[{"data":1,"prerenderedAt":1259},["ShallowReactive",2],{"site-footer-common":3,"glossary:esp-hopper":45,"glossary-related:esp-hopper":209},{"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":52,"category":187,"description":188,"extension":189,"meta":190,"navigation":191,"path":192,"relatedTerms":193,"seo":200,"sources":203,"stem":207,"term":47,"__hash__":208},"glossary\u002Fglossary\u002Fesp-hopper.md","ESP hopper",[49,50,51],"ESP ash hopper","precipitator hopper","dust hopper",{"type":53,"value":54,"toc":180},"minimark",[55,74,79,124,127,131,144,148],[56,57,58,59,62,63,68,69,73],"p",{},"An ",[60,61,47],"strong",{}," is the inverted-pyramid (or trough) vessel below each ",[64,65,67],"a",{"href":66},"\u002Fglossary\u002Felectrostatic-precipitator","ESP"," field that collects ash dislodged from the ",[64,70,72],{"href":71},"\u002Fglossary\u002Fcollecting-electrode","collecting electrodes",". Ash falls into the hopper and is extracted by pneumatic, drag-chain or hydraulic conveyors. ESP hoppers are one of the most chronic failure points in a coal, biomass, WtE or cement-plant flue-gas train.",[75,76,78],"h2",{"id":77},"why-esp-hoppers-fail","Why ESP hoppers fail",[80,81,82,92,101,107,118],"ul",{},[83,84,85,91],"li",{},[60,86,87],{},[64,88,90],{"href":89},"\u002Fglossary\u002Fbridging","Bridging"," — the ash forms a stable arch across the narrowing hopper, stopping discharge.",[83,93,94,100],{},[60,95,96],{},[64,97,99],{"href":98},"\u002Fglossary\u002Frat-holing","Rat-holing"," — a narrow channel forms above the outlet and the surrounding mass packs and hardens.",[83,102,103,106],{},[60,104,105],{},"Sneakage"," — gas short-circuits through hopper voids when extraction stops.",[83,108,109,112,113,117],{},[60,110,111],{},"Pluggage"," — full hoppers back ash up into the field, raising plate-face voltage and triggering ",[64,114,116],{"href":115},"\u002Fglossary\u002Fback-corona","back-corona",".",[83,119,120,123],{},[60,121,122],{},"Failed level switches"," that mask developing pluggage from operators.",[56,125,126],{},"Once an ESP hopper plugs, the affected field must be taken offline; full-load operation may not be possible while the hopper is cleaned by vacuum truck or manual lancing. A single hopper-cleaning outage can cost hundreds of MWh in lost generation.",[75,128,130],{"id":129},"sonic-horns-on-esp-hoppers","Sonic horns on ESP hoppers",[56,132,133,134,138,139,143],{},"A 60–125 Hz ",[64,135,137],{"href":136},"\u002Fglossary\u002Fsonic-horn","sonic horn"," mounted at the hopper wall is the standard mitigation. The horn fires every few minutes during normal operation, keeping the ash mobile and preventing the cohesive structures that lead to bridging and rat-holing. Acoustic horns are particularly favoured over ",[64,140,142],{"href":141},"\u002Fglossary\u002Fair-cannon-air-blaster","air cannons"," here because they cause no impact stress on the hopper structure, no fatigue on weld joints, and can be installed during a routine outage rather than a major shutdown.",[75,145,147],{"id":146},"related-terms","Related terms",[80,149,150,155,161,165,169,175],{},[83,151,152],{},[64,153,154],{"href":66},"Electrostatic precipitator",[83,156,157],{},[64,158,160],{"href":159},"\u002Fglossary\u002Fhopper","Hopper",[83,162,163],{},[64,164,90],{"href":89},[83,166,167],{},[64,168,99],{"href":98},[83,170,171],{},[64,172,174],{"href":173},"\u002Fglossary\u002Ffly-ash-hopper","Fly-ash hopper",[83,176,177],{},[64,178,179],{"href":136},"Sonic horn",{"title":181,"searchDepth":182,"depth":182,"links":183},"",2,[184,185,186],{"id":77,"depth":182,"text":78},{"id":129,"depth":182,"text":130},{"id":146,"depth":182,"text":147},"esp","An ESP hopper is the inverted-pyramid (or trough) vessel below each ESP field that collects ash dislodged from the collecting electrodes. Ash