High-availability, redundant controller for critical systems

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Mitsubishi Electric has expanded its Q series programmable automation controller (PAC) platform with a new high-availability, redundant controller for system-critical applications, known as the QnPRH. This replaces the Q4AR system, which, over the last eight years, has established Mitsubishi as a major player in the large-scale process control market.

The QnPRH is based on dual CPUs, power supplies and bases, connected by a tracking cable - that can be up to 10m long - to ensure that the CPUs are always synchronised and that switchover is instant. Mitsubishi says that the QnPRH is designed to offer a new level of redundancy for system-critical applications.

Furthermore, the QnPRH has a level of simplicity that would normally be expected of smaller PLCs; the concept combines 'out of the box' system building using standard components with customisation by simple parameter setting. Nonetheless, it is configured for total data tracking and extensive physical redundancy so that very high system availability can be guaranteed. This is complemented by the ease of use provided by a powerful engineering environment that Mitsubishi has created around the QnPRH.

Jeremy Shinton, Mitsubishi's Q Series product manager, explains how the new range is pushing the control technology envelopes: "QnPRH is designed to be easy to install. Its intuitive programming tools and operation allow simple and cost-effective design and development of a redundant system project. This is further enhanced by the fact that QnPRH is physically 25 per cent of the size of its Q4AR predecessor, reducing space requirements significantly. For integration with existing systems, QnPRH is fully compatible with other Qn series hardware platforms."

Easy maintenance and simple system reconfiguration

Shinton says that the QnPRH is designed for easy maintenance and simple system reconfiguration: ''The components are 'hot swappable', so can be unplugged and replaced without having to shut down the entire system and thus removes major disruption to system availability. There are facilities for troubleshooting, historical data logging, trend analysis functions, alarms and monitors and a full range of interfaces for communications with other systems and various protocols."

"The QnPRH's inherent flexibility is such that it can be used in virtually all high-integrity environments, from conventional continuous industrial processes, to utilities and power generation. It also has advantages for use in diverse areas such as banking and finance, logistics and transport, security and facilities management, and medical applications. While these are new fields for many process control engineers, Mitsubishi has experience in all of them somewhere in the world.

"An organisation could use QnPRH for a whole range of industrial and non-industrial system-critical applications and achieve a level of rationalisation previously thought impossible."

The QnPRH is flexible and scaleable; for example, it can be used to control a single workstation, machine, manufacturing cell or complete process line. This flexibility means that cost-effective systems can be created, whatever the level of system redundancy required.

SIL2 safety applications

If required, Mitsubishi says that it has the necessary documentation and processes available to enable the QnPRH to be used for safety-related control systems. The company says that, so far, there have been no difficulties in incorporating dual-redundant QnPRH hardware in control systems conforming to SIL2 of EN 61508, depending upon the application circumstances and the other equipment involved.

Communications networking is a critical capability of large-scale controllers, and the QnPRH can be configured to adopt virtually all formats, including peer-to-peer and remote I/O formats. It can use dual-loop fibre-ring networks to ensure high system integrity at all times, so that control of I/O is maintained even if hardware errors occur. The configuration of the QnPRH ensures a high-integrity, robust topology for distributed network control, coupled with supervisory level access.

And, despite all this redundancy, the QnPRH is claimed to be easier to use than any other hardware platform in terms of flexibility for system expansion, development and reconfiguration. This is complemented by backward-compatibility with the Q4AR range.

Significantly, the main base and standby base are discreet units that can be installed in various configurations to enhance the compactness and flexibility of the overall system.

An extensive library of function blocks is available with the Q series, allowing bespoke systems to be built on a simple plug-and-play basis.

Contact Mitsubishi now for more information.

04 May 2006

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