March 2008

Cover story

Lather up with batch

Personal care manufacturer cleans up with new process control

Fast Forward

  • Competition in personal care brands pushes control system update.
  • Production changes, old batch system compromises quality.
  • Switch to scalable architecture process control reduces downtime 90%.
 
By Matthew Leys and Sean Cahill

Unilever knew the success of its personal care consumer goods brands rested on the quality performance of its health and beauty mixing plant and aerosols plant. Economic growth paired with sound environmental management were just part of the strategy. Yet a total process control system update would help guide them to down the road to success.

The North Rocks site in Sydney, Australia, is responsible for the manufacture of personal health and beauty products, aerosols, liquid detergents and cleaning products. With the market for fast-moving consumer goods being more competitive and cost sensitive than ever, maintaining optimal productivity and availability is critical to the future of every site. Manufacturing pressures on sourcing continue to increase. There is a significant need to improve the efficiency of the plant while at the same time to reduce costs. This is critical when looking to secure the long term viability of the plant.

Dirty downtime

Such pressures led Unilever to review the control strategy for North Rocks site in 2002. One particular area for improvement was downtime in the health and beauty mixing plant as well as variation in product quality. Bottlenecks were also restricting the overall throughput of the plant. 

The review revealed a need for standardization across the site to ensure existing and future operations personnel were fully conversant with the automation and operations environment. However, despite such compelling needs for change, there was a limited budget available.

Protecting investments

In the early 1990s, Unilever installed controllers with an HMI and batching system. Toward the end of the decade, the reliability of this mix, combined with changes in the product range, led to production problems due to its non-integrated nature and the need for manual intervention in the process. Such factors led to the decision to change their control strategy, so they switched to a process control system with a scalable architecture while using the existing I/O system. The I/O system "counts for a large portion of the capital outlay on a control system, with its life expectancy often exceeding that of the controller and HMI components," said Siemens' Daraius Battiwalla.

Faced with a limited budget, the company decided to develop the application code in-house with vendor support. This made sense not only to control the costs of the project, but to develop in-house expertise. It ensured they could confidently look beyond the health and beauty mixing project, and take a site-wide view for upgrades and standardization centered on the new control system.
 
Unilever also decided to use an ISA88-compliant batch engine to improve product consistency and reduce cycle times. As a relatively new product, the batch engine, as well as the need for ISA88 compliance, presented another set of challenges for Unilever engineers. But the batching system proved central to obtaining process improvements and ensuring compliance with Therapeutic Goods Administration requirements. Unilever was, however, looking well beyond current requirements and ensuring they implemented a solution that could handle future legislative change. They found the flexibility, traceability, and reporting power in the new process control system and batch engine were ideally suited to handle change. 

Ravishing returns

With a successful delivery within a 12-month time frame, the company moved to the next phase, upgrading the aerosols plant. Although the system was smaller than that of the health and beauty plant, it was presented with the challenge of only having a third of the time frame for completion. Again the manufacturer decided to deliver the project through its in-house engineering team. After developing expertise during the health and beauty project, confidence was high despite the challenging timescales. With standards developed from the first project, the team set to working on the aerosols project, buoyed by the knowledge that the process of design is fairly intuitive with the new control system. 

With another project delivered on time and within budget, Unilever is reaping the rewards of integrated process control and batch architectures. Not only does the company have a common operator environment across the two plants, with the benefit of reduced training costs, it also has seen a significant reduction in the time it takes to identify and resolve process problems. Another result is simplified reporting and the provision of live plant data to ERP systems, thus providing a higher degree of accurate process data for planning purposes. 

On examining significant returns on investment in the short time since implementation, the company found quality of the product has improved with the right-first-time figures, showing an increase in excess of 15%, plus a rise in overall mixing efficiency. The company has also seen a reduction in batch cycle times for shampoo, showing an improvement of 13% over the previous system. This demonstrates not only greater efficiency, but also provides the company with the opportunity to increase overall productivity.

Probably the most telling result from the move to the new system has been the dramatic improvement in plant availability. Unilever monitors all aspects of the processes rigorously to identify potential problems. Monitoring computer and control system downtime has provided an accurate assessment of the improvements since installing the new control system, which show a reduction in downtime approaching 90%.

