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Although some of the first programmable logic controllers (PLCs) installed in the early 1970s are still functioning as designed, many are increasingly vulnerable to failure. Whether they fail tomorrow, next week or five years from now is not an easy thing to predict. Article by Schneider Electric.


With each day of operation, the risk of failure increases and with that come higher replacement costs, downtime, and upgrade decisions driven by urgency rather than strategy. “Fixing” your controls before they break, however, can have tremendous benefits. Most companies find the control system migrations pay for themselves within two years – and once they pay for themselves, the value keeps coming via improved return on all production assets, through improvements in the following areas: Operational profitability; Asset availability; Asset utilisation; Labour utilisation; Operational agility and scalability; and IIoT readiness.

Our report “Breaking Through the PLC Migration Cost Justification Barrier” discusses real-time accounting methods that can provide a baseline cost-justification by analysing and real-time control of only: production value, energy consumption, and raw material costs. Production value is the amount of product produced multiplied by the amount of revenue that that product can produce.

Subtracting energy raw material costs from this, in many industries provides a profitability metric than can be used to correlate technology purchases with profits. Upgrading to a more power controller, for example, might raise production value by monitoring quality control variables in real-time or speeding time to market. A controller with improved connectivity might reduce energy costs by enabling real-time monitoring or reduce material costs by improved feed control.

We call this approach real-time accounting, because it utilises automation systems and empowered operators to control profitability, with the same kind of feedback loop a process plant might use to control temperature, pressure and flow. The rest of this paper addresses also other factors impacting profitability that do not necessarily change in real time.


Improving Asset Availability

Upgrading from a PLC to a more modern PLC or programmable automation controller (PAC) delivers maintenance benefits in at least the following areas: spare parts management, advanced diagnostics, remote maintenance, battery independence, and cybersecurity.

Protection from obsolescence 

Once a control system vendor pulls the plug on product support, the aftermarket soon takes over. Many suppliers are committed to high standards of quality and customer service, but not all. Questions of quality control, compatibility, and even product counterfeiting enter the picture, bringing new risk.

Securing uptime 

Software that can help predict when things are going to fail based on hours of usage is now coming of age, but it needs more bandwidth than is available on older platforms. In addition to having many more years of productive life in them, modern controllers reduce risk with better diagnostics, connectivity, and visibility, making it increasingly likely that you can fix things before they break.

Remote maintenance

Diagnosing, updating and configuring some older PLCs requires going through your facility node by node. If you have multiple locations, travel costs become a factor as well. New control infrastructures are networked so that diagnostics, configuration and patch management can be done remotely, from a central location. They also not only collect data, but can timestamp and synchronize better, so you have a more three-dimensional visualisation of your operations.

Battery independence 

If your legacy PLCs use erasable programmable read-only memories (EPROMS) to store recipes or other critical operating data, you know well of your dependency on the system battery. When that starts to age, as it inevitably will, that content will be gone as soon as you power down. Each time that happens, you would likely require a visit from vendor technician who will re-install and reload software. New PLCs no longer use batteries.


Many company security policies are based on “security through obscurity.” They believe that their data is safe if they are not networked. This is not quite true, however, given that personnel factors, thumb drives and other vulnerabilities can inflict air-gapped systems as well. An arguably greater risk, however, is the stagnation and rigidity that isolated systems create in a global economy that is in constant flux. Modern PLCs and PACs are more likely to have cybersecurity at their core.


Improving Asset Utilisation

In addition to being more maintainable, modern controllers offer improved utilisation. Contributing to improved asset utilisation are advancements in the engineering software used to configure them, capability to run more powerful productivity applications, greater resistance to environmental conditions that can limit performance, and greater network capacity. Better control over asset utilisation is also among the most significant means to increase production value, because it can optimise variables such as product quality, yield, speed to market, or other value factors defined by your competitive strategy.

