A complex mass of plumbing makes up Streets’ processing equipment.
Manufacturing ice cream is a precise and delicate process, requiring tight control to ensure the quality of the final product. The only way to achieve this is through the use of leading technology, like the PCS7 process control solution from Siemens.
The ice cream manufacturing process begins by blending milk and sugar, then adding colours and flavours. The ingredients are then blended further and pasteurised to purify the mix undergoing a homogenising process that breaks down the milk fat to provide a creamy, smooth blend.
The purpose-built Minto plant comprises two main batching tanks, a pasteuriser, homogeniser and more than 30 storage tanks, all connected by a network of pipes. The largest of the storage tanks can hold 12,000 litres of liquid ice cream, while overall the mix plant at the heart of operation produces up to 18,000 kg of mix per hour at full production.
A recipe for success
Although the Minto plant met the demands of consumers during the 12 years since its opening, the plant’s old control system had become increasingly problematic. According to Street’s mix plant manager, Graham Haigh, the aging control system was causing significant problems to the manufacturing process.
"There were issues which the old control system was incapable of helping us to resolve. Also, it was not uncommon for operators to return from their Christmas break only to be faced with a range of issues before they could restart production. This was not only frustrating for the operators but extremely costly for the company," he said.
Having reached breaking point, a decision was made to replace the obsolete control system with a new generation one. Streets embarked on a meticulous evaluation process over many months to clearly identify its plant’s requirements and expectations for the control system platform.
Siemens SIMATIC PCS 7 process control system and its recipe management system SIMATIC Batch was eventually selected, being identified as the system most capable of meeting the stringent demands of the mix plant.
As the Streets plant must produce a wide variety of ice cream blends to meet the requirements of the company’s portfolio, a flexible recipe system was critical. Siemens SIMATIC Batch met this requirement effectively while ensuring product quality and consistency demands were addressed. However, what really convinced Streets was the positive experiences of its sister plant at North Rocks, NSW, which used the same technology.
Unilever North Rocks had installed SIMATIC PCS 7 and SIMATIC Batch on its Health and Beauty and Aerosols plants several years prior. As such, Unilever was in a good position to offer invaluable advice to Streets.
Once a platform was selected, the next major challenge was scheduling a suitable window to switch over. It was a crucial decision with peak demand just around the corner, but with the old system continuing to be temperamental it had to be done.
A smooth, productive outcome
Without any possibility of delaying the upgrade further, system programming began with the goal of full system switchover within six months.
Two engineers worked full-time on the project with occasional support from North Rocks. By July, they were well advanced and in a position to perform early I/O tests.
According to Streets Controls Engineer Ben Pi, a critical part of this success was due to the use of Profibus for the connection of field I/O, which he describes as: "The most flexible and robust network I have ever used."
As peak season and switchover approached, it was still a nervous time for Streets, even though progress so far had been positive. The switchover went smoothly and the first batch of ice cream was produced within four days.
As production ramped up to meet the demands of the summer, minor tweaks to improve the system’s performance continued. Issues with the CIP and pasteuriser were easily addressed with the aid of PCS 7 as was the need to keep production at full capacity to meet the unexpected increase in demand.
Mr Pi reinforced the benefits of performing changes while the plant was running without any detrimental effects to production. "PCS 7 makes it simple to identify areas where the process can be improved and we are continually benefitting from this," he said."
The productivity reward for adhering to the original project timescales and achieving a swift change-over would be revealed in coming months. Record high temperatures were experienced in many states and Streets had to increase its output tonnage by nearly 60% to cope with the increased demand, something that the old system would have been incapable of meeting.
Haigh said there had been many unexpected benefits associated with the switch to the SIMATIC PCS7 and SIMATIC Batch aside from being able to meet the massive increase in demand.
"There has been an increase in yield of over five percent. Also, I now have access to real time data for the first time which means that I am fully informed when attending production meetings.
"With such a clear picture of what is happening, it makes it much easier to adapt production to meet new demands or to identify areas for improvement. In fact, the information at hand is now so complete that we are able to use it as the basis for forward planning for the business as a whole."
Looking to the future, Mr Pi has become reinvigorated since using SIMATIC PCS 7 for the first time. Not content with a successful implementation, he is focused on continually adapting the system to make the mix plant as efficient as possible.
"We are already noticing dramatic improvements in product quality and traceability. Our next step is to integrate more intelligent devices to provide greater diagnostic information. This will allow us to perform predictive maintenance and to monitor equipment efficiency as well as looking to further integrate the system into our ERP systems for greater reporting and scheduling."