Upgrading secondary control systems

These days, it is hard to pick up an industrial publication, attend a user group meeting, or spend time on the Internet without seeing or hearing about major control system upgrades and distributed control system (DCS) migration projects. Given the advanced age of most of the control platforms running process plants, many do need to be upgraded or replaced. But often, companies feel overwhelmed at the thought of taking on such a project.

To make matters worse, the uncertain atmosphere driven by market displacements in the oil and gas industry is causing many manufacturers to adapt a wait-and-see attitude toward launching major projects. Fortunately, there are many smaller scale improvements to secondary process control systems that companies can implement to help reduce operating costs and improve process performance. These should not be overlooked because they can bring significant benefits without major capital outlays or disruptions to production. Benefits of secondary system upgrades include:

  • Control hardware is brought up to modern standards
  • Design/programming/configuration standards are harmonized
  • Improved interconnections between related equipment
  • Consistent designs that are easier to run and support
  • Flexible remote input/output (I/O) solutions
  • Smarter field connections
  • Connectors/fittings and cord sets for improved serviceability
  • Safer working voltages
  • Variable frequency drive (VFD) upgrades for process performance and energy savings
  • Analytics for performance tracking, energy monitoring, and proactive maintenance.

The challenges are recognizing where opportunities lie and making an appropriate case for tackling a specific project.

Realizing benefits

Small projects can bring improvements in energy efficiency, communications, and functionality.

  • Energy efficiency: VFDs and more efficient motors can save energy. However, adding energy consumption tracking can also reveal ways to reduce usage of electricity and other utilities.
  • Communication: Smart and HART field devices are capable of generating enormous amounts of information that can be used to vastly improve diagnostic functions, configuration, and maintenance.
  • Functionality: The capabilities of a PLC or PAC are much more sophisticated than they were even 10 or 15 years ago. Old controllers in a plant may still work, but aren’t doing the kinds of things their more current counterparts can, so upgrading individual controllers can really pay off.

Every potential project has its own mix of benefits, which can be tailored to achieve specific objectives.

Selecting projects

In any facility, the main process and its control system receive the greatest amount of attention. The plant depends on them first and foremost to maintain production and generate income. But secondary systems can make a major difference in plant operations and should be considered one-by-one as opportunities for improvement. Typical examples include:

  • Hot water
  • Chilled water
  • Steam
  • Power distribution
  • Communications
  • Water supplies (soft, filtered, reverse osmosis, water for injection)
  • Clean-in-place systems
  • HVAC
  • Wastewater
  • Compressed air
  • Refrigeration
  • Environmental
  • Emergency power.

Many of these subsystems may be major energy consumers, so one of the first things to examine is how well they are performing from an energy-efficiency standpoint. But there are many more elements related to performance that are more subtle than direct operational costs.

Choose one or two of the systems mentioned and perform a simple audit. Maybe it is operating as expected, but try to ignore the “If it ain’t broke, don’t fix it” mindset. Instead, consider these questions:

  • Is the control hardware in use still manufactured and supported by the original vendor? Are spare parts easily obtainable with quick and reliable delivery times at reasonable prices?
  • Does this control system allow for expansion if we are called upon to expand the plant or otherwise increase production?
  • What software is the system running? Is the operating system supporting it up-to-date? Is the operating system used anywhere else in the plant? Is it upgradeable?
  • Do we have anyone in-house qualified to service this equipment? Is this system anything a younger employee wants to learn? If it breaks down in the next hour, is there a plan for how to respond?
  • Is the hardware and software running on this system aligned with our corporate policies on preferred vendors?
  • How is the physical condition of the equipment? Is the electrical conduit in good condition? Piping? Pneumatic lines? Are the enclosures free of rust and corrosion?
  • Has this subsystem ever been checked for potential cyber security problems? Has anyone checked to see if there are known vulnerabilities associated with the hardware or software? Is it protected from intrusions from the outside?

If the answers to these questions are “no,” “I don’t know,” or “we really haven’t thought about it,” then it might be time to make a serious examination with an eye toward improvements. Otherwise, the new motto could be, “It’s broke, and we can’t fix it.”

The black box problem

In most plants, there are likely to be various subsystems brought in from a machine builder, original equipment manufacturer (OEM), or other type of integrator (see Figure 1). Many of these subsystems have their own control system, some of which are standalone, and some of which are interfaced with the main, plant wide control system.

For purposes of this discussion, assume the control system is performing its desired function. In some respects, such a piece of equipment is like an employee: Some simply do their job and nothing more. Others show initiative, join the company family at a deeper level, and prove value beyond their immediate job description. So it is with subsystems, as some integrate easily with the main control system:

  • The subsystem provides all the information the plant needs to monitor performance and condition in an easy-to-understand format.
  • The controller and HMI software is straightforward and understandable.
  • The controller is from a preferred vendor, is expandable, and is upgradeable.
  • The HMI, when it needs to be used, is clear and intuitive.
  • Connectivity is straightforward using the same methods and protocols as the rest of the plant.

