PLC-5 to CLX – A Path Through The Seen and Unseen Risk

September 8, 2017

Legacy Migration

The need to migrate away from PLC-5 controllers has become a reality at manufacturing sites. The Allen-Bradley PLC-5 has had a useful lifespan, and that lifespan has reached its endpoint with the product line officially being discontinued in June 2017. However, unlike products that can simply be replaced and upgraded, the lifespan of a PLC-5 has included an unforeseen, and many times necessary, integration with new systems that employ more advanced technology.

Over the years this integration with evolving systems, most built on more advanced platforms, included the PLC-5 as the backbone of vital production systems. The versatility and resiliency of the PLC-5 was championed by executives, engineers and plant managers for years. Now that the PLC-5 Product Line has been discontinued and parts are no longer available, the same longevity that ingrained the PLC-5 into so many aspects of production has created an integration challenge that is posing serious risks to industry and adding risk to legacy PLC migrations.

First introduced in 1986 and no longer available for sale, the PLC-5 has been a stalwart and durable controller for decades. Some thought leaders in manufacturing could argue a few more years of unsupported PLC-5 use would not result in significant risk. If the PLC-5 existed in a vacuum, that thought may have merit. However, in the modern production environment, the advanced nature of other integrated components make the PLC-5 a liability that can no longer be overlooked. A sudden failure at the PLC level can result in a complex upgrade that touches upon multiple systems, and this risk should be dealt with proactively and not reactively. Running business critical applications on Windows 95 would never be an accepted business practice, and using 30-year-old PLC technology should be viewed in the same light.

ControlLogix (CLX) controllers provide manufactures the option to implement a fully integrated architecture to drive plantwide optimization. This is the Grantek and industry recommended PLC-5 replacement. There are standard tools and migration strategies for upgrading from the PLC-5 platform to a CLX which significantly reduce engineering efforts, cost, and risk.

With replacement of PLC-5s to CLXs now a best practice, how companies execute this migration, and the risk mitigation they undertake to protect their manufacturing sites has become an important choice.

Two common hesitations behind not upgrading a PLC-5 to CLX, are both legitimate concerns that proper planning can overcome. The first is the realization that a PLC-5 is just too ingrained in other systems. PLC-5s are often the bedrock of a vast, interconnected system which communicates and works with other PLCs, SCADAs, and ERP systems. Any migration attempt that simply involves isolating, removing and reinstalling will jeopardize the entire manufacturing process. A second related hesitation involves compliance data and is also justified. The threat of regulatory violations, or worse a fine, shutdown or recall, if there is a lapse in the documentation of compliance data can prevent companies from starting the needed migration to CLX.

Real Dangers

SCADAs and HMIs are obviously critical to production. A PLC-5 migration that does not properly account for ties to related SCADA and HMI systems will result in migration failure: leading to costly roll-backs or production stoppages. The problem can be intensified if assessment and planning was not properly considered when the MES/ERP was built and expanded. PLC-5’s also rely on old network technology, if that infrastructure isn’t also upgraded ahead of the PLC-5 migration there will be technical problems from the beginning of the process.

When the threat of regulatory violations and fines are considered, historians and data collectors can rival the importance of control systems. Although production may continue in the event of a failure to a historian, the real disruption could only be realized days, weeks or even months after the failure when a regulatory agency requests data or a report is run. Of course, the more regulated the industry the more disruptive, and in the case of food or pharmaceuticals, the more dangerous this failure can become.

Grantek Approach

With the need to replace PLC-5 with CLX clearly established as a best practice, and the potential pitfalls also well known, executives, engineers and plant managers are only left to consider how to undertake this needed migration. There are instances where PLC-5 systems truly are isolated and special consideration for integration with Level 2.5+ systems are not necessary. However, if integration with higher-level system is (or may be) necessary Grantek’s approach is centered around assessment and a specific review of each client’s existing operations, infrastructure and business needs to minimize risk and overall project costs. This assessment goes beyond the PLC-5 migration and considers other aspects of the MES. Grantek is also able to easily leverage a team of over 180 professionals at offices across North America to fully understand the implications a PLC-5 migration can have across the entire enterprise.

Grantek Solution

The assessment and review based solutions employed by Grantek lead to a holistic outcome. The wide scope of professionals at Grantek provides invaluable insight and can stop crippling complications before they arise. Alternatively, a narrow scope greatly increases the chances of the above-mentioned hesitations becoming realized fears. In the event of an unforeseen complication, the lack of experience, planning or scope can result in mounting problems. At that point a positive outcome would be settling for an inconvenient roll back to the original PLC-5 system and a costly re-evaluation and second attempt. The worse outcome that all too often happens is a total shut down when the PLC-5 is unsalvageable after an error during a poorly planned migration attempt.

Sadly, Grantek has provided solutions to panicked manufacturers after another integrator carried out a poorly planned PLC-5 to CLX migration that resulted in MES failure. A completely avoidable situation that should have been celebrated as the introduction of a more efficient MES using a CLX controller.

Grantek has seen situations where manufacturers have failed to consider all of the systems that are required in a legacy PLC migration. In these situations, the expertise required to complete the migration scope may not be available, or a significant portion of project work related to the migration was never scoped or considered. This leads to lost production time, system rollbacks, and significant additions to overall project costs.

If your PLC-5 is or may be a crucial part of a larger, interconnected system, then a holistic system review and assessment will reduce overall risk and cost, and is a critical and often-overlooked component to project success.


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