Troubleshooting Pneumatic Conveying Systems

David Mills, pneumatic conveying consultant, UK, and Vijay Argawal, professor, Industrial Tribology, Machine Dynamics & Maintenance Engineering Centre, Indian Institute of Technology Delhi, will lead a Technical Workshop, Troubleshooting Pneumatic Conveying Systems, on Wednesday, May 8, at the 2014 International Powder & Bulk Solids Conference & Exhibition in Rosemont, IL.
    The workshop is designed for engineers who are experiencing operational problems with an existing pneumatic conveying system, or who want to know how they might be able to adapt their existing system – either to improve its performance or to convey another material. This lecture will also appeal to anyone required to commission a pneumatic conveying system.
    “The influence of material properties, such as particle size and shape, and their distributions, is so marked that different modes of flow of the material in the pipeline are possible,” says Mills. “This then leads to wide variations in the velocity of the air necessary to convey a material, and hence to the volumetric flow rate of the air to be specified for a blower or compressor. Material properties are so influential that the conveying performance of two different grades of the same material can vary widely. With very friable materials it is even possible for the conveying performance of a material to change as a result of being conveyed.
    “A particular problem with pneumatic conveying systems,” Mills continues, “is that the conveying medium, air or some other gas is compressible, and since the driving force for flow is pressure drop, there can be a significant increase in velocity through the conveying pipeline, particularly with high pressure systems. It is the velocity at the start of the pipeline that is the critical parameter in the design of a pneumatic conveying system, and since this is influenced by pressure, and sometimes the mode of flow, it is an obvious area for errors and hence faulty operation.
    “The specification of the air mover, as a result, is not a straightforward task,” says Mills, “and with so many different types of compressor from which to select, each having potentially different operating characteristics, errors can be compounded. The feeding of materials into a pipeline at a controlled rate is a particular requirement with pneumatic conveying, and for positive pressure conveying systems it means feeding into a pipeline maintained at pressure. A wide variety of different devices are available for this purpose, but the influence of air leakage across the device must be taken into account.”
    Material flow rate problems, and pipeline blockage in particular, will be considered during this workshop, as well as why systems may not be capable of the required duty and why output might change with respect to time. In this respect all types of conveying systems (high pressure, low pressure and vacuum as well as dilute and dense phase flow) and system components (compressors, feeders and filters) will be reviewed. Problems with moisture, particle breakage and erosive wear will also be covered. The use of stepped pipelines to enhance system capability will also be included, together with other means of increasing the performance of an existing conveying system.

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