The DCS spirit lives on everywhere

Classic distributed control systems typically remain only in high-availability refining and power applications, but their strategies and capabilities persist in descendants and today’s sophisticated networks.

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Distributed ControlBy Jim Montague, Executive Editor

It’s been more than 10 years since DCSs began to be forced from their proprietary shells by Microsoft-based software, other commercial off-the-shelf (COTS) computing technologies and emerging open-networking standards. However, even as many shunned the DCS label’s connotation of big, old, slow, hardwired systems, developers responded buy making DCSs more flexible and scalable to smaller applications, just as IBM mainframes evolved into desktop PCs.

“By seven or eight years ago, all the proprietary DCSs with their own hardware were dead,” says Rick Pierro, president of Superior Controls Inc., a system integrator in Plaistow, N.H. “Now, all the DCSs run on Dell PCs. They’re set up like PLCs, and have dedicated controllers arranged on the backplane with I/O and network modules.”

Evolution Revolution
“From our perspective, the traditional DCS is a legacy technology that’s been replaced by integrated digital automation architecture, which gives users improved project execution and timing, improves operational efficiency and up-time, helps them build safer plants, and enables smart plants with predictive technology,” says Jane Lansing, marketing vice president for Emerson Process Management. “Today’s architecture is an open, interoperable, fully digital networking of intelligent components. The first-level computing platform is the field devices, which are digitally bussed with highly modular COTS-based automation systems, and the architecture features fully integrated asset health and management applications. Control and asset management integrated in the same architecture is the ‘new world order.’ ” 

In addition, after DCS control made so many of their applications safe, users began to ask how they could help optimize the processes they controlled. “DCSs still provide essential functions for users whose processes must be available 24/7 for four or five years straight, they just run on PCs and laptops now. However, as long as gas can potentially blow up, users will need the high-availability control that only DCSs provide,” says Tim Sweet, product marketing manager for Honeywell’s Experion Process Knowledge System (PKS) DCS platform. “The big breakthrough for DCSs on PCs came in the mid-1990s when they started to ride Intel’s microprocessor power curve, and PCs really started to get data from the processes. Now, plant-floor and IT people are using the same gear, being made to work together, and learning to like each other to survive. IT guys now respect and trust that the plant-floor is segregated enough from business systems by the right firewalls. I don’t get phone calls anymore from plant guys saying they can’t work with IT.”

Roy Tanner, product manager for ABB’s 800xA (extended automation), adds that the scope of DCSs’ “jobs descriptions” have grown, and this has blurred their former boundaries. “DCSs are using a lot more non-proprietary hardware and software, and this has allowed them to get into batch tracking, asset optimization, device management, and safety applications. 800xA even has pre-integrated software plug-ins, so our historian doesn’t require users to redefine everything again when doing configurations.”

     FIGURE 1. NOT YOUR DAD’S DCS
Asset Management System Suite

Predictive diagnostics in Foundation fieldbus allow instruments to help improve maintenance efficiency via Asset Management System (AMS) Suite software at Shell Deer Park refinery.
Source: Emerson Process Management

Migration Concentration
To modernize and increase availability of its catalytic cracker (including a gas fractionization plant), selective hydrocracker, and other process units, Shell Deer Park refinery recently completed a five-year, $125-millon control renovation. This project included implementing Foundation fieldbus via Emerson’s PlantWeb digital plant architecture with DeltaV digital automation system to minimize production losses caused by unexpected equipment failures. After successfully testing DeltaV in 105 fieldbus instruments in its North Effluent Treater, Shell began implementing PlantWeb, DeltaV, and AMS Suite device manager software on 1,100 fieldbus devices in its cat cracker and gas fractionalizaton plants (See Figure 1).

“AMS device manager receives diagnostic data from the control network, and makes it available for maintenance. The open architecture accepts any fieldbus-compliant devices, including our Rosemount pressure, flow, and temperature transmitters and Fieldvue digital valve positioners,” says Roger Erfurdt, Shell Deer Park’s control system manager. “Process information is delivered to and from the controllers via the fieldbus communications protocol, while other systems are integrated by OPC, including the Triconex protective instrument/surge control system and vibration monitoring of 10 critical electric motors and steam turbines/expander turbines.

“Using OPC to facilitate high-speed, two-way communications between the Triconex system and the control room is unique. It’s never been done before, and it was accomplished here only after considerable effort. The OPC connection enables operators to view far more data from the Triconex protective system on the same monitors used for process control than in previous systems.  The operators are also able to communicate with the Triconex system in case some action must be taken. This allows direct control over several large turbines and compressors through Triconex.”

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