A typical Distributed Control System (DCS) consists of functionally and/or spatially distributed digital controllers capable of executing from one to 256 or more regulatory control loops in one controller “box.” The sensor I/O can be integral with the controller or located remotely via a field network. Controllers currently available have extensive computational capabilities and, in addition to continuous PID control, generally can also perform logic and sequence control.
A DCS may employ one or several workstations and can be configured at the workstation or by an off-line personal computer. A control network with transmission over twisted pair, coaxial, or fiber optic cables handles local communication. A server and/or applications processor may be included in the system to provide system services as well as additional computational, data storage, and reporting capability.
Distributed Control System (DCS) Hardware
With the increasingly amorphous nature of evolving DCS architecture and the ever-expanding business model of DCS suppliers, ARC has made an effort to focus its definition of DCS, rather than including all possible inter-related elements of plant automation.
At the hardware level, DCS begins at the sensor I/O and extends all the way through controllers, application processors, workstations, PCs, and the networking equipment falling within the DCS control domain. PLCs and PLC-type controllers sold as part of an integrated system offering, such as the Siemens Simatic PCS 7 and Rockwell Logix Integrated Architecture system, are included in our definition of DCS. Also included are DCS controllers that perform PLC functions only and replace PLCs in an integrated system.
Excluded from the DCS hardware definition are field instruments, control valves, analytical devices, all specialty measurement equipment(such as paper machine gauges and condition monitoring devices), and any other devices that exist outside the I/O level of the system. Also excluded are dedicated supervisory workstations that execute applications such as advanced control, production management, real-time optimization, simulation, or plant asset management.
ARC’s primary segmentation of the DCS marketplace is by DCS size. Segmentation of DCSs into small, medium, and large systems is based on hardware content. Hardware specifically includes all controllers, application processors, I/O modules, workstations, and communications networks. PCs used for system configuration and real-time control are included in DCS scope, as are computers used for supervisory control, if sold as part of the system. ARC also includes PLCs sold by DCS suppliers that are integrated with the DCS.
Distributed Control System (DCS) Software
DCS software includes embedded controller software as well as some, but not all, software sold bundled with a system. DCS software includes control, HMI, systems management software, engineering and configuration software, and plant information management (PIM) software such as bundled data historians in addition to performing HMI functions, DCS HMI software can also perform functions such as I/O communication. HMI software typically resides in the DCS workstation or PC. Control software typically resides embedded in controllers and performs basic control functions. Programming software, used to program and configure the various functions of the control system at startup, accounts for a small part of the total DCS software business.
The DCS definition excludes optional supervisory software that performs production management (MES) and advanced control functions and typically resides in a supervisory DCS server. Supervisory software includes categories such as advanced process control(APC), model-predictive control (MPC), real-time process optimization (RPO), process simulation and optimization (PSO), and plant asset management (PAM) applications.
Distributed Control System (DCS) Applications
From an application perspective, ARC includes all DCSs sold for continuous and batch control. We have included SCADA systems sold on a traditional DCS platform for oil & gas and water & wastewater applications. However, dedicated SCADA systems are not included.
ARC includes quality control systems (QCSs) for paper, plastic sheet, and similar applications, such as those sold by ABB, Honeywell, and Metso. Custom and specialty measurement equipment for these applications, such as profilers and vision systems, are not included. Only the workstations, I/O, and related hardware, software, and services under the DCS definition are included in QCS definition.
ARC’s DCS definition excludes all safety systems. Safety systems and emergency shutdown (ESD) systems are governed by their own set of rules and standards that are distinct from the area of process control and automation. Safety system hardware, software, and services are excluded from the scope of this study regardless of their application.
ARC has also excluded systems serving dedicated automation applications (for example turbine control systems and burner management systems) except when these applications are implemented using DCS equipment. For example, a PLC-like turbine controller provided by a turbine automation specialist would be excluded, while a turbine control system implemented on an Emerson Ovation or ABB Symphony Plus platform would be included.
Distributed Control System (DCS) Project Services
Project services include all services provided by DCS suppliers for installing, configuring, and commissioning DCSs, but only services for the hardware and software included in the DCS scope. It does not include services for field instruments or other non-DCS plant equipment.
The project services segment includes only those services provided by direct employees of DCS suppliers and exclude indirect contributors. For example, project services performed by distributors and authorized systems integrators (SIs) for DCS suppliers are excluded from the overall tabulation. Also excluded are project services performed by representatives of instrument companies. ARC also excluded DCS project services delivered by end users, consultants, EPCs, process equipment manufacturers, and independent SIs