Design approach


The desired mixing in a commercial process is achieved with different types of equipment, eg, agitators, jets, static mixers, air lifts, etc. The design approach requires defining process mixing requirements specifying mixer type and size, and other internals such as baffles and designing mechanical components such as impeller blades, shaft, drive assembly, beatings, and supports.  [c.420]

A further consideration, which is contrary to minimizing the risks associated with a new product or process, can be the timeliness of the discovery. Timing can be the most important factor in a research program, as in the case of securing a new market with a totally new product or attempting to secure a patent position before a competitor. In this situation, the decision may be made to proceed to commercialization earlier than desirable, prior to satisfactorily resolving all design concerns. This usually requires a more conservative and, hence, more expensive design approach.  [c.39]

Supercritical Fluid Extraction. Polycychc aromatic hydrocarbons (PAHs) have been extracted from contaminated land samples by supercritical fluid extraction (SEE) with both pure and modified carbon dioxide (35) (see Supercritical fluids). An experimental design approach, based on central composite design, was used to determine which SEE variable affects the total recovery of 16 PAHs. Pour parameters were chosen for evaluation pressure, temperature, extraction time, and percentage of methanol modifier addition. Accessible levels of each parameter were dependent on instmmental constraints. A statistical treatment of the results indicated that extraction time and percentage of modifier addition were the only variables to affect PAH recovery significantly. The levels of these variables were set at the maximum values while the pressure and temperature were maintained at their midpoint value in design. These conditions were used in a repeatabiUty study n = 7), which extracted an average of 458.0 mg/kg total PAHs from the contaminated land sample with a relative standard deviation (RSD) of 3.1%. Sequential extractions on three of these samples, using identical operating conditions, did not show the presence of PAHs. The results were compared with the Soxhlet extraction and micro wave-assisted (MAE) extraction of the sample, which recovered an average of 297.4 (RSD 10.0%) and 422.9 (RSD 2.4%) mg/kg, respectively.  [c.242]

Although their properties differ widely, all polymers are made up of long molecules with a covalently bonded backbone of carbon atoms. These long molecules are bonded together by weak Van der Waals and hydrogen ("secondary") bonds, or by these plus covalent cross-links. The melting point of the weak bonds is low, not far from room temperature. So we use these materials at a high fraction of the melting point of the weak bonds (though not of the much stronger covalent backbone). Not surprisingly, they show some of the features of a material near its melting point they creep, and the elastic deflection which appears on loading increases with time. This is just one important way in which polymers differ from metals and ceramics, and it necessitates a different design approach (Chapter 27).  [c.220]

The development of the probabilistic design approach, as already touched on, includes elements of probability theory and statistics. The introductory statistical methods discussed in Appendix I provide a useful background for some of the more advanced topics covered next. Wherever possible, the application of the statistical methods is done so through the use of realistic examples, and in some cases with the aid of computer software.  [c.135]

Figure 4.14 Key variables in a probabilistic design approach Figure 4.14 Key variables in a probabilistic design approach
Probabilistic design approach  [c.204]

Deterministic design approach  [c.211]

Product life-time prediction, cost and weight optimization have enormous implications on the business of engineering manufacture. Using large Factors of Safety in a deterministic design approach fails to provide the necessary understanding of the nature of manufacture, material properties, in-service loading and their variability. Probabilistic approaches offer much potential in this connection, but have yet to be taken up widely by manufacturing industry. In Chapter 4, a probabilistic design  [c.416]

Design Approach. The engineering solution of thermal fatigue problems becomes chiefly a matter of design to minimize the adverse factors in the stress formula and alloy selection aimed carefully at the operating conditions. Much effort should be devoted to reducing the thermal gradients or the temperature differential to the practical minimum. This, and avoiding restraint, is a rewarding area where the designer can demonstrate his skill.  [c.268]

A Generalized Design Approach to Power Supplies Introducing the Building-block Approach to Power Supply Design  [c.8]

