Benefits at a Lower Cost - The downturn of global economy has not reduced the need for investing in process automation. It has, however, prompted creative thinking. The value and quality of devices that would have been scrapped just a few years ago is now thoroughly evaluated. In some cases it turns out that all the benefits of a fully automated system can be obtained at lower efforts and lower costs, simply by upgrading of process instrumentation devices already in use. BASF in Ballerup in Denmark has tested the concept and reduced their need for manpower. 

Close Monitoring Required

At the BASF plant in Ballerup, Denmark, two production lines have recently been automated. The plant microencapsulates vitamins for use in the food and beverage industry. During the manufacturing process, nature identical vitamin oil is mixed with antioxidants in an oil vessel. When the ingredients have been mixed, the oil is dosed into two spray vessels and is microencapsulated in a sugar-gelatin solution through an emulsion process. The oil flow between the oil vessel and the two spray vessels is measured by use of two Coriolis mass flow meters from Siemens. Then the microencapsulated solution is dried in a traditional spray drying plant in a spray vessel.

Before the automation of the lines was implemented, an operator had to continuously monitor and control the oil flow from the oil vessel to the spray vessels. This was the only way to ensure that the flow velocity was not too high for the spray vessel and that the dosing was correct. Because the BASF requirements for precision and traceability are very high, it is required that the amount of oil pumped into each vessel is exactly the same. Previously, this was a manual operation, and the process therefore required close monitoring and control to ensure that the two spray vessels reached the same filling quantities at exactly the same time.

Reduced Need For Manpower

Out of the box thinking and a continuous dialogue with the operators about possible improved solutions for the process, made Bo Kilund, project manager for the automation of the two lines, come to a new and unconventional conclusion. The right - and most cost-effective - solution would keep the existing flow sensors but upgrade them with new transmitters and thereby achieving all the benefits of an automated process.

Today, the two Coriolis mass flow meters from Siemens still measure the flow of oil from the oil vessel to the spray vessels, while the need for manpower has been significantly reduced, since manual process control is no longer required. "When we start an oil dosing process, the operator selects the required pump velocity and the maximum flow rate," Kilund explained. "If the flow exceeds the maximum flow rate, the pump velocity is automatically reduced by 1 % every five seconds until the maximum flow rate is no longer exceeded. The operator does not have to monitor the process any longer." As a consequence, the need for manpower has been significantly reduced, while the requirements to quality, precision and traceability are continuously met.

Insignificant Difference

"When we are dosing oil to the two spray vessels simultaneously, the programming of the system is somewhat complex, but the only additional matter the operators have to do is to enter the maximum allowed amount of oil into each spray vessel," Kilund said. When the process is started, the new transmitters continuously transfer the actual flow rate and the total amount of oil being dosed to each of the two spray vessels to the PLC.

The program sequence has a fast and a slow mode, which ensures that the amount of oil dosed to the two spray vessels is exactly the same. In the fast mode, the oil is dosed with maximum flow rate and an allowed total difference between the two vessels of up to 4 kg. If this difference is exceeded, the system automatically stops dosing to the spray vessel with the highest totalized amount of oil, and will not restart until the filling quantities are the same. When the amount of oil in the oil vessel reaches 50 kg, the slow mode is started. In this mode the difference between the two spray vessels must not exceed 1 kg. "We always end up with an insignificant difference between the two spray vessels - and that is quite an achievement as the initial amount of oil in the oil vessel lies between 1,200 and 1,400 kg. What is more important is that we have released resources to other tasks. If any of the dosing parameters are exceeded, the system will send out an alarm message."

State-Of-The-Art System Integration

The operators do not stand next to the line monitoring flow velocity and dosing anymore, as the process has been fully automated. Additionally, it even turned out that the replacement of the old transmitters was a piece of cake.

"Terminals and sensors were the same, and even the wiring was the same as before, so we simply replaced one transmitter by another one," Kilund said. The reason behind the easy replacement is the memory unit technology, storing all sensor specific data in a Sensorprom. When the transmitters were replaced, the Sensorprom memory units were simply moved from the old transmitter to the new one and all sensor specific data thus transferred to the new transmitter. As a result, sensor recalibration was avoided without any loss of accuracy. With all sensor specific data quickly and easily transferred to the new transmitter, programming was made easier. The new transmitters are of the type Siflow FC070 and fully integrated in the Simatic S7 automation system via an ET200M Profibus node.

At a size of no more than 40 mm, Siflow FC070 perfectly matches the well renowned Simatic design features. An even more important improvement is the fact that the users of Siflow FC070 are experiencing the same interface consistency available in the full scale and depth of Siemens instrumentation and control systems. With the fully integrated diagnosing system and the detailed traceability of the dosing process, the operators' possibilities of tracking and resolving any problems that might occur have been enhanced. In this way, BASF has moved from an analog to a digital state-of-the-art solution and reduced the need for manpower, without having to replace the Coriolis flow sensors. On top of this, Kilund estimates that BASF only uses about 10 % of the potential benefits of Siflow FC070.