Issue link: https://www.e-digitaleditions.com/i/1252179
June 2020 / 5 Editor's note: This is one of a series of commentaries by Powder and Bulk Engineering's Editorial Advisory Board members and other experts. The editorials express the individual writer's views of trends affecting powder and bulk industries today. Powder and Bulk Engineering welcomes your response. PBE INDUSTRY PERSPECTIVE "Venting" your frustrations I n these challenging times, it can be useful to take advantage of the lull to consider and reflect on where processing problems have been occurring and what remedial actions could be implemented when normal working conditions become re-established. The reliable flow of powders in processing plants often can be a chal- lenge when using equipment with generic geometry or incorporated features that may not be optimal for the equipment's intended purpose. Aside from the well-known drawbacks of funnel flow for some materials (intermittent discharge, segregation, bulk density variation), an additional focus area when troubleshooting is poor rotary valve venting. This can directly influence bulk solids behavior at the discharge outlet because of excessive air leakage. Rectifying the issue of poor rotary valve venting usually is fairly straightforward by using information relating to the rotary valve and plant operating conditions. Flow problems related to pressure gradients across the hopper can be more difficult to diagnose in instances where poor venti- lation of a feed hopper occurs. In such situations, the absence of air ingress into the head space of a vessel can reduce discharge rates significantly. An example of this occurrence could be due to the progressive blinding of a vent sock, which is a particular risk where vehicle cartridge-type filters are used. They tend to hold dust on the inside but may appear clean on the outside. The common absence of a method for cleaning while in service tends to make blinding a regular feature in the use of this vent method — particularly if installed in a relatively inaccessible position. This most definitely shouldn't be considered a "fit and forget" item! In summary, I hope this very brief overview makes clear the impor- tance of understanding and incorporating appropriate feeder vent arrangements. The basic principles of controlling air ingress to bulk solid powders can be readily understood, but the effectiveness of imple- menting such strategies will be largely defined by the bulk particulate material being handled. Investing time in characterizing these bulk solids behaviors and how they may affect the design and operation of handling equipment components like vents and feeders at the planning stages of a project will invariably pay dividends later. Richard Farnish, The Wolfson Centre for Bulk Solids Handling Technology, University of Greenwich, r.j.farnish@greenwich.ac.uk AGGLOMERATION EQUIPMENT • AIRLOCKS, BLOWERS, AND RELATED EQUIPMENT • BAGGING EQUIPMENT (UP TO 100 POUNDS) • BIN ACTIVATORS, VIBRATORS, AND MATERIAL FLOW AIDS • BIN LEVEL INDICATORS • BULK BAG FILLERS AND DISCHARGERS • BULK BAGS • CUSTOM SERVICES • DRYERS • DUST COLLECTOR MEDIA (BAGS AND CARTRIDGES) • DUST COLLECTORS AND RELATED EQUIPMENT • EXPLOSION VENTING AND SUPPRESSION • FEEDERS • FLOW METERS (SOLIDS) • LININGS (ABRASION RESISTANT) MATERIAL HANDLING MECHANICAL CONVEYORS METAL DETECTORS AND SEPARATORS • MIXERS AND BLENDERS • OTHER • PARTICLE ANALYZERS PNEUMATIC CONVEYING EQUIPMENT • PRODUCT RECLAIM EQUIPMENT SAMPLERS • SEALS • SIFTERS, SCREENERS, AND CLASSIFIERS • SIZE REDUCTION EQUIPMENT STORAGE • VACUUM CLEANING EQUIPMENT VALVES • WEIGHING EQUIPMENT AGGLOMERATION EQUIPMENT • AIRLOCKS, BLOWERS, AND RELATED EQUIPMENT • BAGGING EQUIPMENT (UP TO 100 POUNDS) • BIN ACTIVATORS, VIBRATORS, AND MATERIAL FLOW AIDS • BIN LEVEL INDICATORS • BULK BAG FILLERS AND DISCHARGERS • BULK BAGS • CUSTOM SERVICES • DRYERS • DUST COLLECTOR MEDIA (BAGS AND CARTRIDGES) • DUST COLLECTORS AND RELATED EQUIPMENT • EXPLOSION VENTING AND SUPPRESSION • FEEDERS • FLOW METERS (SOLIDS) • LININGS (ABRASION RESISTANT) MATERIAL HANDLING MECHANICAL CONVEYORS METAL DETECTORS AND SEPARATORS • MIXERS AND BLENDERS • OTHER • PARTICLE ANALYZERS PNEUMATIC CONVEYING www.powderbulk.com/ special-supplier-links