; the ratio of tapped bulk density to loose bulk density; where the greater the ratio, the more. (Note: The terms bulk solid, bulk material, and material are used interchangeably. Discharge of powder from a hopper or bin is a common operation in solid dosage form manufacture. 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. Ratholing is a scenario that powder starts . We can clean your silos, hoppers & vessels. Discharge of powder from a hopper or bin is a common operation in solid dosage form manufacture. On the other hand, NP0 produced mass flow behaviour even for the narrowest orifice diameter of 2 mm. Our comprehensive line of feeding technology can provide: high and low feed rates, batch, continuous, high. Predicting powder flow behavior is important to successful solids-handling processes. Flow and potential rathole formation in conical hoppers. In silos and hoppers it’s often the cause of flow problems like ratholing and bridging. 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 . For calculation of bridges and ratholing in silos, there are two main phenomena to be taken in consideration. Powder blockage in silos. Figure 1. 5D Hopper: A converging sloping wall section attached to the bottom of a silo. 8 B), F > 63 and F > 90 had practically equal outlet diameters (1. 5 % Hang-Up Indices CONSOLIDATION TIME 0 HR 16 HR Arching Index (AI) 1. Arches come in two types: interlocking arches, built up of large, mechanically. Reduce costs in manual labor for unsticking material from chutes and pipes. The large open inlet exceeds most materials’ critical arching diameter, preventing bridging and ratholing. The flowability factor is a easy way to quantitatively select substances with regard to their flowability. More than 70% of all products contain ingredients that are handled in bulk solid form at some point during the production process. Potential issues with powder flow from containers due to improper design include ratholing, arching, or erratic flow. Some products like dry cell battery. hopper that gives mass flow with one powder may give core flow with another. It is the only flow aid that can handle. When bulk solids build up into an arch or dome-like shape over the hopper’s outlet and block the flow, it’s called arching or bridging. powder becomes deaerated in the stagnant region of a funnel flow bin, it usually develops 2. Abstract. It was shown that a very small reduction of pressure changed the critical orifice diameter significantly. Hoppers designed for mass flow with high-quality surface finishes can address these issues. 2. k. Process Control & Automation. The silo influences the powder via the silo diameter, height and the angle of the hopper. The powder influences the silo by the flowability of powder causing bridging and ratholing. 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. Compressibility properties Measure a material’s bulk density as a function of consolidation pressure, which is required in the analysis of bridging, ratholing, and hopper angles. Many of these flow issues can be traced back to improper discharger or feeder designs. Ratholing occurs when only a flow channel located above an outlet discharges product. These problems lead to losses worth thousands of dollars at. The typical problems encountered are either a cohesive arch or ratholing. 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. Factors that affect the flow behavior are discussed. Holmes described two flow issues that commonly occur in bins, hoppers and silos: arching and ratholing. 1991; Holdich. How to prevent ratholingAuthors: Dietmar Schulze. Dimensions to Prevent Arching: Mass Flow Bin. The reason for this is that when a result in a flooding condition at the outlet. Absolute flow factor: FLA = FLR * ρb0. flowsonic supports the flow of powders in silos, pipes, feeders, conveyors and other bulk material handling applications. Even high viscous material can be fed through the feeder and discharger smoothly. Ratholing occurs when discharge takes place only in a flow channel located above the outlet. To mitigate process variations and disturbances caused by such risk scenarios, closed-loop feedback control is required. Includes supplementary material: sn. Learn in this page what are the root causes of both arches and ratholes and how to avoid them. In order to achieve mass flow, tion hoppers) are shown in Figures 5 and 6, respectively. The Circle Feeder is used to reliably discharge all types of granular materials. Most problems that manifest on 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. , 2003). This method may be used for all powders, dairy and non-dairy products. 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. Flowability is the ability of a powder to flow, and it is measured as the time in seconds necessary for a given volume of powder to leave a rotary drum through a slit of a certain size. The simple cure is to use Ball powder. To achieve this, a flow agent should adhere to the surface of particles of solids as shown in Figure 2. size, form, elasticity, water content and temperature, which influence compressibility. The common flow problems in hoppers and silos can be summarised as follows: (a) no flow, (b) segregation, (c) flooding and (d) structural failure. Mass-flow bin. 0 HOPPER DESIGN 5. A _______ provides a signal that simulates the signal from load cells at various weights. Chem Eng Sci. 1. The Cone Valve technology within each of the Matcon IBCs overcomes powder bridging due to both the lifting action of the cone and its integral vibration during lift. piping or ratholing may occur. In this case, powder discharge from hopper is not predictable. Two common flow issues. 