Marteletes desgastados afetam negativamente as características operacionais da moagem e físicas do milho processado em moinho do tipo martelo / Worn hammers affect negatively grinding aspects and physical characteristics of the processed corn by hammer mill

Foi conduzido um trabalho para avaliar os efeitos dos níveis de desgaste de marteletes de moinho tipo martelo, sobre características físicas do milho e operacionais de moagem. Foram utilizados quatro diferentes lotes de milho, um moinho martelo com motor de 3.500 RPM, cinco conjuntos de marteletes com diferentes níveis de desgaste do vértice (0, 20, 43, 57 e 63%) e quatro diferentes peneiras com diâmetros de furos de 1, 3, 5 e 12 mm sob um esquema fatorial 5x4, com quatro repetições em um total de 80 unidades experimentais. O aumento no diâmetro dos furos das peneiras influenciou (P<0,05) com aumento na produção, nos decibéis, no diâmetro geométrico médio (DGM), no desvio padrão geométrico (DPG), na densidade e com redução no consumo de energia elétrica e no ângulo de repouso (AR). O maior desgaste do martelo aumentou (P<0,05) o consumo de energia elétrica, DGM, DPG, AR e com redução (P<0,05) na produtividade e densidade. A análise de Linear response plateau (LRP) indicou piora na produtividade do equipamento a partir dos 55,1% de desgaste. Neste contexto, o desgaste dos marteletes influenciou negativamente as características operacionais do equipamento e físicas do milho. Para favorecer as características físicas do milho moído e evitar perdas na produtividade do equipamento recomenda-se a moagem com martelos isentos de desgaste.(AU)

We investigated the effects of worn hammers on the physical characteristics of ground corn and on the milling equipment itself. We used four corn seed types, a hammer mill fitted with a 3500 RPM motor, five sets of hammers with various wear levels (0, 20, 43, 57 and 63%) and four sieves (1-, 3-, 5- and 12-mm diameters). The experiment was performed in factorial design 5 x 4 (five set of hammers and four sieves) with four replicates, totaling 80 experimental units. Increasing sieve pore diameter produced significant improvements in terms of production, decibel levels, particle size (PS), geometric standard deviation (GSD) and density, as well as significant reductions in electrical energy consumption and the angle of repose (AR) (P <0.05). The hammer with the highest wear significantly increased electric energy consumption, PS, GSD and AR and significantly reduced productivity and density (P <0.05). Linear response plateau (LRP) analysis indicated a worsening in machine productivity from 55.1% wear. Therefore, hammer wear negatively influenced hammer mill characteristics and the physical characteristics of the corn. To promote better physical characteristics of milled corn and to avoid losses in productivity, we recommended grinding with new hammers.(AU)

Marteletes desgastados afetam negativamente as características operacionais da moagem e físicas do milho processado em moinho do tipo martelo / Worn hammers affect negatively grinding aspects and physical characteristics of the processed corn by hammer mill

Foi conduzido um trabalho para avaliar os efeitos dos níveis de desgaste de marteletes de moinho tipo martelo, sobre características físicas do milho e operacionais de moagem. Foram utilizados quatro diferentes lotes de milho, um moinho martelo com motor de 3.500 RPM, cinco conjuntos de marteletes com diferentes níveis de desgaste do vértice (0, 20, 43, 57 e 63%) e quatro diferentes peneiras com diâmetros de furos de 1, 3, 5 e 12 mm sob um esquema fatorial 5x4, com quatro repetições em um total de 80 unidades experimentais. O aumento no diâmetro dos furos das peneiras influenciou (P<0,05) com aumento na produção, nos decibéis, no diâmetro geométrico médio (DGM), no desvio padrão geométrico (DPG), na densidade e com redução no consumo de energia elétrica e no ângulo de repouso (AR). O maior desgaste do martelo aumentou (P<0,05) o consumo de energia elétrica, DGM, DPG, AR e com redução (P<0,05) na produtividade e densidade. A análise de Linear response plateau (LRP) indicou piora na produtividade do equipamento a partir dos 55,1% de desgaste. Neste contexto, o desgaste dos marteletes influenciou negativamente as características operacionais do equipamento e físicas do milho. Para favorecer as características físicas do milho moído e evitar perdas na produtividade do equipamento recomenda-se a moagem com martelos isentos de desgaste.

We investigated the effects of worn hammers on the physical characteristics of ground corn and on the milling equipment itself. We used four corn seed types, a hammer mill fitted with a 3500 RPM motor, five sets of hammers with various wear levels (0, 20, 43, 57 and 63%) and four sieves (1-, 3-, 5- and 12-mm diameters). The experiment was performed in factorial design 5 x 4 (five set of hammers and four sieves) with four replicates, totaling 80 experimental units. Increasing sieve pore diameter produced significant improvements in terms of production, decibel levels, particle size (PS), geometric standard deviation (GSD) and density, as well as significant reductions in electrical energy consumption and the angle of repose (AR) (P <0.05). The hammer with the highest wear significantly increased electric energy consumption, PS, GSD and AR and significantly reduced productivity and density (P <0.05). Linear response plateau (LRP) analysis indicated a worsening in machine productivity from 55.1% wear. Therefore, hammer wear negatively influenced hammer mill characteristics and the physical characteristics of the corn. To promote better physical characteristics of milled corn and to avoid losses in productivity, we recommended grinding with new hammers.

