In some cases through the design procedure it is found that a. Ratholing occurs when material empties out through a flow channel above an outlet. . 9b, although the variation of the blend flow was larger compared to the total powder flow in case study 1. The reason for this is that when a powder becomes deaerated in the stagnant region of a funnel flow bin, it usually develops Ratholing: can occur in a bin when the powder empties through a central flow channel, but the material at the bin walls remains stagnant and leaves an empty hole (rathole) through the material, starting at the bin outlet (Fig. 1991; Holdich. 1 Shear strength. Are they steep enough to prevent ratholing when a powder having an FFC of 7. A Mass Flow Approach to Solving Your Sifting Segregation Issues Using a mass flow pattern will not only prevent the flow problems typically experienced by funnel flow (ratholing, flushing, etc. This results in a no-flow. Discharge of powder from a hopper or bin is a common operation in solid dosage form manufacture. and host "True or False: Bulk Solids Edition" from 1:29 p. User Tools. 2. Factors that affect the flow behavior are discussed. Eliminate Bridging and Ratholing The Carman Vibrating Bin Discharger eliminates. Changing (reformulating) the powder to reduce the cohesive strength and wall fric- tion, however, may reduce the likelihood of ratholing. Powder has a natural ability to move and fall when it is stored in a silo or a hopper. Funnel flow produces 'last in, first out' powder delivery and a greater likelihood of operational problems such as ratholing, segregation, and flooding. The Circle Feeder has a variety of features but widely known for its ability to prevent material arching, bridging, and ratholing. Check out this expert article on Powder Handling in Encapsulation from Right Stuff Equipment, experts in solid dose processing & packaging machinery. Problems associated with ratholing are flooding, substantial variation of density in product, and eventually no-flow. Ratholing is a flow obstruction is a no-flow condition obstruction that can cause erratic that prevents material discharge discharge. The goal of the design process is the determination of the hopper wall inclination necessary for mass flow and the minimum outlet size to prevent flow problems due to arching or ratholing. Bridges of powder can form in your containers preventing flow. (USP 1-May-2024) Changes in flow rate as the container empties can also be. The hopper to be designed is conical. Definitions: Bin: Any upright container for storing bulk solids. Process Control & Automation. • The particle size distribution – indicator of powder flow and the segregation potential • Bulk and tapped density – indicator of powder flow, mixing (fill volume) and tablet die filling. Materials interlock or bond together to form an arch above the outlet, blocking any flow. Under the silo a screw feeder with a varying pitch. Figure 1: Manufacturing pharmaceutical tablets and capsules involves several powder handling steps. Powder bridging occurs when the pressure actually locks the powder granuals together because they simply can not pass though the neck of the case and pressure increases dramatically. to compare flow on a Flodex™ powder flow tester (Teledyne Hanson Research, CA, US) with the tablet configuration to determine whether the powder’s intrinsic flow is close or equivalent to the cross-section of the tablet press die. Ratholing; c. 2. A brief introduction to discrete elemental method (DEM) which computes and models powder. Mixing & Blending. Here, flowability and magnetization were measured for a dual-phase steel powder in size fractions from 20 ⩽ D / μ m ⩽ 40 to > 200 µm. Assessment and predictive modeling of pharmaceutical powder flow behavior in small-scale hoppersForty years ago, Jenike [Gravity Flow of Bulk Solids, Bulletin 108, Utah Engineering Station, 1961] and Johanson [Flow Indices in the Prediction of Powder Behavior, Pharmaceutical Manufacturing. Why Battery Manufacturers Choose the Circle Feeder. Rat-holing causes a funnel flow effect, where the powder flows freely above the outlet but then stops as the compacted powder is held in the silo or hopper. 6). A better approach to predicting flow behavior is to take the characteristics of wall friction (φ w ). The aeration of the disk fluidizer utilizes directional air flow along the wall of the chamber to loosen product and move it to the discharge point. 1. Arching/Bridging & Ratholing. spoilage, flooding, or ratholing are likely to occur, then a mass-flow discharge pattern should be selected. It is critical to measure a powder’s flow properties before designing a handling system or solving a flow problem. Hoppers designed for mass flow with high-quality surface finishes can address these issues. The flow behaviour of the. Ratholing. Where less desirable properties are present, poor powder flow can: lead to challenges during blending (no discharge or ratholing), 4 difficulties when discharging the powder into the hopper 5 or issues regarding weight uniformity in the tablet. was used to control the flow of powder. Keep in mind that the mass-flow bin design process is iterative. , wedge-shaped and transi-usable capacity of the vessel. 2. 