Materials selection

The selection criteria in this data set are based on their common usage for general engineering applications. Certain sectors like aerospace and the 

The data set is further reduced by the availability of published data. The scan of the RAPRA bibliographic base reveals that there is a close correlation between material usage and the amount of published data. Thus there is much information available on glass fibre/polyester, which has been in existence for fifty years, and little on carbon fibre/PEEK, which has only been established during the 1980s. 

This trend is reflected in our choice of materials and data. 

A simple ranking system is used to establish an initial choice (Tables 2.2, 2.4). This provides a way of selecting a material based on a critical design requirement however the level of the other properties or parameters will also need to be checked by using the data set that follows or a database. As the design proceeds, the initial choice may need to be reassessed. 

It is worthy of note that the reinforcement and resin can generally be chosen independently so that this should permit two property levels to be attained. 

Proper selection of materials for process applications requires the following  

The quality of the materials must be confirmed by existing codes and standards (see Table 3-1 for sources) or testing and analysis of materials. 

ASTM American Society for Testing and Materials 1916 Race Street Philadelphia, PA 19103 Provides testing procedures for various process materials to ensure quality and uniformity as defined by the standard. 

ASME American Society of Mechanical Engineers 345 East 47th Street New York, NY 10017 Provides list of recommended metals, welding rods, and electrodes for use on pressure vessels. 

AISI American Iron and Steel Institute 1000 16th St., NW Washington, DC 20036 Provides a standard description of carbon steels and alloy steels. 

In Chapter 17, we vnll look more dosely at materials that commonly are used in various engineering applications. We will also discuss some of the basic physical characteristics of materials that are considered in design. We will examine the application and properties of common solid materials such as metals and their alloys, plastics, glass, and wood and those that solidify over time such as concrete. We will also investigate in more detail basic fluids such as air andvrater. 

Material properties depend on many factors, including how the material was processed, its age, its exact chemical composition, and any nonhomogenity or defect within the material. Material properties also change with tempoatute and time as the material ages. Most companies that sell materials will provide, upon request, information on the important properties of their manufiictured materials. Keep in mind that when practicing as an engineer, you should use the manu cturers material property values in your des calculations. The property values g en in this and other textbooks should be used as typical values—not as exact values. 

In the upcoming chapters, we will explain in detail the properties of materials and what they mean. For the sake of continuity of presentation, a summary of important material properties follows. 

Electrical Resistmly—The value of electrical resisrivi r is a measure of resistance of material 

Densi —Density is defined as mass per unit volume it is a measure of how compaa the material is for a given volume. For example, the average density of aluminum alloys is 2700 kg/m when compared to steel density of78501 /m, aluminum has a density that is approximately one third of the density of steel. 

The case for using a plastics moulding depends upon finding a material which will meet certain critical factors in the performance specification. The most critical areas are  

Requirements also vary as to whether the tests are to be performed with the outer lens in place, or on the directly exposed reflector. 

One customer has a special requirement to resist caustic soda solution which needs special processing. The improvement in corrosion resistance is in the base material - the plastics moulding. The aluminium reflective surface is common to metal and plastics shells. 

Most plastics materials could be used to provide corrosion resistance. Given reasonable care in selection of grades, the mechanical requirement could also be quite easily met, with good design. The chief problem surrounds the high-temperature tolerance. 

of course, vital that the reflector does not deflect in any way when it gets hot, otherwise its optical performance will be affected. 

New plastics and polymer-based composites are continuously being developed, and it is difficult for a designer to be aware of all material types, properties and 

Access to comprehensive materials data bases sudt as CAMPUS [17] and PLASCAMS [18] is also necessary if material selection is to be effective. Such 

In many cases, the filter fabric selection is based on a compromise rather than on locating the Utopian material that wiU do everything required at an economical price. The user of the medium must decide whether he is primarily interested in the filter rate or clarity, and whether the initial price of the material or life is important. 

The three methods for testing filter media are laboratory tests, pilot plant and fiiU-scale tests. The laboratory tests usually consist of a Buchner funnel, in which the filter medium is placed in the mouth of the fiiimel and a sample of the slurry is poured on top of the medium. The slurry is then drawn through the medium and such factors as filtrate clarity and time can be checked. Laboratory tests are quick and economical, but often deceptive. The pilot 

Kind and concentration if liquid is acid, and pH value if known. 

Chemical composition or nature and specific gravity of solids. 

The issues relating to a PP article during its lifetime can be divided into the following categories material selection, design, processing and post assembly, performance in service and environmental and legislative issues. 

Transparency Only contact transparency. Consider using PS, PMMA, TPX or PC if transparency is critical. PP random copolymers have better transparency. Nucleating agents further improve clarity. Material from different suppliers may have different optical properties. Transparency depends on the processing conditions and crystallisation as well. 