Figure 2: Regardless of what the PLC is controlling, it should be up-to-date, serviceable, and have well-documented configuration information. Courtesy: Maverick TechnologiesIf you don’t use those characteristics to describe some of the critical subsystems in your plant, some upgrades might be in order. What is the best approach for such an undertaking?

New versus existing

Some improvements to existing subsystems made as retrofits can be well worth the cost, particularly if they are undertaken as part of a comprehensive rebuilding. Along those lines, what are some elements which should be included, or at least considered?

  • Choose a control platform, usually a PLC, that’s cost-effective, reliable, modular, and scalable (see Figure 2).
  • Select a company-approved PLC supplier that uses an approved product family.
  • Identify operator interface improvements, which can range from basic pushbutton lights to replacing an existing or adding a new HMI.
  • Enhance control interfaces where they might be bridging related utilities.
  • Upgrade to standardized configurations as they are easier and safer to run and maintain because they are familiar to plant personnel.
  • Improve automatic interlocking for a higher level of safety, better operations, and less waste.
  • Improve handshakes between utilities and the main process for greater availability.
  • Improve reporting for better production cost monitoring.
  • Improve diagnostics for better condition monitoring.
  • Improve instrumentation for better raw material use and energy consumption.
  • Schedule energy use to reduce utility costs.
  • Support linking “islands of automation.”
  • Operate control cabinets using low-voltage (24 V dc) equipment for greater safety.

From concept to implementation

Some of the items in the previous list are conceptual and do not call for specific hardware or software upgrades. On the other hand, product upgrades alone can often provide many advantages without requiring engineering concepts to support them. Here are some hardware and software upgrade suggestions that fulfill some of the conceptual advantages mentioned:

  • Tie field devices and remote I/O devices together using a bus system such as EtherNet/IP or Foundation Fieldbus. These protocols provide for reduced field wiring, greater flexibility, high-level diagnostics, and redundancy.
  • Add something as simple as HART connectivity for field devices that can apply a much higher level of communication with minimal hardware upgrades, particularly as many field devices are already HART-enabled.
  • Push your larger communication network farther into the field and even down to the device level to provide a mechanism for smart devices to communicate field data that can be harvested and used.
  • Use I/O blocks with built-in connectors and field wiring to avoid problems due to poor cable terminations and simplify serviceability.
  • Upgrade to VFDs to save energy and provide higher-level diagnostics and operational information captured via smart networks.

These approaches used in support of the concepts mentioned earlier can help fulfill objectives, such as improving energy efficiency, communication, and functionality of new and existing systems. Each element supports one or more of these objectives, with an overall goal of improved plant performance.

Not enough?

The architect Daniel Burnham is remembered for his famous saying: “Make no little plans; they have no magic to stir men’s blood and probably themselves will not be realized.” Architects are known for being a bit out of touch with the real world, but there is some truth in this statement.

To most companies, the suggestions so far, if put into practice, would be significant advances. But say your company needs a little more to stir its blood. What is the next level when it comes to improvements for secondary systems?

  • Big data: The amount of diagnostic and performance information that can be collected via sophisticated networks is enormous. By itself, it is merely data, but with the right analytic capabilities, it can help uncover opportunities for performance improvements and guide sophisticated condition-based maintenance programs.
  • Remote support: Parts of your main control system are probably already reachable from any location via the Web. There’s no reason the same capability cannot be extended to your secondary systems when appropriate and beneficial. Sophisticated networks make such deployments very simple.
  • Virtualization: Most plants have many more PCs than employees. Virtualization and thin clients can reduce this number drastically, making networks far more efficient and easier to maintain while increasing availability and uptime.
  • Fault-tolerant storage systems: PC hard drives configured in arrays can preserve historian data integrity and improve methods of backup and restoration.
  • Cyber security: All this sophistication becomes a liability if it is not adequately protected from cyber criminals. There are many techniques for protecting networks and specific devices using firewalls and other security appliances, but these require careful planning to be effective.

Integrators can assist

As a purely practical matter, many companies may not have the internal resources to take on these kinds of projects. Corporate engineering groups are generally understaffed, and plant personnel are often consumed with day-to-day operations.

Automation systems integrators can help, but they need some level of project management. When a company and integrator have worked together on multiple projects, they develop a working rapport and understand each other, and project management is greatly simplified.

Process plant personnel must be clear with an integrator with regard to project goals, the integrator’s specific scope of responsibility, plant work practices, adherence to corporate standards, and other factors. To define scope, it’s important to start with a few basics:

  • System design concepts
  • Specified vendor lists
  • Typical PLC logic approaches
  • Preferred HMI configurations for consistent look and feel.

These kinds of projects can be very cost effective and create long lasting benefits for companies. But they need to be approached systematically with clear objectives. An integrator can consult with your team and help determine which projects represent the highest potential and fastest payback.

Paul Darnbrough, PE, CAP, is a principal engineer for Maverick Technologies. He has more than 20 years of experience in engineering, documentation, and construction of automated industrial and process control systems. Darnbrough has worked with clients ranging in size from small, single-owner operations up to Fortune 500 companies and government agencies, involving operations in the plastics, food, dairy, chemicals, material handling, discrete manufacturing, water treatment, and pharmaceutical industries.

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