11. Generally, flow is limited to a central flow pattern. Powder rheology is the study of the behaviour of powders as bulk assemblies, consisting of solids, liquids and gases. The obstruction to flow would have a significant impact on the overall CM process as it. to 11 a. Predicting powder flow behavior is important to successful solids-handling processes. Equipment for powdered metals, ceramic powders, pigments, chemicals, super-abrasives. Identifies suitable test methods and helps to interpret and understand their results. How to prevent solids and powder flow stoppages with proper feeder design FREE | October 18,. pharmaceutical tablets, detergents, ceramics, powder metallurgy etc. Ratholing occurs when material empties out through a flow channel above an outlet. The final potential issue is erratic flow, in which flow alternates between ratholing and arching (see Figure 1). Bridges of powder can form in your containers preventing flow. 9 b, although the variation of the blend flow was larger compared to the total powder flow in case study 1. Depending on the flow properties, these materials are difficult to handle. 23Marinelli will discuss how to design the best kind of bin, silo, hopper, or feeder at Powder & Bulk Solids Texas, October 13-14, as one of two conference sessions he will present. Powder Machine Parameter Value/Equation 1 Jenike 1 Inst Flow Function 0. 1 Funnel flow bins When a fine powder is stored in and discharged from a bin having a funnel flow pattern, ratholing and flooding problems are almost inevitable. A bridge forms when wall friction holds up the ends of the arch. Define Ratholing. Kozicki and Mehos found that when potash powder was agglomerated. How it works. The phrases “failure to discharge” and “erratic flow in the. Gravity Flow. Keep product moving by preventing buildup, bridging and ratholing. The bulk material continuously in motion. The rest of powder compacts under vibration and get les flow-able in the time, so if a flow channel is established it will stay on the same place. A _______ provides a signal that simulates the signal from load cells at various weights. Eliminate bridging, rat holes, and stuck material. Powder flow obstruction during hopper/bin discharge, such as arching or ratholing, remains an outstanding risk and cannot be reliably diagnosed using the existing flow function coefficient-based method. The simplest way of explaining the flow function is with the uniaxial unconfined failure test shown in Figure 4, which measures the. Data were presented as mean. Most times it does not present any problems such as ratholing, erratic flow, flooding and segregation, because the discharging material is not cohesive or has a small critical rat-hole dimension. The large open inlet exceeds most materials’ critical arching diameter, preventing bridging and ratholing. 456 inches. flow, including ratholing, erratic flow, flood-ing and segregation. 1 Importance of powder flow in the pharmaceutical industry 6 1. Solids behave differently than liquids, he said, but flow problems are preventable with the proper design and tactics. Powder & Bulk Processing. , useable) capacity, as low as only 10–20% of the bin’s rated storage capacity. More than 70% of all products contain ingredients that are handled in bulk solid form at some point during the production process. The outlet is the smallest flow channel through which the bulk material should move. These problems lead to losses worth thousands of dollars at. "ratholing" can occur, that is, the diameter at which. In plug flow bins, the material flows in the centre of the bin, into which the sides slough as the material is drawn from the bin. ”. Jenike shear testing has determined the following. The powder in a flowing condition is nearly cohesionless. ) the powders are filled into closed cavities; this is followed by compaction using rigid punches and finally the product is ejected from the die. Options for explosion proof and pneumatic vibrators for hazardous. The corresponding control schemes at different levels for the feeding-blending system are provided in Table 6. flow rate through an orifice compressibility index and hausner ratio angle of repose shear cell. 1. Silo discharge solutions for powder bridging and ratholing. k. Figure 2: The two primary flow patterns that occur in gravity discharge are funnel flow and mass flow. Flow difficulties at the blending step often manifest as slow/no discharge or ratholing. Ratholing occurs when cohesive bulk materials are stored and conveyed in vessels with a funnel flow discharge pattern. The two most common flow problems experienced in a silo, bin or hopper are arching (bridging) and ratholing. 26. For calculation of bridges and ratholing in silos, there are two main phenomena to be. Silo and hopper ratholing is an issue which causes the compaction of materials on silo and hopper side walls, which results in a severely restricted material flow. One of the recommended types of flow aids is called Mechanical Agitation. The flow of powder out of a silo is stopping primarily for 2 reasons ; either formation of arches (arching, bridging) or ratholes. For example, when conveying powders that tend to cake or pack, it will be necessary to feed the aeromechanical conveyor from an infeed hopper of steep-wall design that encourages material flow along the hopper walls and prevents bridging and ratholing of the material. 