[{"data":1,"prerenderedAt":930},["ShallowReactive",2],{"site-footer-common":3,"glossary:geldart-classification":45,"glossary-related:geldart-classification":273},{"id":4,"extension":5,"footer":6,"meta":40,"navbar":41,"stem":43,"__hash__":44},"common\u002Fcommon.yml","yml",{"tagline":7,"links":8,"sections":9},"Acoustic cleaning intelligence for industrial fouling, soot, ash, dust and build-up.",[],[10,19,31],{"title":11,"links":12},"Product",[13,16],{"label":14,"to":15},"How it works","\u002F#product",{"label":17,"to":18},"Cost assessment","\u002F#hero",{"title":20,"links":21},"Company",[22,25,28],{"label":23,"to":24},"What we build","\u002F#about",{"label":26,"to":27},"Careers","\u002F#careers",{"label":29,"to":30},"Contact","\u002F#contact",{"title":32,"links":33},"Resources",[34,37],{"label":35,"to":36},"Blog","\u002Fresources\u002Fblog",{"label":38,"to":39},"Glossary","\u002Fglossary",{},{"links":42},[],"common","YocmZRy1AYfBbpgGVms-zhdiABlF8VTxHx6h4rDmZBA",{"id":46,"title":47,"aliases":48,"body":51,"category":255,"description":256,"extension":257,"meta":258,"navigation":259,"path":260,"relatedTerms":261,"seo":264,"sources":267,"stem":271,"term":47,"__hash__":272},"glossary\u002Fglossary\u002Fgeldart-classification.md","Geldart classification",[49,50],"Geldart A B C D","Geldart powder classification",{"type":52,"value":53,"toc":247},"minimark",[54,62,67,157,161,210,214,219,223],[55,56,57,58,61],"p",{},"The ",[59,60,47],"strong",{}," (Derek Geldart, 1973) groups powders by particle size and density into four classes that predict fluidisation, bridging and discharge behaviour. It is the most widely used powder-behaviour map in industrial bulk-solids handling.",[63,64,66],"h2",{"id":65},"the-four-classes","The four classes",[68,69,70,89],"table",{},[71,72,73],"thead",{},[74,75,76,80,83,86],"tr",{},[77,78,79],"th",{},"Class",[77,81,82],{},"Particle size \u002F density",[77,84,85],{},"Behaviour",[77,87,88],{},"Example materials",[90,91,92,109,125,141],"tbody",{},[74,93,94,100,103,106],{},[95,96,97],"td",{},[59,98,99],{},"A",[95,101,102],{},"Small (30–100 µm), low density",[95,104,105],{},"Fluidises well; expands before bubbling",[95,107,108],{},"Cracking catalyst, alumina fines",[74,110,111,116,119,122],{},[95,112,113],{},[59,114,115],{},"B",[95,117,118],{},"Medium (100–500 µm), medium density",[95,120,121],{},"Bubbles immediately on fluidisation",[95,123,124],{},"Sand, salt, larger cement particles",[74,126,127,132,135,138],{},[95,128,129],{},[59,130,131],{},"C",[95,133,134],{},"Very fine (\u003C 30 µm), cohesive",[95,136,137],{},"Hard to fluidise; channels; cohesive arching",[95,139,140],{},"Cement, fly ash, flour, talc",[74,142,143,148,151,154],{},[95,144,145],{},[59,146,147],{},"D",[95,149,150],{},"Large (> 500 µm), dense",[95,152,153],{},"Spouts rather than fluidises",[95,155,156],{},"Coal, gravel, grain",[63,158,160],{"id":159},"why-it-matters-for-hopper-design","Why it matters for hopper design",[162,163,164,192,198,204],"ul",{},[165,166,167,170,171,176,177,181,182,186,187,191],"li",{},[59,168,169],{},"Class C powders"," are the most prone to ",[172,173,175],"a",{"href":174},"\u002Fglossary\u002Fbridging","bridging"," and ",[172,178,180],{"href":179},"\u002Fglossary\u002Frat-holing","rat-holing",". ",[172,183,185],{"href":184},"\u002Fglossary\u002Fsonic-horn","Sonic horns",", ",[172,188,190],{"href":189},"\u002Fglossary\u002Fair-cannon-air-blaster","air cannons"," and aeration are routinely needed",[165,193,194,197],{},[59,195,196],{},"Class A powders"," flow well from properly-designed hoppers; problems usually trace to wet incoming material",[165,199,200,203],{},[59,201,202],{},"Class B powders"," are predictable and