Strides Made in Level Measurement

Strides Made in Level Measurement
In the bulk materials segment, the use of certified devices is of particular importance given the risk of dust explosions. Inadequate protection against explosion can result in consequential damage in silos, mills, and other contained facilities.

Combustible dusts, encountered, for instance, during the manufacture and storage of grain, feed, and fertilizers, frequently ingress into the hazardous range, even reaching the explosive limit. It is specifically fine dusts that generally react with greater intensity than do those with larger grain diameters. Aside from the respective bulk material properties, further factors, such as structural specifics, potential sources of ignition, and the quality of the devices deployed, are important aspects to consider during risk assessment. The fact that explosive dust mixtures can occur in various parts of a facility is exemplified by concentrated feed plants. Here, among other things, dust mixtures can occur during vertical, pneumatic grain filling and the filling of dust-producing materials, as well as in downpipes, filling hoppers, silo chambers, or cyclones.    

Certified MBA rotor series

The German company MBA Instruments GmbH factored in all these influencing variables when developing its digital rotor series MBA800. The series’ devices comply with ATEX Directives and are, moreover, particularly flexible in terms of handling. With the novel, stepper motor-based level measurement devices in the MBA800 series, MBA Instruments meets the most stringent requirements as standard.  Suitability of the devices in explosive zones is – in addition to a host of technical refinements – one of the stated goals of the developers. With the ATEX Type Examination, concluded in 2016, the rotors’ potential deployment in areas prone to dust explosion has now also been officially confirmed. They comply with Directive 94/9/EC as well as the fundamental health and safety requirements stipulated in EN 60079-0:2012 + A11:2013 and EN 60079-31:2014. Category 2D devices are suited to Zone 21 areas. Subject to certain conditions, the shaft in equipment category 1D may also be deployed in Zone 20 areas. The rotors are thus optimally suited to deployment within the explosive bulk materials segment.

New drive for level measurement

MBA Instruments engineers have used a stepper motor instead of the conventional synchronous motor for the very first time in the new rotor series. The amalgamation of the established rotor measurement procedure with this drive signifies a path-breaking technological shift in the domain of bulk material technology. The advantages of the motor in terms of measurement are yielded, among other things, by its integrated magnetic slip coupling and the expansion of the scope of applications. The rotor effects a measurement irrespective of whether the bulk material is lightweight or heavy, whether it falls continuously onto the paddle or whether the device is directly integrated into the flow of bulk material. A crucial function is a change in the direction of rotation.  If, when installed horizontally, bulk material falls onto the blade, for instance, the latter pauses and switches to the opposite direction of rotation until bulk material falls onto the paddle once again. This back and forth movement of the blade continues until the blade is blocked in both directions of rotation simultaneously. A signal is then emitted. This technology enables the rotor to operate without requiring maintenance and with precision, catering to virtually all types of bulk materials.

MBA888 plug and play model 

The compact version of the MBA888 lends itself to particularly swift initial start-up and, likewise, reliable measurement. The series’ plug and play model has a permanently installed connecting cable and housing, which is available in either aluminum or stainless steel. The cover housing and shaft housing, meanwhile, are inextricably connected to one another. The standard blade is already permanently installed to the motor shaft, which again is available in a variety of lengths. Furthermore, the MBA888 is available in a short variant (24 VDC) and a long variant (115-230 VAC). All parameter settings are already pre-defined in this version of the device and are thus fixed. Thanks to the optimally calibrated parameter settings, the MBA888 performs well with virtually all types of bulk materials – irrespective of characteristics such as adhesive force, moisture, portability, or caking. The housing is completely sealed; the connection cable and signal cable are connected to the device by means of an M12 plug connector. Dust, water, and bulk materials cannot enter. An advantage that users quickly come to appreciate. Given the design, signs of mechanical wear and tear are ruled out.

Reliability pays off

In routine deployment, the rotors prove to be true powerhouses, meeting challenges that can result in disruptions to the production process when conventional devices are deployed. Their robust structure desensitizes the measuring systems to heavy dust formation; they defy even vigorous turbulence while concomitantly admitting air and material. Other devices frequently present difficulties on this front, reacting to vigorous vibrations by signaling a fault or switching off entirely. Users of the MBA800 models benefit from these devices also having been jolt and vibration-tested, allowing for 29 g. With no movable parts in the unit head, they operate sensitively, following a principle that is as simple as it is extremely reliable: They rotate, effect constant measurement or react by changing the direction of rotation. In other words: The devices operate without requiring maintenance. The low torque ensures a high degree of sensitivity and facilitates universal deployment in various applications and catering to a variety of bulk materials.

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The SMB Group unites under the SMB and MBA brands the areas filling and conveyor technology, ship loading, storage technology, level measurement and conductivity measurement. With its business focus on planning, development and manufacturing, and the worldwide sale and service of highly complex systems as well as warehousing logistics, SMB Group ...

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