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 flow of powder from hoppers is usually assumed to take place in open atmosphere. Solimar Fluidisers create twice as much aeration action as many lookalikes. 5 Advantages Of In-Home Therapy And Rehabilitation Best Tyre Brands for Your Car NFL COVID PROTOCOLS: OUTBREAK POSTPONES STEELERS-TITANS What’s the Future of the Manufacturing Industry? Best Tyre Brands for Your Car NFL COVID PROTOCOLS: OUTBREAK POSTPONES STEELERS-TITANS What’s the Future of the Manufacturing. While addition of magnesium stearate had improved powder flow, ratholing was still observed for T100M across all orifice diameters. This might include vibration, free flow, or free fall. Our pneumatic and electric bin and hopper vibrators will: Promote the consistent and controlled material flow of dry or semi-dry bulk materials. They all have one thing in common: none will predict whether or not a powder will flow in a hopper. Flow aid devices are internal or external devices that are used to assist in discharging materials from a bin, hopper, or silo. 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. Before. 3485 Empresa Drive San Luis Obispo, CA 93401 Tel: 805-541-0901. Acoustic cleaners eliminate this issue, ensuring mass flow of material is maintained and production is achieved at maximum efficiency. These problems lead to losses worth thousands of dollars at. There are many consequences of flow problems. Multi-Craft Services. n 1. Native corn starch did not flow from the hopper, so tablets were not compressed and had a severe ratholing problem. Ratholing, another flow arresting situation, is when material directly above the outlet flows but the rest of the powder mass closest to the walls does not, creating a tunnel. Powder Rheology. Material Flow Solutions, Inc. The corresponding control schemes at different levels for the feeding-blending system are provided in Table 6. True. An arching flow p Figure 3. 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. Jenike shear testing has determined the following characteristics given below. 1 Shear strength. Gravity Flow. doi: 10. Critical Rathole Diameters, Df, ft—“D” is the diameter of the opening required to collapse a rathole, while “f” stands for funnel flow. Maintaining reliable powder flow of each ingredient to a continuous blending system is essential for its performance. Circle Feeder is the premier choice feeder that can prevent the segregation during mass flow discharging. Ratholing definition: Present participle of rathole . 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. bridging, ratholing and compacting. The key to feeding cohesive materials in a screw feeder is with the use of Flow Aids. 1. 2. 11. Bioprocess Equipment for biotech and pharmaceutical industries. 3º Peschl 4 Inst Flow Function - Raw 0. Powder strength data at each consolidating stress are plotted on the graph in Figure 4 to produce a graph called a “flow function. 5). However, flow aids are sometimes used when they are unnecessary and. Our comprehensive line of feeding technology can provide: high and low feed rates, batch, continuous, high. 125”; vibrator with 1-¼” piston. This is different from avalanche testing where a rather unconsolidated powder bed rotates inside a rotating drum and therefore, the powder bed properties are evaluated in a practically free flow. Flow aids are used to return to a more regulated flow pattern and are relatively inexpensive. Flow agents are used to enhance the flow behavior of solids by reducing the inter-particle adhesion force. 3. Exceptions are the ore concentrate or fine powder bins which usually are of the mass flow type. This device mixes with the bulk powder to increase. Matcon design and manufacture a range of unique discharge valves to control the flow of bulk powders and overcome the risk of powder flow problems such as bridging, ratholing and segregation. Rat holing is where a central void develops above the discharge outlet in place of the active flow channel. As the level of fly ash in the flow channel drops, a resistance to further flow into this channel occurs due to. Material flow from a bin or silo is inextricably linked to how the feeder extracts the material from the bin outlet. /d. Ratholing is influenced by the bin/hopper geometry and outlet size the material is fed through. 1016/0009-2509 (96)00250-3. Apparatus. This is often not taken into account and can result in arching or ratholing in storage bins or silos, blockage of chutes, flooding of hoppers and other problems that may affect the performance of the plant. g. ), and dry, uniformly-sized larger materials will be free flowing. 4704, or Email Us. Prevent bridging and ratholing. As the level of material in the flow channel drops, a resistance to further flow into. Generally, flow is limited to a central flow pattern. diam Mini Disk fits in pipes, chambers, chutes, and small hoppers with curvatures as small as 4 in. Discharge of powder from a hopper or bin is a common operation in solid dosage form manufacture. Powder Hand Process 4:293–299. 11. 26. Major Testing: Bulk Density Measurement [ USP<616>] Tapped Density. (710, 500, 355, 250, 180, 125, 90 and 63 μm, sieves Retsch) using a sieve shaker (Retsch AS 200 digit, Germany) with a vibratory amplitude of 2 mm [40]. Frequently powders that are deemed easy flowing exhibit flow problems such as bridging, ratholing, or erratic discharge. 4. Reduce costs in manual labor for unsticking materials from bins or hopper walls. 