well-suited to standard hopper geometry",[165,205,206,209],{},[59,207,208],{},"Class D powders"," rarely bridge but are abrasive and shock-loading the hopper",[63,211,213],{"id":212},"acoustic-cleaning-fit","Acoustic-cleaning fit",[55,215,216,218],{},[172,217,185],{"href":184}," are most often deployed on Class C powders — fly ash, cement, lime, fine carbon black, food powders — because that is where cohesive flow problems concentrate.",[63,220,222],{"id":221},"related-terms","Related terms",[162,224,225,231,236,241],{},[165,226,227],{},[172,228,230],{"href":229},"\u002Fglossary\u002Fhopper","Hopper",[165,232,233],{},[172,234,235],{"href":174},"Bridging",[165,237,238],{},[172,239,240],{"href":179},"Rat-holing",[165,242,243],{},[172,244,246],{"href":245},"\u002Fglossary\u002Ffly-ash-hopper","Fly-ash hopper",{"title":248,"searchDepth":249,"depth":249,"links":250},"",2,[251,252,253,254],{"id":65,"depth":249,"text":66},{"id":159,"depth":249,"text":160},{"id":212,"depth":249,"text":213},{"id":221,"depth":249,"text":222},"hoppers-silos","The Geldart classification (Derek Geldart, 1973) groups powders by particle size and density into four classes that predict fluidisation, bridging and discharge behaviour. It is the most widely used powder-behaviour map in industrial bulk-solids handling.","md",{},true,"\u002Fglossary\u002Fgeldart-classification",[262,175,180,263],"hopper","fly-ash-hopper",{"title":265,"description":266},"Geldart classification (A\u002FB\u002FC\u002FD) — powder behaviour map for bulk-solids handling","The Geldart classification groups powders by particle size and density into A, B, C and D classes. Predicts fluidisation, bridging and discharge behaviour.",[268],{"title":269,"url":270},"Wikipedia — Geldart classification","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FGeldart_classification","glossary\u002Fgeldart-classification","ZNR1dvtOZBK6Zw0u8RvjOYajHOiEu_9J39jSWHljRes",[274,431,624,749],{"id":275,"title":230,"aliases":276,"body":280,"category":255,"description":414,"extension":257,"meta":415,"navigation":259,"path":229,"relatedTerms":416,"seo":422,"sources":425,"stem":429,"term":230,"__hash__":430},"glossary\u002Fglossary\u002Fhopper.md",[277,278,279],"hoppers","storage hopper","process hopper",{"type":52,"value":281,"toc":409},[282,313,317,349,353,369,371],[55,283,284,285,287,288,186,292,186,296,186,300,304,305,186,309,312],{},"A ",[59,286,262],{}," is an inverted-pyramid or conical vessel designed to store bulk solids and discharge them through a converging outlet. Hoppers appear under ",[172,289,291],{"href":290},"\u002Fglossary\u002Felectrostatic-precipitator","ESPs",[172,293,295],{"href":294},"\u002Fglossary\u002Fbaghouse","baghouses",[172,297,299],{"href":298},"\u002Fglossary\u002Feconomiser","economisers",[172,301,303],{"href":302},"\u002Fglossary\u002Fair-heater","air heaters"," and process equipment of every kind across cement, power, ",[172,306,308],{"href":307},"\u002Fglossary\u002Fwaste-to-energy","WtE",[172,310,311],{"href":307},"biomass",", refining, pharma, food and mining.",[63,314,316],{"id":315},"universal-failure-modes","Universal failure modes",[162,318,319,326,333,339],{},[165,320,321,325],{},[59,322,323],{},[172,324,235],{"href":174}," — stable arch forms above the outlet",[165,327,328,332],{},[59,329,330],{},[172,331,240],{"href":179}," — narrow channel above the outlet; surrounding material packs and hardens",[165,334,335,338],{},[59,336,337],{},"Pluggage"," — total blockage that stops discharge",[165,340,341,348],{},[59,342,343,344],{},"Funnel flow vs ",[172,345,347],{"href":346},"\u002Fglossary\u002Fmass-flow-vs-funnel-flow","mass flow"," — first-in, last-out behaviour leading