High reliability supervisory control system with built-in redundancy

Citation

(2001), "High reliability supervisory control system with built-in redundancy", Pigment & Resin Technology, Vol. 30 No. 2. https://doi.org/10.1108/prt.2001.12930bad.002

High reliability supervisory control system with built-in redundancy

High reliability supervisory control system with built-in redundancy

Keywords: Eurotherm, Process control

What is described as a powerful new "strategy engine" distributed process controller, capable of performing both continuous and sequential control functions within critical applications, has been launched by Eurotherm Limited. Called Process Supervisor, the unit features two independent processors for exceptional reliability. Unusually, if one processor fails then the other will, it is said, seamlessly take over.

Process Supervisor has evolved from, and replaces, the company's T100, T102 and T103 Unit Controllers. The system has a fully configurable, open network architecture which allows simple interfacing to up to 16 Eurotherm Process Interface (2500 System) I/0 modules as well as other third-party devices. By separating processing functions from the I/0 section, the system allows physical distribution of the I/0 modules, saving on wiring costs.

Built-in support for PROFIBUS DPVI (as master), MODBUS RTU (both as master and slave) and advanced peer-to-peer communications on ALIN, Eurotherm's proprietary instrument networking protocol, has resulted, it is said, in a truly distributable system. The unit is therefore capable of supporting both Profibus and Modbus simultaneously

When used for continuous control situations, an overall control strategy is built up by interconnecting function blocks from a large library of analogue and logic elements. The function block library includes control timing, logic, maths, etc. There is also a set of control module software blocks, based on the ISA-S88 standard, representing physical plant equipment such as valves and pumps. These include all the functionality required to control a device in a single block. In addition to fixed function blocks, ACTION blocks support user-algorithms written in ST (structured text).

The sequential control capability of Process Supervisor is said to allow the configuration of phases for batch processes as defined by the ISA-S88 process model. Sequence strategies are built using a powerful and intuitive SFC configurator, and act in a supervisory role relative to the continuous control mode. They can be loaded and unloaded as required.

Both continuous and sequential control strategies are ideally created using Project Studio, an exceptionally powerful configuration module within the recently announced EurothermSuiteC family of integrated hardware and software solutions. Project Studio runs on any standard Windows 95 or NT platform.

Process Supervisor has space for two separate processor modules, each of which contains a 586 133MHz processor. These can operate either independently (simplex), or in redundant (duplex) mode. In redundant mode, the processor modules can be made to synchronise as required. In redundant mode, either processor can be designated as the primary processor, backed-up by the secondary in case of failure. If this occurs, the switch from primary to secondary will be automatic, initiated by hardware watchdog circuits and software checks. A high-speed data link between the processors provides exact tracking of the control database so that the switch to the secondary processor is seamless. Redundancy is enhanced by the provision of two independent power sources, which can be external UPS in case of power failure.

This optional redundancy of processor modules is thought to allow inherently high availability control solutions to be provided for critical processes, as well as the capability for "live" replacement of faulty processor modules to avoid interruption of control sequences.

Eurotherm explains that when used with an ALIN control network, Process Supervisor can communicate with all other nodes in the control layer and with the operations layer. ALIN allows peer-to-peer communications between nodes via a daisy-chain configuration, or via a central ALIN hub. All ALIN nodes appear as a part of a coherent distributed database, the database in any element being accessible to any other network element, thus allowing complete flexibility in strategy interconnection.

According to Matt Safi, Eurotherm's product manager process automation, process supervisor will be of considerable interest to both designers and operators of large-scale systems across a wide spectrum of key processing industries. He comments: "In processes where high reliability, flexibility. scalability and generation of management information are prime requirements, we believe that Process Supervisor offers a truly state-of-the-art solution. As part of our recently announced EurothermSuite family, it is perfectly complemented by a comprehensive array of fully compatible hardware and software offerings, allowing it to be tailored to fit just about any critical control requirement. We believe that this is one of the most versatile control products we have ever produced."

Details available from: Eurotherm Ltd. Tel: +44 (0)1903 268500; Fax: +44 (0)1903 695666; E-mail: info@eurotherm.co.uk Website: http://www.eurotherm.co.uk