English Translation \u2013 Material Sticking and Flow Blockage Mechanisms<\/p>\n
Flow blockage does not belong to the four types of wear because, in this case, the lining material is not gradually lost from the surface; instead, the handled material builds up and accumulates on the equipment walls<\/strong>. As the build-up layer increases, the flow cross-section narrows, the material flow slows down, and the conditions for further accumulation become increasingly favorable. Material can adhere to the surface under the action of two types of forces:<\/p>\n A common condition requiring attention is the moisture content of the material<\/strong>. As the amount of water decreases, the effect of liquid bridges also decreases. Blockage does not necessarily increase at a constant rate over time. Once a build-up layer has formed, it can itself make the flow conditions less favorable.<\/p>\n This cycle explains why a location can operate relatively steadily for a period and then transition more rapidly into a blocked condition. Not all flow-blockage phenomena involve the same mechanism.<\/p>\n These three forms should not be addressed in the same way. Both terms involve \u201cadhesion,\u201d but they describe two different phenomena.<\/p>\n One indication that can be checked at the location is the thickness condition at the surface<\/strong>. If the thickness increases because an additional build-up layer has formed, the problem cannot be considered solely as wear loss of the lining. Three questions help narrow down the phenomenon:<\/p>\n If the flow stops while material remains above, the possibility of arching<\/strong> needs to be checked.<\/p>\n If the flow continues but mainly through the central region while the material adjacent to the walls remains stagnant, ratholing<\/strong> needs to be considered.<\/p>\n If material progressively builds up on the walls and the cross-section becomes increasingly smaller, wall build-up<\/strong> should be prioritized for investigation.<\/p>\n These questions help identify the governing form, but they do not mean that the three phenomena always occur completely independently.<\/p>\n After identifying the type of blockage, the next step is to determine which group of factors needs to be checked.<\/p>\n The latter two groups are no longer purely material-related problems.<\/p>\n If the primary cause lies in geometry or the condition of the material, replacing the lining may change the timing of blockage occurrence but may not eliminate the cause.<\/p>\n Hardness is relevant when the surface needs to resist hard particles cutting, scratching, or producing mechanical action.<\/p>\n In a material-sticking problem, the primary phenomenon is instead material being retained on the surface<\/strong>. Therefore, simply increasing hardness does not directly affect the mechanism by which the build-up layer forms.<\/p>\n The characteristics that need to be considered shift toward the ability to promote sliding flow and the interaction between the material and the surface<\/strong>.<\/p>\n The selection of material groups for this case is presented in the Principles of Material Selection<\/strong> knowledge cluster.<\/p>\n Before deciding to replace the lining, the response of the flow can be checked when geometric conditions or flow-assistance actions are changed.<\/p>\n If increasing the sliding angle restores the flow, the influence of geometry<\/strong> should be prioritized for consideration.<\/p>\n At locations where the angle cannot be changed directly, the response of the flow after light tapping or vibration can also provide additional information. If the flow is released after this action, the possibility of arching<\/strong> needs to be checked.<\/p>\n These checks only help narrow down the cause and do not replace measurement of the actual material-flow and geometric parameters.<\/p>\n A flow-blockage survey needs to focus on the build-up layer and material-flow behavior<\/strong>, rather than only measuring the remaining lining material.<\/p>\n Four groups of information need to be recorded:<\/p>\n The angle to be measured is the angle of the working surface at the surveyed location; the value shown on the design drawing should not be used alone.<\/p>\n Once a build-up layer has formed, the geometry actually contacted by the material flow may also differ from the original condition of the equipment.<\/p>\n Comments such as \u201cfrequent blockage\u201d or \u201crequires frequent clearing\u201d are not sufficient for comparison between different periods or for evaluating the impact on operations.<\/p>\n The information should be obtained from the operating log<\/strong> and recorded numerically.<\/p>\n Three data points that can be monitored include:<\/p>\n Converting the intervention history into numerical data enables comparison of the condition before and after a change in the solution.<\/p>\n Moisture content and material condition may change with the season.<\/p>\n If conditions differ between the dry season and the rainy season, data from one point in time should not be used as representative of the entire year.<\/p>\n Therefore, the record needs to clearly state the survey timing, material conditions, and the season in which more severe blockage occurs according to operating data<\/strong>.<\/p>\n This information is particularly important when comparing different surveys or evaluating the effectiveness of a change at the location.<\/p>\n To evaluate the material’s tendency to adhere and slide in greater detail, three indicators need to be considered:<\/p>\n
