Control Systems

New Batch Control System Boosts Solvent Plant

Upgrading obsolete controls helps improve quality control and throughput

By Nancy Givens, DuPont

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 play a crucial role in maintaining a high level of purity in these small and delicate microelectronics.

DuPont’s small-batch production facility in Hayward, Calif., makes semiconductor cleaning solvents in dozens of varieties. Unfortunately, the batch control systems used in the plant started showing their age in recent years.

The systems no longer were supported. They also were creating production issues, such as pop-up alerts that frustrated operators and alarms that were difficult to manage. More importantly, a customer audit found the systems lacked recipe-based automation that could help improve quality control in the production process.

The plant faced a choice: replace the legacy batch control systems, or stay with the status quo and lose thousands of dollars in monthly business. The plant moved forward with the upgrade. In doing so, it not only improved quality control but also helped raise plant throughput to create new monthly sales.

Limitations Of Existing Systems

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 1- and 5-gal containers to 200-gal 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 because of the need to carry out another task. Instances like these created the potential for slight product variations.

The legacy systems also at times disrupted production.

The human/machine interface (HMI) was configured in such a way that a pop-up alert appeared every time a valve was opened or closed. If an operator opened three valves, three alerts would pop up. This frustrated the operators. Even worse, it created opportunities for errors because the cluttered interfaces could result in opening or closing the wrong valves.

Alarms were another issue. The legacy systems used a mix of hard-coded and user-editable 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 priorities.

These issues — combined with the customer’s demand for greater quality control — necessitated a control system upgrade.

Phase One: Controls Upgrade

The company 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, which ran from January through late summer 2015, they replaced the batch system’s programmable logic controller (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.

DuPont didn’t want just to duplicate or convert the code. So, during May and June of 2015, the team went back to the functional requirements of the system to significantly clean up and improve the code. The code then was incorporated into the PlantPAx-based process objects library, which has been customized over the years to DuPont’s specific needs.

The control system’s new HMI used modern visualization practices to give operators a better viewing experience.

The legacy HMI employed multiple colors that could create cluttered screens. The new grayscale HMI highlights items in red to alert operators to critical issues. Since implementing the new HMI, spot checks have shown that the operators now always know where to pay attention — without missing a thing.

Phase Two: Batch Automation

In phase two, which took place from January to July 2016, the Rockwell Automation global solutions team worked directly with DuPont to configure and install FactoryTalk Batch software to achieve full recipe control and sequential automation.

The DuPont team wanted to follow the ISA S88 standard that lays out the framework for implementing batch systems. This required Rockwell Automation first to build a physical model of the production equipment and then to create a procedural model of the automated manufacturing phases. These phases then serve as building blocks for use whenever needed in different recipes.

Phase management features within the batch software allowed DuPont to explicitly follow the S88 standard. This saved significant time. The team only had to configure a phase, such as mixing or addition, once. It then could be reused multiple times — a much more efficient process than creating new code for each recipe.

The team also utilized the batch software for manual processes such as sampling and recipe reviews. The software provides manual phases that integrate with automated phases to give users a seamless operating experience between the two. This feature is easier and smoother to implement than writing manual-process code in the controller.

Finally, the team worked with Rockwell Automation to install the software for tracking materials in the plant’s storage tanks. The software replaced a paper-based logging system that required manual inventory tracking.

It also incorporates automatic tank switching. Previously, if a tank ran out of material during an addition phase, operators had to track how much material was added and calculate the remaining amount needed from the tank. Now, the software automatically determines the remaining amount of material necessary, switches tanks, and adds the required amount of material until it reaches the setpoint.

A Big Boost To The Bottom Line

The new automated system was implemented in one week, all during scheduled downtime.

The upgrade took the plant from obsolete to fully supported platforms. In addition, the new HMI resolved the pop-up and alarm-management issues that had frustrated operators.

The Rockwell Automation library of process objects cut design, configuration and deployment time. In fact, I reckon the library helped trim programming configuration time by 40%. Even today, with the new system up and running, the library continues to provide efficiency savings.

The library also helps during maintenance and troubleshooting. If the team wants to change a description, they don’t have to go into an engineering workstation or programing software. Instead, the change can be made right in the HMI using the faceplates. When troubleshooting, say, when a valve won’t open, an operator just needs to access the appropriate faceplate and then click on an interlock icon to see what’s wrong. In the past, the operator might have had to configure a screen to see the valve interlocks or sift through paper documents to troubleshoot the issue. Now, the answer is just a couple clicks away.

Meanwhile, the batch software took the plant from very limited automation to full batch automation, including automated cleaning processes. This helped achieve the level of quality control that DuPont’s customer wanted. In addition, after modifying the software to improve coordination between the different production units, the plant saw a significant boost in throughput.

The plant is working to expand the project to other areas. This includes replacing the plant’s legacy input/output, putting in an Ethernet network and automating some portable tanks that still use manual processes. This should deliver additional efficiencies and productivity on top of what the plant already has achieved.


 

NANCY GIVENS is an Atlanta-based automation and process control engineering consultant for DuPont. Email her at Nancy.H.Givens@dupont.com.