Unilever Replaces an Old Water Softening Control System
Remember “Broken Telephone”? The game where everyone sits in a circle and one person whispers a phrase to the person next to them, who whispers it to the next, and so on and so on. The last person then says the phrase out loud and hilarity generally ensues. It’s amusing and even astonishing just how much the story changes as it makes its way around the room. And often, it no longer resembles the original version at all.
Replacing older control systems can seem like the dynamic that occurs during the game. The control system may have older, incomplete drawings, making it harder and less intuitive to follow. And many of those who operate the system do so with “hand-me-down” training or tribal knowledge obtained by deploying workarounds as the system ages. Parts of the system may have been programmed by a third party, a step that may or may not be known to the operators. And in many cases, the original programmer may no longer be available for consultation.
Unilever faced just such a challenge when they decided to replace and upgrade the PLC system in a critical water softening system at one of their facilities. The problems they faced were like the progression of the game. For the aging PLCs within the system, spares were no longer available. And even if exact replacements had been available, the technology they were built upon was obsolete, raising potential compatibility issues with other newer components required for the upgrade. Having experienced undocumented control software in the past, Unilever was determined to find a more consistent way for the system to operate long term.
Designing a Better Control System Story
With this daunting list of challenges in mind, Unilever turned to WonderLogix to upgrade its control system. To ensure that the new control system addressed these challenges, WonderLogix used an object oriented design software approach to the redesign of the system and for its re-integration with the mechanical and physical components.
First, they observed and learned the physical system to understand its functions. Using older drawings of the equipment and its components to augment their observations, they created a top-level process description and flow. With the old system, function, logic and connectivity were fragmented and tenuous. The WonderLogix approach allowed them to understand each phase of production and what programming would be required in a way that could be accurately coded and passed on and understood by those tasked with maintaining the system throughout the lifecycle of the system.
Second, they combined all the common equipment modules and grouped them into classes. WonderLogix defined the various inputs and outputs using Natural Language logic sentences with the Logic Editor within the platform. It also allowed for the creation of State Machines–whereby components of the system can have more than one state, but at any given moment only fulfills one of them, a function critical to a machine such as Unilever’s water softening system.
Third, with the desired control action accurately defined, WonderLogix was then tasked to use its Verify Model Logic feature to test the integrity of the entire logic system prior to actual installation. In this way, they were able to identify potential errors and correct them and see the model displayed graphically. This solution helped reduce a key Unilever concern over extended implementation and commission time.
Finally, the verified model was exported to a functional spec document which was then approved by Unilever. The specification document now serves as the reference document for future programming, all done within the WonderLogix platform and with the approved PLC program ready to run.
A Happy Ending
By designing the logic and programming model in advance with object oriented design principles, and by using the WonderLogix platform’s native Logic Editor and Verify Model Logic functionality, the new system was installed and online within two hours with no code changes required.
This approach benefitted Unilever in several ways:
- Using the Natural Language Logic Editor ensures that everyone over the life cycle of the system is using common understandable sentences to program any changes that are needed. This is not only safer, it allows for accurate repeatability across the system.
- With the development of well-defined and consistent classifications of common equipment, the system can be viewed as a whole rather than as a conglomeration of individual parts. By defining, mapping and planning the system as a whole, it reduces the tendency for programmers and technicians to work around an individual component. As PLCs become obsolete and newer iterations are available, use of the Natural Language Editor within the program will ensure that again, all aspects of the system are communicating in a uniform and standardized manner that optimizes machine performance.
- And finally, this approach meant that down time and recommissioning–a key concern for Unilever–was reduced significantly. This was not only a benefit in the present, it also allowed them to gain confidence in the ability of in-house staff to quickly and accurately deploy programming changes as needed in the future.
An object oriented software design approach, in conjunction with WonderLogix and its Natural Language capability, allows customers to use a holistic approach to programming complex control systems. This eliminates workarounds and confusing programming of individual components by untrained staff or by programmers unintentionally working at counter purpose with one another. And it allows for the programming of PLCs within the whole to tell a consistent “story” throughout the lifecycle of the system.