Programmable logic controllers and

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

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... 

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. 

All capsule pipeline systems include a pipe, many capsules, an injection system to inject capsules into the pipe, a pumping system to pump the fluid and capsules through the pipe, an ejection system to eject the capsules from the pipe, an instrumentation system to monitor the flow rate, pressure, temperature, and the passage of capsules at key locations, and an automatic control system that uses programmable logic controllers and an SCADA (Supervisory Control and Data Acquisition). 

In commercial plants, programmable logic controllers and process computers enable both process automation and labor-savings. The present and likely future uses of computer applications to fermentation processes in pilot and industrial plants are summarized in Table 5. In the table, open circles indicate items that have already been discussed in other reports while the open triangles are those topics to be elaborated here. 

NOTE This data represents typical programmable logic controllers and distributed control systems. Lower Allure rates can be achieved by BPCS logic solvers that meet the requirements of lEC 61508 or ANSI/ISA-84.00.01-2004-1, Clause 11.5. 

Advanced training in controller operation (PLC (programmable logic controller) and DCS (distributed control system))... 

PLCs (Programmable Logic Controllers) and their Languages... 

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. 

Discrete logic. Sequence logic can be implemented via ladder logic, and this approach is common when sequence logic is implemented in programmable logic controllers (PLCs). 

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. 

Programmable Logic Controllers The programmable logic controller (PLC) originated as a solid-state replacement for the hardwired relay control panel and was first used in the automotive indus-tiy for discrete manufacturing control. Today, PLCs are used to implement Boolean logic functions, timers, counters, and some math functions and PID control. PLCs are often used with on/off process control valves. 

The average prices of the batch centrifuge are shown in Fig. 18-154. All the models include the drive motor and control. In Fig. 18-154, the inverting filter, horizontal peeler, and the advanced vertical peeler are the premium baskets especially used for specialty chemicals and pharmaceuticals. Control versatility with the use of programmable logic control (PLC), automation, and cake-heel removal are the key features which are responsible for the higher price. The underdriven, top-driven, and pendulum baskets are less expensive with fewer features. 

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. 

A process requiring accurate and instant speed controls must adopt static tnotor controls, described in Section 6.9, and their control schemes must be activated through programmable logic controllers (PLCs) discussed above. 

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... 

Programmable logic controllers are used for the control and interlocking of processes where a sequence of operating steps has to be carried out such as, in batch processes, and in the start-up and shut down of continuous processes. 

The three major types of electronic controllers are timers, electromechanical relays, and programmable logic controllers (PLCs), which are often called digital relays. Each of these types of controller is discussed in more detail below. 

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