Nestlé saw the need to upgrade its infant formula production plant in Harrismith from a continuous mixing plant to a batching plant. The process involved a complete redesign on the mechanical and process installation. The result was a simplified structure that surpassed product efficiency and accuracy expectations.
The plant has one spray dryer and two continuous-dosing dry-mix lines feeding the two filling lines, which fill 400 g, 900 g and 1,8 kg cans. The two continuous dry-mix processes mixed the ingredients at a flow rate of 6 tons/hour with minimum buffer capacity between the dry mix and the filler. Each time the filler stopped for whatever reason, the dry-mix line also had to stop.
“In order to ensure the best quality product in the can, each time the dry-mix line started, we diverted the first 20 seconds of product to the rework hopper creating waste,” says Casper Naudé, project manager at Nestlé Harrismith. “With Nestlé’s continual drive to minimise waste, we decided to invest in two batch mixing lines where we can ensure that the prepared batch is within norm before we release the product into the mixer. This resulted in reducing the waste by at least 70% and improving the accuracy of our dosing rates.”
The need for change
Nestlé’s Harrismith plant has a track record of production excellence and efficiency and the company wanted to improve on these achievements by increasing efficiency and optimising production volume. This would need a redesign of the infant formula plant and the investigation of other techniques that would help the realisation of this goal. Nestlé decided to adopt the batch mixing model as this would not only help achieve the production objectives but would also offer an excellent opportunity to bring the Harrismith site in line with Nestlé’s global engineering strategy.
“The criterion was simple,” says Naudé. “The solution needed to comply with the global software standard defined by Nestlé’s Product Technology Centre because notably, we are the first Nestlé plant to implement this type of batching/mixing system worldwide, and the solution would need to be rolled out to numerous sites globally. Therefore the software needed to be well-structured and easy to follow.”
The scope of the project would include process control, recipe management and batch reporting.
Solution selection
Since Nestlé’s Global strategy is based on the Invensys Wonderware suite of solutions and the Harrismith plant had confidence in its existing Wonderware assets, it made sense to continue on that path. “Wonderware is able to provide a product offering for any production requirement and they come standard and backed by excellent support,” says Juan Le Roux, project manager at Convenient Software Solutions, the system integrator chosen by Nestlé for this project. “Nestlé Harrismith would also not be left vulnerable through a shortage of skills as most system integrators are familiar with the Wonderware range and backed by an expert call centre.”
The Wonderware solutions used included System Platform (based on ArchestrA technology and including Application Server), InTouch (Scada/HMI), Historian Client, Historian and Information Server. Application Server is well known for its flexibility and scalability and this would serve Nestlé well since this project was regarded as the first phase of many future initiatives.
“The Application Server Galaxy Repository would provide a central point of configuration, making the maintenance of standards through Application Server much less costly and time-consuming than it would otherwise be,” adds Le Roux. “ArchestrA’s redundancy feature would ensure that production would never be interrupted because of a planned or unplanned event.”
Implementation
As there are two production lines, Nestlé was in a position to run full production on one line while the other was dismantled and rebuilt. The project took one year for each line.
“In a project of this magnitude, it is most important to include everyone involved right from the start,” says Le Roux. “It is easy for a developer to conceptualise a solution, but without consulting the operators and supervisors of the line, it is difficult to arrive at the optimum solution.”
The project was required to follow Nestlé’s strict implementation process. First the proof of concept needed to be passed with the mechanical equipment. Once the OK was given, a complete system FAT was carried out over a two week period. Thereafter, a number of dry runs were done to ensure system reliability followed by a number of trial batches which were sent to the Nestlé laboratories for analysis. The results came back better than expected and the go-ahead was given to start production batches.
“What was particularly challenging was working with a project design team in a foreign country while developing the software locally and implementing new global standards,” says Le Roux. “But in a way this was also one of the most outstanding aspects of this project because we felt part of a global community that would be able to reuse these standards over and over again with little effort.” Redundant Application Object Servers were installed and the load sharing was optimised for each line so as not to overwork one server while the other is idle waiting for an exceptional event. Currently the Wonderware InTouch Recipe Manager is used but this is only a stepping stone as the end goal is to move this to the MES environment.
Reporting is achieved in one of three ways:
* Expert analysis by means of Historian Client.
* Custom production reports using Microsoft Excel and VBA scripting.
* Quick and detailed reports by means of Information Server which can be accessed from any workstation.
“Previously, both lines were dependent on a single PLC”, says Le Roux. “In the new implementation, each line has its own PLC so that maintenance can be carried out on one line without affecting the other. Another advantage is that, should another identical line be installed, the logic can be duplicated with little effort, as was the requirement from Nestlé Global Engineering.”
Nestlé has developed an application (Nestlé Engineering Automation Toolbox or NEAT) for object modelling and creation which forces adherence to the Nestlé global standard as well as to the ISA-88 international model. Use of the application also means that PLC control modules and shell logic are built automatically as are the ArchestrA models and objects. New revisions of this tool are rolled out regularly and upgrading to the new version is painless and does not affect legacy code.
With regard to alarms, a decision was taken not to clutter screens with pop-ups and alarms. An alarm object was created to explicitly declare each alarm. This allowed for the easy addition of alarms as well as housekeeping should alarms become redundant. The entire process network is on one intranet allowing engineers to initiate and complete a task from any workstation.
Provision was made for the future integration of MDT’s AutoSave change management solution with the batch management system. This will be used for the automatic tracking and logging of all PLC, HMI/SCADA and Application Server software changes. AutoSave will also provide Nestlé with a comprehensive software change audit trail and the ability to recover from any software malfunction by instantly installing and running a previous working version.
Benefits
Improved dosing accuracy – in the past Nestlé Harrismith produced products at 90% dosing accuracy. Today this has been increased to more than 99%.
* Production efficiency improved by 100%.
* Reduction in rework – reduced by 70%.
* 50% reduction in downtime.
* Increased production volume and quality.
* Current Software conforms to Nestlé’s global standard.
* Simplified solution – easily understood by all concerned.
* ‘Cut-and-paste’ site made possible.
Conclusion
At Nestlé Harrismith, high quality product is now par for the course. The reliable batching system has minimised the negative effects of human error on quality. With a reliable batch server and a well-designed batch model, recipes can now be optimised for the benefit of the plant while increasing production and cost efficiencies.
“In my opinion, the most impressive aspect of this project was the improvement in dosing accuracy,” says Naudé. “Also, the Nestlé global standard combined with Wonderware’s best practices have resulted in a simplified, easy–to-understand methodology that is simple to follow by everyone concerned.”
For more information contact Jaco Markwat, Invensys Operations Management, +27 (0)11 607 8100, [email protected], www.iom.invensys.co.za
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