When an installation is being planned, it is recommended that the API Standard 618 be reviewed in detail. The pulsation level for API 618 at Design Approach 1, the outlet side of any pulsation control device regardless of type, should be no larger than 2% peak-to-peak of the line pressure, or the value given by the following equation, whichever is less  [c.84]

The theory relating stress, strain, time and temperature of viscoelastic materials is complex. For many practical purposes it is often better to use an ad hoc system known as the pseudo-elastic design approach. This approach uses classical elastic analysis but employs time- and temperature-dependent data obtained from creep curves and their derivatives. In outline the procedure consists of the following steps  [c.200]

Cooper, 1994. David Cooper and F. Alley, Air Pollution Control A Design Approach. 2" Edition, Wave and Press, Prospect Heights, IL, 1994,  [c.489]

The slope of the line is Lj/Gs. This proeedure provides the minimum theoretieal solvent requirements. In praetiee, however, liquid rates are seleeted at least 25 to 100% greater than the theoretieally ealeulated minimum rate. Typieally, paeking manufaeturers suggest that liquid rates between 2 and 5 gpm/tf result in the best operation. Higher liquid flow rates will effeet the degree to whieh the paeking surfaees beeome fully wetted. Obviously, higher liquid flow rates will result in a greater portion of the paeking surfaee being wetted, thereby giving higher aetive liquid gas eontaeting area and a higher rate of mass transfer. When approaehed from an economic standpoint, higher liquid flow rates results in a higher efficiency of scrubbing per unit tower volume, but lower concentration of the solute in the solvent. This results in a higher quantity of scrubbing liquid used, which generally means a higher operating cost, especially where solvents are valuable. However, this design approach results in minimum initial capital investment. Where lower liquid flow rates are considered, tlie result is larger scrubbing towers, resulting in higher initial capital investment cost, but lower operating usage of scrubbing liquid. Scrubbing manufacturers advise that above a certain liquid flow rate, known as "minimum wetting rate" (MWR), there is virtually no increase in mass transfer rate. This is due to the fact that at this rate, the full effective surface area is wetted by the scrubbing liquid. In the selection of a solvent for any particular scrubbing system, several aspects of tlie scrubbing liquid should be considered. These factors are (1) the solubility of tlie gas should be relatively high to enhance the rate of absorption and to decrease the quantity of solvent required (2) the solvent should have relatively low volatilities to reduce solvent loss due to evaporation (3) the solvent should be as non-corrosive as possible to reduce the construction and maintenance costs of the equipment (4) the solvent should be inexpensive and readily available (5) the solvent should have relatively low viscosity to increase tower capacities and reduce flooding potentials (6) the solvent should be non-toxic, non-flammable, chemically stable and have a low freezing point.  [c.263]

A multihearth furnace is typically used in the regeneration process. The multihearth furnace employs a simple design approach. It consists of a steel sheet lined with refractory inside. This refractory can be a castable as used in the 30-inch units, or brick as used in the larger sizes. The latter can also have 4.5 inches of insulating blocks which make the walls a total of 9 inches thick for the small furnaces or 13.5 inches on the larger furnaces where high temperatures are used. The interior space of the furnace is divided by horizontal brick arches into separate compartments called hearths. Alternate hearths have holes at the periphery or at the center for the carbon to drop through from one hearth to the next. Through the center of the furnace goes a rotating shaft driven at the bottom by a speed reducer with variable-speed drive. It is scaled at the top and bottom by special sand seals to prevent air or gas leakage. The shaft is hollow and has sockets where arms, called rabble arms, are fitted. An inner tube in each arm and in the shaft provides the means for air cooling of both to prevent damage by the intense heat. This cooling air is blown in through a special connection at the bottom of the shaft. The arms are, in turn, fitted with rabble teeth, placed at an angle, and impart a motion to the carbon when the  [c.315]

