and to comply with company or national standards. During installation the features to consider are foundations, selection of materials, fabrication, assembly, supports, pressure testing etc. 

The selection of materials, fabrication practices, examinations, testing procedures and chemical control of the reactor coolant to prevent stress corrosion cracking should be such as to preclude in-service deterioration and to ensure structural integrity. 

Q Ensure the design (including selection of materials) fabrication, assembly, test, and inspection of piping systems containing flammable liquids is suitable for the expected working pressures and structural stresses. 

The woven fabrics have various yarn patterns for different spacings between the yarn fabrics (Table 4-14). There is a wide variety of choices for not only the materials of construction but the tightness of weave and the size of the yarn. All of these factors along with the others noted earlier, make the selection of bag fabric an art that requires manufacturer s and plant s actual field tests. Woven fabrics have a low ratio of weave openings for yarn area and generally have a limited face velocity for air flow of about 1.5 to 3.0 cu ft/min/sq ft [47]. 

NOTE Good design practice should be followed in the selection of fabrication methods, welding procedures, and materials for vendor-furnished steel pressureretalning parts that may be subject to temperatures below the ductile-brittle transition temperature. The published design-allowable stresses for metallic materials in internationally recognised standards such as the ASME Code and ANSI standards are based on minimum tensile properties. Some standards do not differentiate between rimmed, semi-killed, fully killed hot-rolled and normalised material, nor do they take into account whether materials were produced under fine- or course-grain practices. The vendor should exercise caution in the selection of materials intended for services between 0 °C (-20 °F) and 40 °C (100 °F). 

A selection of items fabricated from thermosetting materials is shown in Figures 27 and 28. 

Although the operating concept of SOFCs is rather simple, the selection of materials for the individual components presents enormous challenges. Each material must have the electrical properties required to perform its function in the cell. There must be enough chemical and structural stability to endure fabrication and operation at high temperatures. The fuel cell needs to run at high temperatures in order to achieve sufficiently high current densities and power output ... 

Any engineering design, particularly for a chemical process plant, is only useful when it can be translated into reality by using available materials and fabrication methods. Thus, selection of materials of construction combined with the appropriate techniques of fabrication can play a vital role in the success or failure of a new chemical plant or in the improvement of an existing facility. 

The primary challenge in commercialization of MCFC remains in the proper selection of materials for the cathode. The life expectancy of the electrode structure is aimed toward 40,000 hr for successful commercialization of MCFC. The following cathode properties were recognized as of fundamental importance with respect to the cell performance 1) high electronic conductivity at 650°C (cr > 1 S/cm) 2) low chemical reactivity and solubility in the electrolyte 3) thermodynamic stability at 650°C in carbonate electrolyte at different partial pressures of O2/CO2 mixtures 4) high electrocatalytic activity for the oxygen reduction reaction and 5) suitability for the fabrication of porous electrodes. ... 

NORRIS, ROBERT E. SCHULZ, M. D. Selection of Materials to be Utilized in Fabrication Tooling for Electron-Beam Curing of Composites. Proceedings of the 28th International SAMPE Technical Conference, vol. 28, (1996) 890. 

Guide to Selection of Materials for Fabrication of Composite Membranes... 

Service—Change of service condition by the user inexperienced operations or maintenance personnel upset conditions. Some types of service which require special attention both for selection of material, design details, and fabrication methods are as follows ... 

Materials of Construction. The principal materials of construction are ferrous throughout, but different grades are used for the different components. Casings usually are in cast iron or cast steel, and impellers may be in the same materials or in fabricated steel. Early designs of centrifugal compressors used riveted assembly for impellers castings or welded construetions are preferred today. Shafts usually are of carbon steel with hardened or stainless steel sleeves at points where erosion is likely. The selection of materials for smaller components that may be subject to friction is particularly important because of the danger of comlnistion. 

Let us examine the mechanism of repulsion (dust-repellent coatings) and attraction (dust-collecting coatings) of airborne dust particles as they approach a painted surface and the adhesion of the particles after they come into contact with the surface. Work along these lines was performed by Frederick [223], who studied the electrical properties of dust in relation to the selection of filter fabric materials. In order to evaluate the possibility of binding dust to a substrate due to electrical forces. Frederick divided dusts into three classes. We will modify Frederick s classifications slightly, in that we will consider both dust repulsion and dust collection. 

In addition, a change in a specific polymer parameter may affect processability and basic physical properties. Both of these factors can interact in governing the behavior of a fabricated article. Comprehensive experimental data are therefore necessary to understand effectively the behavior of plastic materials, and to give a realistic and reliable guide to the selection of material and grade. 

Table 6-27 provides a basic outline that identifies the D 4000 line callouts (specifications). The classification system and its subsequent line callouts is intended to be a means of identifying plastic materials used to fabricate end items or parts. It is not intended for the selection of materials. Material selection should be made after careful consideration of the design and performance required of the part, the environment to which it will be... 

Wang et al. (2004) and Zhang (2008). Systematic modifications at the fabrication stage include (i) the selection of materials (e.g., carbon or metal-oxide-based support materials, Pt or Pt-alloy catalyst materials, perfluorinated or alternative ionomer materials), (ii) size dispersion of catalyst and support particles, (iii) gravimetric composition of the ink (amounts of carbon, ionomer, and Pt) and solvent properties, (iv) thickness of the CL, and (v) fabrication conditions (temperature, solvent evaporation rate, pressure, and tempering procedures). 

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