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. • Low-maintenance because of few wear points. the types of flow problems that can occur and the flow patterns. Depending on their makeup, products in powder or bulk form are prone to cling to surfaces, especially if they’re high in fat or moisture. Ratholing/ funneling 5 Inconsistent flow 3 Electrostatics Flowability Compaction . A key variable that will have an impact on the flow is its cohesive strength. It is only possible to compare materials using the same reference stress. Once the central flow channel has emptied, all flow from the silo stops. 7” to 0. However, when the fine iron is held inside a coagulation of powder, then it could be held out of the reach of the maximum magnetic force. Minor powder flow issues during R&D can turn into major headaches once scale-up to industrial production begins. offers powder testing services (flowability, friction, time consolidation, strength as used for comparative tests, silo design for flow and silo design for strength) and. 26. Posted by Control Concepts USA on September 13, 2022 7:13 pm. Table 1 – Flow Property Parameters Measured on Three Powders with the Jenike and Peschl Testers . Feeding, Weighing, Scaling 2. 26. A mass flow screw feeder prevents preferential flow which can lead to ratholing and arching problems. The core flow pattern can also be described as funnel flow where mainly the core is in movement and the powder pattern resembles that of a funnel. May be formed by 1. Ratholing. was used to control the flow of powder. Definitions: Bin: Any upright container for storing bulk solids. Calculation of a Hopper Geometry for Mass Flow An organic solid powder has a bulk density of 22 lb/cu ft. In this study, we showed that the. The silo influences the powder via the silo diameter, height and the angle of the hopper. Minor powder flow issues during R&D can turn into major headaches once scale-up to production begins. Such hoppers are sensitive to arching and ratholing. The flow pattern of a powder in a storage container or system is dependent on the powder itself as well as the container design. It allows users to measure the dynamic flow and shear properties of powders as well as quantifying bulk properties such as density, compressibility and permeability. Understanding the rheological properties of the. Kozicki and Mehos found that when potash powder was agglomerated. aid, modifying the feeder, or using gas injection. The flow behaviour of the. 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. It is critical to measure a powder’s flow properties before designing a handling system or solving a flow problem. Visually detectable local ratholing and cratering in the fluid bed: Compressed air too moist, contains oil; relative humidity is too high inside the room in which the powder is processed. Figure 1. A brief introduction to the flow properties of bulk solids, and common instruments and tests used to measure them, is given first, followed by a detailed summary of the research works. spoilage, flooding, or ratholing are likely to occur, then a mass-flow discharge pattern should be selected. Robert Sedlock. Flow occurs in most powder-based processes, opposed by various cohesive forces. Bridging, ratholing, arching and comparable behaviors are the bane of powder handling and formulating. 10. Figure 3: Stagnant, cohesive powders can form a stable rathole in funnel flow. Cohesive Arching Ratholing (Piping) B. , 1998,. 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. The solid dosage form (tablets and capsules) is manufactured by either dry-blending of fine powder ingredients or combining the ingredients in a wet granulation step, followed by drying. Solids behave differently than liquids, he said, but flow problems are preventable with the proper design and tactics. Silos and hoppers are particularly prone to this issue if the. , will present "Solids Flow Properties That Affect Your Feeder Design" as part. It is critical to understand the type of hang-up that you may be experiencing. These flow problems can result in powder caking, production delays, increased operator intervention, or product losses. 2. critical pressure at the abutment of the dome ê $) in hopper design principles, is the stress that facilitates powder flow Pharmaceutical powder discharge from a hopper Buildup in the silo is an indication of ratholing and potentially asymmetric flow, which can increase pressure loads inside silo walls. 1. 2. flowsonic supports the flow of powders in silos, pipes, feeders, conveyors and other bulk material handling applications. The phrases “failure to discharge” and “erratic flow in the. 2. g. 1. Particle size also affects wetting. ) the powders are filled into closed cavities; this is followed by compaction using rigid punches and finally the product is ejected from the die. g. The large open inlet exceeds most materials’ critical arching diameter, preventing bridging and ratholing. Two modes of flow can result in dense phase, namely piston/plug flow and. 9 b, although the variation of the blend flow was larger compared to the total powder flow in case study 1. In silos and hoppers it’s often the cause of flow problems like ratholing and bridging. :4167–4181. 