German-based manufacturer, Walter Rau, specialises in customised vegetable fat and oil production. In addition to producing frying fats, the company also produces specialty fats for the baking confectionary and dairy industries. It also services the non-food market, focusing on fuels for cogeneration units, biodiesel and diesel substitutes.
The production facility is located adjacent to a harbour allowing materials such as sunflower oil, palm oil and coconut oil to be delivered via barges. Materials are loaded directly from barges to heated storage tanks for further processing. The raw oil is drawn from the storage tanks and then processed in the refinery to consumable edible oil.
Challenge
The raw oil in the tanks must be stored within specified temperature ranges to avoid quality issues and crystallisation. Each tank contains integrated heating coils that, however, can interfere with level measurement. Operators at the facility were using conventional float systems and wanted a more reliable and accurate level measurement system. In addition to ignoring obstructions in the tank, they also required the transmitters be unaffected by ambient conditions such as temperature while keeping the overall expenses to a minimum.
Solution
The Siemens Sitrans LR250 was installed on two tanks. It is a 2-wire non-contacting radar transmitter that measures the level of liquids and slurries accurately and is unaffected by temperature and atmospheric conditions. The high frequency (25 GHz) makes the LR250 ideally suited for accurate level measurements of liquids in storage tanks.
The devices are programmed via an infrared handheld programmer and the available approvals allow its use in hazardous locations. Remote programming is via the universal Simatic PDM software, offering extensive diagnostic and analysis functions via HART protocol. Level readings or diagnostic information can be viewed on the local display, for example, echo curves can be shown graphically on the unit.
Process Intelligence and the Auto-False-Echo suppression feature automatically ignore interferences from vessel obstructions such as the heating coil. Density variations of the product over the fluctuating temperature changes can be used to enhance the level measurement accuracy. Operators at Walter Rau AG installed continuous temperature measurement devices at different points in the storage vessels. The readings from these temperature devices combined with the measurement variables in the Siemens PLC and temperature versus density curves for the different products are calculated together to give the most accurate level readings possible. Level measurement inaccuracies caused by density changes become a thing of the past.
Benefits
Operators at Walter Rau AG are satisfied with the Sitrans LR250 for their level measurement needs. The 2-wire transmitter meant that no additional wiring was required and the small antenna allowed installation directly on the existing nozzles. Extensive welding and emptying and cleaning of the vessel was not required.
Integrating the Sitrans LR250 in the communications network gives Walter Rau operators precise and accurate readings of level in all of their storage tanks on a continuous basis. The system is maintenance free and provides reliable results regardless of the process conditions.
For more information contact Keshin Govender, Siemens Southern Africa, +27 (0)11 652 2412, [email protected], www.siemens.co.za
| Tel: | +27 11 652 2000 |
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