Controls and Process Applications Can Be Restored

Restoration Possible: Many Distributed Control Systems (DCSs) Are Rapidly Aging and Risk Breaking Down. Luckily, There Are Many New Tools and Innovative Methods for Supporting and Breathing New Life Into Controls and Process Applications

By Jim Montague

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They add the biggest constraints on automation in their plants include budget (28%); capital expenditure priorities (26.5%); resources (19.5%); integration of platforms (9.7%); maintaining legacy systems (8.6%); and planning (7%).

To improve their applications, close to half of the respondents plan to expand with new automation systems (47%) within the next 24 months, while about a third each plan to add remote support for data and controls (37.8%); integrate controls with their enterprise/business systems (33.5%); and/or migrate their legacy automation systems (33%).

For more detailed results of Maverick's survey, visit ControlGlobal.com/1306_MaverickSurvey.

Plan is Key, Schedule is King

Before securing the most suitable hardware and software for upgrading a DCS, the most important task is evaluating what's truly needed by the application and the overall business, drafting a thorough plan meet those requirements and following a precise, but flexible schedule.

For instance, Indonesia-based PT. Pertamina recently migrated the DCS that runs its paraxylene plant, which is part of Unit IV at its Cilacap refinery. It worked with Azbil Corp. and local affiliate Azbil Berca Indonesia (ABID), and together they planned a combined cold changeover (CCO) and hot changeover (HCO), minimized switchover time by retaining all sensors, valves and terminal panels in good working condition, and migrated only the plant's DCS to Azbil's Harmonas-DEO monitoring and control system.

Read Also: Addressing Control Applications Using Wireless Devices

"The DCS was replaced while part of the plant was shut down for planned maintenance, so the timing would change depending on how the maintenance work progressed," says Erfan Gafar, deputy section head of Pertamina's project engineering department. "Despite repeated schedule changes, switchover was completed as originally planned without delays."

Likewise, the Langkawi cement plant in Kedah, Malaysia, has two production lines producing 3.3 million tons of clinker per year. The facility is one of three operated by Lafarge Malayan Cement (LMC), and its Line 2 was run by an aging Polysius DCS for which spare parts were no longer easily available.

So beginning in 2007, Lafarge planned and undertook a four-phase, five-year revamping of the line's controls with help from ABB Malaysia and its associated Operation Center in India (INOPC). The third phase shifted key process areas of Line 2 to ABB's 800xA control system in June 2011, and the final phase was completed in June 2012 (Figure 2). This new DCS included with 11 AC 800M controllers for 14,000 I/O points, integration of existing 5 AC 800M controllers for 6000 I/O points, and seven operator workstations.

To upgrade the plant's safety capabilities at the same time, Lafarge also planned to renovate the line's electrical systems and installed visible cut-off, switch-power isolation and control units on more than 300 motors and local control units for 13 high-tension (HT) motors, and added about 100 pulse-controlled speed sensors for critical drives. This allowed 800xA to provide safety instrumented systems (SISs) that comply with IEC 61508 and IEC 61511.

"Our operators now have full control over energy and raw material consumption with 800xA and can keep vital processes running without interruption," says Mohamad Fadzil Ramli, Lafarge's methods manager. "For instance, with a fully integrated control system, the average temperatures in the kiln can be adjusted for minimum energy requirements. When an operator combines process knowledge with 800xA, energy consumption can be reduced by 10%."

Divide and Conquer

Because migrating an old DCS is such a complex project, the best way to carry out its upgrade and replacement plan is to break it up into a logical series of workable chunks.

For example, Golden Triangle Energy Cooperative (GTEC) in Craig, Mo., makes about 20 million gallons of ethanol and 160,000 tons of wet livestock feed per year. It had been controlled by a DCS installed when the plant was built in 2001, but just a few years later its manufacturer reported it was obsolete and would no longer be supported.

"The supplier would still repair some rundown parts, but the refurbishment process could take up to three weeks," explains Roger Hill, GTEC's general manager. "One day of downtime can cost us $35,000 in lost profit, and unexpected shutdowns can cause unsafe conditions for our employees. We started shutting down operations at every threat of a thunderstorm just to avoid the risk of an outage. We were even browsing online auction sites to find backups for our critical components."

To solve these problems and replace the old DCS, GTEC sought help from system integrator Bachelor Controls Inc. in Sabetha, Kan., and together they implemented PlantPAx process automation system and ControlLogix PLCs from Rockwell Automation, and minimized costs by retaining all existing field wiring and devices and reverse engineering control logic and strategies from the old DCS.

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