to ageing material remaining indefinitely",[63,350,352],{"id":351},"why-acoustic-cleaning-works-on-hoppers","Why acoustic cleaning works on hoppers",[55,354,355,357,358,186,362,186,364,368],{},[172,356,185],{"href":184}," excel on hoppers because the geometry is small enough for the sound wave to fill the whole vessel and the dust is dry and friable. Compared with mechanical alternatives — ",[172,359,361],{"href":360},"\u002Fglossary\u002Fbin-vibrator","bin vibrators",[172,363,190],{"href":189},[172,365,367],{"href":366},"\u002Fglossary\u002Fwhip-hammer","whip hammers"," — they cause no structural stress, no fatigue, and no impact damage to the hopper itself.",[63,370,222],{"id":221},[162,372,373,379,385,391,395,399,404],{},[165,374,375],{},[172,376,378],{"href":377},"\u002Fglossary\u002Fsilo","Silo",[165,380,381],{},[172,382,384],{"href":383},"\u002Fglossary\u002Fbunker-coal-bunker","Bunker \u002F coal bunker",[165,386,387],{},[172,388,390],{"href":389},"\u002Fglossary\u002Fbin","Bin",[165,392,393],{},[172,394,235],{"href":174},[165,396,397],{},[172,398,240],{"href":179},[165,400,401],{},[172,402,403],{"href":346},"Mass flow vs funnel flow",[165,405,406],{},[172,407,408],{"href":184},"Sonic horn",{"title":248,"searchDepth":249,"depth":249,"links":410},[411,412,413],{"id":315,"depth":249,"text":316},{"id":351,"depth":249,"text":352},{"id":221,"depth":249,"text":222},"A hopper is an inverted-pyramid or conical vessel designed to store bulk solids and discharge them through a converging outlet. Hoppers appear under ESPs, baghouses, economisers, air heaters and process equipment of every kind across cement, power, WtE, biomass, refining, pharma, food and mining.",{},[417,418,419,175,180,420,421],"silo","bunker-coal-bunker","bin","mass-flow-vs-funnel-flow","sonic-horn",{"title":423,"description":424},"Hopper — converging vessel for storing and discharging bulk solids","A hopper is an inverted-pyramid or conical vessel for storing and discharging bulk solids. Bridging and rat-holing are the universal failure modes; sonic horns are a clean, low-maintenance remedy.",[426],{"title":427,"url":428},"Wikipedia — Hopper (particulate collection container)","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FHopper_(particulate_collection_container)","glossary\u002Fhopper","yaS0yQSinQlli40xEUR0l9zzxphPNmE4Pi2XHYeAc4k",{"id":432,"title":235,"aliases":433,"body":438,"category":255,"description":608,"extension":257,"meta":609,"navigation":259,"path":174,"relatedTerms":610,"seo":611,"sources":614,"stem":621,"term":622,"__hash__":623},"glossary\u002Fglossary\u002Fbridging.md",[434,435,436,437],"arching","arch formation","hopper bridging","silo bridging",{"type":52,"value":439,"toc":602},[440,457,461,464,484,488,502,506,578,580],[55,441,442,444,445,448,449,451,452,448,454,456],{},[59,443,235],{}," (also ",[446,447,434],"em",{}," or ",[446,450,435],{},") is the formation of a stable mechanical arch of bulk-solid material above the discharge outlet of a ",[172,453,262],{"href":229},[172,455,417],{"href":377},". Once a bridge forms, no material flows out of the outlet even though the vessel above is full. Bridging is the universal failure mode of bulk-solids storage.",[63,458,460],{"id":459},"how-a-bridge-forms","How a bridge forms",[55,462,463],{},"Cohesive forces between particles — moisture films, electrostatic charge, chemical bonding — combine with the converging-flow geometry to lock particles into an arch shape. The arch is self-supporting against the load above. Cohesion increases with:",[162,465,466,472,475,478,481],{},[165,467,468,469,471],{},"Fine particle size (especially Geldart-C powders — see ",[172,470,47],{"href":260},")",[165,473,474],{},"Moisture",[165,476,477],{},"Hygroscopic chemistry (urea, ammonium nitrate, lime)",[165,479,480],{},"Long residence time (consolidation under sustained load)",[165,482,483],{},"Temperature cycling",[63,485,487],{"id":486},"diagnosing-a-bridge","Diagnosing a bridge",[162,489,490,493,496,499],{},[165,491,492],{},"Outlet flow stops while the level above remains high",[165,494,495],{},"Mass-flow indicators report no movement",[165,497,498],{},"A simple tap on the hopper outside the discharge cone produces a hollow sound",[165,500,501],{},"Borescope inspection from the inlet shows the arch directly",[63,503,505],{"id":504},"remedies","Remedies",[68,507,508,518],{},[71,509,510],{},[74,511,512,515],{},[77,513,514],{},"Technique",[77,516,517],{},"Notes",[90,519,520,529,539,549,559,570],{},[74,521,522,526],{},[95,523,524],{},[172,525,408],{"href":184},[95,527,528],{},"Continuous prevention; non-contact; minimal infrastructure",[74,530,531,536],{},[95,532,533],{},[172,534,535],{"href":189},"Air cannon",[95,537,538],{},"High-intensity periodic; effective on hard bridges; structural stress",[74,540,541,546],{},[95,542,543],{},[172,544,545],{"href":360},"Bin vibrator",[95,547,548],{},"Continuous vibration; can compact powder further if poorly sized",[74,550,551,556],{},[95,552,553],{},[172,554,555],{"href":366},"Whip hammer",[95,557,558],{},"Manual; legacy; HSE concerns",[74,560,561,567],{},[95,562,563],{},[172,564,566],{"href":565},"\u002Fglossary\u002Ffluidisation-pad-aeration-pad","Fluidisation pad",[95,568,569],{},"Aerates the lower vessel; not suitable for wet material",[74,571,572,575],{},[95,573,574],{},"Mechanical screw extractor",[95,576,577],{},"Bypasses the bridge entirely; high capex",[63,579,222],{"id":221},[162,581,582,586,590,594,598],{},[165,583,584],{},[172,585,230],{"href":229},[165,587,588],{},[172,589,378],{"href":377},[165,591,592],{},[172,593,240],{"href":179},[165,595,596],{},[172,597,403],{"href":346},[165,599,600],{},[172,601,408],{"href":184},{"title":248,"searchDepth":249,"depth":249,"links":603},[604,605,606,607],{"id":459,"depth":249,"text":460},{"id":486,"depth":249,"text":487},{"id":504,"depth":249,"text":505},{"id":221,"depth":249,"text":222},"Bridging (also arching or arch formation) is the formation of a stable mechanical arch of bulk-solid material above the discharge outlet of a hopper or silo. Once a bridge forms, no material flows out of the outlet even though the vessel above is full. Bridging is the universal failure mode of bulk-solids storage.",{},[262,417,180,420,421],{"title":612,"description":613},"Bridging — stable arch above the discharge of a hopper or silo","Bridging (also arching) is the formation of a stable arch of bulk solids above the discharge outlet of a hopper or silo, stopping material flow. The universal failure mode of bulk-solids storage.",[615,618],{"title":616,"url":617},"Powder & Bulk Solids — Preventing Rat-Holing and Bridging in Powder Silos","https:\u002F\u002Fsgsystemsglobal.com\u002Fglossary\u002Fsilo-rat-holing-and-bridging\u002F",{"title":619,"url":620},"Accendo Reliability — Bridging in Silos and Hoppers","https:\u002F\u002Faccendoreliability.com\u002Fbridging-silos-hoppers\u002F","glossary\u002Fbridging","Bridging (bulk-solids)","qG-iJwvR3z5_NliCxfeui3lEL9wxjVY3kU3rO9JWn8g",{"id":625,"title":240,"aliases":626,"body":630,"category":255,"description":739,"extension":257,"meta":740,"navigation":259,"path":179,"relatedTerms":741,"seo":742,"sources":745,"stem":747,"term":240,"__hash__":748},"glossary\u002Fglossary\u002Frat-holing.md",[627,628,629],"rat holing","rathole","piping (silos)",{"type":52,"value":631,"toc":733},[632,646,650,676,680,698,702,709,711],[55,633,634,636,637,448,639,641,642,645],{},[59,635,240],{}," is