falls into the hopper and is extracted by pneumatic, drag-chain or hydraulic conveyors. ESP hoppers are one of the most chronic failure points in a coal, biomass, WtE or cement-plant flue-gas train.","md",{},true,"\u002Fglossary\u002Fesp-hopper",[194,195,196,197,198,199],"electrostatic-precipitator","hopper","bridging","rat-holing","fly-ash-hopper","sonic-horn",{"title":201,"description":202},"ESP hopper — bridging, pluggage and sonic-horn de-bridging","An ESP hopper is the inverted-pyramid vessel below each ESP field that collects rapped-down fly ash. Bridging and rat-holing are common failures; sonic horns are the standard mitigation.",[204],{"title":205,"url":206},"Power Engineering — Tuning in to Acoustic Cleaning","https:\u002F\u002Fwww.power-eng.com\u002Fcoal\u002Ftuning-in-to-acoustic-cleaning\u002F","glossary\u002Fesp-hopper","ahXWkBIudy7ZPXa82rBmYAWPJ32yu6Pvp9wqbeOrGtU",[210,380,533,734,859,1034],{"id":211,"title":212,"aliases":213,"body":216,"category":187,"description":356,"extension":189,"meta":357,"navigation":191,"path":66,"relatedTerms":358,"seo":365,"sources":368,"stem":378,"term":154,"__hash__":379},"glossary\u002Fglossary\u002Felectrostatic-precipitator.md","Electrostatic precipitator (ESP)",[67,214,215],"electrostatic precipitators","dry ESP",{"type":53,"value":217,"toc":350},[218,233,237,253,257,288,292,324,326],[56,219,58,220,223,224,228,229,232],{},[60,221,222],{},"electrostatic precipitator (ESP)"," is an air-pollution-control device that removes particulate matter from a flue-gas stream by electrostatically charging dust particles and collecting them on grounded plate electrodes. ESPs are the dominant particulate-control technology on coal-fired boilers, cement kilns, ",[64,225,227],{"href":226},"\u002Fglossary\u002Fwaste-to-energy","waste-to-energy"," plants, ",[64,230,231],{"href":226},"biomass"," plants, sinter strands and many other heavy-industry off-gas streams.",[75,234,236],{"id":235},"how-an-esp-works","How an ESP works",[56,238,239,240,242,243,247,248,252],{},"Flue gas flows horizontally between a parallel array of vertical ",[64,241,72],{"href":71}," (plates) and ",[64,244,246],{"href":245},"\u002Fglossary\u002Fdischarge-electrode","discharge electrodes"," (high-voltage wires or rigid spikes). A negative DC potential of 40–80 kV applied to the discharge electrodes generates a ",[64,249,251],{"href":250},"\u002Fglossary\u002Fcorona-discharge","corona discharge"," that ionises the gas. Charged dust particles drift to the collecting plates, accumulate as a dust layer, are rapped down into hoppers below and removed by ash-handling equipment.",[75,254,256],{"id":255},"where-sonic-horns-fit","Where sonic horns fit",[56,258,259,260,263,264,267,268,272,273,277,278,280,281,283,284,117],{},"ESPs accumulate dust faster than mechanical rapping can release it, and hoppers below ESP fields routinely ",[64,261,262],{"href":89},"bridge"," and choke. ",[64,265,266],{"href":136},"Sonic horns"," installed on the ESP ",[64,269,271],{"href":270},"\u002Fglossary\u002Fesp-penthouse","penthouse"," and on hopper walls keep dust dislodged, supplement ",[64,274,276],{"href":275},"\u002Fglossary\u002Fesp-rapper","rappers",", prevent ",[64,279,116],{"href":115}," by limiting plate dust thickness, and eliminate hopper ",[64,282,197],{"href":98}," without the structural fatigue of ",[64,285,287],{"href":286},"\u002Fglossary\u002Ftumbling-hammer-rapper","tumbling-hammer rappers",[75,289,291],{"id":290},"common-failure-modes","Common failure modes",[80,293,294,300,306,312,318],{},[83,295,296,299],{},[60,297,298],{},"High opacity \u002F particulate emissions"," from thick dust layers reducing collection efficiency",[83,301,302,305],{},[60,303,304],{},"Back-corona"," in high-resistivity ash that reverses ionisation and collapses