3’ diameter opening is required to collapse a rathole, even at this low head. 93+0. The two most common flow problems experienced in a silo, bin or hopper are arching (bridging) and ratholing. Schulze RST which is equipped with either S-cell that is shown in fig. Figure 10. Example: Calculation of a Hopper Geometry for Mass Flow An organic solid powder has a bulk density of 22 lb/cu ft. Many consumer products, such as detergent or soap, can be prone to poor flow due to arching or ratholing during routine storage and handling. :4167–4181. Buildup in the Silo is an Indication of Ratholing. Process Control & Automation. Irregular flow; d. 25”; vibrator with 2. In all applications, this fluidizer prevents bridging, ratholing, and material hang-ups. 2 Flowability indicators used in industries 7 1. Holmes described two flow issues that commonly occur in bins, hoppers and silos: arching and ratholing. VIBCO Vibrators offers affordable, effective and reliable air cannons to suit many industrial or construction applications. For system manufacturers, process engineers, and operators: The timely application of flow enhancing solutions is recommended to prevent quality issues and production interruptions, such as bridging, ratholing and demixing. The Circle Feeder can be manufactured with several outlets for “one. Powder flow is critical to a range of pharmaceutical manufacturing processes. The depth of the trough into which the powder is filled is 12 mm and. 4704, or Email Us. , 2018). Unload and produce good faster in your production process. "Rotoflo is the best silo discharger!Ratholing can occur when coal flow takes place in a channel located above the silo, bunker or hopper outlet. aid, modifying the feeder, or using gas injection. In most cases, the vessel or bin can be attached to a vibrator, which shakes the vessel to pack the powder together. The reason for this is that when a result in a flooding condition at the outlet. powder flow problems. Aside from funnel flow, powder bridging is another undesirable flow issue which can occur in the hopper (Fig. This can usually be overcome by. 5). Larger particles are more likely to penetrate the surface than fine particles. Unload and produce good faster in your production process. flowsonic supports the flow of powders in silos, pipes, feeders, conveyors and other bulk material handling applications. The best way to establish flowability is to compare flow on a Flodex powder flow tester with the tablet configuration to determine whether the powder’s intrinsic flow is close or equivalent to the cross-section of the die. Prevent segregation with mass flow. The silo influences the powder via the silo diameter, height and the angle of the hopper. Of course the outlet of the hopper has to be large enough to prevent bridging above the feeder. All figures are courtesy of the authors. Bulk solids and powder flow properties testing is considered mandatory when designing screw conveyors and screw feeders for handling difficult to manage products. 5). FLOW PROBLEMS 2. powder addition easier. Flow splitting increases capacity and saves floor space. May be formed by 1. Discharge of powder from a hopper or bin is a common operation in solid dosage form manufacture. UNIT- 3: HANDLING OF SOLIDS (2 HOURS) Sliding and flow of powder, Method for free flowing powder and granules, methods for cohesive powders Bins, Vacuum and conveyor. Acceptable flow is required in powder transfer operations such as the emptying of tumble bins and conveyance of powders by gravity or screw feeders. 3. the powder flows at the place of the smallest flow resistance. Expanded flow: Term used to describe flow in a vessel that combines a core flow converging hopper with a mass flow attached below it. Our in-house testing laboratory measures the flow properties of your material so our solutions are robust - your product will flow through your system without hang-up, arching, , ratholing, blocking or other flow issues. 5). While these vessels are simple in design, the choice of instruments and devices fitted will often make the difference to whether the material floes or not. 125” to 0. powder becomes deaerated in the stagnant region of a funnel flow bin, it usually develops 2. Check drier is switched on. 2. In this study, we showed that the. 2002). The requirement that the funnel-flow bin be capable of self-cleaning can usually be met by making the hopper slope 15 deg. 3 Calculation of Minimum Required Outlet. These problems can result in limited live capacity. (Note: The terms bulk solid, bulk material, and material are used interchangeably. No ratholing! The slow rotating vanes move the material radially from the center to the outlet ensuring "first in -first out" mass flow; Slow rotating parts insure gentle product handling and minimum downtime; Turndown ratio up to 10:1; Low maintenanceHopper and Silo Ancillaries. poor flow properties, which leads to ratholing. 4. Jenike & Johanson is presenting the following AIChE sponsored courses June 18-20 at the Canadian Management Centre in Toronto:Flow of Solids in Bins, Powder Bulk Solids is part of the Informa Markets Division of Informa PLCRat-holing problem: * is one of common powder flow problems * When powders are released via a butterfly or slide valve, flow takes place directly above the container outlet. 