a bulk-solids flow pattern in which material discharges through a narrow vertical channel directly above the ",[172,638,262],{"href":229},[172,640,417],{"href":377}," outlet, while the surrounding material remains stagnant and progressively consolidates. The result is a ",[172,643,644],{"href":346},"funnel-flow"," condition gone to the extreme: most of the silo contents never move.",[63,647,649],{"id":648},"why-rat-holing-matters","Why rat-holing matters",[162,651,652,658,664,670],{},[165,653,654,657],{},[59,655,656],{},"Effective storage volume collapses"," — only the narrow flowing column is usable",[165,659,660,663],{},[59,661,662],{},"Stagnant material consolidates and ages"," — eventually hardens beyond recovery without manual cleanout",[165,665,666,669],{},[59,667,668],{},"First-in, last-out becomes never-out"," — older material is trapped indefinitely",[165,671,672,675],{},[59,673,674],{},"Catastrophic collapse risk"," — when the rat-hole eventually breaks open under load it can release tonnes of compacted material suddenly into downstream equipment",[63,677,679],{"id":678},"causes","Causes",[162,681,682,685,688,695],{},[165,683,684],{},"Narrow outlet relative to silo diameter",[165,686,687],{},"Steep but insufficiently steep cone angle",[165,689,690,691,694],{},"Cohesive material below its ",[172,692,693],{"href":346},"mass-flow"," threshold",[165,696,697],{},"Failure of a discharge aid (vibrator, aeration) that previously prevented funnel flow",[63,699,701],{"id":700},"prevention","Prevention",[55,703,704,705,708],{},"The structural remedy is to redesign the cone for mass flow — steeper angle, larger outlet, smoother wall finish. Where that is not feasible, ",[172,706,707],{"href":184},"sonic horns"," mounted on the cone wall continuously vibrate the stagnant material and break the rat-hole pattern, restoring closer-to-mass-flow behaviour.",[63,710,222],{"id":221},[162,712,713,717,721,725,729],{},[165,714,715],{},[172,716,230],{"href":229},[165,718,719],{},[172,720,378],{"href":377},[165,722,723],{},[172,724,235],{"href":174},[165,726,727],{},[172,728,403],{"href":346},[165,730,731],{},[172,732,408],{"href":184},{"title":248,"searchDepth":249,"depth":249,"links":734},[735,736,737,738],{"id":648,"depth":249,"text":649},{"id":678,"depth":249,"text":679},{"id":700,"depth":249,"text":701},{"id":221,"depth":249,"text":222},"Rat-holing is a bulk-solids flow pattern in which material discharges through a narrow vertical channel directly above the hopper or silo outlet, while the surrounding material remains stagnant and progressively consolidates. The result is a funnel-flow condition gone to the extreme: most of the silo contents never move.",{},[262,417,175,420,421],{"title":743,"description":744},"Rat-holing — narrow flow channel surrounded by stagnant material","Rat-holing is a flow pattern in which material discharges through a narrow vertical channel above the outlet, while the surrounding material remains stagnant and consolidates.",[746],{"title":616,"url":617},"glossary\u002Frat-holing","3n3tr5ikWPxS_JBE88L9ukEJEOBUqUYJL_CIAM9Xol8",{"id":750,"title":246,"aliases":751,"body":754,"category":915,"description":916,"extension":257,"meta":917,"navigation":259,"path":245,"relatedTerms":918,"seo":921,"sources":924,"stem":928,"term":246,"__hash__":929},"glossary\u002Fglossary\u002Ffly-ash-hopper.md",[752,753],"fly ash hopper","ash hopper",{"type":52,"value":755,"toc":910},[756,780,784,787,791,794,879,881],[55,757,284,758,761,762,186,764,186,767,770,771,774,775,186,777,779],{},[59,759,760],{},"fly-ash hopper"," is any inverted-pyramid or trough-shaped vessel