The line ran Monday to Friday across two shifts and filled to order. There was no shutdown available inside the financial year and there was no second line to move volume to. What there was: fifty-two weekends, of which the plant would give us six.The line ran Monday to Friday across two shifts and filled to order. There was no shutdown available inside the financial year and there was no second line to move volume to. What there was: fifty-two weekends, of which the plant would give us six.

The existing controller had been out of support for four years. The plant held two spare CPUs and neither had been powered up since 2019. The risk was not that the retrofit was urgent, it was that an unplanned failure would take the line down for as long as it took to find hardware on the secondary market, which at the time was quoted at eleven weeks.The existing controller had been out of support for four years. The plant held two spare CPUs and neither had been powered up since 2019. The risk was not that the retrofit was urgent, it was that an unplanned failure would take the line down for as long as it took to find hardware on the secondary market, which at the time was quoted at eleven weeks.

Every weekend had a point, agreed in advance and written on the plan, after which we stopped adding and started restoring. If the new arrangement was not proven by that point, the old one went back and Monday ran as normal. We used that reversal twice out of six. Both times it was the right call and neither cost a single hour of production.Every weekend had a point, agreed in advance and written on the plan, after which we stopped adding and started restoring. If the new arrangement was not proven by that point, the old one went back and Monday ran as normal. We used that reversal twice out of six. Both times it was the right call and neither cost a single hour of production.

Weekend one: new panel installed alongside the old, both powered, nothing switched. Weekends two and three: field devices moved section by section, each section proven on the new controller before the next was touched. Weekend four: reversal, after a drive fault that turned out to be a parameter set nobody had documented. Weekend five: the same section, completed. Weekend six: the remaining sections, the HMI cutover and a full production run before Monday.Weekend one: new panel installed alongside the old, both powered, nothing switched. Weekends two and three: field devices moved section by section, each section proven on the new controller before the next was touched. Weekend four: reversal, after a drive fault that turned out to be a parameter set nobody had documented. Weekend five: the same section, completed. Weekend six: the remaining sections, the HMI cutover and a full production run before Monday.

We surveyed the field wiring from the as-built drawings and lost most of weekend four to the difference between those drawings and the panel. Two days of tracing before the first weekend would have paid for itself four times over. On every live retrofit since, that survey is a line item, and clients who query it get shown this job.We surveyed the field wiring from the as-built drawings and lost most of weekend four to the difference between those drawings and the panel. Two days of tracing before the first weekend would have paid for itself four times over. On every live retrofit since, that survey is a line item, and clients who query it get shown this job.

Zero unplanned downtime attributable to the migration. The line came back to rate on the first Monday after cutover. The plant now holds a documented drawing set for a panel that, before this, existed only in the memory of one contractor who had retired.Zero unplanned downtime attributable to the migration. The line came back to rate on the first Monday after cutover. The plant now holds a documented drawing set for a panel that, before this, existed only in the memory of one contractor who had retired.