PlantPAx Distributed Control System Important User Information Read this document and the documents listed in the additional resources section about installation. CONTROL AND MONITORING FOR HEAT TRACING SYSTEMS In todays plant environments, control and monitoring plays an essential role in heat tracing system performance. A Distributed Control System DCS is a digital processor control system for a process or plant, wherein controller functions and field connection modules are. Een distributed control system DCS is een onderdeel van een productiesysteem. Distributed control systems worden gebruikt in industrile en civieltechnische. Industrial control system Wikipedia. Industrial control system ICS is a general term that encompasses several types of control systems and associated instrumentation used for industrial process control. Such systems can range from a few modular panel mounted controllers to large interconnected and interactive distributed control systems with many thousands of field connections. All systems receive data received from remote sensors measuring process variables PVs, compare these with desired set points SPs and derive command functions which are used to control a process though the final control elements FCEs, such as control valves. The larger systems are usually implemented by Supervisory Control and Data Acquisition SCADA systems, or distributed control systems DCS, and programmable logic controllers PLCs, though SCADA and PLC systems are scalable down to small systems with few control loops. Such systems are extensively used in industries such as chemical processing, pulp and paper manufacture, power generation, oil and gas processing and telecommunications. Discrete controllersedit. Panel mounted controllers with integral hard displays. The process value PV, and setvalue SV or setpoint are on the same scale for easy comparison. The controller output CO is shown as MV Manipulated variable range 0 1. A control loop using a discrete controller. Field signals are process variable PV from the sensor, and control output to the valve the Final Control Equipment FCE. TC7118.jpg' alt='Distributed Control System Dcs Pdf' title='Distributed Control System Dcs Pdf' />A valve positioner ensures correct valve operation. The simplest control systems are based around small discrete controllers with a single control loop each. These are usually panel mounted which allows direct viewing of the front panel and provides means of manual intervention by the operator, either to manually control the process or to change control setpoints. A PROGRAMMABLE LOGIC CONTROLLER PLC is an industrial computer control system that continuously monitors the state of input devices and makes decisions based upon a. Originally these would be pneumatic controllers, a few of which are still in use, but nearly all are now electronic. Quite complex systems can be created with networks of these controllers communicating using industry standard protocols, which allow the use of local or remote SCADA operator interfaces, and enable the cascading and interlocking of controllers. However, as the number of control loops increase for a system design there is a point where the use of a PLC or DCS system is more cost effective. Distributed control systemseditA Distributed Control System DCS is a digital processor control system for a process or plant, wherein controller functions and field connection modules are distributed throughout the system. They are used when the number of control loops makes DCS more cost effective than discrete controllers, and enable a supervisory view over large industrial processes. In a DCS a hierarchy of controllers is connected by communication networks, allowing centralised control rooms and local on plant monitoring and control. The introduction of DCSs enables easy configuration of plant controls such as cascaded loops and interlocks, and easy interfacing with other computer systems such as production control and scheduling. It also enabled more sophisticated alarm handling, introduced automatic event logging, removed the need for physical records such as chart recorders, allowed the control racks to be networked and thereby located locally to plant to reduce cabling. DCS structureedit. The Falling Sand Game 4 there. Functional manufacturing control levels, DCS and SCADA operate on levels 1 and 2. A DCS typically uses custom designed processors as controllers, and uses either proprietary interconnections or standard protocols for communication. Input and output modules form the peripheral components of the system. No Limits Coaster Tracks. The processors receive information from input modules, process the information and decide control actions to be performed by the output modules. The input modules receive information from sensing instruments in the process or field and the output modules transmit instructions to the final control elements, such as control valves. The field inputs and outputs can either be continuously changing analog signals e. A dc current loop or 2 state signals that switch either on or off, such as relay contacts or a semiconductor switch. DCS systems can normally also support such as Foundation Fieldbus, profibus, HART, Modbus, PC Link and other digital communication bus that carries not only input and output signals but also advanced messages such as error diagnostics and status signals. SCADA systemseditSupervisory control and data acquisition SCADA is a control system architecture that uses computers, networked data communications and graphical user interfaces for high level process supervisory management, but uses other peripheral devices such as programmable logic controllers and discrete PID controllers to interface to the process plant or machinery. The operator interfaces which enable monitoring and the issuing of process commands, such as controller set point changes, are handled through the SCADA supervisory computer system. However, the real time control logic or controller calculations are performed by networked modules which connect to the field sensors and actuators. The SCADA concept was developed as a universal means of remote access to a variety of local control modules, which could be from different manufacturers allowing access through standard automation protocols. In practice, large SCADA systems have grown to become very similar to distributed control systems in function, but using multiple means of interfacing with the plant. They can control large scale processes that can include multiple sites, and work over large distances. It is one of the most commonly used types of industrial control systems, however there are concerns about SCADA systems being vulnerable to cyberwarfarecyberterrorism attacks. Referring to the functional hierarchy diagram in this article Level 1 contains the PLCs or RTUs. Level 2 contains the SCADA software and computing platform. The SCADA software exists only at this supervisory level as control actions are performed automatically by RTUs or PLCs. SCADA control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process to a set point level, but the SCADA system software will allow operators to change the set points for the flow. The SCADA also enables alarm conditions, such as loss of flow or high temperature, to be displayed and recorded. A feedback control loop is directly controlled by the RTU or PLC, but the SCADA software monitors the overall performance of the loop. Programmable logic controllersedit. Siemens Simatic S7 4. PSU, CPU, interface module IM and communication processor CP. PLCs can range from small building brick devices with tens of IO in a housing integral with the processor, to large rack mounted modular devices with a count of thousands of IO, and which are often networked to other PLC and SCADA systems. They can be designed for multiple arrangements of digital and analog inputs and outputs IO, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery backed up or non volatile memory. It was in the automotive industry in the USA that the PLC was created.