collection",[83,307,308,311],{},[60,309,310],{},"Re-entrainment"," as rapper puffs return dust to the gas stream",[83,313,314,317],{},[60,315,316],{},"Hopper bridging"," that stops ash extraction and triggers field shutdowns",[83,319,320,323],{},[60,321,322],{},"Discharge-electrode breakage"," from rapper fatigue or sparking",[75,325,147],{"id":146},[80,327,328,333,338,342,346],{},[83,329,330],{},[64,331,332],{"href":71},"Collecting electrode",[83,334,335],{},[64,336,337],{"href":245},"Discharge electrode",[83,339,340],{},[64,341,304],{"href":115},[83,343,344],{},[64,345,47],{"href":192},[83,347,348],{},[64,349,179],{"href":136},{"title":181,"searchDepth":182,"depth":182,"links":351},[352,353,354,355],{"id":235,"depth":182,"text":236},{"id":255,"depth":182,"text":256},{"id":290,"depth":182,"text":291},{"id":146,"depth":182,"text":147},"An electrostatic precipitator (ESP) is an air-pollution-control device that removes particulate matter from a flue-gas stream by electrostatically charging dust particles and collecting them on grounded plate electrodes. ESPs are the dominant particulate-control technology on coal-fired boilers, cement kilns, waste-to-energy plants, biomass plants, sinter strands and many other heavy-industry off-gas streams.",{},[359,360,361,362,363,364,116,199],"wet-esp","collecting-electrode","discharge-electrode","corona-discharge","esp-hopper","esp-rapper",{"title":366,"description":367},"Electrostatic precipitator (ESP) — how it works and how it fouls","An ESP removes particulate from flue gas by charging dust and collecting it on plate electrodes. Sonic horns are widely used to dislodge ash from plates and to keep hoppers from bridging.",[369,372,375],{"title":370,"url":371},"Wikipedia — Electrostatic precipitator","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FElectrostatic_precipitator",{"title":373,"url":374},"EPA — Monitoring Knowledge Base: Electrostatic Precipitators","https:\u002F\u002Fwww.epa.gov\u002Fair-emissions-monitoring-knowledge-base\u002Fmonitoring-control-technique-electrostatic-precipitators",{"title":376,"url":377},"Babcock & Wilcox — Basics of ESP Operation","https:\u002F\u002Fwww.babcock.com\u002Fhome\u002Fabout\u002Fresources\u002Flearning-center\u002Fbasic-esp-operation","glossary\u002Felectrostatic-precipitator","hT_C4hmid3iZaYWhLpiSJ2tBfL0bSJ-uhzn7TY4Vtj4",{"id":381,"title":160,"aliases":382,"body":386,"category":516,"description":517,"extension":189,"meta":518,"navigation":191,"path":159,"relatedTerms":519,"seo":524,"sources":527,"stem":531,"term":160,"__hash__":532},"glossary\u002Fglossary\u002Fhopper.md",[383,384,385],"hoppers","storage hopper","process hopper",{"type":53,"value":387,"toc":511},[388,417,421,452,456,472,474],[56,389,390,391,393,394,397,398,397,402,397,406,410,411,397,414,416],{},"A ",[60,392,195],{}," is an inverted-pyramid or conical vessel designed to store bulk solids and discharge them through a converging outlet. Hoppers appear under ",[64,395,396],{"href":66},"ESPs",", ",[64,399,401],{"href":400},"\u002Fglossary\u002Fbaghouse","baghouses",[64,403,405],{"href":404},"\u002Fglossary\u002Feconomiser","economisers",[64,407,409],{"href":408},"\u002Fglossary\u002Fair-heater","air heaters"," and process equipment of every kind across cement, power, ",[64,412,413],{"href":226},"WtE",[64,415,231],{"href":226},", refining, pharma, food and mining.",[75,418,420],{"id":419},"universal-failure-modes","Universal failure modes",[80,422,423,430,437,442],{},[83,424,425,429],{},[60,426,427],{},[64,428,90],{"href":89}," — stable arch forms above the outlet",[83,431,432,436],{},[60,433,434],{},[64,435,99],{"href":98}," — narrow channel above the outlet; surrounding material packs and hardens",[83,438,439,441],{},[60,440,111],{}," — total blockage that stops discharge",[83,443,444,451],{},[60,445,446,447],{},"Funnel