tailieunhanh - Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 30

Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 30 studies the combination of various methods of designing for reliability, availability, maintainability and safety, as well as the latest techniques in probability and possibility modelling, mathematical algorithmic modelling, evolutionary algorithmic modelling, symbolic logic modelling, artificial intelligence modelling, and object-oriented computer modelling, in a logically structured approach to determining the integrity of engineering design. . | Application Modelling of Reliability and Performance in Engineering Design 273 Fig. Hazards criticality analysis logistics worksheet Distributed control systems are dedicated systems used to control processes that are continuous or batch-oriented. A DCS is normally connected to sensors and actuators and uses set-point control to control the flow of material through the plant. The most common example is a set-point control loop consisting of a pressure sensor controller and control valve. Pressure or flow measurements are transmitted to the controller usually through the aid of a signal conditioning input output I O device. When the measured variable reaches a certain point the controller instructs a valve or actuation device to open or close until the flow process reaches the desired set point. Programmable logic controllers PLCs have recently replaced DCSs especially with SCADA systems. A programmable logic controller PLC or programmable controller is a digital computer used for automation of industrial processes. Unlike general-purpose controllers the PLC is designed for multiple inputs and output arrangements extended temperature ranges immunity to electrical noise and resistance to vibration and impact. PLC applications are typically highly customised systems compared to specific custom-built controller design such as with DCSs. However PLCs are usually configured with only a few analogue control loops where processes require hundreds or thousands of loops a DCS would rather be used. Data are obtained through a connected supervisory control and data acquisition SCADA system connected 274 3 Reliability and Performance in Engineering Design Fig. Hazards criticality analysis logistics spreadsheet to the DCS or PLC. The term SCADA usually refers to centralised systems that monitor and control entire plant or integrated complexes of systems spread over large areas. Most site control is performed automatically by remote terminal units RTUs or by .

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