Heat deflection temperature Good maximum operating temperature without stresses. However, it is severely limited in the presence of stresses. Consider using engineering plastics, e.g., acetal, PPE, polysulphone or polycarbonate. 

Impact properties Significant cause of in-service failure. High brittle temperature. For impact demanding applications or sub-ambient applications, consider block copolymerised or elastomer-modified grades but improvement in impact properties at the expense of stififiiess. Avoid accidental mixing of homopolymer and copolymer 

Wear and friction Not very suitable for wear and friction applications. Consider PA or acetals. 

A typical CFRP liner system consists of primers, thickened resins, resins, reinforcing fabric, and topcoat. The most effective resin systems for long-term civil infrastructure rehabilitation applications, such as rehabilitation of PCCP lines, are ambient-cure thermoset epoxy systems. In order to minimize environmental hazards present inside the pipehne during application of the materials, epoxy systems that are made of 100% solids and are VOC compliant are utilized. 

The primer layer of epoxy applied to the pipe consists of a low-viscosity epoxy that penetrates into the concrete substrate, providing an adhesive bond for the thickened epoxy filler and saturating layers as well as subsequent layers of the CFRP system. 

Rehabilitation of Pipelines Using Fiber-reinfOTced Polymer (FRP) Composites 

The thickened epoxy filler system consists of the saturating resin and sdica fiime that have been mixed together in accordance with the manufacturer s recommended procedure in order to provide a smooth surface for appheation of the carbon fiber material. The thickened epoxy filler is used to fill voids and even out the concrete substrate it is also used in between layers of CFRP to ensure intimate contact of the CFRP system at aU locations within the CFRP Uner. 

The topcoat of the CFRP is typically thickened epoxy, either with or without a pigment added for ease of inspection. In wastewater or industrial environments where high concentrations of H2S or aggressive chemicals arc anticipated, a topcoat that is formulated for heightened chemical resistance is often used. In circumstances where the CFRP system is applied to the outside of the pipe, a UV-rcsistant topcoat is utilized. 

Each step includes many parameters which need to be optimized in order to obtain a high performance membrane. Among these steps, the carbonization process is the most important and can be regarded as the heart of the CMS membrane fabrication process. Methods to control the carbonization conditions for making an optimized carbon membrane are described in Section 15.2.5. 

The chemical structure and physical properties of the polymer should be primarily considered for the choice of polymer materials. However, there are only a few literature reports on the influences of chemical structure of polymers on the properties of the derived carbon membranes, e.g. by Park et al and Xiao et The latter reported the structure and properties relationship for polymers based on the experiment and simulation approaches, which provided considerable information for the choice of suitable polymers for carbon 

A suitable polymer material for preparation of carbon membranes should not cause pore holes or any defects after the carbonization. Up to now, various precursor materials such as polyimide, polyacrylonitrile (PAN), poly(phthalazinone ether sulfone ketone) and poly(phenylene oxide) have been used for the fabrication of carbon molecular sieve membranes. Likewise, aromatic polyimide and its derivatives have been extensively used as precursor for carbon membranes due to their rigid structure and high carbon yields. The membrane morphology of polyimide could be well maintained during the high temperature carbonization process. A commercially available and cheap polymeric material is cellulose acetate (CA, MW 100 000, DS = 2.45) this was also used as the precursor material for preparation of carbon membranes by He et al They reported that cellulose acetate can be easily dissolved in many solvents to form the dope solution for spinning the hollow fibers, and the hollow fiber carbon membranes prepared showed good separation performances. 

Application of CFRP is in the Boeing 111 CFRP floor beam design where an aluminum splice channel is used to avoid attaching the floor beam directly to the primary structural frame. 

EMA ethylene-methacrylic acid EVA ethylene-vinyl acetate MA methacrylic acid VA vinyl acetate  

The selection of the grade for each application and the corresponding processing technique is made 

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DILLON Materials Selection for the Chemical Process Industries freeman Hazardous Waste Minimization... 

Table 2. Summary of Criteria for Material Selection and Performance Evaluation ...

Other above-ground continuous flow systems have been designed and operated for SCWO processes. A system developed by ModeU Development Corp. (Modec) uses a tubular reactor and can be operated at temperatures above 500°C. It employs a pressure letdown system in which soHd, Hquids, and gases are separated prior to pressure release. This simplifies valve design and material selection on the Hquid leg. 

Plaspec Material Selection Database Data Resources, Inc. Dialog, STN detailed engineering and design data, chemical descriptions, and trade names for over 11,500 grades of plastics materials... 

The American Society of Mechanical Engineers (ASME) United Engineering Center 345 East 47th Street New York, NY 10017 The ASME Boiler and Pressure Vessel Code, under the cognisance of the ASME PoHcy Board, Codes, and Standards, considers the interdependence of design procedures, material selection, fabrication procedures, inspection, and test methods that affect the safety of boilers, pressure vessels, and nuclear-plant components, whose failures could endanger the operators or the pubHc (see Nuclearreactors). It does not cover other aspects of these topics that affect operation, maintenance, or nonha2ardous deterioration. 

