At F2 Chemicals’ plant in the U.K. (shown above), a radar level measurement failed repeatedly due to the adhesive buildup of vapor-born contaminants on the cone. These problems caused inaccurate and intermittent level readings, requiring the regular removal of the old instrument for cleaning and recalibration. This hazardous procedure work involved the emptying of the tank, with subsequent costly process downtime.
For a solution, the chemical company looked to a manufacturer that it already had a working partnership with. Ultimately, a drop-shaped antenna version of the existing radar would be installed to accurately measure and monitor the level of highly corrosive, dilute hydrofluoric acid stored in a 3,200-liter polypropylene holding tank.
F2 develops direct fluorination technology for the production of organic compounds and manufacture of high specification Flutec Fluids (perfluorocarbons).
Knowing existing level measuring instrumentation from the same manufacturer was operating successfully in other parts of its site, F2 sought the manufacturer’s recommendation. Careful consideration was given to the process application itself and the chemical-resistive properties of the new instrument’s polytetrafluoroethylene coated drop-shaped antenna.
Hycontrol’s VG7 radar was fitted to a flanged coupling on the top of the tank and is connected to the plant’s control system to provide constant live level readings that are required for process monitoring. The commissioned instrument was programmed to match the reflective properties of the process liquid in order to optimize accuracy and reliability.
The instrument, a two-wire Frequency Modulated Continuous Wave (FMCW) radar product, provides high levels of accuracy over a maximum range of 80 meters. The technology works well with a range of liquid products, utilizing either the horn or drop antenna versions. For process vessels with complex internal structures such as pipes, heating coils or agitators/stirrers, the optional ETS (Empty Tank Spectrum) software is required. ETS effectively maps out all unwanted signals by viewing the tank empty and memorizing all the return signals from internal structures such as pipes, heating coils and agitators. The radar will then only monitor the moving liquid levels and ignore the static objects based on data from the empty tank spectrum.
The instrument is unaffected by changes in dielectric constant, pressure, temperature or viscosity and can operate in vacuum, foam and dust. The FMCW radar uses a high frequency 26 gigahertz signal, which increases in frequency during the measurement. The emitted signal is reflected back from the product surface and received after a time delay. Further signal processing of the difference between transmit and receive frequencies provides a signal directly proportional to the level.
F2 Chemical’s senior electrical and instrument engineer David Johnson said he is pleased with the installation. “Reliable and accurate level measurement is essential for such corrosive applications,” he said. “The VG7 instrument has now been installed for over eight months, and we have not experienced any problems.”
Maurice Mahoney has been export sales manager at Hycontrol Ltd. for 20 years, where he works with a network of distributors to provide level measurement solutions worldwide. For more information about Hycontrol products, contact Mahoney at firstname.lastname@example.org or visit hycontrol.com.