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News Release from: Mitsubishi Electric Automation Systems | Subject: Programmable automation controllers
Edited by the Manufacturingtalk Editorial
Team on 05 November 2007
PACs keep production moving
It is now possible to build a redundant network out of standard hardware and increase the operational availability of any production system, writes Jeremy Shinton.
One of the key factors when looking at system availability is 'risk' Not in terms of potential physical injury, but rather the risk of stopping a costly process or losing expensive production time due to equipment breakdown which in turn leads to machine idleness and lost production
This article was originally published on Manufacturingtalk on 6 Jun 2008 at 8.00am (UK)
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In brief, safety systems offer protection to life and limb; redundant systems are used to maintain critical production services, even when other systems fail.
The concept of risk encompasses such issues as non-availability of spares or raw materials, unscheduled downtime for repairs, loss of work in progress, loss of reputation and damage to commercial image, consequential losses, and various knock-on effects.
Some of these are easy to envisage, other more difficult, so let's look at some examples.
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In a glassworks, the molten raw material cannot be allowed to set in the production machinery under any circumstances.
Manufacture of cars, white goods, and consumer electronics is only profitable if production is maintained to schedules set to meet the voracious appetites of global retailers.
Food and drug production is similarly highly intensive.
In many sectors production outages lead to punitive damages being awarded to customers.
All of these are risks to the business.
Their consequences can be calculated in terms of financial cost multiplied by the likelihood of the event happening.
The simplest, and often only, way to reduce the risk is to reduce the frequency of production non-availability.
Today's control systems are already very reliable, but this can lead to complacency.
It behoves production engineers to consider the consequences of a total or partial shut down of their manufacturing capability.
They should ask themselves the following questions.
* Are there systems within the plant that must complete/maintain their function.
* What are the financial and commercial consequences of lost production, * What would happen to part-processed materials.
A rigorous risk analysis usually makes return on investment of a programmable automation controller (PAC) based redundant control system seems so attractive that the only question to ask is: 'How have we survived until now'.
* Technical considerations - the basic premise of a high availability system is to duplicate some or all of the control system.
The amount of equipment that is duplicated defines the type of system.
The simplest level is based on twin power supplies; whilst at the other end of the spectrum can include total duplication of the whole system.
In high level process applications, full system redundancy is required.
Traditionally, the cost of implementing redundant systems confined their use to these high end systems.
There are many other applications however, which warrant some level of redundancy but previously, the high cost was prohibitive.
Consider, for example, Tier 2 automotive suppliers who suffer severe penalties if they do not meet delivery schedules, food processors supplying the major supermarkets, processes in which materials have to set or go off.
All these situations have system critical functions whose failure could lead to significant consequences, yet budgets are never going to stretch to a full duplicate system * Redundant systems - for the above, the answer is a redundant system, which offers a flexible architecture and provides the ability to match the level of required redundancy, to the level of risk and project budget.
The development of the latest generation PACs, such as Mitsubishi's new Qn Series opens the option of redundant systems to almost all applications.
The new QnPRH is the successor to the highly successful Q4AR system, which over the last eight years has established Mitsubishi as a major player in the large scale process control market.
Designed to offer a new level of redundancy for system-critical applications QnPRH is based on dual CPUs, power supplies and bases.
It combines 'out of the box' system building using standard components with customisation by simple parameter setting.
The QnPRH has a level of simplicity normally expected of smaller PLCs.
It is configured for total data tracking and extensive physical redundancy so that ultra 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.
* Easy installation - QnPRH is designed to be easy to install.
It's 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% of the size of it's Q4AR predecessor, reducing space requirements significantly.
For integration with existing systems QnPRH is fully compatible with other Qn series hardware platforms.
In use 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 flexibility inherent in the new QnPRH is such that it can be used in virtually all high-integrity environments, from the 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.
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 solutions are possible what ever level of system redundancy is required.
* Communications networking - communications networking is a critical capability of large scale controllers, and the QnPRH can be configured to adopt 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, flexibility for system expansion, development and reconfiguration is easier than for any other hardware platform.
This is complemented by backwards compatibility with the Q4AR range - Significantly, the main base and standby base are discreet units which 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.
In conclusion, a redundant system implemented with PACs will be a fraction of the cost of a DCS solution.
So now a whole swathe of engineers can consider improving their production availability by at least one (and realistically several) orders of magnitude.
* About the author - Jeremy Shinton is with Mitsubishi Electric. Request a free brochure from Mitsubishi Electric Automation Systems ...
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