The fifth component is the stmcture, a material selected for weak absorption for neutrons, and having adequate strength and resistance to corrosion. In thermal reactors, uranium oxide pellets are held and supported by metal tubes, called the cladding. The cladding is composed of zirconium, in the form of an alloy called Zircaloy. Some early reactors used aluminum fast reactors use stainless steel. Additional hardware is required to hold the bundles of fuel rods within a fuel assembly and to support the assembhes that are inserted and removed from the reactor core. Stainless steel is commonly used for such hardware. If the reactor is operated at high temperature and pressure, a thick-walled steel reactor vessel is needed. 

Ways to Succeed, 1993—1994 Materials Selection Guide, Eorm No. 304-00286-1292X SMG, The Dow Chemical Co., Midland, Mich., 1993. 

J. R. Hague, J. F. Lynch, A. Rudnick, F. C. Holden, and W. H. Duckworth, eds., Eefractory CeramicsforMerospace A. Materials Selection Handbook, The American Ceramic Society, Inc., Columbus, Ohio, 1964. 

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. 

Careflil material selection is required to prevent brittle failure of tanks at low temperatures. In addition, for tanks where the service temperatures are reduced, it is essential that an engineering analysis be performed to ensure that the tanks are not subject to brittle failure at the house temperature. The tank and vessel codes usually specify allowable materials based on design temperature. Further information about selection of metals for low temperature is available (8). 

The case is the largest portion of the container. The case is divided into compartments which hold the cell elements. The cores normally have a mud-rest area used to collect shed soHds from the battery plates and supply support to the element. Typical materials of constmction for the battery container are polypropylene, polycarbonate, SAN, ABS, and to a much lesser extent, hard mbber. The material used in fabrication depends on the battery s appHcation. Typical material selections include a polypropylene—ethylene copolymer for SLI batteries polystyrene for stationary batteries polycarbonate for large, single ceU standby power batteries and ABS for certain sealed lead—acid batteries. 

Other Types of Portland Cements. White Portland cementis standard Type I or III Pordand cement with raw materials selected and controUed to have negligible amounts of Hon and manganese oxides, which impart the gray color. The white Pordand cement is used in decorative and architectural appHcations like precast curtain waUs, terra22o surfaces, stucco, tile grout, and decorative concrete. 

The final product has a low ash and/or low iron content achieved by raw material selection or special processiag. 

Processing is key to the reproducible manufacture of ceramics. The tolerance of a finished ceramic to defects determines the raw materials selected, and the control that must be exercised during processing. More expensive advanced ceramics require higher quaUty, more expensive raw materials coupled with more carefully controlled manufacturing processes. 

These standards specify design, construction, and testing details such as material selection, shop inspection and tests, drawings and other uses required, clearances, construction procedures, and so on. 

Temperature. The temperature of the liquid being pumped is important because it affects the seal face material selection as well as the wear life of the seal face. 

The hydrostatic test is, in one sense, a method of examination of a vessel. It can reveal gross flaws, inadequate design, and flange leaks. Many beheve that a hydrostatic test guarantees the safety of a vessel. This is not necessarily so. A vessel that has passed a hydrostatic test is probably safer than one that has not been tested. It can, however, stiU fail in service, even on the next appheation of pressure. Care in material selection, examination, and fabrication do more to guarantee vessel integrity than the hydrostatic test. 

The tubeside fluid must be clean or at least chemically cleanable. With a large number of tubes in the coil, cleaning of inside surfaces is not totally rehable. Fluids that attack stressed materials such as chlorides should be reviewed as to proper coil-material selection. Fluids that contain sohds can be a problem due to erosion of relatively thin coil materials unlike the thick plates in spiral-plate units and multiple, parallel, fluid passages compared to a single passage in spiral-plate units. 

Tube to tubesheet joints, a weakness of most nonmetallic units, are fused by special techniques that do not severely affect the chemical suitabihty of the unit. Some nonmetallics use Teflon or O rings that add an extra consideration to material selection. 

Membrane manufacturers require a standard test to maintain batch-to-batch quality. Few use proteins. Materials selected are ones for which the complications are minimized, the probe is simple, fast, and cheap to detecl , does not readily biodegrade, and gives results, whatever they are, which are reproducible. There is no standardization of these tests within the industry. 

In the absence of factual corrosion information for a particular set of fluid conditions, a reasonably good selection would be possible from data based on the resistance of materials to a very simifar environment. These data, however, should be used with some reservations. Good practice calls for applying such data for preliminary screening. Materials selected thereby would reqmre further study in the fluid system under consideration. 

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