A Risk That Builds Quietly
Programmable logic controllers do not fail often, but when a legacy PLC does fail on a critical production system, the consequences can be severe if a replacement is not readily available. Many FMCG manufacturers are running control systems installed a decade or more ago, on hardware platforms that manufacturers such as Allen Bradley and Siemens have since superseded, moved to reduced support status, or discontinued entirely. Obsolescence risk on these systems tends to build quietly over years, largely invisible during normal operation, until the moment a component fails and a replacement cannot be sourced quickly, or at all.
Understanding PLC Lifecycle Status
Both major PLC manufacturers operate structured lifecycle programmes for their hardware platforms. Allen Bradley, for example, moves products through active, active mature, and discontinued phases, with spare parts availability and technical support generally becoming more limited as a product moves through this lifecycle. Siemens operates a broadly similar structure. Understanding where each PLC platform on a production site sits within its manufacturer’s lifecycle is the foundation of any sensible obsolescence management strategy, yet many manufacturers have never conducted this kind of audit across their installed control system base.
A PLC platform reaching discontinued status does not mean it will fail imminently, many continue running reliably for years afterward, but it does mean that when a failure eventually occurs, sourcing a genuine replacement part becomes progressively more difficult and expensive, often requiring purchase through secondary markets with less certainty around part authenticity and condition.
The True Cost of Reactive Obsolescence Management
Manufacturers who address PLC obsolescence reactively, only when a failure actually occurs, face a genuinely difficult position. A critical production line is down, the specific PLC module required is no longer available through normal supply channels, and the options narrow quickly to an expensive expedited sourcing effort through secondary markets, or an emergency control system replacement project undertaken under significant time pressure, with all the cost and risk that entails compared to a planned upgrade.
This reactive scenario is where the real cost of obsolescence becomes apparent, not in the eventual cost of an upgrade itself, which is often unavoidable regardless of timing, but in the lost production, expedited freight and labour costs, and compressed decision making that comes from managing the situation as an emergency rather than a planned project.
Building a Practical Obsolescence Management Approach
A structured approach starts with an audit of installed PLC hardware across a facility, documenting the specific platform, model, and lifecycle status of each control system, alongside how critical each one is to production continuity. This creates a clear picture of where genuine risk sits, distinguishing a discontinued PLC controlling a critical refrigeration system from a similarly aged PLC on a less critical, non production line application.
From this audit, a manufacturer can make informed, risk based decisions about spare parts holding, maintaining critical spare modules on site or readily accessible for the highest risk, highest consequence systems, rather than either holding excessive spares across every piece of equipment or holding none at all and relying entirely on reactive sourcing when a failure occurs.
Planned Migration as an Alternative to Reactive Replacement
For control systems that are approaching or have already reached discontinued status on genuinely critical production equipment, planned migration to a current platform is generally a far better outcome than waiting for a failure to force the decision. A planned migration allows adequate time for proper design, testing, and commissioning, scheduling the changeover during a planned shutdown rather than an unplanned emergency, and often allows the opportunity to improve the control logic and functionality at the same time, rather than simply replacing like for like under time pressure.
This is a genuinely different project, both in cost and outcome, to an emergency replacement forced by an unexpected failure. Manufacturers who plan migrations proactively, informed by a clear understanding of their obsolescence risk, consistently achieve better outcomes than those managing the same eventual transition reactively.
Balancing Spares Holding Against Capital Tied Up in Inventory
Holding spare PLC modules for every piece of equipment on a site is rarely a sensible approach, since it ties up capital in inventory that may never be used, particularly for lower risk, non critical applications. The more practical approach is a risk weighted strategy: holding genuine critical spares for the highest consequence systems, where downtime cost clearly justifies the inventory investment, while accepting a higher tolerance for sourcing delay on less critical applications where a brief period of downtime, while not ideal, does not represent a genuine production or safety crisis.
Working With Manufacturer End of Life Notices
Allen Bradley and Siemens both issue formal end of life and discontinuation notices as products move through their lifecycle, typically with a defined window during which spare parts and technical support remain available before a platform moves to fully unsupported status. Manufacturers who actively track these notices for the specific hardware installed across their site gain valuable lead time to plan a response, whether that is securing critical spares before a discontinued window closes, or beginning the design process for a planned migration project. Manufacturers who do not track these notices typically only discover a platform’s status at the point of failure, when the option to plan calmly has already been lost.
Subscribing to manufacturer notification services, or working with an engineering partner who monitors this information as part of ongoing client support, is a low cost way to ensure these notices translate into timely action rather than being missed entirely.
Documenting Control System Configuration as a Risk Reduction Measure
Beyond hardware obsolescence itself, a related and often underappreciated risk is the loss of accurate configuration and programme documentation over time, particularly where a system has been modified by multiple parties across its service life without consistent version control. When a PLC eventually does need replacement, whether due to failure or planned migration, having accurate, current documentation of the existing control logic, I/O configuration, and any custom modifications significantly reduces the cost, time, and risk of the replacement project. Maintaining this documentation as an ongoing discipline, rather than attempting to reconstruct it after the fact, is a genuinely valuable and often overlooked part of managing obsolescence risk.
Making Obsolescence Management Part of Ongoing Engineering Practice
Obsolescence management works best as an ongoing discipline rather than a one off exercise, reviewed periodically as manufacturers update their lifecycle status and as production priorities evolve. An engineering partner with genuine, ongoing familiarity with a site’s control systems, of the kind BevTech develops through long term FMCG client relationships, is well placed to flag emerging obsolescence risk before it becomes a genuine emergency, and to support both spares strategy decisions and planned migration projects when the time comes. To discuss an audit of your facility’s PLC obsolescence risk, contact BevTech at 25 Silvio St, Richlands QLD 4077, or admin@bevtech.com.au.