Engagement Context
A Central European chemical processing group required integration of their operational technology environment (14 production sites, three DCS platforms, six different PLC vendors) with a new enterprise ERP system. The integration was required to support production scheduling, quality management, and energy management use cases. All sites were in continuous production with no scheduled shutdown windows available for the integration programme.
Architecture Approach
The integration architecture was based on ISA-95 Part 2 (object model definitions) and Part 4 (production operations management), using OPC-UA as the field-level communication standard for all new integration points. Legacy Profibus and Modbus field buses were connected through OPC-UA gateways at the site edge layer, normalising data before it reached the integration layer.
The IEC 62443 security framework was applied at all integration boundaries, with a defined security conduit between each site's process control zone and the enterprise integration layer. All data flows were unidirectional from OT to IT at the site boundary — write commands from ERP to production systems were explicitly excluded from scope.
Transition Sequencing
The 14-site rollout was sequenced by production criticality: the three highest-criticality sites were addressed last, after the integration architecture had been validated across lower-criticality environments. Each site transition followed a defined phase sequence: OPC-UA gateway installation and validation, historian integration and data quality validation, ERP integration go-live with parallel operation, and legacy integration decommission.
Zero production downtime was achieved by ensuring that no transition phase created a dependency on the new integration infrastructure for production continuity. The new systems ran in parallel with existing production workflows until validated; production systems were never dependent on the new integration layer being operational.
Documented Outcomes
All 14 sites were integrated within 9 months. Zero production hours were lost to the integration programme. ERP production scheduling accuracy improved from a baseline of 78% (measured as proportion of production orders completed within scheduled time window) to 91% in the six months following integration go-live, attributed to real-time production status visibility in the scheduling system.