Making the most of advanced engineering software

Engineering software has advanced significantly in the past decades. Standards-based, object-oriented technology that enables designing and configuring systems with drag-and-drop ease are becoming the norm, but using this with older PLCs is cumbersome if possible at all.

Maximising equipment effectiveness 

Generally, the more accurately you can measure effectiveness, the better you can control it; but the larger your facility, the more difficult it is to accomplish this with older control systems. New systems have the bandwidth and connectivity to take advantage of advanced MES performance monitoring software that can centralise gathering and analysis of sensor data that tracks performance from shift-to-shift, day-to-day and along numerous other dimensions.

Resisting ageing

While aging PLCs may continue to perform their basic function, performance consistency may degrade over time. The more environmentally challenging the installation location, the more rapid the performance degradation. In addition to being designed for even greater reliability than their predecessors, newer PLCs are also more environmentally hardened.

Improving network performance 

While inadequately networked PLCs present one barrier to growth and improvement, first-generation networks can also be maxed out as well. When a communication network is first installed, it usually works just fine, but over time, added devices and increased data traffic can lead to sporadic slowdowns or even breakdowns. Networks and their controls must be sized based on realistic node configurations and traffic patterns. Newer PLCs have the higher bandwidth and memory that may be needed to manage increased traffic.


Labour Utilisation

Modern controllers can improve efficiency of individuals and workgroups and reduce training costs, and improve documentation.

Improving staff efficiency 

Automation, almost by definition, has made it easier for companies to accomplish more with fewer people, but today’s technology is focused as much on empowering individuals and workgroups to make a greater contribution to profitability. Upgraded controllers have the bandwidth and connectivity that can augment operators with more visualisation, greater context and real-time collaboration they need to keep operational profitability on track.

Reducing training costs

If you installed PLCs more than 10 years ago, odds are good that many of the people who can program and diagnose them have either left or are looking at the door. This also leaves you with a dilemma regarding the value of investing in training new hires on equipment that is nearing the end of its life. The solution is to invest in the modern controllers they will be using a few years from now and which are also more digital-native friendly.

Complete and consistent documentation 

Compounding the gap between retiring and new talent is the fact that in many companies, system documentation is haphazard or incomplete. Much of the system history is in the minds of the people who will be leaving and recreating the knowledge is costly. Modern systems have the power to participate in more advanced documentation management tools, plus are compatible with object-oriented engineering environments which can capture much operating knowledge before it leaves the building.


Industrial Internet Of Things Readiness

Twenty to thirty years ago, the proliferation of automation advanced industrial productivity by bringing devices such as relays, instrumentation, and valves under computer control.

We are now experiencing the next level of industrial efficiency, which is characterised by heightened connectivity — not only among traditional automation components, but also among industrial devices and applications — ie: the IIoT.

While the IIoT is still very much in its infancy, expectations around it are high. In a September 2016 survey of more than 2,000 participants from nine major industrial sectors in 26 countries, PwC found that senior executives are looking for a return on IIoT investments within two years.

Migration to modern controllers to deliver most of the benefits discussed thus far will also likely have the capability to exploit the full capability of the IIoT. Schneider Electric’s Modicon M580 Ethernet enabled programmable controller (ePAC,) for example, has the features that will help deliver on many of the objectives mentioned above, while at the same time delivering the following capabilities that will be essential for success in the emerging IIoT:

  • High bandwidth and faster scan times for enhanced overall performance and ability to handle larger data sets and analytical software more easily.
  • Ethernet connectivity, which enables improved communications and greater visibility to operations.
  • Embedded cybersecurity, which enables users to take advantage of the open connectivity necessary to tap the full potential of the IIoT, with less risk of cyber intrusion.
  • Ability to embed real-time accounting metrics, which can be applied to data from production and other operations to provide historical and real-time analyses, which can guide real-time profitability improvements.



So, whether your concerns are at the unit, area, division or enterprise level, upgrading to modern PLCs or PACs, could help you address today’s maintenance, production or operational challenges, while equipping you for the new challenges you may be facing tomorrow.







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