Migrating Provox DCS to DeltaV

Jan. 29, 2004
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

Upgrades Justified

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.

Path Forward

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.

As the project got under way, Noltex improvement team members became increasingly convinced that its control system migration project, along with the field device upgrades it undertook, would lay a solid foundation for current and future process control operations.

All Hardware Changed Out

Two choices were available when it came time to migrate the Distillation Area's process control system to the new DCS. The first choice was to remove all existing hardware except termination panels, pre-mount the controllers in new cabinets offsite, and prepare pluggable links between the termination panels and the control's I/O using a pre-fabricated flexible-connection cable system.

Choice two dictated removing all existing hardware and then installing the new hardware and termination panels in the empty cabinets. With either choice, field wiring remained, field devices did not require replacement, and the system software could be configured and tested prior to installation.

Employing a pre-fabricated cabling system is an ideal solution if cutover and startup must take place within a short time frame, but Noltex management had a scheduled an extended outage so the plant would be shut down during DCS implementation. Under these circumstances, the second option the better choice. Consequently, all the old hardware was removed, and because the new system has a smaller footprint, more room became available for future upgrades.

During this first phase of the project Noltex and vendor technicians replaced four (of 13 existing) redundant sets of controllers. To reduce cross-communications, I/O was reassigned among seven controllers (four of which were upgraded and three of which were not).Completing the new system's installation were small marshaling panels for field wiring (the previous system had no marshaling panels), interposing relays for discrete points, and installing multiconductor cables between marshaling panels and the DCS I/O.

Challenging Configuration

The new system was configured using graphical function block diagram and sequential function chart languages through a combination of manual work, plus the application of several Provox-to-DeltaV conversion utilities developed for the Noltex project by Puffer-Sweiven, a systems integrator located in Stafford, Texas. Because of the configuration's complexity, seven programmers, plus a Noltex liaison person worked full time for 12 weeks to finish this critical part of the project.

Most of January 2003 was spent defining the project's scope and developing the conversion utilities. During February and March Noltex concentrated on configuring functions and graphics in time for the April factory acceptance testing (FAT), installation and checkout in May, and startup in June.

The conversion utilities helped Noltex managers decide which points should be migrated to the new DCS and which should be transferred to the manufacturing area's Provox controllers. Correspondingly, some points in manufacturing area were best transferred to the new system's controllers. Other points were eliminated as they were no longer in service.

Also identified and listed by the conversion utilities were those control points whose information had to travel between DeltaV and Provox. Noltex's engineers decided that critical points would be hardwired, while informational points were to be passed through the Provox-to-DeltaV Integrator using OPC Mirror and Emerson utilities. For example, a pump might have I/O in DeltaV, but show up on both systems' graphical user interface and be commanded from either system. The upgrade was done so that operator function would be transparent regardless of which system had I/O control.

Utilities were of little help in loop configuration because many of the non-standard functions programmed into the Provox loops are built into the new control system. If a utility was run to pull FST information out of Provox configurations it ended up with unnecessary code. Basic loop functionality (alarms, ranges, tuning parameters, fail action, etc.) was converted from Provox using the new utilities. Associated interlocks and FSTs were configured manually by deciphering Provox code and implementing the same functions in the new DCS. A certain amount of intelligent re-engineering was thereby gained; mostly simplification, but accompanied by a certain degree of control improvement.

To confirm interlock design and keep the new DCS as clean as possible, interlocks and sequencing were also prepared manually. This allowed for technical review to correct errors or identify improvement opportunities. The interlock and sequence code configured in DeltaV function blocks was much simpler to read, troubleshoot, and modify than the coding custom FSTs in with the old system.

The four sets of redundant controllers have 300 to 350 device signal tags each, which left approximately 400 available for additional devices under the present license. The controllers memories are only 15-20% loaded, which allows for scan times at configured individual module rates.

Graphics Improved

To meet time constraints, the distillation system's 132 screens were jointly prepared by a third-party vendor and the Emerson Solutions Group. Utility tools were initially considered in order to convert the VAX graphics, but any gains realized from doing that would be more than offset by time spent cleaning up pages, etc. So, graphics were created from scratch using the new system's object-oriented design tools. Nevertheless, utilities were later used to correlate points with icons, check functionality behind color conditions, and perform other functions.

Noltex improvement team members established standards for display navigation and graphical representation of the process. To mitigate any issues resulting from changes to the operator interface, graphics were designed to resemble the old system's pages. In spite of that, graphics creation was expedited because programmers were able to take advantage of the new system's object-oriented dynamos. In the end, the interface's graphics were freshened, but the basic layout remained the same as far as the operators are concerned.

FAT Performed Offsite

Software and staged-hardware FAT took place separately over a three-week period. Everything in the listings and drawings created from the FSTs was checked carefully so that once the equipment was onsite, it could be plugged in and the I/O immediately checked. All hardware functions -- including interlocks -- were tested and all I/O was exercised. Function and input verification and I/O exercising were conducted using appropriate utilities, along with some custom graphics and code. This allowed hardware and software testing to occur simultaneously.

Pump Control Refined

Instrument stand and pumps run by DeltaV automation.

Prior to acceptance testing, the DCS system's manufacturer provided key Noltex personnel with on-site training. This training allowed for the early completion of the FAT and proved valuable during on-site checkout, commissioning, and startup. Software review was performed simultaneously by three separate teams comprised of a Noltex operator and process control specialist, plus a process control specialist supplied by Puffer-Sweiven, which also assisted Noltex with hardware acceptance testing.

After the FAT, installation crews completed hardware changeout during two long weeks of 10-hour days. After installation, Noltex engineers and specialists spent three weeks downloading device configurations, shooting every loop from the field to the new systems controllers, checking every interlock, double-checking graphics, and physically verifying that every motor ran and every device activated. All told, commissioning the new DCS, which began during the second week of installation, required seven I&E technicians, two process control system specialists and two board operators working 12-hour days.

In addition to the early training of key production personnel, on-site training was provided to operators and technicians. Training concentrated on understanding and using the logic in DeltaV Control Studio for troubleshooting. Puffer-Sweiven loaded the completed configuration and graphics, plus Mimic (www.mynah.com) simulation software, into an off-line DeltaV workstation so Noltex personnel could learn and practice operating the new systems.

Fresh Operator Interface

Freshened graphics, but based on previous system's iconography helped the transition to the new system.

Because of the hard work and concerted efforts of everyone involved, the automation upgrade project came together on-time and on-budget and startup was uneventful. Good product was made right off the bat. Based on operating experience gained since the migration, Noltex is experiencing a number of benefits as listed in Table 1.

The Future

In the very near future, Noltex plans to set up a permanent DCS system development/training hardware unit in the control room to train new technicians and operators, run refresher courses, allow tinkering and practicing, and prepare for bus-connected I/O in future projects. The unit will be especially helpful for learning bus commissioning, decommissioning, uploading, downloading, and changing configurations.

Noltex is in the process of evaluating the advanced control capabilities of the new DeltaV-based DCS, and the model-predictive controller is planned to replace some standard PID controller modules in difficult applications.Noltex operators are also using features built in to the new DCS such as Inspect for monitoring loop performance and Diagnostics for monitoring hardware. DeltaV version control and audit trail software has been added to monitor configuration changes as well. Meanwhile, Noltex process engineers and maintenance technicians continue to rely on the asset management software, but use it as a stand-alone system for monitoring and configuring smart devices.

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