Successful Obsolescence Mitigation
Designing an obsolescence mitigation plan to detect and solve mitigation risks before they occur is key to avoiding costly downtime and a potential catastrophe in control environments.
The first step toward creating a substantial obsolescence mitigation plan is to know the lifecycle stage of each of the hardware and software components in an automated system. With this information at hand, along with the automation life cycle model, we have the basis to work on a plan.
Risk and Impact Analysis
The International Electrotechnical Commission (IEC) has issued norm IEC 62402 to provide guidance, requirements, and best practices for obsolescence management. IEC 62402 establishes that a successful obsolescence mitigation program is cost-effective because it reduces downtime and write-offs. In addition, this norm provides a helpful guideline for creating customized programs in industrial automation systems.
Figure 1. A general strategy for effective obsolescence management. Image provided by Control.com
We have previously covered the first two steps of the process flow in Figure 1. Next, the impact and risk assessment is made using the bill of materials (BOM) and a matrix like the one in Figure 2. The probability axis refers to the likelihood of a component becoming unavailable. The further into the component's phase-out stage, the harder it is to find. So then, the next question is, if the part were to fail and it is not available on the market, what would be the impact on the automated system?
Figure 2. Probability vs. Impact assessment. Image provided by Control.com
When the central controller is nearing the end of the phase-out stage, it becomes harder to find replacements in an automated system. Furthermore, if the PLC were to fail, the impact on the system would be severe. It could likely result in a total system shutdown. Therefore, an obsolete PLC poses a critical operational risk.
The other end of the spectrum are components with a low probability of scarcity and low system impact. This is where many low-cost commercially available parts can be categorized: generic photo eyes, encoders, wires, cables, etc.
We will have better visibility into what needs to be prioritized when the assessment is completed for all the elements of the BOM. Often, with respect for time management, the most impactful components can be readily identified, and the mitigation plans established for those items can be moved to a higher priority, leaving the remainder of the BOM for a lower priority.
Obsolescence Mitigation Strategies
The next step is to think about the best way to reduce the risks identified in the assessment. There are many possibilities here, and the solution will be customized to meet the needs of the business and the control system. In this section, we will discuss a few examples of possible scenarios.
In the simplest case, when only one component is identified as a critical or high risk, the process is straightforward. Then, we need to put together a project to replace the obsolete component. The project requires a careful analysis of efforts and possible repercussions.
Figure 3. Even the most high-tech systems will eventually become obsolete. Image used courtesy of Canva
The preferred option for the upgrade would be the direct replacement of the component. The details on direct replacement can be obtained from the OEM. Sometimes this information is available online in guides referred to as ‘migration’ documents. This is the preferred option because this most likely will result in the lowest risks and lowest costs.
However, sometimes, even when a direct replacement is available, the upgrade of a component affects compatibility with other devices. There are many reasons why a new component could become incompatible with the rest of the existing system. Size, communication protocols, operative system, firmware, and operating range are some reasons.
It is crucial to study the compatibility topic during the early stages of the project, as there could be significant cost calculation errors if the estimates are missed. Also, if the obsolete component is present in many parts of the system or manufacturing facility, it is best to execute a pilot test first. This type of test is a rehearsal for the major project, which helps discover any missed design considerations.
When several critical or high-risk components have been identified, the situation becomes more complex. The first thought is to replace all the affected parts, but this might be too risky or too costly to do in one step. The best approach, in this case, is to study the replacement of each component individually, focusing on the interconnectivity to the other obsolete components. Generally speaking, the more the obsolete components work together in the system, the more recommended it is to replace them. Doing this reduces the number of mismatched old and new interfaces to worry about.
Plans and Policies
Let us say we have an automated system with no current obsolescence risks, either because we just bought a state-of-the-art system or because we just completed a significant obsolescence mitigation project. What comes next? What is the right time to worry about obsolescence again? The answer is right now.
Figure 4. Obsolescence upgrades can come in the form of products, processes, or even policies. Image used courtesy of BHS Corrugated
This is the ideal time to establish business-wide obsolescence management policies. Unfortunately, the reality is that obsolescence mitigation is a capital expenditure with little or no return on investment. Therefore, these projects are hard to justify and approve. However, with a policy in place, businesses are compelled to, at the very least, frequently analyze the lifecycle status of their hardware and software. This focused approach produces opportunities to detect (and solve) mitigation risks ahead of time.