Such returns have not only justified Unilever's original decision to go with the new system and the batch engine, but they have also given the company the confidence to expand the system into future areas. The most sensible way forward is to incorporate additional process equipment into the system-an approach which goes a long way to meeting the company's commitment to exceptional standards of performance.

ABOUT THE AUTHORS

Matthew Leys is a project engineer at the North Rocks site of Unilever Australia in Sydney. Sean Cahill is business development manager of process automation with Siemens Energy and Automation in Sydney, Australia. 

 

Return to flexible batch automation

By Michael Carey

The ISA88 standard is easy to comprehend, but gaining in-depth understanding is a long process that takes understanding process operation and software engineering. Tools that support the standard make implementing it easier, but without a firm understanding, you could end up with a system that is not optimized, not flexible, and difficult to maintain. Equipment modules are just one of those components of ISA88 that, if you implement correctly, work incredibly well. But if you implement it incorrectly, it can place a large burden on all parts of the system life cycle.

The purpose of the ISA88 standard is to provide a model for flexible batch automation. More batch manufacturers are implementing ISA88 in practice, using the artifacts of the standard-control modules, phases, recipes, and the like. But they overlook the purpose of the standard-batch flexibility. The major culprit is the proliferation of inter-unit valve matrices, implemented using equipment modules. Valve matrices are inflexible, make documentation more difficult to understand, and make maintenance more difficult.

Flexible batch manufacturing is the ability to make multiple products without having to reprogram the automation system or modify processing hardware (processing equipment or process piping). The product change-over (or adding new products) only requires a different recipe. The processing hardware first limits the flexibility of the system. But if you assume the processing hardware is flexible, that does not mean the software should be inflexible. You can achieve flexibility in the ISA88 model by designing phases that are general enough for reuse in multiple processing steps. The phases organize through recipes, which drive the manufacturing sequence. You can manufacture different products on the same process hardware without having to reprogram the controllers. The recipes dictate which equipment to use and how to use it. All manufacturing systems in initial design are flexible enough to manufacture the products they were designed for, but a truly flexible batch system is capable of manufacturing future products with minimal or no automation system programming. 

Quite a few batch automation implementations are inflexible because they implement valve matrices through equipment modules to control fluid flow paths. Valve matrix programming is a common PLC programming practice in which all valve commands copy as a block from a memory table to the valves based upon a step or sequence index.  

The equipment module design is inflexible because all the transfer routes are programmed in the controller and are not configured in the recipe. If you need to create a new path, you will need to update the controller code. To further muddy the water, if these lines require cleaning in place or steam in place it may not be possible to operate on the entire path. You will need to segment the path. Segmenting the paths creates new equipment module states, thus increasing the number of paths. The states themselves now become more complicated because you now have to identify the individual segments.

The problems with documentation and maintenance are similar in that the number of valves and the number of possible paths make the documentation difficult to work with. When maintaining the automation system, the documentation is critical because it details the states of all the valves for all the equipment module set points. The valve matrix required for this example requires 22 columns and 24 rows. If these lines require cleaning in place or steam in place as discussed above, assuming two segments per path, the number of rows increases to 53.  The large complex valve matrix makes reviewing and programming the sequence more difficult because only the equipment module set point, as a number, is identified. You'll need to cross reference the equipment module set point between the valve matrix and the piping and instrumentation diagram (P&ID) to identify not only the correct set of valves states for the path you are using but also to ensure all other valves are in the correct state. Cross referencing the process flow description or code to the valve matrix and P&ID makes document reviewing and troubleshooting difficult.

When ISA88 was a proposal, valve matrix equipment modules were not in vogue, and we individually actuated valves in the phase steps. The excessive use of valve matrix equipment modules seems to have come about recently as some control system vendors are providing equipment modules as software artifacts and PLC systems are being used more and more as distributed control systems. Contrary to most automation vendors who market their products as solutions, automation products are just components in the solution, not the solution in themselves. Thus the coupling of a conceptually easy to understand ISA88 standard and products that support it has created an atmosphere where we view the challenges of designing a flexible batch facility as the product not the experienced automation engineer's design. Just because products have features or previous control strategies functioned, does not mean it is wise to implement them. Thus valve matrices have no place in flexible batch automation.

ABOUT THE AUTHOR

Michael Carey is director of MES and information systems at Panacea Technologies Inc., an automation systems consulting firm in Fort Washington, Penn. Contact him at careym@panaceatech.com.

 

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