2 Flowability indicators used in industries 7 1. 10). and host "True or False: Bulk Solids Edition" from 1:29 p. These problems lead to losses worth thousands of dollars at. 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. a cohesive arch when particles bond together ii. Use the following guidelines for impacting vibrators: Wall Thickness of 0. Use of Inverse Cones – A cone placed in the powder bowl can help fight the negative effect of poor flowing powders. Acoustic cleaners eliminate this issue, ensuring mass flow of material is maintained and production is achieved at maximum efficiency. In: Brown CJ, Nielsen J (eds) Silos – fundamentals of theory, behaviour and design. bulk solid materials exhibit in bins and silos. The critical dimensions of ESP hoppers, such as the outlet opening and hopper half angle must be confirmed to. See Fig. 125”; vibrator with 1-¼” piston. To ensure issues don’t persist or escalate, it’s important to fix the issue as. Flow agents are used to enhance the flow behavior of solids by reducing the inter-particle adhesion force. 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 and other industries. Consequently, meas-urement of the wall friction characteristic of a. Discharging aids. As a general rule, extremely fine powders (<200 mesh) deaerate and pack readily (dusts, talc, etc. Mass flow is the ideal flow pattern where all powder moves downwards towards the opening, and is often recommended by powder consultants for consistent and reliable flow. Matcon designs and manufactures powder handling equipment that can be used to improve manufacturing processes across a range of applications. Silo design for gravity flow; most economic. b. 3485 Empresa Drive San Luis Obispo, CA 93401 Tel: 805-541-0901. Air pads may be needed to move the first material and merely gravity or small vibrations can be sufficient for the second. In powder technology, the flow conditions are from. 2. Powder flow is a critical attribute of pharmaceutical blends to ensure tablet weight uniformity and production of tablets with consistent and reproducible properties. They all have one thing in common: none will predict whether or not a powder will flow in a hopper. Arching or bridging is a flow-arresting situation whereby the powder mass creates a structure (such as a dome or a bridge) above the outlet hole inhibiting flow completely. Powder blockage in silos. 3 and Fig. Comparison of the flow properties of eight commercial dairy powders5. UK-based powder flow solutions firm Freeman Technology offers this video on how particulate materials react when aerated, loosely packed or. m. Arching occurs when large particles interlock to form an arch at a hopper outlet and stop flowing due to shape, pressure, moisture or temperature. The mass flow hopper section ensures a uniform, controlled. These are examples of material flow problems. Pivotal work on the development of the theory of bulk solids flow began in earnest in the early 1950s, when. Bridging, ratholing, arching and comparable behaviors are the bane of powder handling and formulating. 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. 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. The behavior is irregular and often catastrophic for achieving regular powder flow. The Wolfenbuttel, Germany) is used for measuring the flow properties of bulk solids or powder ( fig. 1 is handled? Is the 100-mm diameter outlet of the hopper large enough to prevent an obstruction to flow?Powder flow tester, Software for silo design. Identifies suitable test methods and helps to interpret and understand their results. Solimar Fluidisers create twice as much aeration action as many lookalikes. The limiting condition for flow: c y ff - to reveal conditions under which the flow will occur. 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. 361 14. Typical powder flow issues found in the hopper are ratholing, bridging and segregation. Everything flowing smoothly =. TheWolfenbuttel, Germany) is used for measuring the flow properties of bulk solids or powder ( fig. Home; Blog; Case Studies; 770-255-1322. , 2018). A commercial system to study avalanching in powders was first described by Kaye et al [18]. 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. 4. Efficiency– As explained earlier ratholing powder flow can be likened to creating a “funnel effect”,meaning silos and hoppers cannot be used to their full storage capacity. 4. The reason for this is the strength (unconfined yield strength) of the bulk solid. True. Pumps, Motors & Drives. Posted by Control Concepts USA on September 13, 2022 7:13 pm. 4 Flow FactorsArching, ratholing, caking, segregation and flooding are some of the commonly encountered flow problems in the handling of fine powders. 46+0. Discharge of powder from a hopper or bin is a common operation in solid dosage form manufacture. The API AeroFlow® automated flowability analyzer was tested using 6 pharmaceutical excipients. No flow due to arching or ratholing. As the silo empties, side material flows into the middle channel. . flowability to avoid problems during blending, compression, filling and transportation (Räsänen et al. 4 Flow FactorsCohesive arching, jamming, particle segregation, and ratholing are all common occurrences during the production cycle. to 20 deg. This can usually be overcome by. Buildup in the Silo is an Indication of Ratholing. Powder & Bulk Processing. 