Polystyrene Plant Gains Extra Output and More

Automation upgrade also extends asset life and boosts reliability

By Adolfo Suiffet and Alberto Gorbaran, Petrobras Zarate, and Mario Blanco, Emerson Process Management Argentina

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Figure 1. Better control and more data enhance the operation of polymerization reactor.
Figure 2. Operators now see more plant data on each screen, speeding and improving their decision-making.
Figure 3. Asset-management software helps maintenance staff predict and analyze equipment malfunctions.

Petrobras Zarate, in Zarate, 80 km. north of Buenos Aires, Argentina, produces high impact and general purpose (crystal) polystyrene. The firm, a part of Petrobras Energia, an integrated energy company based in Buenos Aires, sells 90% of the polystyrene to customers in Argentina, with the remainder exported to other South American countries, including Peru, Chile, Bolivia and Brazil. The company also makes bi-oriented polystyrene, which is exported to North and South America and Europe. However, its plant, which operates 24/7, couldn’t expand output to take advantage of a strong polystyrene market.

The plant, which started production in 1986, was limited by its 1980s-era distributed control system (DCS). That system lacked modern tools to facilitate a predictive maintenance strategy that would help reduce emergency maintenance and downtime, better optimize aging assets and boost production. The company also wanted a system that would produce reliable data that could be shared by decision-makers at all levels of the organization, including upper management interested in the facility’s key performance indicators.

So, management decided that modernization of the automation system was necessary — and that it must be accomplished in stages and without stoppages to stay within budget and minimize risk. Re-instrumentation was needed but the new digital network also would have to seamlessly connect to some existing assets. Along with the technological migration, the company would have to bring operators and maintenance staff on-board quickly and realign work practices to follow a predictive, intelligence-based maintenance philosophy. Training would be needed to ensure that staff knew how to use the new tools as well as could analyze and properly employ the new, rich data provided to make better maintenance and operations decisions.

Petrobras Zarate selected Emerson Process Management as its automation supply partner based on the company’s strong performance record in the field of digital control technology and its global support network. Plant managers sought greater plant availability, improved asset reliability and advanced control tools with the ability to integrate several fieldbuses. They chose a PlantWeb digital plant architecture, which utilizes a DeltaV automation system and AMS Suite asset-management software.

Phased implementation
The modernization was accomplished in phases, beginning with the least complicated migration. In 2002, Provox DeltaV Integrators bridged the obsolete Provox interface controlling the plant’s air and water utilities to the DeltaV system. This provided valuable experience for the later, more complicated phases. In 2004, the company migrated the reactor operations of its high-impact and crystal polystyrene units to digital control (Figure 1). Then, in 2005, without stopping operations, the remaining variables under Provox control were transferred to the DeltaV controllers. This “hot cutover” saved Petrobras $1.13 million by avoiding a shutdown. The entire migration was performed in-house by facility employees, saving the company $150,000.

The new digital network fully supports Foundation Fieldbus and other bus technologies. The PlantWeb architecture also taps data from existing devices, including the plant’s HART transmitters and its Liebert uninterruptible power supply. The wealth of new information now delivered has empowered operators and maintenance personnel to make more reliable decisions about process quality and asset health.

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