Programmable logic control systems

Virtually all new pilot plants will be computer controlled and heavily automated due to the high cost of operating labor, need for high accuracy and repeatability, and ease of data gathering and work-up. Stand-alone computer and programmable logic controller systems will continue to dominate the... 

Stand-alone computer systems, usually based on a personal computer (PC) or programmable logic controller (PLC), provide a separate computer system for each pilot plant. This allows for economical expansion for new units, separates pilot plants completely for maintenance and troubleshooting, and often has the lowest initial cost. Standardization can be a problem and software control, data gathering, and storage packages can be limited in size, scope, and capabiUty these are usually acceptable trade-offs. 

PCC = process control computer PLC = programmable logic controller and PGCS = process gas chromatograph system. 

Figure 8-62 depicts a hypothetical distributed control system. A number of different unit configurations are illustrated. This system consists of many commonly used DCS components, including multiplexers (MUXs), single/multiple-loop controllers, programmable logic controllers (PLCs), and smart devices. A typical system includes the following elements as well ... 

The component controllers used in the controller subsystem portion of the DCS can be of various types and include multiloop controllers, programmable logic controllers, personal computer controllers, singleloop controllers, and fieldbus controllers. The type of elec tronic con-troUer utihzed depends on the size and func tional characteristic of the process apphcation being controlled. See the earlier section on distributed control systems. 

Part 5 (Draft) Programmable logic controllers for safety applications (August 1998) VDIA DE 3542, Safety terms for automation systems. 

Programmable Logic Controller (PLC) A microcomputer-based solid-state control system which receives inputs from user-supplied control devices such as switches and sensors, implements them in a precise pattern determined by instructions stored in the PLC memory, and provides outputs for control or user-supplied devices such as relays and motor starters. 

Moderate to microproces.sor-based, fully programmable logic controls and feedback control systems are available, to provide smooth speed controls as good as a.c. drives... 

Integrated control systems are mainly found on factory-assembled equipment, but the increased use of programmable logic controllers for process control is giving designers and installation mechanics the experience to apply these methods to custom-built refrigeration systems [26]. 

Programmable logic control (PLC) systems, which automatically control the RO process to sustain output and quality specifications... 

PA PCP PCR PFA PGB PHA PID PLC PMACWA PMD POTW ppm PRH PRR psi psig PTFE PVDF PWS picric acid pentachlorophenol propellant collection reactor perfluoroalkoxy product gas burner preliminary hazards analysis proportional integral differential controller programmable logic control Program Manager for Assembled Chemical Weapons Assessment projectile mortar demilitarization (machine) publicly owned treatment works parts per million projectile rotary hydrolyzer propellant removal room pounds per square inch pounds per square inch gauge polytetrafluoroethylene (Teflon) polyvinylidene fluoride projectile washout system... 

Technology advances in electronics such as process control instrumentation systems, computer capabilities, programmable logic controllers, and the use of independent PC s (personal computers) at field locations for special dedicated functions present new challenges to incident investigation. Some of the advances are so rapid that the team may not have the internal expertise to determine failure scenarios, sequences, and modes. The suppliers and manufacturers of these high-tech devices are sometimes the only source of credible information on failure modes of these devices. 

The control system is based on an industrial programmable logic controller (PTC). It includes all software required for the completely automatic operation, maintenance, and troubleshooting of the accelerator. ... 

Qualification tests shall be carried out in order to check the transmission of one-bit binary information sent by sensors and safeties to the computerized control system or programmable logic controller. 

Control is provided either by programmable logic controllers or by using a PC-based control system. 

Hydrogen dispensers will likely make use of programmable logic controllers or PC-based control systems. Both liquid hydrogen and compressed hydrogen dispensers will need to be able to monitor pressures and temperatures, open and close valves, turn on pumps, and interface with fire and emergency shut-down systems. 

Stand-alone systems. Multiloop controllers) or programmable logic controllers (PLC) typically used to control part of a process, and larger supervisory control and data acquisition (SCADA) systems/distributed control systems (DCS) used to control the process or service as a whole (e.g., bulk primary production plant, building management systems). These self-contained systems are a component of an automated manu-... 

Control System Included in this classification are Supervisory Control and Data Acquisition Systems (SCADA), Distributed Control Systems (DCS), Statistical Process Control systems (SPC), Programmable Logic Controllers (PLCs), intelligent electronic devices, and computer systems that control manufacturing equipment or receive data directly from manufacturing equipment PLCs. 

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