Modernizing Legacy DCS for Reliable Operations at a Large-Scale Chemical Facility

Hargrove Controls & Automation supports a full control system migration while improving reliability and streamlining operations.

OBJECTIVE: The facility chose to migrate to a modern Honeywell Experion system to improve reliability, simplify maintenance, and reduce downtime by improving recovery from system failures. The project also included streamlining the control system by removing obsolete equipment and unused logic. It had a defined outage window for completion, with a focus on minimizing downtime and ensuring a safe startup.

CHALLENGE: The system included approximately 2,500 I/O points, more than 200 operator graphics, and 15 complex sequences. This scale, significantly larger than a typical migration, increased the effort required to validate each element to ensure proper operation. The volume of work also increased the risk of rework, as small inconsistencies could have scaled across the entire system.

System cleanup added another layer of complexity. The team performed an initial assessment using system drawings and logic reviews to identify equipment that was no longer connected or in service. Unused equipment then required coordination with operations to review and approve each removal.

A late-stage issue added pressure to the schedule. An incorrect I/O module type identified during early planning required updates across the system near the end of the project. The team reworked the configuration and validated changes within the existing schedule, maintaining the planned startup.

BACKGROUND: A large-scale chemical facility in southeastern Texas operated with a legacy Honeywell TDC 3000 distributed control system (DCS) from the 1980s. The system became difficult to maintain over time as replacement parts were scarce and hardware failures could impact multiple points in the process.

Decades of incremental changes had left the system cluttered. Decommissioned equipment and outdated test configurations remained in graphics and control logic, which added complexity for operators and increased the risk of confusion during operations and maintenance.