flow vs ",[64,448,450],{"href":449},"\u002Fglossary\u002Fmass-flow-vs-funnel-flow","mass flow"," — first-in, last-out behaviour leading to ageing material remaining indefinitely",[75,453,455],{"id":454},"why-acoustic-cleaning-works-on-hoppers","Why acoustic cleaning works on hoppers",[56,457,458,460,461,397,465,397,467,471],{},[64,459,266],{"href":136}," 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 — ",[64,462,464],{"href":463},"\u002Fglossary\u002Fbin-vibrator","bin vibrators",[64,466,142],{"href":141},[64,468,470],{"href":469},"\u002Fglossary\u002Fwhip-hammer","whip hammers"," — they cause no structural stress, no fatigue, and no impact damage to the hopper itself.",[75,473,147],{"id":146},[80,475,476,482,488,494,498,502,507],{},[83,477,478],{},[64,479,481],{"href":480},"\u002Fglossary\u002Fsilo","Silo",[83,483,484],{},[64,485,487],{"href":486},"\u002Fglossary\u002Fbunker-coal-bunker","Bunker \u002F coal bunker",[83,489,490],{},[64,491,493],{"href":492},"\u002Fglossary\u002Fbin","Bin",[83,495,496],{},[64,497,90],{"href":89},[83,499,500],{},[64,501,99],{"href":98},[83,503,504],{},[64,505,506],{"href":449},"Mass flow vs funnel flow",[83,508,509],{},[64,510,179],{"href":136},{"title":181,"searchDepth":182,"depth":182,"links":512},[513,514,515],{"id":419,"depth":182,"text":420},{"id":454,"depth":182,"text":455},{"id":146,"depth":182,"text":147},"hoppers-silos","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.",{},[520,521,522,196,197,523,199],"silo","bunker-coal-bunker","bin","mass-flow-vs-funnel-flow",{"title":525,"description":526},"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.",[528],{"title":529,"url":530},"Wikipedia — Hopper (particulate collection container)","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FHopper_(particulate_collection_container)","glossary\u002Fhopper","yaS0yQSinQlli40xEUR0l9zzxphPNmE4Pi2XHYeAc4k",{"id":534,"title":90,"aliases":535,"body":540,"category":516,"description":718,"extension":189,"meta":719,"navigation":191,"path":89,"relatedTerms":720,"seo":721,"sources":724,"stem":731,"term":732,"__hash__":733},"glossary\u002Fglossary\u002Fbridging.md",[536,537,538,539],"arching","arch formation","hopper bridging","silo bridging",{"type":53,"value":541,"toc":712},[542,559,563,566,588,592,606,610,688,690],[56,543,544,546,547,550,551,553,554,550,556,558],{},[60,545,90],{}," (also ",[548,549,536],"em",{}," or ",[548,552,537],{},") is the formation of a stable mechanical arch of bulk-solid material above the discharge outlet of a ",[64,555,195],{"href":159},[64,557,520],{"href":480},". 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.",[75,560,562],{"id":561},"how-a-bridge-forms","How a bridge forms",[56,564,565],{},"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:",[80,567,568,576,579,582,585],{},[83,569,570,571,575],{},"Fine particle size (especially Geldart-C powders — see ",[64,572,574],{"href":573},"\u002Fglossary\u002Fgeldart-classification","Geldart classification",")",[83,577,578],{},"Moisture",[83,580,581],{},"Hygroscopic chemistry (urea, ammonium nitrate, lime)",[83,583,584],{},"Long residence time (consolidation under sustained load)",[83,586,587],{},"Temperature cycling",[75,589,591],{"id":590},"diagnosing-a-bridge","Diagnosing a bridge",[80,593,594,597,600,603],{},[83,595,596],{},"Outlet flow stops while the level above remains high",[83,598,599],{},"Mass-flow indicators report no movement",[83,601,602],{},"A simple tap on the hopper outside the discharge cone produces a hollow sound",[83,604,605],{},"Borescope inspection from the inlet shows the arch directly",[75,607,609],{"id":608},"remedies","Remedies",[611,612,613,626],"table",{},[614,615,616],"thead",{},[617,618,619,623],"tr",{},[620,621,622],"th",{},"Technique",[620,624,625],{},"Notes",[627,628,629,639,649,659,669,680],"tbody",{},[617,630,631,636],{},[632,633,634],"td",{},[64,635,179],{"href":136},[632,637,638],{},"Continuous