How to slash downtime with a phased approach to PLC migration

 

PLC migration insights

• Migrating a programmable logic controller (PLC) can be a large project that can be tackled in phases.
• Building out a plan to migrate an outdated PLC is critical.
• Even though migrating an outdated PLC is a costly and time-consuming process, the savings –– in both time and money –– could be worth the initial investment.

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Consider the process of buying and renovating an older house. Before any renovations can begin, appraisals and inspections are necessary, especially for an aging home. Once the property is purchased, decisions must be made about which renovations to prioritize and the order in which to complete them. Renovating the entire house at once may not be feasible, so the work is often done in phases. Should leaky plumbing be addressed first, or perhaps the house needs a fresh coat of paint?

Determining where to begin is crucial. In many ways, upgrading obsolete programmable logic controllers (PLCs) in a facility mirrors this process.

The problem with aging machinery

As machinery ages, obsolescence and the likelihood of failure increases. Additionally, options for repairs and direct replacements decreases, leading to downtime, wasted resources and frequent troubleshooting — ultimately causing significant operational headaches. Legacy PLCs can also introduce cybersecurity vulnerabilities. Additionally, a 20-year-old PLC relying on parts sourced from online auctions can create operational risks.

It no longer offers the reliability or performance that facilities need. A PLC migration can help resolve these issues while also providing cost savings through improved uptime, higher-quality throughput, and reduced energy consumption. However, upgrading machines and systems all at once is often too costly and time-consuming for most facilities to manage without causing significant disruptions to production.

Fortunately, a phased PLC migration allows for two key benefits: spreading the cost over time and reducing the amount of downtime needed for each stage. The following factors will help in planning the right phases, determining the upgrade path, and budgeting for a phased PLC migration.

The key considerations for PLC migrations

Before beginning any PLC migration, let’s break down some steps that can help plants ease into a PLC migration.

Evaluating the current state

A PLC doesn’t function in isolation, so any upgrade must start by assessing the current system’s network, hardware, and communication connections for compatibility and integration with the entire control system. This also includes looking at what the existing documentation reveals about the equipment, which network the PLC is on, and what additional components will be required to ensure smooth operation after the update.

Some components to assess for potential impact during the migration include:

Human Machine Interfaces (HMIs)

Older Human Machine Interfaces (HMIs) typically lack sufficient memory, processing power and proper communication protocols to keep up with modern PLCs. Therefore, if the HMIs involved in the migration are also outdated, they typically need to be upgraded along with the legacy PLC. However, newer HMIs are often made backwards compatible, supporting older communication protocols.

Network

The industrial communication network — such as Ethernet/IP, Profinet or Profibus — the PLC uses to communicate with its I/O cards and other devices plays a crucial role in determining the upgrade path, especially if the network, like the PLC, is outdated. If the network relies on outdated serial protocols, such as RS-232 or RS-485, the entire network must be updated to support modern communication standards like Ethernet/IP or Profinet.

Several strategies exist for upgrading an outdated network. One is to lay the new network cables in advance, which minimizes downtime by preparing the infrastructure before a scheduled shutdown. Also, the new network can be installed in parallel with the old one, gradually transferring the load to the modern system to reduce disruption.

Obsolete motion controls

Modern PLCs may not support analog communication directly or may lack the proper interfaces needed to connect with older analog motion control systems. If the system relies on analog motion control, the upgraded PLC may not communicate with it effectively, making it necessary to upgrade the motion control systems as well.

Software

Additional system components — such as the software code — may also need to be upgraded to ensure compatibility with the new PLC. Properly updating the software is crucial to avoid integration issues and fully utilize the capabilities of the modern PLC.

Building a plan for successful PLC migration

Breaking up a successful PLC migration into phases can help minimize disruption to throughput and provide greater flexibility in managing the upgrade process. In some cases, running simulations before implementing the migration can be highly effective. Performing a full simulation — replicating real-world processes, such as a virtual conveyor system — can help ensure the new software functions correctly before shutting down production for installation. Although this approach involves programming both the simulation and the actual system, it greatly reduces debugging time and lowers the risk of software issues during the migration.

There are several ways to divide the upgrade into phases; here are a few examples of independent phases that could start the project:

• Upgrade the HMIs first. They are often compatible with older PLCs, allowing for smoother communication during the transition.
• Lay new network cables in parallel with the existing network to support newer protocols, minimizing downtime. These cables will be connected to the new PLC once it’s installed.
• Install the new PLC in tandem with the old one. This allows both to receive system inputs. The older PLC can continue handling outputs while the newer one is tested and debugged. As the migration progresses, controls are gradually transferred to the new PLC. Another option is using the new PLC only to control migrated equipment until all of it can be converted. New PLCs operate well, communicating and working with legacy PLCs.

With numerous interconnected components and potential upgrade paths, creating a detailed, well-informed plan based on a thorough facility assessment is critical to ensure a smooth and successful migration.

1. Allocating the right resources

Adequate and thorough planning is often a challenge for PLC migrations, whether phased or all at once. A solid plan must consider every component connected to the upgraded PLC, the project timeline, and the roles and responsibilities of everyone involved. Engineers, project managers, operations, and maintenance teams should collaborate in the planning process to ensure no critical documentation or perspectives are overlooked.

It’s also important to remember that adding more personnel doesn’t necessarily speed up the project. Allocating the right resources is essential, but some tasks must occur sequentially.

When choosing a migration partner, it’s important to select one that focuses on finding the best upgrade path for the facility, rather than just pushing a preferred software vendor. While some facilities may prefer to stick with a specific platform, big brand hardware vendors often come with a higher price tag. In many cases, equivalent functionality can be achieved at a fraction of the cost without solely relying on one specific vendor.

Downtime is always required for a PLC upgrade, but a well-developed plan can significantly minimize its impact. Additionally, budget constraints or underestimating costs can complicate the process, making accurate financial planning essential.

2. Budgeting for a phased PLC migration

A well-developed plan that addresses key components and current performance will lead to a more accurate budget and timeline, while helping calculate return on investment. The cost of the project can be justified in several ways, such as through quality improvements, increased throughput, and reduced energy usage.

PLC migrations can reduce operational expenses by improving system accuracy, reliability and performance. Upgrading to modern PLCs enhances process control, leading to fewer errors, defects and less rework. This improvement aligns with increased throughput, as reducing errors and defects allows more efficient production and a higher volume of quality output from the facility.

In justifying the budget, older equipment often relies on pneumatics for automation, which is costly in terms of energy consumption. Replacing pneumatics with electric actuators or servo systems can result in significant cost savings. Energy consumption savings are a common way to help justify the budget for a PLC migration, with projects often paying for themselves in as little as three months due to reduced energy costs.

3.     Selecting the right migration resource

A good migration partner will conduct a thorough on-site assessment before drafting a proposal, ensuring they recommend the best upgrade options. Transparency is key — an ideal partner will clearly explain their approach and the reasons behind it, leaving no ambiguity. Strong communication and a commitment to building a solid relationship with you are essential for a successful project.

4.     Pulling it all together

Simultaneously upgrading machines and systems is costly, time-consuming, and disruptive to production. An assessment of your current system’s network, hardware and communication connections, along with the proper division of phases and allocation of the right resources, are all components needed to execute a successful phased PLC migration so you can minimize downtime, reduce costs and improve your system’s performance.

Phasing for success

Now that you’ve put all the pieces together, you can successfully upgrade your PLCs in phases, maximizing your return on investment and keeping your facility’s downtime to a minimum.

 

Kerry White, FS Engineering, is an engineer with Hargrove Controls & Automation.

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