The above factors represent considerations that the design engineer must account for to ensure compatibility between components and equipment materials. In addition to these, there are geometric considerations that can minimize corrosion problems if accounted for in design. The following are general guidelines pertaining to geometry in a design aimed at minimizing corrosion. The overall design approach involves the selection of the optimum geometry for a piece of equipment that is less likely to undergo certain types of corrosion, either directly or indirectly. Such shapes, forms, combinations of forms and their method of attachment, along with their fabrication technique and treatment, should not aggravate corrosion.  [c.42]

Thus the basis of the LEFM design approach is that  [c.130]

Huang, Y. L., and Edgar, T. F. (1995). Knowledge based design approach for the simultaneous minimization of waste generation and energy consumption in a petroleum refinery. In Waste Minimization Through Process Design (A. P. Rossiter, ed.), pp. 181-1%. McGraw Hill, New York.  [c.82]

Some specific design methods have been developed for particular appHcations. Several procedures have been pubHshed for the design of gas dryers. The y-function has been appHed to siUca gel dryers after a correlated correction factor accounted for the nonisothermaUty (114). In other work on drying with activated alumina and siUca gel, constant-pattern LUBs were shown appHcable for designs at H2O contents of less than 0.003 kg/kg air (115). Equilibrium and kinetic parameters for H2O on activated alumina were deterrnined for a more rigorous nonisothermal model that predicted adiabatic behavior (116). Breakthrough times for several organic vapors on activated carbon respirator cartridges have been found to be predictable by using a theory of statistical moments. In one study, equiUbrium data was correlated by the Potential Theory and breakthrough was calculated using the normal probabiUty distribution curve (117). In another, the equiUbrium data was represented by a Ereundhch equation (118). Eor heavy hydrocarbon recovery from natural gas on sihca gel, the equiUbrium data were fit to a Ereundhch isotherm and the breakthrough composition was found to have a power dependence on the extent of adsorptive saturation of the adsorbent (111). A WUB design approach was found to predict breakthrough for several organics on activated carbon using a Potential Theory equiUbrium curve (119). Correlations of equiUbrium capacity and WUB were also found appHcable in the removal of H2S from natural gas using 5A zeoHte (120).  [c.286]

The classic systems design approach is becoming more common ia the 1990s for the overall iastmmentation and control systems design. First, a control philosophy is developed that sets some general guidelines and objectives. Next, a functional definition of the iastmmentation and control system is developed. The functional definition, which should iaclude a clear statement of specific control objectives, provides the basis for determining the relative benefits of alternatives and for the system selection process. Using the functional definition, alternative iastmmentation and control systems can be roughly configured to satisfy the functional definitions to different degrees. Rough cost estimates and rough benefit—cost ratios can then be developed.  [c.79]

Betabellin (Fig. 9) is an example of a de novo designed P-sheet protein. BetabeUin contains two identical four-stranded sheets that dimerize via interaction of their hydrophobic faces to form an antiparahel P-sandwich, ie, a P-sheet, beU-shaped protein. Unlike the modular, minimalist design approach used in hehcal protein designs, one of the initial design criteria for the betabeUins was the constmction of a protein-like sequence containing normal amino acid composition, but avoiding direct homology with any natural protein. Other design criteria included secondary stmcture prediction, statistical preference of residues for positions in P-strands and P-tums, a pattern of alternating hydrophobic and hydrophilic residues to form two opposite faces of the sheet, and consideration of internal packing interactions (53).  [c.202]

The design approach is particularly feasible for those reactions in which chemical and pore diffusion rates are most important. For flow related phenomena semi-empirical, dimensionless correlations must be relied on. Therefore in this book scale-up will be used in the more general sense with the airri of using methods that are fundamentally based wherever feasible.  [c.1]

Deterministic design is still appealing because of its simplicity in form and application, but since factors of safety are not performance related measures, there is no way of indicating if the design is near optimum (Haugen, 1980). With increasing concern over minimizing the cost of failure, the probabilistic design approach will become more important (Dieter, 1986). Probabilistic design gives the designer a better feel of just how conservative or unconservative the design is (Ullman, 1992). In order to determine this, however, it is important to make decisions about the target reliability level (Ditlevsen, 1997).  [c.33]

