Both level (left) and pressure (right) are measured in the autoclave. Image Credit: VEGA
High levels of skill and intuition are necessary to produce lubricants, printing inks and industrial chemicals. Zeller+Gmelin ensures that every product leaving their production site in Eislingen, near Göppingen, is individually tailored to the customer. The medium-sized company puts great emphasis on holistic solutions. Therefore, research, development and production all come from a single source
VEGA has been a reliable partner with Zeller+Gmelin for 15 years, and is always available to answer questions concerning pressure and level measurement. Zeller+Gmelin uses almost 1,000 sensors, and almost all of them are visible via the VEGA Inventory System.
VEGA Inventory System
The VEGA Inventory System is a web-based software used for data acquisition and the visualization of level data. Not only does the software make inventory management possible, but the data can be processed further and used in ERP systems as well.
Zeller+Gmelin also imports said data directly into the SAP system. The data is transmitted directly from the sensor to the cloud. The supplier is then able to initiate the delivery of a product after processing the data, for example.
In one autoclave at Zeller + Gmelin, temperatures of up to 270 °C and pressures of up to 5.2 bar prevail. The apparatus can also contain strong acids or alkalis. Because the measuring instruments in contact with the process quickly reached their limits, an 80-GHz radar sensor was deployed instead, allowing measurement of the level through an inspection glass. Image Credit: VEGA
Returning to production, there are particularly adverse process conditions present in autoclave 3, with high temperatures of up to 270 °C, elevated pressure up to 5.2 bar, as well as the presence of strong acids or alkalis.
Almost any measuring instrument would be brought to its limits in these conditions. Soap is produced at this point in the process, and oil with organic acids and alkalis are filled into the autoclave and the mixture is stirred and heated under pressure. This happens until saponification occurs, and measurement in these conditions is made anything but simple.
When the going gets tough, level radar has to be able to measure through an inspection glass. Image Credit: VEGA
The cooking process generates turbulent surfaces, and the agitator causes interference from additional signals. Not only this, but build-up constantly forms on internal elements as well as on the inside walls of the vessel.
Additionally, the already difficult measuring situation is elevated further. Due to the internal conditions, an autoclave cannot be opened during an on-going process. But, VEGA offered a compelling solution for this challenging problem, proposing that it would be possible to measure the level in this vessel through an inspection glass instead.
VEGAPULS 64 Radar Sensors
In all other production processes, radar sensors with a measuring frequency of 26 GHz were mainly being used. But, due to the very challenging conditions in the autoclave, the automation team opted to try VEGAPULS 64, which measures with a frequency of 80 GHz. In particular, it's better focusing (by a factor of 3) and greater dynamics promised a lot.
On these tanks, vibrating level switches with WHG approval are used as overfill protection. Image Credit: VEGA
This is because a radar sensor requires a clear, high-quality level echo to measure the level correctly. The dynamic range of a radar sensor, i.e. the difference between the largest and smallest signal, determines which applications the sensor can be used in. The greater the dynamics, the wider the application range of the sensor and the higher the measurement certainty, and the VEGAPULS 64 has a very large dynamic range.
This is especially advantageous in situations when there is foam, condensate, build-up or an extremely turbulent product surface in the vessel, which is almost always the reality in an autoclave.
Only when there is high measurement certainty is reliable measurement made possible, and this certainty allows the level to be accurately measured even when it is very close to the bottom of the vessel, with an accuracy of +/- 1 mm.
The VEGAPULS 64 is optionally equipped with the plics concept, and Zeller+Gmelin has experienced first hand the additional operating convenience it provides. Zeller+Gmelin firmly believes that this standardized user interface built into VEGA instruments makes daily work much easier.
Advanced Sensor and Vibrating Level Switch
At the same time, VEGABAR 81 sensors monitor the pressure in the autoclave. For overfill protection, a VEGASWING 66 was installed, ensuring operation according to AwSV guidelines (systems for handling substances hazardous to water). This vibrating level switch is perfectly suited to extremes making it an ideal option for the high temperatures in autoclaves.
VEGASWING 66 has a patented inductive drive that actuates the tuning fork even under extreme temperatures, which is in contrast to conventional vibrating level switches. This allows the user to take advantage of the simple handling of vibrating level switches, but still have an extended application range of -196° to +450 °C and -1 to +160 bar.
In summary, the combination of VEGAPULS 64, VEGASWING 66 and VEGABAR 81 pressure transmitters has made measurement in Autoclave 3 100% safe and reliable. Zeller+Gmelin has worked alongside VEGA for many years and wholly appreciates the partner-like relationship between the two companies, particularly when solutions for highly challenging measuring points need to be found.
This information has been sourced, reviewed and adapted from materials provided by VEGA Grieshaber KG.
For more information on this source, please visit VEGA Grieshaber KG.