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. 2. The powder in a flowing condition is nearly cohesionless. 4. e. 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. Angle of repose. Critical Rathole Diameters, Df, ft—“D” is the diameter of the opening required to collapse a rathole, while “f” stands for funnel flow. Storage Silos 101. 93+0. To improve the flowability of powders, flow aids or lubricants such as magnesium stearate are often incorporated in. Effective feeder design not only enhances the flow within bins, hoppers, and stockpiles but also. 1. This can lead to problems like buildup on the interior of tubes or vessels, or “ratholing” or “bridging” of product in hoppers. ‘Rat-holing’ (shown in Figure 2a) is the principle flow obstruction in a core-flow vessel where the powder in the flow-channel above the outlet discharges and leaves a stable. Driveshaft Removal:is a scenario that powder starts. The flow behaviour of the. It may lead to injury and hazardous plant environments, and compromise product safety. 2. Study with Quizlet and memorize flashcards containing terms like What are most type of powdered formulations?, What does flowability mean in powder flow?, What do we mean by free flowing powder? and more. The Circle Feeder can be manufactured with several outlets for “one. bridging, ratholing and compacting. Topics covered in this lecture include flow problems due to arching and ratholing, flooding issues, limiting discharge rates and segregation problems. Still, the material at the bin walls remains stagnant and leaves. Powder rheology is used in a wide range of industries to. 71 Funnel / core flow. The technology is a microcontroller actuated portable device that can be remotely controlled. 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. 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. Example of powder ratholing in a hopper. Issues covered in the segment include ratholing, arching (bridging), erratic flow, flushing, and more. Mechanical Agitation when used properly will condition the material to a uniform bulk. This occurs when particles are conveyed in the gas stream at a velocity that is less than the saltation velocity. The most common causes of these issues are: Improper storage; Poorly selected binder that is too cohesive with the API;. Powder Machine Parameter Value/Equation 1 Jenike 1 Inst Flow Function 0. 2. The gravy mix was scooped into the trough, and the. 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. This device mixes with the bulk powder to increase. When a stable rathole develops, the bulk material remaining in the vessel is stagnant and will not discharge. T or F A water column is a boiler fitting that reduces the movement of boiler water to provide an accurate. 1 Test Methods. Finally. at the Tech Theatre (Booth 127). Robert Sedlock. It may be necessary to apply several linear vibrators when the entire bin must be cleaned. They all refer. 3. One of the recommended types of flow aids is called Mechanical Agitation. Materials interlock or bond together to form an arch above the outlet, blocking any flow. a. The Influence of External Variables on Powder Flow Freeman Technology on YouTube. Define Ratholing. 2. It is critical to understand the type of hang-up that you may be experiencing. 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. Typical powder flow issues found in the hopper are ratholing, bridging and segregation. 19 5 Inst Flow Function - Prorated 0. Mass flow eliminates ratholing and maximizes the pers with planar geometries (e. com. Ratholing is affected by consolidating pressure; thus, large funnel-flow bins have a higher ratholing tendency. "ratholing" can occur, that is, the diameter at which. 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. 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. Material flow from a bin or silo is inextricably linked to how the feeder extracts the material from the bin outlet. LEARN MORE Powder Cone Valve System. When the flow channel empties and material flow ceases, it can form a stable rathole that may collapse and block the opening. We Resolve Storage Structure Ratholing. Our pneumatic and electric bin and hopper vibrators will: Promote the consistent and controlled material flow of dry or semi-dry bulk materials. Core or Ratholing Flow: The material starts flowing from the top surface in the form of a cylinder at the central portion of the hopper and all the material surrounding this central hole upto the wall is stagnant. The design of a silo is based on the most economical case: gravity flow. The hopper design plays a role in this as hoppers with sharp angles and rough surfaces can inhibit powder flow. The lifting action of the cone breaks up bridged product and prevents material from rat. Arching/Bridging & Ratholing. The field of bulk solids handling was developed due mainly to the work of Dr. The flow properties that govern whether a powder is prone to ratholing include cohesive strength, wall fric-tion, and bulk density [1-5]. 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. Reduce costs in manual labor for unsticking materials from bins or hopper walls. Discharge of powder from a hopper or bin is a common operation in solid dosage form manufacture. In this study, we showed that the. pharmacopeial methods to characterise powder flow. a. If you are experiencing issues with dust in your manufacturing facility, it is probably due to open processing. 