Solidly reliable level measurements with guided radar

Endress+Hauser’s highly successful Levelflex M guided radar level measuring unit with patented End-of-Probe (EOP) Algorithm, SIL 2 rating, and as the only guided radar level measuring device with full IEC Ex approvals (Gas and Dust) make it a compelling choice for bulk solid applications.

Levelflex M provides a sophisticated yet low-maintenance solution that delivers continuous, accurate and reliable measurement in bulk solids vessels up to 70m in height. Unlike other measuring systems, Levelflex M is unaffected by media property changes like angles of repose, changes in dielectric, moisture, density, particle size or dust.

Although guided radar has been proved as the only measurement principle to provide reliable levels measurement during noisy and dusty filling, it still performs poorly when the interface between the air and the material is not clearly defined. This "fuzzy" surface condition typically occurs when the material is conveyed pneumatically, or when the material is fluidised to ensure easy emptying. This aerated product blanket has a dielectric constant similar to air, so that the radar signal is not reflected at the product surface but simply continues along the rope and dissipates at the end of the probe, resulting in an incorrect, or no, level being recorded, with possible expensive consequences.

This is where the patented EOP algorithm differentiates the Levelflex M from guided radar devices from other manufacturers. At calibration the End-of-Probe distance and signature is recorded. When there is a ‘fuzzy’ surface condition and hence no reflection from a definite dielectric change, the signal continues beyond the material surface and travels down the rope until the rope end, at which point it dissipates.

Although the dielectric of the media is too low to cause a reflection, it is still higher than the dielectric of air. This results in the signal’s transmission speed being reduced whilst travelling in the media, which has the effect that the rope end (EOP) ‘appears’ to be further than what it was at calibration. The EOP position is tracked continuously; making it is possible to relate the ‘virtual’ changes in rope length to the height of material in the vessel.

Products like; sugar, flour, cement, PE, PVC, lime, coal and fly ash; all have low dielectric constants and are often pneumatically conveyed and fluidised. The EOP algorithm is even more important in these instances for ensuring reliable level measurement.

Levelflex M suits a wide range of level measurement applications, including chemical processing, mining and grain and other bulk solids. It is compatible with all tank materials and geometry, and is available with a rod probe, a coaxial probe or a high tensile strength, small-diameter rope probe for silos and tanks up to 70 m tall. All probes are interchangeable, user-replaceable and suitable for use in temperatures up to 400 degrees C, and pressures up to 400 bar.

Direct configuration and system integration are available through Profibus PA or Foundation Fieldbus systems. All models are equipped with the HART communication protocol, ensuring compatibility with any existing analogue topologies.

Endress+Hauser’s state-of-the-art, PC-based Time of Flight software is included free with Levelflex M and enables simple and safe commissioning, maintenance, diagnosis and documentation. Also included is an LCD display panel, with four-line, 80-character text screens and high resolution display for displaying envelope curves, providing the user with access to easy on-site set-up and the capability of high level diagnostics.

The precision, reliability and safety of Levelflex M in measuring powdery and granular bulk solids (and a wide range of liquid media) has been demonstrated in more than 50,000 installations worldwide – including over 1000 installations around Australia. "With IEC Ex certification and SIL 2 rating, Levelflex M is unquestionably the measurement solution of choice for bulk solid storage situations," says John Immelman of Endress+Hauser Australia. "It offers great features and benefits and superior performance at an affordable price, and we provide the most suitable and economical probe for each particular application."

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