SLC 500 to CompactLogix Churn Upgrade
Obsolete SLC 500 controls replaced proactively, cutting spares costs by around a third.
Scope & approach
Bulla's ice cream churns ran on Allen-Bradley SLC 500 PLCs and I/O that were approaching obsolescence, with spares getting harder to source. The churns are central to production, so a controller failure would have meant an unplanned stop on a core line rather than a peripheral inconvenience. Bulla chose to upgrade before that happened, replacing the SLC 500 controls on two churns with CompactLogix PLCs, I/O and new HMIs. Metromotion Controls delivered the SLC 500 upgrade as a hybrid migration: existing control logic was ported across rather than rewritten from scratch to keep the project cost-effective, then simplified and commented so the code would be easier to navigate and maintain going forward. The two churns are functionally identical but differ in some internal detail, so each line was engineered separately rather than treated as a single duplicate job. The upgrade also extended to the recipe management system, increasing the number of recipes it could store and bringing its logic in line with how the plant actually runs the churns day to day. The full migration, cutover and commissioning were completed within a single one-week shutdown window.
What was delivered
- Two churns central to Bulla's ice cream production were moved off obsolete SLC 500 controls proactively, before a failure could force an unplanned shutdown.
- A hybrid migration approach ported and simplified the existing control logic rather than rewriting it, keeping the upgrade cost-effective while making the code easier to navigate for ongoing maintenance.
- Spares holding costs fell by around a third under the CompactLogix platform compared to sourcing parts for the obsolete SLC 500 system.
- Recipe management was upgraded to store more recipes and to match how the plant actually operates the churns, rather than the structure inherited from the original build.
- The full migration, cutover and commissioning across both churns was completed inside a single one-week shutdown.
Scope items
- Migration of two SLC 500 PLC and I/O platforms to CompactLogix, including new HMIs
- Hybrid logic migration: existing control code ported across and simplified, with added commenting for maintainability
- Separate engineering for each churn to account for internal differences between the two otherwise identical lines
- Recipe management upgrade supporting a greater number of stored recipes, aligned to actual plant operation
- Commissioning support across a one-week shutdown window, including assistance with refrigeration system issues that surfaced during cutover
Services and sectors behind this work
Automation upgrades and retrofits
Modernise legacy PLC, SCADA, HMI and control infrastructure with staged cutover planning.
PLC programming Melbourne
PLC programming, troubleshooting, commissioning and legacy migration for Melbourne production sites.
Dairy processing automation Australia
Controls for yoghurt and cheese plants, milk receival, pasteurisation, CIP and production reporting.
Tibaldi automated inventory management
Automated inventory tracking integrated with production controls for real-time stock visibility and traceability.
Reliable plant data
The right tag for each count and one meaning for each state, validated against the line and placed in context.
SLC 500 and PLC-5 end-of-life upgrades
Upgrading SLC 500 and PLC-5 systems to CompactLogix and ControlLogix: routes, code conversion, HMIs and the Bulla churn case study.
Legacy PLC migration planning
Planning an upgrade without losing production on a live Australian manufacturing site.
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