Material selection design, importance

Galvanic corrosion is of particular concern in design and material selection. Material selection is important because different metals come into contact with each other and may form galvanic cells. Design is important to minimize differing flow conditions and resultant areas of corrosion buildup. Loose corrosion products are important because they can be transported to the reactor core and irradiated. 

Fabric weave stractures are the types of forms in which the yams are constmcted to produce various aesthetic designs through weaving. The material selection, design and constmction method all play very important roles to ensure the product meets the required geometry as well as the physical mechanical properties. 

Excellent materials selection, design, and detailed specification for construction of a plant or a piece of equipment may be set forth, but they can be essentially meaningless if they are not followed. Proper inspection is a must - particularly for critical components operating under hazardous conditions. Inspectors should scrutinize critically during fabrication and construction, not Umiting inspection to the final product only. In addition to being capable and well qualified, inspectors should have substantial authority. Inspectional aspects are as important as design and material selection. 

At very high and very low temperatures, material selection becomes an important design issue. At low temperatures, the material must have sufficient toughness to preclude transition of the tank material to a brittle state. At high temperatures, corrosion is accelerated, and thermal expansion and thermal stresses of the material occur. 

Proper material selection for chemical and process equipment is one of the first important problems encountered by the designer. Among the many parameters that must be considered are structural strength specifications, heat resistance, corrosion resistance, physical properties, fabrication characteristics, composition and structure of material and cost. 

This book is designed as a handy desk reference covering fundamental engineering principles of project planning schemes and layout, corrosion principles and materials properties of engineering importance. It is intended as a general source of typical materials property data, useful for first pass materials selection in process design problems. 

The previous section has given an indication of the range of plastics available to the design engineer. The important question then arises How do we decide which plastic, if any, is best for a particular application Material selection is not as difficult as it might appear but it does require an awareness of the general behaviour of plastics as a group, as well as a familiarity with the special characteristics of individual plastics. 

The interaction of a metal or alloy (or a non-metallic material) with its environment is clearly of vital importance in the performance of materials of construction, and the fact that the present work is largely confined to a detailed consideration of such interactions could create the impression that this was the sole factor of importance in materials selection. This, of course, is not the case although it is probably true to say that this factor is the one that is the most neglected by the design engineer. 

Another factor to consider in the early stages of design is material selection in relation to cost per volume rather than by weight. This subject volume vs. weight will be reviewed latter in this chapter entitled Analysis Method. Since the material value in a plastic product is usually over one-half of its overall cost, it becomes important to select a candidate material with extraordinary care. 

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