Both level (left) and pressure (right) are measured in the autoclave.
Runs Like Clockwork
A lot of intuition and skill is required in the production of printing inks, industrial chemicals, and lubricants. Each of the products leaving the Zeller+Gmelin production site – located in Eislingen, close to Göppingen – is specifically tailored to customer requirements. This company is medium-sized, and focuses specifically on holistic solutions. Consequently, it offers research, development, and production all from one source.
In one of Zeller+Gmelin’s autoclaves, pressures reaching 5.2 bar and temperatures as high as 270 °C prevail. Strong acids and alkalis can also be contained within the apparatus. An 80 GHz radar sensor was deployed as the measuring instruments in contact with the process reached their limits quickly. This allowed the level to be measured using an inspection glass.
VEGA: A Reliable Partner on Level Measurement and Pressure
For 15 years, VEGA has been on hand as a reliable partner to Zeller+Gmelin, always answering questions about level measurement and pressure. At Zeller+Gmelin, almost 1,000 sensors are used. Using VEGA’s Inventory System – a web-based software which is used for the visualization of level data and data acquisition - nearly all of these are visible. Not just inventory management is made possible by this. These data can also be processed further and used in ERP systems.
The data is also imported directly into the SAP system by Zeller+Gmelin. The data is processed by the supplier after being transmitted from the sensor directly to the cloud. The supplier can then, for instance, initiate the product’s delivery.
In the realm of production, particularly adverse process conditions are present in autoclave 3. These include high pressures of as much as 5.2 bar, elevated temperatures reaching as high as 270 °C, and the presence of strong alkalis or acids. All of these factors test the limits of almost any measuring instrument.
Soap is produced at this point in the process. Oil which contains organic alkalis and acid is filled into the autoclave. Inside the autoclave, the mixture is heated under pressure and stirred until saponification occurs.
As a result of these and other factors, measurement is not easy. Turbulent surfaces are generated by the cooking process, and interfering signals are caused by the agitator. Furthermore, build-up forms constantly on internals as well as the inside walls of the vessel.
Radar Level Measurement
In addition, the tricky measuring situation is exacerbated by the issue that, as a result of the internal conditions, it is not possible to open an autoclave during an ongoing process. But VEGA had a convincing proposal for this as well: simply measure the level in this vessel through an inspection glass.
Radar sensors which have a measuring frequency of 26 GHz are usually used in all other production processes. However, the automation team made the decision to sample VEGAPULS 64, as a result of the inhospitable conditions inside the autoclave.
This measures with a frequency of 80 GHz, and due to its superior focusing (by a factor of 3) and greater dynamics in particular, it promised a great deal.
When the going gets tough, level radar has to be able to measure through an inspection glass.
In difficult situations, level radar must be able to measure via an inspection glass. This is because the level can only be correctly detected by a radar sensor if there is a clear level echo of a high-quality.
The difference between the smallest and largest signal – known as the radar sensor’s ‘dynamic range’ – determines the applications in which the sensor can be used. Greater dynamics mean a wider application range for the sensor, and a higher certainty of measurement.
VEGAPULS 64 has an extremely large dynamic range. This is of a particular advantage in conditions which occur in an autoclave, such as condensate, foam, build-up, or an extremely turbulent product surface in the vessel. Measurement can only be conducted reliably when there is a high measurement certainty, and this certainty allows for accurate measurement of the level even near to the very bottom of the vessel. The accuracy is +/- 1 mm.
VEGAPULS 64 is optionally equipped with the plics concept, and Zeller+Gmelin has first-hand experience of how this concept brings additional operating convenience. The company is certain that this standardized user interface, which is incorporated into VEGA instruments, makes day-to-day work much simpler.
On these tanks, vibrating level switches with WHG approval are used as overfill protection.
At the same time, the pressure inside the autoclave is monitored by VEGA sensors of the VEGABAR 81 type. Operation according to guidelines outlined by AwSV (systems for the handling of substances which are hazardous to water) is ensured by the installation of a VEGASWING 66 as overfill protection. This is a vibrating level switch which is ideally suited to extremes. As such, it is perfect for the high temperatures inside autoclaves.
VEGASWING 66 has patented inductive drive, as opposed to conventional vibrating level switches. This can actuate the tuning fork even when faced with extreme temperature conditions. As a result, the user can benefit from the simple handling of vibrating level switches, while also having the advantage of an extended application range between -1 to +160 bar and -196° to +450 °C.
Measurements inside Autoclave 3 are now completely safe and reliable, courtesy of the combined abilities of VEGASWING 66, VEGABAR 81, and VEGAPULS 64. For several years, Zeller+Gmelin and VEGA have worked together, appreciating each other’s partner-like relationship – particularly in the field of identifying solutions for extremely difficult measuring points.
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.