Instrumentation/control systems case study

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. 

The case study described here concerns a human factors audit of a computer controlled process system which was being introduced in a distillation imit of a chemical plant. The unit was in transition from replacing its pneumatic panel instrumentation with the new system. However, control had not yet been transferred and the staff were still using the panel instrumentation. The role of the project was to evaluate a preliminary design of the computer-based display system and provide recommendations for future development. 

The third case study consists of a well-instrumented experimental distillation column that has been interfaced to an industrial distributed control system. In this... 

Instrument application design is one of the most extensive activities, in terms of the number of types of instrument and the associated paperwork, and requires a logical, carefully controlled approach. A change to an instrument tag number or the addition/deletion of an instrument can affect up to ten different documents. However, with good document control, it is possible to produce a system of documentation that will allow instrument applications, both simple and complex, to be validated and easily maintained. This case study has described the instrument application design process commonly used in the industry and how this can be used to support validation. 

In this text the reader can find material related to computer-instrument-process communication, data acquisition and control, reliability of process control computer systems, management aspects of in-plant computer installations, and a large number of case studies. Additional general references on digital computers and their application in the real-time environment are the following ... 

The barometric setting provided by the flight crew on the Display Control Panel is not relevant for pressure altitude, and it is therefore not considered further in this case study. Other elements of the upgraded system, such as the Standby Flight Instrument and Inertial Reference System (IRS), are also not considered in this case study. 

Sanchez, SIL application in burner management systems - a case study thermal burner, in Safety Control t Instrumentation Systems Conference, IDC Technologies, 2009. 

Runaway Reactions Experimental Characterization and Vent Sizing This instruction module describes the ARSST and its operation, and illustrates how this instrument can easily be used to experimentally determine the transient characteristics of mnaway reactions, and how the resulting data can be analyzed and used to size the relief vent for such systems. Rupture of a Nitwaniline Reactor This case study demonstrates the concept of runaway reactions and how they are characterized and controlled to prevent major losses. 

The method of complete electrolysis is also important in elucidating the mechanism of an electrode reaction. Usually, the substance under study is completely electrolyzed at a controlled potential and the products are identified and determined by appropriate methods, such as gas chromatography (GC), high-performance liquid chromatography (HPLC), and capillary electrophoresis. In the GC method, the products are often identified and determined by the standard addition method. If the standard addition method is not applicable, however, other identification/determination techniques such as GC-MS should be used. The HPLC method is convenient when the product is thermally unstable or difficult to vaporize. HPLC instruments equipped with a high-sensitivity UV detector are the most popular, but a more sophisticated system like LC-MS may also be employed. In some cases, the products are separated from the solvent-supporting electrolyte system by such processes as vaporization, extraction and precipitation. If the products need to be collected separately, a preparative chromatographic method is use-... 

In situ measurements of the emission and absorption characteristics of the atmosphere always lag behind theoretical developments and laboratory studies. This is primarily attributable to equipment limitations. The laboratory environment is basically friendly, and there, experimenters are not usually faced with limitations of equipment weight, size, and power, and there is no necessity to design to meet adverse environmental conditions. This is not the case when field measurements are undertaken. In the field the elements mentioned above must be considered and solutions provided in order to conduct successful measurement programs. This paper provides a brief synopsis of developments in IR spectroscopy, compares basic system components, and discusses some of our recent efforts to extend measurements techniques, which are now common under controlled laboratory conditions, to the more difficult situation of actual atmospheric measurements. He have not presented a detailed study of a specific single example. Rather, we chose to discuss two typical field instruments and highlight the development of the components of these instruments that ultimately allowed successful system deployment. 

Closed automated systems designed for particular tests in an instrument have been developed. They are closed systems because the reagents and IA protocols were controlled by the manufacturer. Examples are the Roche Cobas FARA II , DuPont ACA , and Miles Immuno 1 analyzers. The reagents are expensive, and in many cases the applications are fixed and may not be adaptable for PK and PD study purposes. 

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