Standard designs

The overall requirement is 1.0—2.0 s for low energy waste compared to typical design standards of 2.0 s for RCRA ha2ardous waste units. The most important, ie, rate limiting steps are droplet evaporation and chemical reaction. The calculated time requirements for these steps are only approximations and subject to error. For example, formation of a skin on the evaporating droplet may inhibit evaporation compared to the theory, whereas secondary atomization may accelerate it. Errors in estimates of the activation energy can significantly alter the chemical reaction rate constant, and the pre-exponential factor from equation 36 is only approximate. Also, interactions with free-radical species may accelerate the rate of chemical reaction over that estimated solely as a result of thermal excitation therefore, measurements of the time requirements are desirable. 

Design Standard channel-plate designs, unique to each manufacturer, are developed with limited modifications of each plates corrugation depths and included angles. Manufacturers combine their different style plates to custom-fit each seiwice. Due to the possible combinations, it is impossible to present a way to exactly size PHEs. However, it is possible to estimate areas for new units and to predict performance or existing units with different conditions (chevron-type channel plates are presented). 

For thermosyphon reboilers, the hydraulic aspects are as important as the heat transfer aspects. The design of thermosyphon reboiler piping is too broad a subject for this handbook. Some good articles on the subject can be found in References 2-14. Reference 3 is particularly good for horizontal thermosyphon reboilers. Table 1 has typical vertical thermosyphon design standards. 

Use inherently safer strategies when establishing company design standards, guidelines, or practices. 

Design standards The appropriate industrial, national, or international stan dards covering... 

Quality of conformance is the extent to which the product or service conforms to the design standard. The design has to be faithfully reproduced in the product or service. 

The verification plan needs to cover some or all of the following details as appropriate A definition of the product design standard which is being verified. 

Definition of the verification activities that are to be performed to qualify or validate the design and those which need to be performed on every product in production as a means of ensuring that the qualified design standard has been maintained. 

The configuration of the product in terms of its design standard, deviations, nonconformities, and design changes to be recorded prior to and subsequent to the tests... 

To accomplish this, you need to specify either in the quality plan or the documented procedures, the inspections and tests you intend to carry out to verify that the product meets specified requirements. In Part 2 Chapter 4 there is a description of a Design Verification Plan and this includes a specification of the tests and inspections to be performed on each production item as a means of ensuring that the qualified design standard is being maintained. This requires that you produce something like an Acceptance Test Plan which contains, as appropriate, some or all of the following ... 

The as-built configuration is the same as the issue status of all the parts, sub-assemblies, assemblies, etc. specified by the design standard. 

Are recorded and maintained indicating their serviceability and their design standards, including records of repairs and modifications. 

Don t use training equipment for operational purposes unless it is certified to current design standards before operational use. 

A model of a design that is both physically and functionally representative of the design standard for production and used to verify and validate the design. 

One major oil and chemical company has collected data on the cost of accidents, the equipment involved and the cause of the failure for more than 50 years. These data are analyzed annually to help decide where to focus efforts to reduce losses and/or to modify design standards to prevent recurrence. This analysis also identifies failures of the PSM and ESH management system. These can be compared with the cost of delivering the systems and adjustments made to expenditures to improve the cost/benefit balance. Any such changes must be carefully considered as normal statistical variation may cause you to take unjustified action. 

Electronic computer programs for these design standards... 

Figure 3-36C illustrates the change in performance for the exact same pump, same impellers, but for different rotating speeds of 1750 and 3550 rpm. (Note that the respective motor designated standard speeds are 1800 and 3600 rpm, but the pump manufacturer cannot count on these speeds under load in order to provide performance information the customer needs for design of a system.)... 

However, incorporating these changes in an existing unit is a major project, usually more complicated than building a new unit. The two critical components of a successful mechanical upgrade (or erection of a new unit) are effective project management and proper design standards. 

Many aspects of FCC development have been the result of trial and error. The development of present design standards is as much art as it is science. Consequently, it is appropriate to review some of the key developments that have influenced the current design philosophy behind the FCC reactor and regenerator ... 

Manufacturing economics require that many devices be fabricated simultaneously in large reactors. Uniformity of treatment from point to point is extremely important, and the possibility of concentration gradients in the gas phase must be considered. For some reactor designs, standard models such as axial dispersion may be suitable for describing mixing in the gas phase. More typically, many vapor deposition reactors have such low L/R ratios that two-dimensional dispersion must be considered. A pseudo-steady model is... 

Precision The repeatability characterizes the degree of short-term control exerted over the analytical method. Reproducibility is similar, but includes all the factors that influence the degree of control under routine and long-term conditions. A well-designed standard operating procedure permits one to repeat the sampling, sample work-up, and measurement process and repeatedly obtain very similar results. As discussed in Sections 1.1.3 and 1.1.4, the... 

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