that collects particulate ash from a combustion plant's flue-gas-cleaning equipment — ",[172,763,291],{"href":290},[172,765,295],{"href":766},"\u002Fglossary\u002Ffabric-filter",[172,768,769],{"href":298},"economiser"," hoppers, ",[172,772,773],{"href":302},"air-heater"," hoppers, duct dropouts. Fly-ash hoppers across the gas-path system are notorious for ",[172,776,175],{"href":174},[172,778,180],{"href":179}," and pluggage.",[63,781,783],{"id":782},"why-fly-ash-bridges","Why fly ash bridges",[55,785,786],{},"Dry fly ash is a Geldart-C type powder — fine, cohesive, and prone to forming stable arches across narrowing geometries. Cohesion increases with moisture pickup, condensation at the cold end, residual unburnt carbon and chemical composition (high CaO ashes from biomass and lime are especially sticky). Once an arch forms, it tends to consolidate under continued dust accumulation above it.",[63,788,790],{"id":789},"sonic-horns-vs-air-cannons-on-fly-ash-hoppers","Sonic horns vs air cannons on fly-ash hoppers",[55,792,793],{},"The two technologies compete head-to-head:",[68,795,796,811],{},[71,797,798],{},[74,799,800,803,807],{},[77,801,802],{},"Attribute",[77,804,805],{},[172,806,408],{"href":184},[77,808,809],{},[172,810,535],{"href":189},[90,812,813,824,835,846,857,868],{},[74,814,815,818,821],{},[95,816,817],{},"Mechanism",[95,819,820],{},"Continuous low-amplitude vibration",[95,822,823],{},"Periodic high-pressure blast",[74,825,826,829,832],{},[95,827,828],{},"Coverage",[95,830,831],{},"Whole hopper volume from one unit",[95,833,834],{},"Localised to the cannon nozzle",[74,836,837,840,843],{},[95,838,839],{},"Structural stress",[95,841,842],{},"None",[95,844,845],{},"Significant; fatigue cracking documented",[74,847,848,851,854],{},[95,849,850],{},"Air consumption",[95,852,853],{},"Continuous, low",[95,855,856],{},"Episodic, high",[74,858,859,862,865],{},[95,860,861],{},"Retrofit complexity",[95,863,864],{},"Single roof or wall mounting",[95,866,867],{},"Multiple wall mountings + reservoirs",[74,869,870,873,876],{},[95,871,872],{},"Best suited to",[95,874,875],{},"Most ash types, retrofit-friendly",[95,877,878],{},"Hardest-packed deposits, large silos",[63,880,222],{"id":221},[162,882,883,889,893,897,901,905],{},[165,884,885],{},[172,886,888],{"href":887},"\u002Fglossary\u002Fesp-hopper","ESP hopper",[165,890,891],{},[172,892,230],{"href":229},[165,894,895],{},[172,896,235],{"href":174},[165,898,899],{},[172,900,240],{"href":179},[165,902,903],{},[172,904,408],{"href":184},[165,906,907],{},[172,908,909],{"href":189},"Air cannon (air blaster)",{"title":248,"searchDepth":249,"depth":249,"links":911},[912,913,914],{"id":782,"depth":249,"text":783},{"id":789,"depth":249,"text":790},{"id":221,"depth":249,"text":222},"esp","A fly-ash hopper is any inverted-pyramid or trough-shaped vessel that collects particulate ash from a combustion plant's flue-gas-cleaning equipment — ESPs, baghouses, economiser hoppers, air-heater hoppers, duct dropouts. Fly-ash hoppers across the gas-path system are notorious for bridging, rat-holing and pluggage.",{},[919,262,175,180,421,920],"esp-hopper","air-cannon-air-blaster",{"title":922,"description":923},"Fly-ash hopper — pluggage problems and sonic-horn flow aids","A fly-ash hopper collects particulate ash from ESP, baghouse, economiser and air-heater equipment. Bridging and rat-holing of fly ash are persistent operational problems.",[925],{"title":926,"url":927},"Power Engineering — Tuning in to Acoustic Cleaning","https:\u002F\u002Fwww.power-eng.com\u002Fcoal\u002Ftuning-in-to-acoustic-cleaning\u002F","glossary\u002Ffly-ash-hopper","bMJn5P2k_mbOQpek1uyPwzpxFkcSFi5BK-ujWWfDvwc",1782613740976]