The migration programme was to take place over three non-co-located mixing lines that feed a significant part of the end user’s plant. At the actual mixing stations, it comprised the replacement of Allen-Bradley® PLC-5® controllers and ageing Allen Bradley 1784-T30C Plant Floor Terminals with Allen-Bradley ControlLogix® programmable automation controllers (PAC) and SCADA systems with FactoryTalk® Batch clients feeding off a modern server-based batch management solution.
According to Mark Lane at Optima Control Solutions: “To maximise system availability we designed and deployed an EtherNet/IP™ device level ring connecting the ControlLogix PAC on each of the mixing lines in a robust factory level network with the Batch server.
An additional Batch server was configured as a backup server. Each mixing line has a Rockwell Automation integrated-display computer running FactoryTalk® View Site Edition (SE) supervisory-level HMI software with a Batch client accessed via an ActiveX. The local PCs are used to select and start recipes on the Batch server. Batch then dictates the quantities of each ingredient and the sequence of mixing operations.
“In operation, the central server loads the recipe and batch data to the controllers and the controllers manage the mixing process,” he continues. “Thanks to the EtherNet/IP network, The Connected Enterprise solutions feeds these process-specific parameters back to the servers – and to the company’s SAP system – for logging, quality control and historical analysis. Another interlinked controller was used on the bulk feed stem too.”
Optima Control Solutions also implemented the Batch solution in accordance with S88 standards as requested on the functional design specification. Recipes are executed from the FactoryTalk® Batch software and the operations required to make product are broken down into phases and allocated to equipment modules. When executing a recipe, multiple phases can execute simultaneously on different modules.
The recipes that are used also follow the principles of S88, with each product requiring a Master recipe, which can only be created by authorised personnel. These Master recipes act as templates to create individual batches. To produce a batch, a control recipe is created from the relevant Master recipe and can be adjusted as necessary to create the batch.
“When we developed the first of the systems,” Mark Turner, Engineering Director at Optima Control Solutions explains, “the intention was to fully utilise the features of FactoryTalk Batch so it would create a batch record of each control recipe, storing time-stamped default and user-specified information about the batch as it is made. Typically with these systems a new batch would be created and then started for each mix of product.”
However, the customer operates its mixing differently. The customer requirement is for a recipe to be selected, a batch created and started and then the recipe steps in this batch to be repeated continuously until the operator selects that the recipe should end. Optima Control Solutions was able to use the FactoryTalk Batch software to achieve the same workflow, which was the biscuit manufacturer’s top priority.
"We have significant experience of these sorts of upgrades and were able to bring this experience into this job. The conversion process itself is made immeasurably easier thanks to the migration solution Rockwell Automation has developed. These include a swing-arm wiring conversion system, developed to help users migrate from legacy PLC solutions to modern Allen-Bradley® ControlLogix® controllers. Test and commissioning of the system took place over several weekends to fit around the needs of production. On each Saturday morning we removed the PLC5 rack and replaced it with the ControlLogix rack, and swing arm adapter kit. Then, on the Sunday evening we reversed the process, leaving the PLC5 in control, so that production could continue. Using the conversion kit this change-over was completed in less than 45 minutes.”
The swing-arm adapter solution from Rockwell Automation not only makes migration projects easier, but thanks to conversion modules, it also makes them less prone to error through the reuse of existing wiring. It is also quicker – in a rack containing ten 32-I/O module slots, savings in the range of 10 hours per rack are not unheard of.