Increased demand for the company’s fresh and long life milk, juices and powder-based products as well as the high volumes processed at the Port Elizabeth facility of Parmalat, one of South Africa’s largest producers of dairy products, created a need for a fully automated milk reception and handling system that would improve quality and efficiency while reducing product losses. Process Dynamics, a Siemens certified systems integrator with extensive experience in the food and beverage industry, was chosen by Parmalat to implement the SIMATIC PCS 7-based process control system, a prime example of the totally integrated automation (TIA) concept from Siemens.
Continuous operation and production
The system design includes four milk reception bays, four new raw milk silos, six pasteurised milk silos, 400 automated valves, 28 product pumps/agitators and various instruments including flow, level, temperature and pressure transmitters. An extra cleaning in position (CIP) station also formed part of the system to cater for the wash-down of the new equipment.
The four milk reception bays unload a milk tanker into one of four 120/150 cubic metre raw milk storage tanks, from here the milk is transferred for production to one of three pasteurisers. The pasteurisers produce milk for any one of nine destinations, including six pasteurised milk silos, sterilising, powder and custard manufacturing. Routes can be checked and interlocked to prevent product losses and product mixing. Continuous operation and production is ensured while certain plant sections are cleaned, further route management and interlocking of select processes has also been implemented.
A new foundation
By selecting SIMATIC PCS 7 for the plant, Parmalat has laid a new foundation for software and hardware standardisation. PCS 7 provides maximum flexibility, alarming and historical archiving, while at the same time reducing the engineering and software development required. Although the PCS 7 library was customised to suit Parmalat’s requirements, the use of standard PCS 7 functionality reduced engineering time considerably and also ensured seamless integration and changeover to the new system. The PCS 7 standard library and simulation ability also allowed testing of all sequences and routes before implementation and this has reduced the risk of possible production stoppages and losses.
The object-based engineering environment of PCS 7 with its high level intuitive graphical editors integrates the configuration of all control components employed at the different levels and uses an integrated database. As a result integration is achieved for all intelligent field devices, I/O stations, field networks, automation systems, control networks and operator stations.
Reduced installation and commissioning costs
The Parmalat plant is controlled by a single PCS 7 AS 416-2 Automation System. The connection to the process is achieved via various open standard field networks, namely Profibus DP (process field bus for distributed peripherals), Profibus PA (process field bus for process automation), and AS-i (actuator sensor interface bus). By using these open standards it was also possible to integrate third party equipment on Profibus PA (field instruments) and AS-i (DP/AS-i gateways). Using AS-i bus for the valves and Profibus PA for all instruments significantly reduced the installation and commissioning times and hence the overall costs.
The single operator station (OS) is connected to the automation system (AS) via industrial Ethernet. This single station OS can easily be expanded into a redundant server/client architecture for future plant extensions. A central engineering station (ES) is also connected to the AS and OS via industrial Ethernet.
Since quality is one of Parmalat’s main focus areas, the four new milk reception bays require a system to capture tanker and laboratory data for Parmalat’s historical and quality control systems. By using Siemens HMI panels the operator can capture the required information prior to unloading a tanker. The data is then stored in the control system’s historical archive for future reference.
While the individual plant equipment (eg, pumps, valves, indicators and PID controllers) is controlled by blocks from a project function block library, which are parameterised and connected in continuous function charts (CFC), the complex sequencing and route control is realised through the user friendly sequential function charts (SFC) with automatically generated detailed operator faceplates (SFC visualisation). The CFC and SFC interact seamlessly with one another and automatically produce the visualisation for the operator by means of icons, faceplates, events, alarm messages and tag logs.
By making use of tested and proven software, referred to as process tag types, the number of programming errors was reduced to a minimum. There was also a significant reduction in time required for engineering, factory acceptance testing, site acceptance testing and commissioning. Similar benefits will be apparent during plant operation in respect of plant and system maintenance and change management.
For more information contact Keshin Govender, Siemens Southern Africa, +27 (0)11 652 2412, [email protected], www.siemens.co.za or Process Dynamics, +27 (0)11 394 5412, [email protected], www.process-dynamics.co.za
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