4. Motor with gear suitable for running at 30 rpm. Ratholing = funnel flow: discharge. Ratholing is influenced by the bin/hopper geometry and outlet size the material is fed through. flowability. Fluidization is commonly used with pulverized fuel handling, drying operations, reaction processes, and fine powder hopper discharge systems. Flow Function: Line of a powder’s Unconfined Failure Strength versus the Consolidation stress that is applied to it. Eliminate bridging, rat holes, and stuck material. As a consequence of this, the so-called ratholing phenomenon can occur. Powder flow characteristics and vessel design vary tremendously. Mass Flow. Hoppers designed for mass flow with high-quality surface finishes can address these issues. TheWolfenbuttel, Germany) is used for measuring the flow properties of bulk solids or powder ( fig. 10a or M-cell that is. To find out more about Rotoflo, contact rotoflo@severfield. , et al. 20-36 , wherein there is shown a hopper assembly H which utilizes a hopper 401 and a hermetically sealed cover 402. High cohesive strength may result in the formation of a stable rathole. We Resolve Storage Structure Ratholing. refilling) and unexpected events (e. Ratholing: can occur in a bin when the powder empties through a central flow channel, but the material at the bin walls remains stagnant and leaves an empty hole (rathole) through. If the material being handled is cohesive, the material outside of this channel will not flow into it and may cake or agglomerate. 2002). Understanding the rheological properties of the. Vibratory flow-aid devices can also be installed on the infeed hopper to. Process Control & Automation. 24hr Emergency Service. a. • Minimal power consumption. Stauffer et al. (For an illustration of arching and ratholing, see the online version of this article at If a stable rathole forms in a hopper,Powder flow is critical to a range of pharmaceutical manufacturing processes. Getting the powder flow wrong can be highly disruptive to plant performance and productivity, particularly where equipment has to be taken off-line and stripped down for cleaning out blockages. It offers automatic and controlled discharge of virtually any powder type, winning where other systems. Attempts to initiate flow, such as use of vibration on hopper with rubber mallet or increasing powder paddle feeder, did not work. , answered a few questions from Powder & Bulk Solidson common powder handling and flow issues and how operators can take steps to fix or prevent. In ratholing, flow resistance increases as the fly ash level in the silo. Valves & Actuators. Flow stoppages due to arching and ratholing within ingredient feed hoppers and bins are more than just a nuisance, since these problems will directly contribute to the composition of the final blend for a period of time. the powder flows at the place of the smallest flow resistance. When a stable rathole develops, the bulk material remaining in the vessel is stagnant and will not discharge. Powder flow obstruction during hopper/bin discharge, such as arching or ratholing, remains an outstanding risk and cannot be reliably diagnosed using the existing flow function coefficient-based method. In addition, poor flowability can also cause content uniformity concern because of insufficient mixing. At the heart of our valves is Matcon's world-famous Cone Valve Technology delivering efficient and flexible powder handling solutions, serving a range of. The key to feeding cohesive materials in a screw feeder is with the use of Flow Aids. Cohesive Strength – The consolidation of powder may result in arching and ratholing within transfer equipment. PHARMACEUTICAL ENGINEERING. Mass flow exhibits a first-in-first-out flow sequence, allowing the product at the bottom (coarser or heavier particles) to discharge first. While bulk solid and powder handling is extremely common in industry, even some of the most basic fundamentals of material handling remain poorly-understood – largely because our education generally only. In the characterization of the powder flow, all predictions previously formulated were effectively understood. Problems such as arching, bridging, segregation, ratholing, and more, resulting from a material with poor flow properties, can cause issues such as:. Powder rheology is used in a wide range of industries to. Another method to improve flow is. Air pads may be needed to move the first material and merely gravity or small vibrations can be sufficient for the second. The primary design objective when determining the bin geometry is to ensure that bulk solid or powder will flow with the effects of gravity, and without flow obstructions occurring. Our comprehensive line of feeding technology can provide: high and low feed rates, batch, continuous, high. Explains how bulk solids flow influences the design of a plant or an installation. The material forms a narrow passageway above the feed auger or outlet, while the remaining materials in the storage structure are stationary and can begin caking to. Chem Eng Sci. Such hoppers are sensitive to arching and ratholing. As a general rule, extremely fine powders (<200 mesh) deaerate and pack readily (dusts, talc, etc. g. the relationship