Shredders are abundant and species-rich in tropical continental-island low-order streams: Gorgona Island, Tropical Eastern Pacific, Colombia / Trituradoras son abundantes y ricas en especies en corrientes de bajo orden de islas continentales tropicales: Isla Gorgona, Pacífico Oriental Tropical, Colombia

Macroinvertebrate shredders may have been overlooked in tropical streams due to the geographical bias of early studies, methodological limitations, and the complex influences of local-scale factors. While shredders seem to be scarce in most oceanic island streams, we here test if they are abundant in a continental island. Gut content analyses of benthic macroinvertebrates were used to identify shredding taxa in streams located in different types of forest in Gorgona Island (Tropical Eastern Pacific). General dietary overlap (GO) was quantified and relative biomass, relative frequency and the leaf litter percentage in the guts were used to establish the relative importance of each taxon in the shredding guild. Various indices were used to identify the spatial arrangement (i.e. contagious or random) of each taxon and shredding guild among streams. We identified 31 shredding taxa that were divided into specialist-shredders (14 taxa), generalist-shredders (10), and collector-shredders (7). There was a complete GO (0.75, p<0.001) for the guild. Cockroaches (Epilampra) were the most represented shredders due to the greatest contribution to guild total biomass and to the highest content of leaf litter in their guts. These organisms were more important than shrimps and crabs in terms of abundance and biomass in leaf pack samples. Potimirin shrimps ranked second and Stenochironomus midges ranked third. Among aquatic insects, other secondarily important species were Leptohyphes (Ephemeroptera), Macrelmis, Anchytarsus and Tetraglosa (Coleoptera). Ten taxa exhibited contagious spatial pattern and twenty-one exhibited a random distribution. Resource distribution (i.e., leaf packs) between streams was random too. The guild was contagiously distributed, but this result could be highly influenced by the taxa with contagious distribution. Mean abundance, richness and mean biomass of shredders were not significantly correlated with any of the environmental variables measured. Three factors seemly explain the high richness and abundance of shredders in Gorgona Island: (1) its continental origin, (2) its current proximity to the continent (35 km), and (3) the high diversity and availability of leaf litter and woody debris inputs to the streams. Although crabs, shrimps, aquatic insects and semiaquatic-cockroaches coexisted in Gorgona Island, the latter were the most important leaf litter shredders in terms of biomass. Rev. Biol. Trop. 62 (Suppl. 1): 85-105. Epub 2014 February 01.

Existe la posibilidad de que los macroinvertebrados fragmentadores hayan sido subvalorados en las quebradas tropicales debido al sesgo geográfico de los estudios realizados, a limitaciones metódicas y a la influencia de factores de escala local. A pesar de que los fragmentadores son escasos en las quebradas de islas oceánicas, hipotetizamos que son abundantes en Isla Gorgona. Los análisis de contenidos estomacales de estos organismos se usaron para identificar los taxones fragmentadores colectados en quebradas con diferentes tipos de bosque. Se cuantificaron el índice general de sobreposición dietaria (GO por su siglas en inglés), y el índice de valor de importancia de cada taxón en el gremio (con base en biomasa relativa, frecuencia relativa y proporción de tejido vegetal en los contenidos estomacales). El arreglo espacial de cada taxón y el del gremio entre quebradas (i.e., contagioso o aleatorio) se determinó a partir de varios índices. Se identificaron 31 fragmentadores, los cuales se dividieron en especialistas (14 taxones), generalistas (10) y colectores-fragmentadores (7). Hubo un GO completo del gremio (0.75, p<0.001). Debido a su alta contribución de biomasa y de abundancia al gremio, y a la elevada proporción de tejido vegetal consumido, las cucarachas (Epilampra) fueron los fragmentadores-especialistas más representativos, superiores incluso a camarones y cangrejos. El camarón Potimirin fue el segundo taxón más importante seguido por el díptero Stenochironomus. Entre los insectos acuáticos, otros taxones de importancia secundaria fueron Leptohyphes (Ephemeroptera), Macrelmis, Anchytarsus y Tetraglosa (Coleoptera). Diez taxones mostraron un patrón espacial de contagio, y 21 se organizaron aleatoriamente, al igual que los recursos (i.e., “paquetes” de hojarasca). Aunque el gremio se organizó contagiosamente, estos resultados pudieron estar altamente influenciados por los taxones con distribución del mismo tipo. No se encontraron correlaciones significantes entre la abundancia media, la riqueza y la biomasa media con ninguna de las variables ambientales. Tres factores explicaron la alta riqueza y la abundancia de los fragmentadores en Isla Gorgona: (1) el origen continental, (2) su proximidad al continente (35km), y (3) la alta diversidad y disponibilidad de hojarasca y de desechos de madera dentro de las quebradas. Aunque cangrejos, camarones, insectos acuáticos y cucarachas-semiacuáticas coexistieron en la isla, estas últimas fueron, en términos de biomasa, los fragmentadores más importantes.