prevention; non-contact; minimal infrastructure",[617,640,641,646],{},[632,642,643],{},[64,644,645],{"href":141},"Air cannon",[632,647,648],{},"High-intensity periodic; effective on hard bridges; structural stress",[617,650,651,656],{},[632,652,653],{},[64,654,655],{"href":463},"Bin vibrator",[632,657,658],{},"Continuous vibration; can compact powder further if poorly sized",[617,660,661,666],{},[632,662,663],{},[64,664,665],{"href":469},"Whip hammer",[632,667,668],{},"Manual; legacy; HSE concerns",[617,670,671,677],{},[632,672,673],{},[64,674,676],{"href":675},"\u002Fglossary\u002Ffluidisation-pad-aeration-pad","Fluidisation pad",[632,678,679],{},"Aerates the lower vessel; not suitable for wet material",[617,681,682,685],{},[632,683,684],{},"Mechanical screw extractor",[632,686,687],{},"Bypasses the bridge entirely; high capex",[75,689,147],{"id":146},[80,691,692,696,700,704,708],{},[83,693,694],{},[64,695,160],{"href":159},[83,697,698],{},[64,699,481],{"href":480},[83,701,702],{},[64,703,99],{"href":98},[83,705,706],{},[64,707,506],{"href":449},[83,709,710],{},[64,711,179],{"href":136},{"title":181,"searchDepth":182,"depth":182,"links":713},[714,715,716,717],{"id":561,"depth":182,"text":562},{"id":590,"depth":182,"text":591},{"id":608,"depth":182,"text":609},{"id":146,"depth":182,"text":147},"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.",{},[195,520,197,523,199],{"title":722,"description":723},"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.",[725,728],{"title":726,"url":727},"Powder & Bulk Solids — Preventing Rat-Holing and Bridging in Powder Silos","https:\u002F\u002Fsgsystemsglobal.com\u002Fglossary\u002Fsilo-rat-holing-and-bridging\u002F",{"title":729,"url":730},"Accendo Reliability — Bridging in Silos and Hoppers","https:\u002F\u002Faccendoreliability.com\u002Fbridging-silos-hoppers\u002F","glossary\u002Fbridging","Bridging (bulk-solids)","qG-iJwvR3z5_NliCxfeui3lEL9wxjVY3kU3rO9JWn8g",{"id":735,"title":99,"aliases":736,"body":740,"category":516,"description":849,"extension":189,"meta":850,"navigation":191,"path":98,"relatedTerms":851,"seo":852,"sources":855,"stem":857,"term":99,"__hash__":858},"glossary\u002Fglossary\u002Frat-holing.md",[737,738,739],"rat holing","rathole","piping (silos)",{"type":53,"value":741,"toc":843},[742,756,760,786,790,808,812,819,821],[56,743,744,746,747,550,749,751,752,755],{},[60,745,99],{}," is a bulk-solids flow pattern in which material discharges through a narrow vertical channel directly above the ",[64,748,195],{"href":159},[64,750,520],{"href":480}," outlet, while the surrounding material remains stagnant and progressively consolidates. The result is a ",[64,753,754],{"href":449},"funnel-flow"," condition gone to the extreme: most of the silo contents never move.",[75,757,759],{"id":758},"why-rat-holing-matters","Why rat-holing matters",[80,761,762,768,774,780],{},[83,763,764,767],{},[60,765,766],{},"Effective storage volume collapses"," — only the narrow flowing column is usable",[83,769,770,773],{},[60,771,772],{},"Stagnant material consolidates and ages"," — eventually hardens beyond recovery without manual cleanout",[83,775,776,779],{},[60,777,778],{},"First-in, last-out becomes never-out"," — older material is trapped indefinitely",[83,781,782,785],{},[60,783,784],{},"Catastrophic collapse risk"," — when the rat-hole eventually breaks open under load it can release tonnes of compacted material suddenly into downstream equipment",[75,787,789],{"id":788},"causes","Causes",[80,791,792,795,798,805],{},[83,793,794],{},"Narrow outlet relative to silo diameter",[83,796,797],{},"Steep but insufficiently steep cone angle",[83,799,800,801,804],{},"Cohesive material below its ",[64,802,803],{"href":449},"mass-flow"," threshold",[83,806,807],{},"Failure of a discharge aid (vibrator, aeration) that previously prevented funnel flow",[75,809,811],{"id":810},"prevention","Prevention",[56,813,814,815,818],{},"The structural remedy is to redesign the cone for mass flow — steeper angle, larger outlet, smoother wall finish. Where that is not feasible, ",[64,816,817],{"href":136},"sonic horns"," mounted on the cone wall continuously vibrate the stagnant material and break the rat-hole pattern, restoring closer-to-mass-flow behaviour.",[75,820,147],{"id":146},[80,822,823,827,831,835,839],{},[83,824,825],{},[64,826,160],{"href":159},[83,828,829],{},[64,830,481],{"href":480},[83,832,833],{},[64,834,90],{"href":89},[83,836,837],{},[64,838,506],{"href":449},[83,840,841],{},[64,842,179],{"href":136},{"title":181,"searchDepth":182,"depth":182,"links":844},[845,846,847,848],{"id":758,"depth":182,"text":759},{"id":788,"depth":182,"text":789},{"id":810,"depth":182,"text":811},{"id":146,"depth":182,"text":147},"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.",{},[195,520,196,523,199],{"title":853,"description":854},"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.",[856],{"title":726,"url":727},"glossary\u002Frat-holing","3n3tr5ikWPxS_JBE88L9ukEJEOBUqUYJL_CIAM9Xol8",{"id":860,"title":174,"aliases":861,"body":864,"category":187,"description":1023,"extension":189,"meta":1024,"navigation":191,"path":173,"relatedTerms":1025,"seo":1027,"sources":1030,"stem":1032,"term":174,"__hash__":1033},"glossary\u002Fglossary\u002Ffly-ash-hopper.md",[862,863],"fly ash hopper","ash hopper",{"type":53,"value":865,"toc":1018},[866,890,894,897,901,904,989,991],[56,867,390,868,871,872,397,874,397,877,880,881,884,885,397,887,889],{},[60,869,870],{},"fly-ash hopper"," is any inverted-pyramid or trough-shaped vessel that collects particulate ash from a combustion plant's flue-gas-cleaning equipment — ",[64,873,396],{"href":66},[64,875,401],{"href":876},"\u002Fglossary\u002Ffabric-filter",[64,878,879],{"href":404},"economiser"," hoppers, ",[64,882,883],{"href":408},"air-heater"," hoppers, duct dropouts. Fly-ash hoppers across the gas-path system are notorious for ",[64,886,196],{"href":89},[64,888,197],{"href":98}," and pluggage.",[75,891,893],{"id":892},"why-fly-ash-bridges","Why fly ash bridges",[56,895,896],{},"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.",[75,898,900],{"id":899},"sonic-horns-vs-air-cannons-on-fly-ash-hoppers","Sonic horns vs air cannons on fly-ash hoppers",[56,902,903],{},"The two technologies compete head-to-head:",[611,905,906,921],{},[614,907,908],{},[617,909,910,913,917],{},[620,911,912],{},"Attribute",[620,914,915],{},[64,916,179],{"href":136},[620,918,919],{},[64,920,645],{"href":141},[627,922,923,934,945,956,967,978],{},[617,924,925,928,931],{},[632,926,927],{},"Mechanism",[632,929,930],{},"Continuous low-amplitude vibration",[632,932,933],{},"Periodic high-pressure blast",[617,935,936,939,942],{},[632,937,938],{},"Coverage",[632,940,941],{},"Whole hopper volume from one unit",[632,943,944],{},"Localised to the cannon nozzle",[617,946,947,950,953],{},[632,948,949],{},"Structural stress",[632,951,952],{},"None",[632,954,955],{},"Significant; fatigue cracking documented",[617,957,958,961,964],{},[632,959,960],{},"Air consumption",[632,962,963],{},"Continuous, low",[632,965,966],{},"Episodic, high",[617,968,969,972,975],{},[632,970,971],{},"Retrofit complexity",[632,973,974],{},"Single roof or wall mounting",[632,976,977],{},"Multiple wall mountings + reservoirs",[617,979,980,983,986],{},[632,981,982],{},"Best suited to",[632,984,985],{},"Most ash types, retrofit-friendly",[632,987,988],{},"Hardest-packed deposits, large