is called powder flow function Yield locus and family of yield loci Determination of y and c. Arching. Apparatus. Air pads may be needed to move the first material and merely gravity or small vibrations can be sufficient for the second. To ensure issues don’t persist or escalate, it’s important to fix the issue as. flow, including ratholing, erratic flow, flood-ing and segregation. ), and dry, uniformly-sized larger materials will be free flowing. When your bottom line depends on moving product efficiently through your plant, obstructions. Powder flow can be defined as the ease with which a powder will flow under a specified set of conditions. Jenike shear testing has determined the following characteristics given below. their manufacture are in powder form. Its unique construction fulfills allows for quantitative dosing steadily and evenly. , and J. Thus, reliable information of flow properties of the pulverized coal concerned is required for reliable flow from the hopper, which is essentially crucial in handling and processing operations [8], [9]. 1. Silo design for gravity flow; most economic. Of course the outlet of the hopper has to be large enough to prevent bridging above the feeder. 1 Shear strength. The critical arching dimension, of 5. Due to the cohesive strength of fine dry fly ash, the material is a great source of friction. Also in the case of funnel flow, asymmetry is of no help when ratholing has to be avoided. Before. Avoid silo problems, such as bridging, funnel flow, ratholing, arching, segregation and product decay. 2 Mass flow bins sufficient cohesive strength that its critical rathole diameter (the flow channel diameter at Flooding and ratholing problems can be which a rathole becomes. Provided here is a review of shear-cell testing and how the technique can be used to predict arching, ratholing and other behaviors. 2. Keep in mind that the mass-flow bin design process is iterative. 6). Acceptable flow is required in powder transfer operations such as the emptying of tumble bins and conveyance of powders by gravity or screw feeders. • Low-maintenance because of few wear points. At the heart of our Powder Handling System is an IBC fitted with our patented Cone Valve Technology, a unique discharge valve that eliminates typical powder flow problems. LEARN MORE Powder Cone Valve System. Based upon mathematical models, Jenike developed design charts to determine which flow pattern is to be expected during gravity discharge from a bin or hopper. A key variable that will have an impact on the flow is its cohesive strength. On the other hand, NP0 produced mass flow behaviour even for the narrowest orifice diameter of 2 mm. m. 71 Funnel / core flow. 3. Powder flow obstruction during hopper/bin discharge, such as arching or ratholing, remains an outstanding risk and cannot be reliably diagnosed using the existing flow function coefficient-based method. Effective feeder design not only enhances the flow within bins, hoppers, and stockpiles but also positively. The total powder flow can be controlled in the level 1 closed-loop operation as indicated in Fig. Funnel-flow bins lead to ratholing when the non-flowing solid consolidates sufficiently to remain stable after the channel has emptied out, and to flushing of powders as the layers slough off the top of the non-flowing mass and hit the bottom of the channel, or as aerated material rushes through a rathole. Silo: A tall bin, where H > 1. Motors & Drives Valves & Actuators Powder & Bulk Solids. This type of flow pattern is indicative of uniform, first-in-first-out flow, where ratholing, erratic flow, segregation, and flooding problems are mitigated. Typical powder flow issues found in the hopper are ratholing, bridging and segregation. There are two main reasons why no-flow conditions happen: arching and ratholing. Example of powder ratholing in a hopper. Powder blockage in silos. Discharging aids. za NNNEL FLOW i. In: Brown CJ, Nielsen J (eds) Silos – fundamentals of theory, behaviour and design. Different process problems, such as arching, ratholing, and segregation could arise during silo operation due to its poor design or extreme operating conditions. induce material caking. When your bottom line depends on moving product efficiently through your plant, obstructions in the flow of material can bring profitability to a complete stop. We can clean your silos, hoppers & vessels. No matter the design or the materials stored, silos are susceptible to material flow issues caused by blockages. It is critical to understand the type of hang-up that you may be experiencing. 10. In arching, the material forms an arch (or a bridge) above the outlet that prevents further flow. The frequency of the vibration needs careful consideration as it could affect the flow ability of the powder. , flow pattern (mass flow or funnel flow), and obstructions to flow (arching, ratholing). This creates a non-flow regime whereby a discharge aid is needed to re-initiate powder flow from the silo. Containment. 