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Phased Project, Integrated Team Approach Ensures Project Success at Noltex
Noltex LLC is a leading manufacturer of ethylene vinyl alcohol co-polymer. The company's facility in La Porte, Texas recently completed one of the first successful petrochemical industry migrations from a Provox DCS to a DeltaV digital automation system. The plant is extremely important to Noltex because it produces a unique ethylene vinyl alcohol co-polymer resin used to make a gas-barrier film component for food packaging. Sold under the trade name of Soarnol, this unique polymer is most commonly used to create an almost-invisible preservative barrier that prevents food products from oxidizing and spoiling.
The migration was planned as a like-for-like control conversion for the plant's distillation columns, brine water chillers, process gas compressors, and related equipment. Process control strategies were modified by the plant's process and operational managers to reflect plant operating experiences and the new system's strengths. The migration process continues, with additional like-for-like Provox to DeltaV migrations are planned for process trains in the manufacturing area in 2004 and 2005. Manufacturing process trains are run by later model Provox redundant controllers and therefore, scheduled last.
Migration Provides Challenges
|Redundant CPU and Power Supply modules at the top, I/O modules angled below to minimize cabinet space required|
While the existing DCS had been trouble-free, future reliability remained a question mark for the plant's managers. The Provox controllers had become hardware and software point-limited, which precluded adding new devices and logic to improve operational and other process efficiencies. Similarly, the DCS was maxed out when it came to the number of physical devices permitted on its data highway. To add capacity and reach current and future production goals, Noltex would have to add new hardware and process control capability.
The DCS also had data highway loading issues that resulted in scan times as long as 380 milliseconds and prompted concern about data latency. Compounding these issues was the state of the controller configuration which had been modified numerous times over the years and which made troubleshooting and modifications both time consuming and difficult. Lastly, Noltex's process engineers desired the flexibility to deploy bus-connected I/O, OPC, and serial communications, as well as initiate advanced control techniques such as fuzzy logic, neural networks, and model predictive control.
In 2000, Noltex formed a focused, dedicated improvement team to chart a path forward and develop and evaluate plans for the plant's existing DCS control system. This multi-disciplined team, comprised of representatives from operations, technical support, maintenance, engineering, and information technology had to decide whether to upgrade, replace, or migrate to new technology.
The first option the team explored was upgrading its current hardware with the latest HART Smart I/O controllers and new operator consoles. The team's analysis revealed this option did not take advantage of thr latest field device bus technologies nor advanced process control capabilities. Further, current-generation control system advancements such as system speed, configuration utilities, and system troubleshooting would also not be available. Noltex's improvement team members soon realized that future expansions via this technology platform over the long haul would be more costly than replacing the entire system with newer technology.
After evaluating system offerings from several DCS manufacturers the improvement team determined that migrating the existing DCS to Emerson Process Management's DeltaV was the best, most cost-effective choice.
To phase out different generations of controllers in an orderly fashion the implementation was planned in stages. The Provox simplex controllers were upgraded first, then the oldest redundant units second. Finally, the newest redundant controllers will be replaced during the final two project phases. In 2002, Noltex migrated the discrete control system from the plant's packaging area. In 2003, the compressors, solutions preparation, distillation, solvent recovery, demineralization process, and the utilities migration projects were completed. To complete the project, Noltex is now planning to migrate the existing manufacturing facilities in two separate phases.
Smart Field Device Upgrades Integral to Migration
In 1998 Noltex purchased asset management software and correspondingly started upgrading field devices in its existing production areas to the HART protocol. Subsequently, Noltex purchased all new instruments for the migration to the new system based on Foundation Fieldbus or HART communications protocols.
In 2002, Noltex upgraded several electro-pneumatic valve positioners to digital valve controllers (DVCs) which increased the total number of HART DVCs to more than 220. Via the valve-position feedback capabilities of the new DVCs, Noltex's system is now indicating actual valve position on the operator displays rather than having to settle for the old controller's less accurate implied valve position. The new smart field devices, combined with the DCS and the existing asset management software facilitate electronic storage of device configuration and calibrations. This system also helps Noltex process engineers and maintenance technicians monitor control valve degradation and the health status of the company's field devices.
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