Processing, inappropriate

The initially released intermediate is a carbamic add, which is prone to spontaneous decarboxylation this step is, however, quite slow, and makes this process inappropriate for fast kinetic experiments (e.g., in neurophysiology). 

Ultrasonic energy is frequently used to accelerate the dissolution of solid samples under soft conditions of temperature, pressure and chemical reagents. Similar to direct dissolution by agitation, US-assisted soft digestion is not used to the same extent as other operations of the analytical process such as leaching, derivatization or detection. The simplicity of this operation with some types of samples and the operator s lack of awareness of its error contribution are responsible for the absence of optimization studies for this process. Inappropriately conducted soft digestion can result in major errors and affect the quality of the results. 

Analogous effects are caused by the inappropriate use of utilities. Utilities are appropriate if they are necessary to satisfy the enthalpy imbalance in that part of the process. Above the pinch in Fig. 6.7a, steam is needed to satisfy the enthalpy imbalance. Figure 6.86 illustrates what happens if inappropriate use of utilities is made and some cooling water is used to cool hot streams above the pinch, say, XP. To satisfy the enthalpy imbalance above the pinch, an import of (Q mjj,+XP) is needed from steam. Overall, (Qcmin+AP) of cooling water is used. ... 

In design, the same rules must be obeyed around a utility pinch as around a process pinch. Heat should not be transferred across it by process-to-process transfer, and there should be no inappropriate use of utilities. In Fig. 6.13a this means that the only utility to be used above the utility pinch is steam generation and only cooling water below. In Fig. 6.136 this means that the only utility to be used above... 

If the reactor proves to be inappropriately placed, then the process changes might be possible to correct this. One option would be to change the reactor conditions to bring this about. Most often,... 

Following the pinch rules, there should be no heat transfer across either the process pinch or the utility pinch by process-to-process heat exchange. Also, there must be no use of inappropriate utilities. This means that above the utility pinch in Fig. 16.17a, high-pressure steam should be used and no low-pressure steam or cooling water. Between the utility pinch and the process pinch, low-pressure steam should be used and no high-pressure steam or cooling water. Below the process pinch in Fig. 16.17, only cooling water should be used. The appropriate utility streams have been included with the process streams in Fig. 16.17a. 

This big increase in speed has not been without cost. The everyday machine codes and high-level languages (Fortran, Pascal, C, etc.) used to control operations in a standard computer are inappropriate for parallel processing, which needs its own instruction set and has led to the development of special languages for use with the transputer. 

For each alarm, a specific action is expec ted from the process operator. Operator actions such as call maintenance are inappropriate with modern systems. If maintenance needs to know, modern systems can inform maintenance directly. 

Although safety interlocks can inappropriately initiate shutdowns, the process interlocks are usually the major source of problems. It is possible to configure so many process interlocks that it is not possible to operate the plant. 

These listings do not include all the methods in use. The vahdity of a particular method depends on the process and the industiy. An inappropriate method can lead to misleading and even absurd results. 

Human error probabilities can also be estimated using methodologies and techniques originally developed in the nuclear industry. A number of different models are available (Swain, Comparative Evaluation of Methods for Human Reliability Analysis, GRS Project RS 688, 1988). This estimation process should be done with great care, as many factors can affect the reliability of the estimates. Methodologies using expert opinion to obtain failure rate and probability estimates have also been used where there is sparse or inappropriate data. 

Inappropriate Select compatible materials of construction for materials of con- the specific process struction lead to, Change process parameters (e.g., different acid, corrosion and reduce temperature). Evaluate changes with test potential failure. coupons off-line Dillon 1992... 

Change in service may lead to inappropriate instrumentation for the current process. 

Environmental—If a product or its raw materials require special permitting (for example, air permits) or if the client company s facility is inappropriate for the process, tolling could provide a means to achieve the company s production goal. 

Simplified environmental fate estimation procedures are based on the predominant mechanisms of transport within each medium, and they generally disregard intermedia transfer or transformation processes. In general, they produce conservative estimates (i.e., reasonable upper bounds) for final ambient concentrations and the extent of hazardous substance migration. However, caution should be taken to avoid using inappropriate analytical methods that underestimate or overlook significant pathways that affect human health. 

To answer the above-mentioned questions, one can envision so many alternatives they cannot be enumerated. Typically, an engineer charged with the responsibility of answering these questions examines few process options based on experience and corporate preference. Consequently, the designer develops a simulation model, performs an economic analysis and selects the least expensive alternative from the limited number of examined options. This solution is inappropriately designated as the optimum. Normally it is not Indeed, the true optimum may be an order of magnitude less expensive. 

The first set of case studies illustrates errors due to the inadequate design of the human-machine interface (HMI). The HMI is the boundary across which information is transmitted between the process and the plant worker. In the context of process control, the HMI may consist of analog displays such as chart records and dials, or modem video display unit (VDU) based control systems. Besides display elements, the HMI also includes controls such as buttons and switches, or devices such as trackballs in the case of computer controlled systems. The concept of the HMI can also be extended to include all means of conveying information to the worker, including the labeling of control equipment components and chemical containers. Further discussion regarding the HMI is provided in Chapter 2. This section contains examples of deficiencies in the display of process information, in various forms of labeling, and the use of inappropriate instrumentation scales. 

With regard to mistakes, two separate mechanisms operate. In the rule-based mode, an error of intention can arise if an incorrect diagnostic rule is used. For example, a worker who has considerable experience in operating a batch reactor may have learned diagnostic rules that are inappropriate for continuous process operations. If he or she attempts to apply these rules to evaluate the cause of a continuous process disturbance, a misdiagnosis could result, which could then lead to an inappropriate action. In other situations, there is a tendency to overuse diagnostic rules that have been successful in the past. 

An important issue in the writing of procedures is how much information is necessary for the process worker in order to minimize the likelihood of error. Too little may be inappropriate for an inexperienced process worker while too much may encourage a highly experienced worker not to use the procedure. It is obvious that the level of worker expertise and the criticality of the task will determine the level of description. This example shows how lack of detailed information can lead to errors of omission. 

Traditional process flow diagrams are clear, quickly prepared and easily reviewed for conformity with ISO 9000 requirements. However, it is not easy to identify some types of process breakdowns, such as gaps in coverage, processes that follow the organizational hierarchy and inappropriate allocation of tasks within the organization. 

Extend Range of Feedstocks for the Process. Feedstock flexibility can enable maximum advantage to be taken of market fluctuations in the price and availability within the range of feedstocks which can be used. Obviously this is inappropriate in some cases where there is a close chemical link between feedstock and product, e.g. direct oxidation of ethylene to ethylene oxide, but in some processes, e.g. steam-reforming, flexibility is possible and may be advantageous. 

Control of waterside chemistry starts in the pre-boiler section because the lack of, or inappropriate methods for, water treatment creates significant operational difficulties and impacts the economics of the entire process from start to finish. 

Of course, in aqueous solution the reactants and the products exist wholly or partly in their ionized forms the acid, nitrite, and salt exist as H+X , Na+N02, and Na+X , while the diazonium salts are practically completely ionized and the amine is in equilibrium with the corresponding ammonium ion, Ar—NH3. The question of which of these various species are involved in the substitution proper will be dealt with in Chapter 3. Although it is generally desirable to introduce ionized forms into equations, this is inappropriate for the overall equation for the diazotization process, as will become apparent in the discussion of the reaction mechanism (Ch. 3) and from the following remarks. 

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