Evaluating DCS Modernization Options

An oft-cited number when discussing the topic of distributed control system (DCS) modernization is $65 billion. This was the size of the installed base systems reaching their end of their useful lives from an ARC Advisory Group study conducted several years ago.

Emerson’s Cody Long, a migration/modernization consultant, visited a Latin American sugar mill. This mill had two different, non-Emerson distributed control systems (DCS) near their end of lives. They could no longer grow or be expanded because the systems were no longer actively marketed. The mill was also experiencing field failures with this DCS hardware. Beyond the reliability issues, the mill staff wanted better boiler control by applying advanced process control to improve their existing control.

Cody began his visit to the mill with a site walkthrough to assess current operating conditions and to speak with operations and engineering staff about the challenges they faced. The mill staff was quite experienced in process control and advanced process control. The team understood what some of these tools could do in improving existing control performance.

He discussed options ranging from a complete “rip and replace” of the existing DCSs with a DeltaV system, to a connect solution which keeps some of the existing controller and I/O in place and provides new operator workstations and the ability to expand new areas with DeltaV hardware. This connect method also provides a way to switch over control to the new system in small increments over time.

From his visits over time with process manufacturers, Cody has developed some new tools to quickly analyze the contents and complexity of the existing DCS’ database to help immediately formulate a migration strategy.

Project justifications based upon avoiding failures are often difficult to sell to plant management, so typically Cody or a member of the advanced automation team would work with the project team to identify economic benefits based on the operating performance. In this case, it would be through improved boiler control. These benefits would likely include reduced energy usage and fewer boiler trips. These trips impacted overall mill production, which impacts the revenue side of the justification analysis.

The mill staff had this project justification expertise internally, so they were able to get a modernization project approved. The analysis showed the return on investment from a full replacement of the existing DCSs with a DeltaV system justified the cost of the project. The mill would use the existing DCS parts as spares for another mill with similar systems.

Once this project is completed and business results quantified, a similar analysis will be done on the other plant to assess a total replacement or a connect solution.

Posted Friday, June 20th, 2008 under Food & Beverage, Modernization.

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