9b, although the variation of the blend flow was larger compared to the total powder flow in case study 1. Problems with Hoppers • Ratholing/Piping and Funnel Flow • Arching/Doming • Insufficient Flow • Irregular flow • Inadequate Emptying • Time Consolidation. The orifice flow behaviours had thus corroborated with the powders' flow properties. Includes supplementary material: sn. Ratholing occurs when material in the center discharges completely while material nearer the walls of the hopper. High Shear Mixers and. 3 and Fig. Scope. A superb discharge device, it overcomes all the typical powder handling and flow problems of bridging, blockages, mix segregation, flushing and core flow that are commonly associated with butterfly valves. 1 Importance of powder flow in the pharmaceutical industry 6 1. This was attributed to the fact that the poor flowability of APAP could cause ratholing and high flow variations, especially when the powder. Consequently, meas-urement of the wall friction characteristic of a. Moreover, ratholing will not occur in mass flow, as all of the material is in motion. Ratholing is a term used to describe extreme cases of funnel flow where the material nearer the walls is completely stationary and only the central material is discharged . reviewing these solutions, however, it’s important to understand. 363 14. Mechanical Agitation when used properly will condition the material to a uniform bulk density and eliminate bridging/ratholing resulting in the material filling the flights of the feed. The gyrators also reduce particle segregation to make sure each bag is completely. Air Cannons For Solving Tough Material Flow Problems. The. Erratic flow results when ratholes collapse, causing the powder to arch as it impacts the out-let. The flow pattern of a powder in a storage container or system is dependent on the powder itself as well as the container design. Critical Rathole Diameters, Df, ft—“D” is the diameter of the opening required to collapse a rathole, while “f” stands for funnel flow. Finally. 3b) occurs in case of funnel flow if only the bulk solid above the outlet is flowing out, and the remaining bulk solid - the stagnant zones – is consolidated and forms the rathole. Ratholing. For system manufacturers, process engineers, and operators: The timely application of flow enhancing solutions is recommended to prevent quality issues and production interruptions, such as bridging,. 10). 3’, meaning that an 18. T or F A bulk solid is a granular solid, such as gravel, sand, sugar, grain, cement, or other solid material, that can be made to flow. Addressing Powder Flow and Segregation Concerns during Scale-Up of Nutraceutical Solid Formulations . Powder flow is a critical attribute of pharmaceutical blends to ensure tablet weight uniformity and production of tablets with consistent and reproducible properties. 59 2 Effective Angle Intl Friction 53. See Fig. PBS: Why is the handling and processing of. 2 pcf Bin Density Index (BDI) 40. 448 m, respectively), corroborating the previous results that demonstrated that shape had more. Posted by Control Concepts USA on September 13, 2022 7:13 pm. This method may be used for all powders, dairy and non-dairy products. Powder flow characteristics are often. Despite being a simple test of compressibility, it can be useful for identification of powder flow behavior. The large open inlet exceeds most materials’ critical arching diameter, preventing bridging and ratholing. Uneven flow, ratholing, segregation or bridging during tablet. Flow aids are used to return to a more regulated flow pattern and are relatively inexpensive. The hopper must be designed so the outlet diameter is larger than the outlet rathole critical diameter. The powder flow is measured using an X-ray-based mass flow meter (SETXvue XP-300, Enurga, Inc. Mechanical Agitation when used properly will condition the material to a uniform bulk. Abstract. Rat holing is where a central void develops above the discharge outlet in place of the active flow channel. Potential issues with powder flow from containers due to improper design include ratholing, arching, or erratic flow. Mass-flow bin. At this point,. True. If you’re in supplement processing and need expert advice or equipment related to powder handling, supplement or food production, call Right Stuff Equipment at 303. Aside from funnel flow, powder bridging is another undesirable flow issue which can occur in the hopper (Fig. Powder is moist. True. m. The finest fraction did not flow through a Hall flowmeter, then. What Can Cause A. For each of these bins type, the critical outlet diameter, to avoid arching and ratholing, should be calculated in order to ensure a good flow. This can lead to ratholing and bridges. Arching, ratholing, caking, segregation and flooding are some of the commonly encountered flow problems in theAlso in the case of funnel flow, asymmetry is of no help when ratholing has to be avoided (Fig. Unstick material and promote even flow. The reason for this is that when a powder becomes deaerated in the stagnant region of a funnel flow bin, it usually develops Flow function is only half of the solution because it’s a measure of powder cohesiveness: Powder flows if: Ì % = σ1/ffc The external stress arising from gravity, (a. Granular materials can exhibit complex solid- and liquid-like behaviours which are not fully understood. Due to the pressure, some solids tend to be more cohesive , when powders become cohesive, they can form archs or rathole , 2 phenomena very detrimental to the flow of powder and. Robert Sedlock.