5). e. Magazine Events News & Notes Videos Podcasts Webinars White Papers Breakthrough Products Awards. This can usually be overcome by. 57. Joe will describe uses for liners such as TIVAR 88 and 2B stainless steel along with coatings such as electrostatic powder coatings and Plasite 7122 epoxy coating. Ratholing is affected by consolidating pressure; thus, large funnel-flow bins have a higher ratholing tendency. Discharge of powder from a hopper or bin is a common operation in solid dosage form manufacture. refilling) and unexpected events (e. 4. g = gravity constant. 770-255-1322. ) but it. 2. Mechanical Agitation when used properly will condition the material to a uniform bulk. Ratholing. Typical powder flow issues found in the hopper are ratholing, bridging, and segregation. Ratholing. 3. These problems can result in limited live capacity. Powder flow inside horizontal silos is essential to ensure the efficient operation of the spacecraft using powder engines under horizontal flight positions. 8 lb/min Feed Density Index (FDI) 24. . Researchers at Purdue University have developed a new technology that solves the caking, bridging, and ratholing that occurs in powder flow from hoppers and bins in agriculture. The powder flowability is defined as the ability of a material in the form of particles to flow in a desired manner when used in specific equipment [33]. Reaching a certain level in the bin where the material has time to consolidate. 2 feet 2. Uneven flow, ratholing, segregation or bridging during tablet. Scope. Changing (reformulating) the powder to reduce the cohesive strength and wall fric- tion, however, may reduce the likelihood of ratholing. powder becomes deaerated in the stagnant region of a funnel flow bin, it usually develops 2. induce material caking. Ratholing; c. This was attributed to the fact that the poor flowability of APAP could cause ratholing and high flow variations, especially when the powder. The gyrators also reduce particle segregation to make sure each bag is completely. Bridging or ratholing in the silo can block the whole process and cause a discontinuity with high technical and financial consequences. 3’ diameter opening is required to collapse a rathole, even at this low head. The behavior is irregular and often catastrophic for achieving regular powder flow. This creates a non-flow regime whereby a discharge aid is needed to re-initiate powder flow from the silo. adhesive nature of a material could influence the feedability of materials over time through screw layering or bridging/ratholing, limiting the powder flow through. Process Control & Automation. In the case of my Allen Mags, the 257 and 6. Dimensions to Prevent Arching: Mass Flow Bin. Whether powder will flow smoothly or in an erratic manner inside a bin or a hopper depends on the flow pattern inside that equipment. Ratholing is influenced by the bin/hopper geometry and outlet size the material is fed through. Acceptable flow is required in powder transfer operations such as the emptying of tumble bins and conveyance of powders by gravity or screw feeders. 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. Systems supplied by PTSA often include silos, hoppers, and other storage vessels. Ratholing occurs then there is excess build up on the walls of a storage structure, so much so that there is a thin and restricted passageway for materials to flow down the vessel. Typically, they are used when flow by gravity alone will not work or when it is impractical to provide the design that is required for reliable flow. Finally. Ratholing. Keep product moving by preventing buildup, bridging and ratholing. Check out this expert article on Powder Handling in Encapsulation from Right Stuff Equipment, experts in solid dose processing & packaging machinery. 20-36 , wherein there is shown a hopper assembly H which utilizes a hopper 401 and a hermetically sealed cover 402. Obstruction to flow due to bridging arises when a stable arch forms over the hopper outlet, which prevents material from being discharged . to 2:15 p. 5D Bunker: A shallow bin, where H < 1. discharge) and its flow rate have been used to measure (USP 1-May-2024) powder flow. Air pads may be needed to move the first material and merely gravity or small vibrations can be sufficient for the second. However, in powder pressing industries (e. Meet hygiene and safety requirements and remove the risk of cross-contamination. Arching; b. For each bulk powder the low powder percentage retainedFlow and discharge of powders in process vessels are well known to give rise to significant handling problems in a range of processes, for example in the pharmaceutical, mineral, chemical and food industries. 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. Pumps, Motors & Drives. Our engineers can solve two common types of flow issues. 19 5 Inst Flow Function - Prorated 0. Funnel flow silos are usually more cost effective to construct, costing between 20-30% less than mass flow silos, but are not suitable for all materials. Particle size distribution (PSD) estimation by sieving of the two powders was performed according to Ph. They all refer. 26. Despite being a simple test of compressibility, it can be useful for identification of powder flow behavior. In ratholing, for HPMC2208 (Fig. downtime and degraded product quality. 