Migrating a Distributed Control System (DCS)

25 January, 2021 | Blog

Steve Bélanger

Steve Bélanger, P. Eng., MEM

Engineer, Control Systems Programming

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Clients sometimes expose themselves to operational risks by holding on to obsolete distributed control systems, commonly known as DCSs. Spare parts for these systems are becoming increasingly scarce and maintenance costs exorbitant.

Some of the issues with outdated DCSs include:

  • A shortage of spare parts that can jeopardize or even interrupt production for several days or even weeks
  • A shortage of original display consoles for operator stations
  • Subpar spare parts sold online through third party resellers
  • Outdated operating systems that are exposed to cyber threats, including:
    • Windows 8 and earlier versions
    • Windows Server 2008, 2008 R2 and earlier versions
  • Difficulty finding labour to operate these systems

If you see yourself here, you may need a DCS migration, but where should you start?

Starting your migration project

Before even considering how to carry out a system migration project, you must first ask yourself what it will be used for. If your facility already has a DCS, why should you migrate to a newer system? To answer this question, you need to assess the cost of risks: production shutdowns, equipment breakdowns, production losses, overtime during breakdowns, poor information quality provided by operational teams, cyberattacks, etc.

Once your organization understands the merits of a DCS migration project, here are the possible avenues:

  • Status quo
  • Radical approach
  • Phased approach

The status quo approach is hardly desirable in the long term. Despite the appearance of cost savings by postponing a DCS migration, the accumulation of breakdowns, production losses, the overtime required by maintenance teams and the increased costs of spare components adds up. The key benefit of a new system isn’t immediate productivity gains, it’s the reduction of operating losses. However, a modern DCS can result in medium- and long-term optimizations that were simply impossible beforehand.

The radical approach means replacing the old system with a new one. This approach is usually risky and difficult to implement if you don’t plan for any extended shutdowns. BBA fosters the phased approach to minimize risks and spread out costs over time. Sector by sector, your facility is refurbished; the old system can even be used for troubleshooting.

Phased migration

At the highest degree, phased migration includes two major components:

  • Phase 1 – Operational infrastructure and human-machine interfaces (HMIs)
  • Phase 2 – Migration of industrial controllers, I/O and control programs

Phase 1 is generally the most counterintuitive in its early stages. As surprising as it may seem, a modern DCS is inevitably dependent on information technology (IT). The following operations technologies (OT) are therefore involved:

  • Ethernet connectivity
  • Data servers
  • Virtualization technologies

Before investing any amount of money in automation equipment, you need to ensure you have adequate network connectivity. If it was state-of-the-art in the 1980s and 90s, your OT network is now a thing of the past if it uses coaxial or twisted pair cabling. Until your network is up to speed, your plant doesn’t have the “nervous system” it needs.

Along with networking, you should consider installing new data servers and virtualization technologies at this stage. The combination of these two elements makes it easier to modernize facilities and upgrade the system in the long term. This digital shift also makes it possible to implement new features that weren’t originally planned.

All required operating system configurations are stored in the virtual machines so they can be easily migrated or recovered if the physical servers become obsolete or fail.

Figure 1. DCS – IT and OT duality

Once the networking, data servers and virtualization systems are in place, a crucial step in DCS migration can begin: modernizing the HMIs. From this point on, it is essential to receive support from the operational team. The various stages of screen-page conversion have their share of unforeseen events. It is strongly recommended to use computer-aided HMI conversion rather than manual conversion. In general, the quality of results is better, and the risk of error is minimal. Software is used to process critical configurations for each screen page, which minimizes human error. BBA has in-house tools to make it easier to convert certain HMI technologies. In an upcoming blog article, we’ll provide an overview of BBA’s computer-aided screen-page conversion tools.

After completing Phase 1 of the migration, the best is yet to come. Phase 2 focuses on modernizing more conventional components for a DCS:

  • Industrial controllers
  • Inputs and outputs (I/O)
  • Control programs

During Phase 2, most migration efforts are spent reprogramming control strategies and connecting instruments to the new inputs and outputs. Computer-aided conversion of control programs is rarely possible, given the disparity between the source programming language and its destination. However, there are some exceptions. In the next blog article, we’ll discuss the specific challenges in Phase 2 of DCS migration and the best practices to adopt.

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