Level revelation

The new high frequency bulk solids radar level sensor from VEGA delivers affordable reliability.

Radar level sensors are a proven a success story for bulk solids level. In some industries they have superseded electromechanical and ultrasonic measuring devices many sectors. This is due to their immunity to in-flight dust, pressure, temperature, good focusing and no loss of echo - even during pneumatic filling, so the areas of application extended. Although users are increasingly adopting microwave technology, a level sensor which truly covers all applications has still not yet been realised. With a higher frequency and performance capability of 80GHz, the new VEGAPULS 69 radar designed for bulk solids comes a big step closer to this ideal.
This new level device operates with a frequency in the range of 80 GHz, enabling a much tighter focusing of the transmission signal, this means it easily avoids all interference from internal structures or build up inside vessels. Also with the latest generation microwave components, even the tiniest reflection signals can be measured. This means previously difficult to measure products with very poor reflective properties, such as high purity plastics, fine cement powders or wood chips, can now be measured with confidence both during filling and emptying. VEGAPULS 69 offers versatility over a wider application range. It has a measuring capability from one or two metres...right up to 120 m, a speed of response <1sec and an accuracy of ±5 mm, with enough performance reserves for the more ‘unusual’ assignments, such as fast response positioning for conveyor car systems and stockpile cranes.

Focused on measurement reliability
The ‘beam angle’ of the radiated radar energy and therefore the focusing, depends on two factors: the transmission frequency and the active antenna area. This means at a higher frequency, much better focusing is achieved with a smaller antenna size. The VEGAPULS 69 operates with a transmission frequency of approximately 80 GHz and a 3”/75 mm antenna, that achieves a beam angle of only 4° (compared to 10° with 26 GHz at the same size) Why is this angle so important? The narrower beam avoids all internal installations and vessel wall build up, which makes the measurement more accurate and reliable right to the bottom. This ability makes commissioning much easier and faster, with fewer ‘tweaks’ like ‘false signal suppression’, ‘masking’ or ‘mapping’ (depending on manufacturer terminology). This focusing also means more signal is reflected back to the sensor, so any applications which previously returned very small reflections, like plastic pellets and fine powders with very low dielectric figures, greatly benefit from this focusing.

Solving challenging application areas
Plastic powders or pellets are usually stored in high, very narrow silos. Circumferential welds, even if they are only a few millimetres wide, can cause repeat interference reflections in silos over tens of metres, which can interfere with the useful signal. It is always difficult, especially with plastic powders with very low reflective properties, to choose the right signal. In some cases large parabolic antennas are used to achieve the focusing needed to reduce the interference signals. But these large antennas are not always practical. Easy to install small antennas with narrow beam angles and high signal return solves this.

Aggregate blending silos
Another application which benefits particularly from this narrow beam angle is measurement in segmented hoppers or mixing silos in the cement and building materials industry. These multi-compartment silos often have corrugated reinforced plates as the partitions. In comparison with the signal reflected from the product level, these plates can cause very heavy interference, which can be ignored with complex evaluation algorithms, but not always successfully. Another option is using guided wave radars or capacitive based systems, but the problems of roof loading, cable wear from the stones, changing materials and cable fixing at the bottom, is far from ideal. Radar technology, immune to inflight dust and filling noise with narrow beam angle to avoid the walls provides excellent reliability for this application.

Foodstuffs
Food based bulk solid products vary greatly and range from abrasive grains, to very fine adhesive powders like sugar and dusty wheat feed by-products . These are level measurements you need to rely on and a non contact measurement is preferred (i.e. with no cables for cross contamination, wear, roof loading or even breakage), and a radar level is the perfect answer for foodstuff inventory management. In large facilities the products are usually stored in high, slim silo blocks to concentrate a high volume and store the widest variety possible into a compact footprint. Increasingly these higher silos are being used, which brings many measuring principles up to their physical limits, including weighing systems. In smaller sites, the whole plant can be dependent on a supply from only one or two silos. A reliable level measurement in all these different applications is essential for production and logistics planning, as well as enabling optimised inventory replenishment and appropriate route planning by suppliers.
One device, VEGAPULS 69, works reliably on all these applications, from a few meters up to 120m. Using the right measurement data avoids unnecessary production halts and expedited delivery costs.

Dynamic performance
Because of the very large dynamic range (or sensitivity) of the new VEGAPULS 69, even the smallest reflections can be detected reliably. This of course achieves excellent results on media with good reflection properties such as coal, ore and rocks, but even products with poorer reflection properties such as plastic powders, fine cement, fly ash or dry sawdust can be measured confidently by the new technology. With the possibility of measuring with ever smaller reflection signals, even polystyrene pellets or extremely light fumed silica applications have been measured successfully. This universal capability offers great advantages especially in applications in which very different media are stored. For example, in the grain processing industry, the silos often fill with different products from wheat, corn or bran, as required. Because of the high dynamics of VEGAPULS 69 one sensor now covers all areas of application.

Fast and versatile
The measuring range is also a sign of the performance capability. Thanks to the good focusing and the high dynamic range, the VEGAPULS 69 can reliably measure poorly reflecting bulk solids, even at a distance of 120 m. Longer ranges are common in quarrying and mining, where the higher focusing also plays a role in deep shafts by avoiding the rock walls with a rough surface that can produce interference signals. The system is designed so that the sensor also operates with the same performance over much smaller measuring ranges. This comes as a benefit to users of conveyor belts, for example, in which distance measurements need to be made under very harsh conditions. A fast measurement is also necessary because the level on the belts changes very quickly. The cycle time of the new VEGAPULS 69 is less than one second with an accuracy of ±5 mm. So even applications monitoring moving plant for positioning or in crushers, where very fast moving stone levels need to be monitored, are ideal for VEGAPULS 69.

Device options and Bluetooth communications
The new VEGAPULS 69 is available in two versions, a simple version with a robust plastic antenna of PP and an integrated encapsulated lens antenna, in an affordable package that is suitable for most standard temperature applications. (The encapsulated antennas are insensitive to deposits and ensure trouble-free operation even under harsh conditions) The flanged version has a flush antenna with stainless steel integrated swivel holder to align the sensor in a range of ±10°. On this version an purge air connection, for efficient cleaning across the antenna face in extreme applications, is provided as standard. This is ideal, for example, in the measurement of very dusty wood based products or some foodstuffs.

VEGA engineers came up with something special. They have developed a free App to wirelessly communicate and set up the device with Bluetooth from smartphone, tablet or PC, ideal for the more inhospitable or inaccessible areas of the plant and, inspired by the spirit level Apps on smartphones, there is even a tool to help with sensor aiming or alignment in the silo.

The main benefit is the reliability right from the start. Quick delivery, simple installation, handling small transducers, easy wiring, simple to set up, even from a smart phone if preferred. Aim the sensor with the most highly directional of signals to measure from top to bottom, with smooth analogue measurement, not a series of jumps, while being immune to filling dust and antenna deposits. VEGAPULS 69 is delivering a higher level of confidence from plant engineers and managers to process operators about their sensor performance, stock availability, process control and improves efficiency.

If you would like a demo or to trail a unit on your chosen application, VEGA would be happy to come to site with one of the battery powered demonstration units.

Associated Businesses

  • Maresfield, TN22 2DU