Opening your options: Control system migration
Inside Process: Aging process control systems (PCSs) create nine major problems. There are three good reasons to migrate distributed control systems before obsolescence.
Obsolescence is a huge issue in the process industry. There are tens of thousands of aging control systems; many of them are two or three decades old. At the same time, only a few hundred new plants requiring distributed control systems (DCSs) are built each year — and fewer still of any scale.
This means the migration of older systems to modern technology provides the greatest opportunities for businesses and industries to boost their productivity, efficiency and safety. Failure to address obsolescence, meanwhile, will limit potential improvements.
Nine aging control system problems
Yet, in many cases, aging systems are left in place, and, as a result, operators encounter a range of problems:
- Decreasing reliability and availability as systems age
- Rising maintenance costs with more frequent work required
- Limited or expensive spare parts adding to costs and remediation time
- Decreasing process efficiency as operators struggle with alarm floods
- Skills gaps and rising labor costs as workers with systems expertise retire
- Increased vulnerability to cyberattacks
- Regulatory and compliance penalties as the ability to operate within limits deteriorates
- Potential risks to safety
Old controls: Risks and opportunities
However, there are a number of reasons to not address obsolescence despite these potentially significant consequences.
One is the nebulous nature of the concept. Even in a strict sense, obsolescence occurs in phases, from the lack of availability of parts or updates to complete withdrawal of support. In most cases, good control system manufacturers will continue to help plants patch up the control system and source replacement parts for years after they are no longer available off the shelf.
The result is the costs and problems of aging systems accrue gradually and are set against the comparatively larger up-front costs of migration to a new system. Perhaps the most significant cost of obsolescence is difficult to accurately quantify: The lost opportunity of gains that could be realized through improvements to operations that a new system would allow, either through enhanced control, or through other technology and software not supported by the existing system.
Three reasons to migrate before obsolescence
Aging control technology limits the ability of plants to adapt to changes, restricts possibilities to expand cost-effectively to meet capacity requirements, and prevents plants taking advantage of new technological developments such as the Industrial Internet of Things (IIoT) and advanced process control (APC), which can improve yields and reduce energy costs. Indeed, there is a range of events in a plant lifecycle that may prompt a migration even while the existing system is technically not obsolete:
- Mergers and ownership changes prompting groups to standardize on one technology
- New business opportunities, resource constraints or cost changes requiring changes to the operation
- Changes to regulations requiring new solutions to comply.
Considering risks, alternatives
The risk of disruption to the process is another potential cost that acts as a barrier to migration. Mistakes can result in unplanned downtime and lack of availability. This risk not only results in plants persisting with obsolete technology; it also often limits the range of options the company is willing to consider. Even if operators decide to migrate, they will often stick with the existing control system manufacturer’s technology as the lowest risk route to modernization.
This is understandable, and in some cases, choosing an updated system from the provider of the existing system may ease graphic and application migration. Ultimately, limiting the choice in this way is misguided for several reasons, however.
For a start, at least part of the reason to migrate may be frustration with characteristics or limitations of the existing system, and these may be replicated with the new system. As the issue of obsolescence shows, operators will live with their choice of control system for years and possibly decades to come. It simply does not make sense to ease the migration at the cost of forgoing real and long-term benefits an alternative system with better capabilities could provide: A new control system is for life; not just for the migration process.
It also is not necessarily the case that sticking with the same vendor will result in the lowest risk migration. This ignores the huge influence that skill, experience and technology can have on the migration process and its success.
Migration project scope
Plants must decide at the outset on the extent of the work and how it should be completed – from just implementing a new human-machine interface (HMI), providing a short-term extension to the life of the control system and new operator and cybersecurity capabilities, to a rip-and-replace overhaul to deliver the benefits of modern controllers and a HMI.
In most cases, plants can minimize disruption and control costs with a phased migration. This consists of introducing new controllers to improve support, reliability and control, while integrating with field networks and using existing wiring. With strategic planning, engineering expertise and the right tools, existing investments in applications, wiring and networking infrastructure can be protected even when migrating to a different platform.
If operators choose the right partner, there is no reason to restrict technology choice. With the control system, central to the success of the plant, they should instead choose the right solution for their needs from a range of possible options.
Steel plant controls migration
Many of these principles can be seen in practice in the work Honeywell has done for a Middle Eastern steel producer, migrating control at its mill. This involved not only moving from a combination of third-party control systems to a modern process control system (PCS), but actually building new logic from scratch to facilitate the migration.
Several expansions at the plant had increased capacity in the past, but its control system – a combination of a competitor’s distributed control system (DCS), programmable logic controllers (PLCs) and traditional panel mounted control desks – was frustrating the plant’s ambitions. At thirty years old, it suffered from a lack of available spare parts, absence of technical support, and signal wiring interconnections that made troubleshooting complicated and time-consuming.
The system was affecting the plant’s efficiency and reliability as well as its ability to improve production: With no support and technology that had not been updated since the plant’s commissioning, enhancements and logic modification were not options. In most cases, existing control system details, configurations and backups were no longer available.
The plant decided migration was its only option and sought to move to a single, integrated, state-of-the-art control system. However, the company was keen to minimize disruption and the shutdown period.
The complexities and challenges of the project highlight the importance of the approach to migration. Engineers from the control system provider worked in close partnership with the plant’s operators to enable them to understand the plant’s process and its requirements at the outset. This collaboration enabled them to build new logic that served as the design basis for configuration of controls in the new DCS, and was employed for simulation software used during factory acceptance testing (FAT). The latter was leaned on for extensive training for maintenance and operation teams prior to commissioning.
This approach proved to be a significant success for the plant. The migration of the control system was completed in 27 days, against a 30-day schedule. The total shutdown duration was 35.5 days overall, against a schedule of 37 days. The migration enabled the plant to move to the next-generation process automation solution of its choice, delivering new capabilities and one common platform for control. With the new process control system, operators can visualize and control operations across the plant through an HMI and benefit from improved alarm and event management.
The move addressed the obsolescence issues, giving the plant an up-to-date flexible system that is supported now, and for the life of the plant.
KEYWORDS: Process control system migration, DCS
Distributed control systems need to be upgraded.
Aging process controls cause specific problems.
Migration case study shows benefits.
Will these reasons help justify your process control system migration?