In this method of conveying bulk solids, tracking the system pressures is far more challenging than for the flow of gases alone. Reliable measurement of pressure along pneumatic -conveying pipelines requires the pressure tappings, and any connecting lines to a pressure-measurement device, to remain unblocked by the conveyed material. Pressure tappings invariably block at the start of a conveying cycle, or as a result of pressure pulsations that may occur during conveying. Measuring the pressure drop across abend typifies the difficulties of pressure measurement in pneumatic-conveying pipelines. Reliable pressure measurement at any given point requires the flow to be both steady and wholly axial. Otherwise, the pressure will include dynamic as well as the desired static components, and inconsistent or false readings may result. The dynamic component may add to or subtract from the static value, depending upon the geometry of the flow. An increase in pipeline bore part of the way along the length of a pipeline is a common feature of both high-pressure and high-vacuum conveying systems. Such stepups are employed in order to prevent the very high values of conveying air velocity that would otherwise result toward the ends of such pipelines. Although the energy loss due to bends in a pneumatic-conveying pipeline can be very significant, particularly if there are a large number of them, the pressure drop in the straight runs generally dominates in most pipelines. To determine the pressure drop, or pressure gradient in a long section of pipeline, pressure tappings should be installed at a minimum of six equally spaced locations. By this means, reasonable data can be obtained even if one or two of the tapping points block. Because gas-solids-flow still involves far more empiricism than theory, experimental results related to pressure drop and other pressure-related behavior in pneumatic-conveying systems can be especially illuminating. We next discuss such results, with respect to a variety of pipeline configurations. As an approximation for scaleup, the ratio of full-scale to laboratory or pilot-plant flowrate can be assumed to be proportional to the square roots of the respective conveying-line diameters. If the resulting air supply pressure proves to be too high, scaleup to a larger bore will result in a lower value for the pressure. Because of the problems associated with the accurate measurement of pressure, the generation of such data is an expensive process and so,additionaly, there is a reluctance to undertake research work in this area.


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    Titel :

    Measuring pressure on pneumatic-conveying systems


    Beteiligte:
    Mills, D. (Autor:in)

    Erschienen in:

    Erscheinungsdatum :

    2001


    Format / Umfang :

    5 Seiten, 9 Bilder, 10 Quellen



    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch





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