Distributed Control / Asset Management

A forced march from Dow Chemical’s MODV DCS to Experion PKS

After acquiring its polypropylene unit in Schkopau, Germany, Braskem Europe had to return Dow’s proprietary DCS hardware.

By Jim Montague, executive editor

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Sometimes, even the most legendary process control solutions can use a leg up, especially when their age and complexities become apparent after years of faithful service. Such was the case with a polypropylene unit at Braskem Europe GmbH's facility in Schkopau, Germany, which recently required a major upgrade from Dow Chemical Co.'s MODV proprietary distributed control system (DCS) to Honeywell Process Solution's Experion Process Knowledge System (PKS) R430.

Formed in 2002 by the merger of six petrochemical firms, Braskem had acquired four polypropylene manufacturing facilities from Dow, including two with MODV, and had agreed to return the proprietary DCS hardware and software following the migration. The project in Schkopau began in 2013, and I/O cutover, loop checks and startup occurred in August and September 2015 during a regular downtime period scheduled every five years. The second migration to PKS R431 is presently underway at Braskem's other polypropylene plant in Oyster Creek, Texas, and is scheduled for completion in 2017.

"This was a very complicated and risky migration that required many resources," said Michael Martin, senior process control engineer at Braskem. "We've had no DCS-related plant shutdowns since cutover, and we gained many new technologies and capabilities from this migration. Production rates and online time percentages have been greater than or equal to our yearly targets, and Braskem's management has deemed the migration a total success."

Martin presented "MODV DCS Migration to Experion R430" on the on the first day of Honeywell Users Group Americas 2016, this week in San Antonio. 

Overall, the MODV to PKS R430 migration at the Schkopau facility included:

    • About 7,000 I/O;
    • More than 700 MODV graphics migrated to Experion HMI;
    • More than 1 million lines of MODV software code and comments;
    • Tracking, documenting and migrating about 100,000 MODV variables;
    • Transitioning more than 6,000 MODV modules to about 4,500 Experion control modules;
    • Migrating more than 50,000 AspenTech IP21 historian tags;
    • Moving nine Siemens GC Analyzer data links to Modbus/TCP via peer control data interface (PCDI) blocks; and
    • Developing 30 control module templates.

"We also used Honeywell's worldwide cloud development system, which was employed by users in Germany, India, the Czech Republic, the U.S. and elsewhere," explained Martin. "We had to understand MODV's state-based control and automation architecture so we could replace the sequence for each unit with sequence control modules (SCMs) as state drivers. Each sequence was comprised of modules for alarms, digital output (DO) logic, analog output (AO) logic, step logic, special calculations and other tasks, and they had to be replaced with control modules."

Martin added that migration challenges and solutions in Braskem's MODV to Experion upgrade included:

    • Identifying and developing similar functions when updating its HMI solutions;
    • Translating and normalizing MODV's equations;
    • Evaluating and updating the polypropylene application's alarms because MODV had limited alarms, and had combined many of its process and hardware alarms to keep totals down; and
    • Replacing MODV's interface to third-party devices with Honeywell Peer Control Data Interface (PCDI) and Modbus TCP.

"MODV uses logic to enable and disable alarms, so we had to ask, 'How do you program this?' and 'How do you effectively visualize alarm status and trip points?' MODV's instrumentation failure logic also had failures driving process variables (PVs) to positive full scale (PFS) and negative full scale (NFS), and generating combined process and instrumentation failure alarms. This was replaced with Experion single alarming and custom faceplates. We also converted MODV analog output ranges and code from MODV 0-22 mA to 0-110%, and from Honeywell 4-20 mA to 0-100%. We also had to convert MODV's analog filter times.

"MODV operators were required to read Dowtran code to run their plant, so MODV was a closely combined basic process control system (BPCS) and safety instrumented system (SIS), which we had to break apart. This also meant migrating from MODV PIDs with output ranges depending on fail open/fail closed to Honeywell PIDs, as well as converting PID tuning constants, correctly capturing setpoint (SP) ranges, and capturing input failure, interlock and other PID actions."

MODV HMI graphics that required a lot of space for shapes and added symbols for alarms and logic were removed and transitioned to Experion, which needs much less space for shapes, removes unneeded symbols, and uses dynamic alarm symbols. "MODV DO and digital abort (DA) logic was replaced with Honeywell's Interlock function block, and reading code was replaced with its Dynamic Logic Faceplate," added Martin. "Also, MODV dynamic alarm logic was replaced with custom data block and logic, while MODV DMLatch alarms were replaced with template logic, HMI and message block to acknowledge and clear latched alarms."

Martin adds that migrating from MODV to Experion gave the Schkopau polypropylene plant a variety of new technologies and capabilities, such as:

    • A virtual computing solution for L3.0 and L3.5 servers and PCs, including virtual machine replication across redundant host servers, and rapid deployment of new servers and PCs;
    • Integrated disaster recovery, including automated Acronis backups for all physical servers and PCs, automated virtual machine replications and backups, and tape backup for offsite storage;
    • AspenTech IP21 data link migrated to OPC, which allowed improved architecture with redundant data collectors and Experion redundant OPC servers, and increased the application data resolution 10 times;
    • GPS radio with times synchronized from the C300 controllers to the IP21 server;
    • Field Device Manager (FDM) deployed to interface with more than 800 DCS and SIS HART devices;
    • Metso PlantTriage loop-tuning solution, which minimized plant optimization tasks after the successful plant startup; and
    • Safety management by integrating Control Builder software and HMI graphics, as well as implementing universal Rusio I/O modules that work with all I/O types, are HART-enabled, and communicate directly to FDM via FTE Ethernet networks.