Solvent Plant Scrubs Aging Batch Control Systems
The small but powerful semiconductors in our smartphones and other devices can take several weeks and hundreds of steps to manufacture. During production, cleaning solvents are crucial to maintaining a high level of purity in these small and delicate microelectronics.
DuPont’s small-batch production facility in Hayward, California, makes semiconductor cleaning solvents in dozens of varieties. But the batch control systems used in the plant started showing their age in recent years.
The systems were no longer supported. They were also creating production issues, such as pop-up alerts that frustrated operators and alarms that were difficult to manage. More importantly, a customer audit found that the systems lacked recipe-based automation, which could help improve quality control in the production process.
The plant was faced with a choice: upgrade the legacy batch control systems, or stay with the status quo and lose thousands in monthly business. The plant moved forward with the upgrade. And in doing so, it did more than improve quality control – it also helped improve the plant’s throughput to create new monthly sales.
Old Systems Limit Operations
Most of the legacy control systems at the Hayward plant were manually operated. Only the bulk addition of material from a storage tank to a blend tank was automated.
Operators manually added all other materials using a drum-pumping station and solids-conveying station. Operators also set the timing for the materials to blend and circulate through filters, and took product samples. Once the desired product was achieved, operators manually sent it to the filling systems in the packaging area. Here, workers dispensed product into packages that ranged from small 1- and 5-gallon containers to large 200-gallon totes.
These manual processes introduced the potential for errors. For example, an operator might intend to mix a material for 15 minutes but end up mixing for 18 minutes while they carried out another task. Instances like these created the potential for slight product variations.
The legacy systems were also at times disruptive to production.
“The HMI was configured in a way that it generated a pop-up alert every time we opened or closed a valve,” said Nancy Givens, an automation and process control engineering consultant for DuPont. “If the operator wanted to open three valves, they’d get three pop-ups. This was frustrating for operators. And it created opportunities for errors. Cluttered interfaces could result in operators opening or closing the wrong valves.”
Alarms were another issue. The legacy systems used a mix of user-editable and hard-coded alarm setpoints. The hard-coded alarms were difficult to manage, with operators often struggling to locate specific code. The alarms also didn’t use modern alarming best practices, such as the ability to assign alarm priorities.
These issues – combined with the customer’s demand for greater quality control – necessitated a control-system upgrade.
Phase One: Controls Upgrade
Givens worked with system-integrator TechKnowsion and Rockwell Automation, a DuPont Global Alliance Supplier, to plan and execute the controls upgrade.
The team carried out the upgrade using a two-phased approach. In the first phase, they replaced the batch system’s PLC and HMI with a PlantPAx® distributed control system (DCS). This involved reverse engineering the legacy PLC’s code to determine the requirements for new control code.