silos",[75,990,147],{"id":146},[80,992,993,997,1001,1005,1009,1013],{},[83,994,995],{},[64,996,47],{"href":192},[83,998,999],{},[64,1000,160],{"href":159},[83,1002,1003],{},[64,1004,90],{"href":89},[83,1006,1007],{},[64,1008,99],{"href":98},[83,1010,1011],{},[64,1012,179],{"href":136},[83,1014,1015],{},[64,1016,1017],{"href":141},"Air cannon (air blaster)",{"title":181,"searchDepth":182,"depth":182,"links":1019},[1020,1021,1022],{"id":892,"depth":182,"text":893},{"id":899,"depth":182,"text":900},{"id":146,"depth":182,"text":147},"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.",{},[363,195,196,197,199,1026],"air-cannon-air-blaster",{"title":1028,"description":1029},"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.",[1031],{"title":205,"url":206},"glossary\u002Ffly-ash-hopper","bMJn5P2k_mbOQpek1uyPwzpxFkcSFi5BK-ujWWfDvwc",{"id":1035,"title":179,"aliases":1036,"body":1039,"category":1236,"description":1237,"extension":189,"meta":1238,"navigation":191,"path":136,"relatedTerms":1239,"seo":1246,"sources":1249,"stem":1257,"term":179,"__hash__":1258},"glossary\u002Fglossary\u002Fsonic-horn.md",[817,1037,1038],"sonic cleaning horn","industrial sonic horn",{"type":53,"value":1040,"toc":1229},[1041,1067,1071,1079,1083,1145,1149,1185,1189,1197,1199],[56,1042,390,1043,1045,1046,1050,1051,397,1053,397,1055,397,1059,1063,1064,117],{},[60,1044,137],{}," is a pneumatically-driven sound emitter that produces high-intensity, low-frequency sound waves — typically between 60 and 400 Hz at sound pressure levels of 140 to 180 dB — used to dislodge particulate fouling from inside industrial process equipment. Sonic horns are the most common form of ",[64,1047,1049],{"href":1048},"\u002Fglossary\u002Facoustic-cleaner","acoustic cleaner"," and the default specification for cleaning ",[64,1052,396],{"href":66},[64,1054,401],{"href":876},[64,1056,1058],{"href":1057},"\u002Fglossary\u002Fselective-catalytic-reduction","SCR catalysts",[64,1060,1062],{"href":1061},"\u002Fglossary\u002Fsuperheater","boiler heat-transfer surfaces"," and ",[64,1065,1066],{"href":159},"hoppers and silos",[75,1068,1070],{"id":1069},"how-a-sonic-horn-works","How a sonic horn works",[56,1072,1073,1074,1078],{},"Compressed plant air admitted through a ",[64,1075,1077],{"href":1076},"\u002Fglossary\u002Fsolenoid-valve","solenoid valve"," drives a metal diaphragm — typically titanium or 316 stainless — into resonant oscillation at the horn's fundamental frequency. The oscillating pressure field is amplified by an exponential bell horn and projected into the vessel as a near-spherical sound wave. Particulate already deposited on internal surfaces receives an oscillating acceleration that overcomes adhesion; loosened material is then carried out with the gas flow before it can sinter, bridge or bond. Because the cleaning is acoustic and non-contact, the horn can fire while the plant is online without tube erosion, refractory damage or thermal shock.",[75,1080,1082],{"id":1081},"key-parameters","Key parameters",[611,1084,1085,1095],{},[614,1086,1087],{},[617,1088,1089,1092],{},[620,1090,1091],{},"Parameter",[620,1093,1094],{},"Typical range",[627,1096,1097,1105,1113,1121,1129,1137],{},[617,1098,1099,1102],{},[632,1100,1101],{},"Fundamental frequency",[632,1103,1104],{},"60–400 Hz",[617,1106,1107,1110],{},[632,1108,1109],{},"Sound pressure level",[632,1111,1112],{},"140–180 dB",[617,1114,1115,1118],{},[632,1116,1117],{},"Compressed-air consumption",[632,1119,1120],{},"8–14 Nm³\u002Fmin at 4–7 bar",[617,1122,1123,1126],{},[632,1124,1125],{},"Operating temperature (with appropriate materials)",[632,1127,1128],{},"−40 °C to +500 °C",[617,1130,1131,1134],{},[632,1132,1133],{},"Firing cycle",[632,1135,1136],{},"5–15 s burst, repeated every 3–15 minutes",[617,1138,1139,1142],{},[632,1140,1141],{},"Mass",[632,1143,1144],{},"15–60 kg depending on horn size",[75,1146,1148],{"id":1147},"frequency-selection","Frequency