Figure 4.1 gives an indication that engineers in the 1950s were beginning to think differently about design with the introduction of a true margin of safety, and a probabilistic design approach was being advocated. It shows that the design problem was multifactored and variability based. With the increasing use of statistics in engineering around this time, the theories of probabilistic design and reliability were to become established methods in some sectors by the 1960s.  [c.133]

Figure 4.2 shows the probabilistic design concept in comparison to the deterministic approach. Not fully understanding the variable nature of the stress and strength, the designer using the deterministic approach would select a suitable factor of safety which would provide adequate separation of the nominal stress and strength values (for argument s sake). Selecting too high a factor of safety results in overdesign too low and the number of failures could be catastrophically high. In reality, the interference between the actual stress and strength distributions dictates the performance of the product in service and this is the basis of the probabilistic design approach. The degree of interference and hence the failure probability depends on (Mahadevan, 1997)  [c.135]

In this the final case study we have touched on a probabilistic approach in support of designing against fatigue failure, a topic which is actually outside the scope of the book. A fatigue analysis for the con-rod would need to take into account all factors affecting the fatigue life, such as stress concentrations and surface finish. However, it has indicated that a probabilistic design approach has a useful role in such a setting. Readers interested in more on stress concentrations and probabilistic fatigue design are directed to Carter (1986), Haugen (1980) and Mischke (1992).  [c.249]

For those installations where a detailed pulsation analysis, API 618 Design Approach 2 or 3, is required,. several consulting companies offer these services. Until the 1980s, the most common method was to perform the pulsation analysis on the analog simulator of the Pipeline and Compres.sor Research Council of the Southern Gas Association. The  [c.85]

The brute force allowables method described above of testing numerous substrate thicknesses and bond widths is still not that much more cost-effective than a point-design approach. A more efficient and analytical method of designing and analyzing adhesive bonds relies on more detailed knowledge of adhesive mechanics. Mechanics of bonded joints become very complex very quickly because of the large difference in stiffness and strength of the adhesive and adherends, the significant deformations these adhesives exhibit before ultimate fracture, and the common need to bond adherends of different thicknesses and shapes. Modeling these complex joints requires knowledge of the adhesive stress-strain response up to ultimate fracture at temperatures of interest. This information has been gathered by various methods such as the napkin ring shear and thick-adherend lap shear (ASTM D5656) extensometer testing. Fig. 12 shows typical thick adherend stress-strain data for a standard 250°F curing epoxy film adhesive.  [c.1151]

Cooper Alley, 1994. C. D. Cooper and F. C. Alley, Air Pollution Control A Design Approach, Second Edition, Waveland Press, Inc. IL.  [c.490]

Cooper Alley, 1994. C. D. Cooper and F. C. Alley, Air Pollution Control A Design Approach, Second Edition, Waveland Press, Inc. IL.  [c.491]

Cooper, 1994. David Cooper and F. Alley, Air Pollution Control A Design Approach, 2 Edition, Waveland Press, Prospect Heights, IL, 1994.  [c.492]

Cooper, 1994. David Cooper and F. Alley, Air Pollution Control A Design Approach, 2" Edition, Waveland Press, Prospect Heights, IL, 1994.  [c.493]

Cooper, 1994. David Cooper and F. Alley, Air Pollution Control A Design Approach, 2" Edition, Waveland Press, Prospect Heights, IL. 1994.  [c.493]

Cooper, 1994. David Cooper and F. Alley, Air Pollution Control A Design Approach. 2 " Edition, Waveland Press, Prospect Heights, IL, 1994.  [c.494]

Cooper, 1994. David Cooper and F. Alley, Air Pollution Control A Design Approach, 2" Edition, Waveland Press, Prospect Heights, IL, 1994.  [c.495]


See pages that mention the term Design approach : [c.1441]    [c.135]    [c.204]    [c.54]    [c.251]   
See chapters in:

Pollution prevention through process integration  -> Design approach


Designing capable and reliable products (2000) -- [ c.0 ]