\nTherefore, a location can transition from slow-flow conditions to complete blockage within a short period. Before selecting a corrective approach, it is necessary to distinguish three common forms: wall build-up, arching, and ratholing<\/strong>, because each form is associated with different surface, geometry, and material-flow conditions.<\/p>\n1. Mechanisms of material sticking and flow blockage<\/span><\/h2>\n
1.1. Moisture creates conditions for material to adhere to the surface<\/span><\/h3>\n
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\nTherefore, in material-sticking problems, moisture content is one of the variables that needs to be checked before concluding that the cause lies in the hardness or wear resistance of the lining.<\/p>\n1.2. The build-up layer can create an increasingly rapid accumulation cycle<\/span><\/h3>\n
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\n Step<\/strong><\/th>\n Progression<\/strong><\/th>\n<\/tr>\n<\/thead>\n\n \n 1<\/strong><\/td>\n Material begins to adhere to the surface<\/td>\n<\/tr>\n \n 2<\/strong><\/td>\n The build-up layer narrows the flow cross-section<\/td>\n<\/tr>\n \n 3<\/strong><\/td>\n The reduced cross-section slows the material flow<\/td>\n<\/tr>\n \n 4<\/strong><\/td>\n The slower flow increases the contact time with the surface<\/td>\n<\/tr>\n \n 5<\/strong><\/td>\n Material continues to adhere and the accumulation layer becomes thicker<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nOperating conditions do not necessarily need to change suddenly immediately before the blockage occurs. The build-up layer may have accumulated over multiple cycles until the remaining cross-section is no longer sufficient for the material flow to pass through.<\/p>\n1.3. Wall build-up, arching, and ratholing exhibit different characteristics<\/span><\/h3>\n
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\n Type of blockage<\/strong><\/th>\n Phenomenon<\/strong><\/th>\n Identifying sign<\/strong><\/th>\n<\/tr>\n<\/thead>\n\n \n Wall build-up<\/strong><\/td>\n Material accumulates on the walls and progressively reduces the flow cross-section<\/td>\n A build-up layer appears on the walls and the flow gradually decreases<\/td>\n<\/tr>\n \n Arching<\/strong><\/td>\n The material becomes self-supporting above the discharge outlet<\/td>\n Flow stops even though material remains above<\/td>\n<\/tr>\n \n Ratholing<\/strong><\/td>\n Only the material in the central region continues to flow while the material adjacent to the walls remains stagnant<\/td>\n Flow continues but the flow rate decreases, while material accumulates around the walls<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nWall build-up is closely related to the interaction between the material and the surface<\/strong>. Arching and ratholing also require consideration of the wall angle, cross-section, and material-flow geometry<\/strong>.
\nTherefore, incorrectly identifying the type of blockage may lead to replacement of the lining without addressing the primary cause.<\/p>\n2. How to identify the cause in the field<\/span><\/h2>\n
2.1. Distinguishing adhesive wear from material sticking and flow blockage<\/span><\/h3>\n
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\n Phenomenon<\/strong><\/th>\n Mechanism<\/strong><\/th>\n Material condition at the surface<\/strong><\/th>\n Evaluation direction<\/strong><\/th>\n<\/tr>\n<\/thead>\n\n \n Adhesive wear<\/strong><\/td>\n Two surfaces come into contact, localized adhesion occurs, and material is then transferred from one surface to the other<\/td>\n Material is lost from the surface<\/td>\n Evaluate the wear mechanism and contact conditions<\/td>\n<\/tr>\n \n Material sticking and flow blockage<\/strong><\/td>\n Material accumulates on the surface and obstructs the flow<\/td>\n Material builds up on the surface<\/td>\n Evaluate moisture, surface condition, wall angle, and material-flow geometry<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nThis is the initial distinction to be made before proceeding to more detailed measurements.<\/p>\n2.2. The type of blockage needs to be identified from the material-flow condition<\/span><\/h3>\n
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2.3. The cause may lie in the surface, geometry, or material conditions<\/span><\/h3>\n
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\n Factor group<\/strong><\/th>\n When it should be prioritized for consideration<\/strong><\/th>\n Items to be checked<\/strong><\/th>\n<\/tr>\n<\/thead>\n\n \n Surface<\/strong><\/td>\n Material adheres directly to the wall<\/td>\n Surface characteristics and ability to promote sliding flow<\/td>\n<\/tr>\n \n Angle and cross-section<\/strong><\/td>\n Arching or ratholing occurs<\/td>\n Wall angle, discharge outlet, and material-flow geometry<\/td>\n<\/tr>\n \n Material conditions<\/strong><\/td>\n Moisture changes significantly or is an underlying factor<\/td>\n Moisture content, material sampling point, and storage conditions<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n 2.4. Increasing hardness does not directly address the material-sticking mechanism<\/span><\/h3>\n
2.5. Changing flow conditions can help narrow down the cause<\/span><\/h3>\n
3. Data that need to be recorded at a flow-blockage location<\/span><\/h2>\n
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3.1. Blockage-clearing history needs to be converted into data<\/span><\/h3>\n
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3.2. The survey season must be recorded together with the data<\/span><\/h3>\n
4. Three indicators need to be evaluated separately when assessing material sticking<\/span><\/h2>\n