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New hybrid systems from GE combine advantages of DCSs and PLCs

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In the early days of process automation control, a plant manager had two basic choices: Distributed Control Systems (DCSs), or Programmable Logic Controllers (PLCs). Though they performed similar functions, the two were different, and each had its own advantages and disadvantages.

Distributed control

A Distributed Control System was an elaborate, monolithic network of microprocessors that controlled various aspects of a process system.

They were complex and expensive, and typically used proprietary hardware and software including control languages, so only the company that built them could service and support them. And once the system was in place, it was difficult to adapt, as process requirements changed over time. But they were capable of handling large and complex processing systems, making them a major step forward for continuous processing industries like Power & Energy, Oil & Gas, Water & Wastewater, and Pulp & Paper.

Programmable logic

Programmable Logic Controllers, or PLCs, were small, fast computers developed to control one or more real-world processes, such as equipment in a process system. They replaced hard-wired relays that had to be rewired by hand with each modification to the process or product, making changes costly and inefficient. With a PLC, all that had to be done was reprogramming. Early PLCs actually used ladder logic that mirrored a relay diagram so that traditional engineers would be able to read them easily.

Where DCSs were rigid, PLCs were flexible. Where DCSs were large, self-enclosed systems, PLCs were modular and scalable, making them good solutions for small and medium-sized process systems, especially in batch and discrete sectors like Food & Beverage, Personal Care, and Life Sciences. And because they were modular they were generally less expensive, at least at the beginning of a project.

The hybrid promise

In the last decade, both historic DCS and PLC companies have moved toward a space that both call "hybrid," in which they attempt to offer the power and complexity of DCSs and the flexibility, openness and low cost of PLC systems. DCS companies have done this by reducing the footprint of their systems while PLC companies have begun linking their components together to create more complete systems.

But though many were commercially successful, these hybrid systems have never fully delivered on the original hybrid promise. For one thing, the DCS hybrids have been unable to tailor their systems to become modular enough to work with both OEMs & End Users and scaleable, flexible enough to handle applications that range from small to large. In addition, the speeds of high speed sequential or discrete processes, sometimes measured in the tens of milliseconds, are typically too fast for DCS hybrids to accommodate making applications like packaging or metal stamping or simple motor control difficult if not impossible to control.

So a hybrid plant with batch, continuous and discrete environments or a large continuous processing plant with high speed sequential control needs as well still had to acquire a second process system for their discrete areas, with all the extra cost, integration problems, increased training and maintenance that entailed. Many of the historic PLC systems attempting to deliver Hybrid Systems fell short of offering true system capability often lacking system services such as global namespace and system alarming / eventing to name a few.

Whether from the traditional DCS or PLC technology heritage, most all these systems fell short of tightly integrating with the information layer. Closing the information and automation gap to effectively control and optimise production and increase performance of operations was done in multiple systems with multiple databases driving high costs of ownership. Contextualised role based visibility into process operations was simply not economically available.

Delivering on the hybrid promise, closing the information and automation gap

Now, GE Fanuc introduces Proficy Process Systems, a Process automation and control system that delivers on the hybrid promise, providing the power and effectiveness of a distributed control system with the flexibility, openness and affordability associated with programmable logic controllers. With the company’s Proficy software layer inherently architected into its process control system, optimisation and analytics, production management are simply layered on.

Partnering with GE Fanuc for process control needs provides benefits that can give the required edge in today's competitive global economy:

· Results: With GE Fanuc Process Solutions, improved performance, increased productivity and lower Total Cost of Ownership can be achieved.

· Experience: Long a leader in process technologies, GE Fanuc's network of qualified system integrators and the company’s professional services teams work together to deliver the industry- and application-specific domain experience necessary to create a solution that is right for the business.

· Freedom: The solutions offered eliminate the restraints of traditional DCS and PLC systems, and offer the flexibility to configure, scale, deploy, and maintain the system as required.

· Contemporary solutions: The company’s technological competence, flexible service and innovative support model creates a customised solution that is tailored to suit business needs.

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