selection",[56,1150,1151,1152,397,1156,1160,1161,397,1165,1168,1169,397,1172,1176,1177,1063,1181,117],{},"Lower frequencies (60–125 Hz) project longer wavelengths and penetrate further into large open vessels — ",[64,1153,1155],{"href":1154},"\u002Fglossary\u002Fpreheater-cyclone","preheater cyclones",[64,1157,1159],{"href":1158},"\u002Fglossary\u002Frecovery-boiler","recovery-boiler superheaters",", large ",[64,1162,1164],{"href":1163},"\u002Fglossary\u002Fesp-field-bus-section","ESP fields",[64,1166,1167],{"href":480},"silos",". Higher frequencies (230–400 Hz) carry more energy per unit volume and suit finer dust loads in ",[64,1170,1171],{"href":876},"fabric-filter compartments",[64,1173,1175],{"href":1174},"\u002Fglossary\u002Fhoneycomb-catalyst","catalyst layers"," and smaller hopper geometries. See ",[64,1178,1180],{"href":1179},"\u002Fglossary\u002Flow-frequency-acoustic-cleaner","low-frequency acoustic cleaner",[64,1182,1184],{"href":1183},"\u002Fglossary\u002Fhigh-frequency-acoustic-cleaner","high-frequency acoustic cleaner",[75,1186,1188],{"id":1187},"sonic-horn-vs-steam-sootblower","Sonic horn vs steam sootblower",[56,1190,1191,1192,1196],{},"Sonic horns are increasingly specified alongside or in place of ",[64,1193,1195],{"href":1194},"\u002Fglossary\u002Fsteam-sootblower","steam sootblowers"," because they consume no boiler-grade steam, cause no tube erosion, require almost no moving parts and can fire every few minutes without operator intervention. They are less effective on hard, fused slag than retractable steam lances, so on furnace waterwalls and high-temperature superheaters they typically complement rather than replace mechanical cleaning.",[75,1198,147],{"id":146},[80,1200,1201,1206,1212,1218,1224],{},[83,1202,1203],{},[64,1204,1205],{"href":1048},"Acoustic cleaner",[83,1207,1208],{},[64,1209,1211],{"href":1210},"\u002Fglossary\u002Fsonic-sootblower","Sonic sootblower",[83,1213,1214],{},[64,1215,1217],{"href":1216},"\u002Fglossary\u002Fbell-horn","Bell horn",[83,1219,1220],{},[64,1221,1223],{"href":1222},"\u002Fglossary\u002Fdiaphragm-horn","Diaphragm horn",[83,1225,1226],{},[64,1227,1228],{"href":1179},"Low-frequency acoustic cleaner",{"title":181,"searchDepth":182,"depth":182,"links":1230},[1231,1232,1233,1234,1235],{"id":1069,"depth":182,"text":1070},{"id":1081,"depth":182,"text":1082},{"id":1147,"depth":182,"text":1148},{"id":1187,"depth":182,"text":1188},{"id":146,"depth":182,"text":147},"core-technology","A sonic horn is a pneumatically-driven sound emitter that produces high-intensity, low-frequency sound waves — typically between 60 and 400 Hz at sound pressure levels of 140 to 180 dB — used to dislodge particulate fouling from inside industrial process equipment. Sonic horns are the most common form of acoustic cleaner and the default specification for cleaning ESPs, baghouses, SCR catalysts, boiler heat-transfer surfaces and hoppers and silos.",{},[1240,1241,1242,1243,1244,1245],"acoustic-cleaner","acoustic-cleaning-system","sonic-sootblower","bell-horn","diaphragm-horn","low-frequency-acoustic-cleaner",{"title":1247,"description":1248},"Sonic horn — definition, frequency, SPL and industrial applications","A sonic horn is a pneumatically-driven low-frequency sound emitter (typically 60–400 Hz at 140–180 dB SPL) used to dislodge particulate fouling from boilers, ESPs, baghouses and process vessels.",[1250,1253,1254],{"title":1251,"url":1252},"Power Engineering — Sonic Horns: A User's Introduction","https:\u002F\u002Fwww.power-eng.com\u002Fcoal\u002Fsonic-horns-a-userrsquos-introduction\u002F",{"title":205,"url":206},{"title":1255,"url":1256},"Wikipedia — Sonic soot blowers","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FSonic_soot_blowers","glossary\u002Fsonic-horn","YzrhN0kKzqSaQo0wfn0rueNZ-V43mcg5zahqeWi3lnU",1782613734987]