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. A Brookfield Powder Flow Tester, equipped with Powder Flow Pro software for automated instrument control and data acquisition, was used to test this name brand baby formula. The flow channel drains material in the middle first. Ratholing can be avoided if you pay attention to calculations. Improper design of storage vessels causes problems, such as arching, ratholing, flooding etc. Keep in mind that the mass-flow bin design process is iterative. Besides that, powder flow can be determine by the angle of repose make by the powder itself when poured onto a flat surface throughout the hopper. and host "True or False: Bulk Solids Edition" from 1:29 p. : Fine Powder Flow Phenomena in Bins, Hoppers and Processing Vessels. The lifting action of the cone breaks up bridged product and prevents material from rat. Mass flow develops when all the material in a silo is in motion whenever any is withdrawn. Many laboratories are equipped with shear cell testers, which measure the fundamental flow properties of powders, i. For example, testing on a Flodex™ may show that a neat API powder has flowability of 26 mm, with a round tabletDischarge of powder from a hopper or bin is a common operation in solid dosage form manufacture. ; the ratio of tapped bulk density to loose bulk density; where the greater the ratio, the more. . It can also cause storage and handling related problems including hopper/bin arching and ratholing, resulting in no flow. FLOW PROBLEMS 2. Of course the outlet of the hopper has to be large enough to prevent bridging above the feeder. A brief introduction to discrete elemental method (DEM) which computes and models powder. Cohesive Strength – The consolidation of powder may result in arching and ratholing within transfer equipment. The technology is a microcontroller actuated portable device that can be remotely controlled. Flow splitting increases capacity and saves floor space. The hopper design plays a role in this as hoppers with sharp angles and rough surfaces can inhibit powder flow. As occurrences of bulk powder flow issues are strongly affected by the flow pattern during discharge. PHARMACEUTICAL ENGINEERING. It is critical to understand the type of hang-up that you may be experiencing. C - For flow, D> y or ff y (a) powder has a yield stress greater than c/ff no flow occurs. One of the recommended types of flow aids is called Mechanical Agitation. Predicting powder flow behavior is important to successful solids-handling processes. Eur. 24hr Emergency Service. Bridges of powder can form in your containers preventing flow. Mass Flow. 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. Eliminate bridging, rat holes, and stuck material. 2. Valves & Actuators. Wall Thickness of 0. A bin experiencing ratholing will have limited live (i. In most cases, the vessel or bin can be attached to a vibrator, which shakes the vessel to pack the powder together. You would think after all these years that our industry would realize that there is a scientific approach to solids handling and therefore silo design. 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. Rotoflo is designed to help with material handling ensuring that silo discharge is free-flowing and controlled when handling a number of diverse materials. 2. flowsonic supports the flow of powders in silos, pipes, feeders, conveyors and other bulk material handling applications. Includes supplementary material: sn. . Under the silo a screw feeder with a varying pitch. Powder is moist. The material that is. • Easy to clean due to detachable components. Figure 3: Stagnant, cohesive powders can form a stable rathole in funnel flow. capacity — as low as only 10–20% of the bin’s rated stor- age capacity. Shear cell techniques were used to measur e the following powder flow pro-perties: powder flowfuncti on, effective angle of internal fricti on and angle of wall friction. No-flow conditions such as arching or ratholing, erratic flow, flooding, limited discharge and segregation are typical flow problems. (USP 1-May-2024) Of particular significance is the utility of monitoring flow continuously, since pulsating flow patterns have been observed even for free-flowing powders. 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. 2 pcf Bin Density Index (BDI) 40. Powder Mix Segregation. LIW feeder flow rates can be compromised when the sudden change of the powder weight (e. b. Flow problems related to food powders, such as arching, ratholing and erratic flow are thoroughly described and reviewed by Marinelli (2005). It is the only flow aid that can handle. W. Check drier is switched on. Arches come in two types: interlocking arches, built up of large, mechanically. If the material is even slightly cohesive, material may stick to the walls and eventually become part of the bin structure. ratholing (when the powder flows out only from the center leaving the rest of the material static against the walls). 31+0. Maintaining reliable powder flow of each ingredient to a continuous blending system is essential for its performance. Lower the total height requirement. Arching. Let us explain how the use of vibration or sudden large blasts of air solve material flow problems. 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. m. Measuring flow properties leads to proper equipment selection and process reliability. Home; Blog; Case Studies; 770-255-1322. The reason for this is that when a result in a flooding condition at the outlet. , 2003). 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. Unload and produce good faster in your production process. The Circle Feeder can be manufactured with several outlets for “one. The powder in a flowing condition is nearly cohesionless. 