Modernization of control systems doesn’t have to be a nightmare of lost revenue and horrific shutdowns as evidenced by a Latin American eucalyptus pulp mill when they set out to revamp their one painting and four printing machines that were running on control technology from the 1990s.
The plant was experiencing unplanned shutdowns equaling over 30 hours per year for the preceding three years and were requiring manual backups of the PLCs amounting to 162 hours per year. This became an even bigger issue when the company signed a large contract for cardboard with a tight delivery date that required their large MB6 machine to operate nonstop at maximum speed with no failures. Prior to receiving the contract, the company believed their only path to upgrade was to replace the entire system, however, after signing the agreement, such a plan was unacceptable.
After consulting with Emerson, the company was amazed to discover that the upgrade could be performed within their stringent requirements over a period of time without extensive shut downs to the whole system. Emerson determined that 58 racks had to be modernized including 14 obsolete peripheral controllers. Obsolete 9070 and 9030 PLCs would be replaced with new Emerson PACSystemsTM RX3i control systems and the Genius I/O would be replaced by Profinet. The system would be upgraded in partial replacements without ever shutting down for a prolonged time, which, of course, required that the new technology be compatible with the legacy system.
Three additional challenges further complicated the process:
Because of the limited availability of budget, the modernization was performed in three partial upgrade phases including replacement of software, hardware and the communications network. New engineering stations were replaced in all electrical rooms and an automatic backup system was included.
The figure above shows replacement with the RX3i, while the main upgrade of software to PAC Machine Edition happened automatically. Because the PLCs employ the same electrical, the I/O racks could be replaced in only a couple hours.
Over a period of two-and a half years, Emerson prepared a plan, which had technical, commercial and financial teams working together to fit the upgrade to the available budget. The old system ran simultaneously with the new since communications were fully compatible. The system went from 30 hours of unplanned downtime per year to zero. The 162 hours of manual backup for the PLCs was eliminated, and the system has a new ease and agility in diagnostics and highly improved operations. Most important, they have been able to deliver top quality product on schedule from a continuously running, high performance machine system – without ever breaking their stride.
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