MechChem Africa September-October 2022

⎪ Minerals processing and materials handling ⎪

ate interfering signals. Radar measurement inside a standpipe is usually preferred for this application. In times past, six-metre long pipes – the maximum available length – were welded together to make longer standpipes; but the weld seams disturbed the measuring signal. Vega was able to drastically reduce these interfering reflections with its special patented weld for such pipes. Level measurement is necessary not only in the storage and cargo tanks, but in the liquefaction and regasification plants as well. Some liquefactionplantsare locatedat seaand Vegasensorsaredeployedthereaswell. These plants are relatively complex and extend over multipleprocess stages. Ineachstage, the level is an important variable that plays amajor role in protecting compressors. Level instruments have to function reliably at high pressures (16 to 18 bar) and very low temperatures (-163 °C) in heavy seas. Since the tanks used here are usually smaller and have extremely fast filling or emptying cycles, the surfaceof theproduct is oftenquite turbu lent. Differential pressure measurement, for example, could be used here, but because of the low temperatures it is extremely difficult in practice: the pressure detecting elements, the diaphragm seals, get covered with layers of ice. The Vegaflex 86 sensor is being used more and more for the continuous measure ment of levels in the various process stages of the liquefaction plants. This robust guided

radar sensor is ideal for the task because it measures without being affected by media properties such as density or dielectric con stant. Its ruggedmechanical construction and secondprocess seal, the so-called ‘second line of defence’, protect the sensor. TheVegaflex 86 guided radar sensormea sures down to -196 °C and is not affected by turbulent surfaces. Installing these sensors on board a ship requires a lot of experience, however. In applications on land, the sensor can simply be mounted in the intended tank openingorbypass,withmeasurement starting moreor less immediately. On ships, the sensor has to be installed in a special way, in order to compensate for the heeling movement in heavy seas. Reliable limit level detection LNG processes, whether on land or on ships, requirenotonlycontinuous levelmeasurement butalsopoint leveldetection.TheVegaswing66 level switch isoftenchosen for this task. Ingen eral, vibrating level switches are very popular amongusers inthechemical andpetrochemical industry as well as in refineries because they are extremely easy to operate and ensure safe, reliablemeasurement. In contrast to float systems, Vegaswing 66 offers a much higher level of security, as the sensor constantly performs self-diagnosis and monitors the sensing element. However, it wasn’t previously possible to use these devices

at very low temperatures. Vega has nowdevel oped a patented drive that excites the tuning fork at these temperatures. The user benefits greatly from the simple handling of this vibrating level switch and its extended application range down to -196 °C – the normal temperature in the LNG environ ment – and a pressure range of -1 to +160 bar. Because the sensor measures so reliably, irrespective of density, it is perfect for high and high-high alarms in various stations on the ship as well as on land. It is used, for example, in the pump pits of liquefaction terminals to keep the pumps from running dry. Thanks to theplics ® interfaceconcept, Vega sensors use the same interface for every Vega measuring instrument, regardless of the mea suring method. All these sensors have become even easier to operate through the combina tion of Plicscom and Bluetooth. Their wireless Bluetoothcommunication isparticularlyuseful for hard-to-reach areas, harsh industrial envi ronments and Ex hazardous areas. Plicscom is backward compatible and can be used for the entire installed base of plics ® sensors – in pressure and level applications, with 70 different types of instruments and the service-proven adjustment structure – and no software updates are required. This allows the user to configure and parameterise plics ® sen sors conveniently from a safe distance using a smartphone or tablet. www.vega.com/en-za

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