2002). Powder flow is a critical attribute of pharmaceutical blends to ensure tablet weight uniformity and production of tablets with consistent and reproducible properties. Poor flowability of powders in a hopper means that flow obstruction due to arching occurs or uneven flow causes ratholing. bulk solid materials exhibit in bins and silos. A high fat powder (HFP) with 73% milk fat content, whey permeate powder (WPP) with 86% lactose, rennet casein powder (RCP) and sodium caseinate powder (SCP) were donated by Kerry Ltd. It offers automatic and controlled discharge of virtually any powder type, winning where other systems. k. Check drain valve on drier is open: check oil and water separator : Poor fluidisation of the powderRatholing Ratholing is a condition in which the stored material does not slough into the central flow stream for discharge and instead forms a core. 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. The typical problems encountered are either a cohesive arch or ratholing. Example: Calculation of a Hopper Geometry for Mass Flow An organic solid powder has a bulk density of 22 lb/cu ft. m. The cell has a fixed shearing rate of 7 mm min −1 and external and internal diameters of 164 and 120 mm, respectively. If you are filling your bin with a material and it drops close to the outlet, the P-Factor should be calculated as follows: P-FACTOR = (1 = m) [w/ (A B γ)] 2h/g where: w = weight flow rate into bin h = height of fall. Problems such as arching, bridging, segregation, ratholing, and more, resulting from a material with poor flow properties, can cause issues such as:. 2. (For an illustration of arching and ratholing, see the online version of this article at If a stable rathole forms in a hopper,They also prevent ratholing of hoppers and prevent lump formation. Predicting the flow characteristics of powders during manufacture is especially important for the pharmaceutical engineer. Rhodiola rosea (Rhodiola) is grown at high altitudes and northern latitudes. Carson, “Fine Powder Flow Phenomena plastic powder, food products, and pharmaceuticals. Matcon designs and manufactures powder handling equipment that can be used to improve manufacturing processes across a range of applications. The flow of powder in a hopper is linked to 3 properties : The powder internal friction : how easy the powder particle can move from each other. Flow rate evaluationThe model elucidated the impact of the material descriptors for density; powder flow; particle size; compressibility; permeability and wall friction angle on the feeding process. Ratholing occurs when material in the center discharges completely while material nearer the walls of the hopper. Ratholing is a common flow issue in storage structures. Figure 1: Manufacturing pharmaceutical tablets and capsules involves several powder handling steps. It is a superb discharging device overcoming all manner of powder flow problems. Modeling of particle mixing and segregation in the transverse plane of a rotary kiln. 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. If a mass-flow bin is required based on the flow char-acteristics of the powder or bulk solids, the next step is to determine an appropriate outlet size and feeder. Ratholing can lead to costly powder flow problems. Effective feeder design not only enhances the flow within bins, hoppers, and stockpiles but also positively. When the flow channel empties and material flow ceases, it can form a stable rathole that may collapse and block the opening. Issues covered in the segment include ratholing, arching (bridging), erratic flow, flushing, and more. Powder rheology is the study of the behaviour of powders as bulk assemblies, consisting of solids, liquids and gases. to 20 deg. Discharge of powder from a hopper or bin is a common operation in solid dosage form manufacture. Ratholing occurs when material empties out through a flow channel above an outlet. Boateng AA, Barr PV. Jenike shear testing has determined the following. Also in the case of funnel flow, asymmetry is of no help when ratholing has to be avoided. Knowledge about bulk density of materials is essential for avoiding ratholing and arching effects in silos and hoppers. ”. A proven and practical scientific approach for designing bins and feeders based on a material’s flow properties. 5 % Hang-Up Indices CONSOLIDATION TIME 0 HR 16 HR Arching Index (AI) 1. Powder blockage in silos. Sometimes, slow mixing paddles can keep bridging and ratholes under control. 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. 14. They are most often used in storage bins and chutes to promote flow of stored material, but they can also be used in continuous flow process vessels and. For powders such as T100 and T100M which exhibit arching and. at the Tech Theatre (Booth 127). 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. 327. That’s why. The raising and lowering of the Cone Valve within the IBC, combined with the internal vibration disturbs & agitates the full cross section of the powder in the container reducing the risk of a. , flow pattern (mass flow or funnel flow), and obstructions to flow (arching, ratholing). 2. 2. The most common causes of these issues are: Improper storage; Poorly selected binder that is too cohesive with the API;. Various powder flow properties, such as cohesion, unconfined yield strength,. flow channel empties, flow stoppages will occur when powder along the walls remains stagnant. The bin activator works discharges not over the full covered area, but only in a small unpredictable area and coarse ratholing. Ratholing, and Poor Material Flow .