8 9 Dissolution can be improved by improved. His first conference session, “Design Theory: Best Bets for Hoppers, Silos, and Feeders”, will focus on the fundamentals to ensure reliable material flow and will. Additionally, when vibrators are used, the Magnetic. 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. capacity — as low as only 10–20% of the bin’s rated stor- age capacity. Flow obstructions occur when the forces opposing motion exceed the forces promoting. Silo discharge solutions for powder bridging and 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. , “Increase Powder. Predicting powder flow behavior is important to successful solids-handling processes. LIW feeder flow rates can be compromised when the sudden change of the powder weight (e. The powder has relatively low cohesive strength. Rotoflo is designed to help with material handling ensuring that silo discharge is free-flowing and controlled when handling a number of diverse materials. 3’, meaning that an 18. Multi-Craft Services. Preventing Flow Stoppages in Powder Handling Processes. 125” to 0. Check drier is switched on. Expanded flow silos and stockpiles are recommended for storing large quantities of non-degrading materials and for modifying existing funnel-flow silos to correct problems caused by arching, ratholing and flushing. What Can Cause A. n 1. 1. The total powder flow can be controlled in the level 1 closed-loop operation as indicated in Fig. m. . As the level of fly ash in the flow channel drops, a resistance to further flow into this channel occurs due to. The primary focus of this chapter is to provide guidance in designing bulk solids (powder) handling equipment to provide consistent, reliable flow, and the required product uniformity by minimizing segregation. , useable) capacity, as low as only 10–20% of the bin’s rated storage capacity. Unload and produce good faster in your production process. Mass Flow. readiness of a powder to flow -. Ratholing, and Poor Material Flow . 2. In systems not designed with the material type in mind, powders and bulk solids can. Prevent segregation with mass flow. include modifying the hopper, adding a bin insert, using a flow. 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. com. Problems of powder flow a. 3º Peschl 4 Inst Flow Function - Raw 0. Powder preparation. Bulk solids and powder flow properties testing is considered mandatory when designing screw conveyors and screw feeders for handling difficult to manage products. their manufacture are in powder form. In the pharmaceutical industry, powder flow assessment methods are of great interest for the development and manufacture of solid dosage. Ratholing. Two modes of flow can result in dense phase, namely piston/plug flow and. 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. 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. 5). Solution: Reduce Movement. Google Scholar Wilms H (1992) Inserts in silos for blending. As a consequence of this, the so-called ratholing phenomenon can occur. , wedge-shaped and transi-usable capacity of the vessel. Example: Calculation of a Hopper Geometry for Mass Flow An organic solid powder has a bulk density of 22 lb/cu ft. Referring now to another embodiment shown in FIGS. Breakthrough Products Awards. The entire process is user-controlled and transparent: Diagrams and extrapolations. Ratholing. 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. All figures are courtesy of the authors. Feeding, Weighing, Scaling 2. 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. Powder is moist. 1 Importance of powder flow in the pharmaceutical industry 6 1. reviewing these solutions, however, it’s important to understand. Ratholing. Keywords: live bottom, cohesive, powder, hopper design. censorious. As occurrences of bulk powder flow issues are strongly affected by the flow pattern during discharge. 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. Motor with gear suitable for running at 30 rpm. Obstruction to flow due to bridging arises when a stable arch forms over the hopper outlet, which prevents material from being discharged . Kozicki and Mehos found that when potash powder was agglomerated. Depending on the flow properties, these materials are difficult to handle. The training set Y data included the observed flow patterns of mass flow, funnel flow, ratholing, and bridging (4. It is a superb discharging device overcoming all manner of powder flow problems. Purutyan H. 9b, although the variation of the blend flow was larger compared to the total powder flow in case study 1. The powder flow function is a plot of unconfined yield strength versus major principal. 1. 363 14. The phrases “failure to discharge” and “erratic flow in the. Eliminate bridging, rat holes, and stuck material. 20-36 , wherein there is shown a hopper assembly H which utilizes a hopper 401 and a hermetically sealed cover 402. This is indicated in hopper calculations as “Free Flow” or “0. Typical component concentrations in. The energy requirements are very dependent on the bulk solids or powder flowability properties, including cohesion and internal shear angle. This was attributed to the fact that the poor flowability of APAP could cause ratholing and high flow variations, especially when the powder. Keep product moving by preventing buildup, bridging and ratholing. 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. 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. 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]. 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. Mass flow exhibits a first-in-first-out flow sequence, allowing the product at the bottom (coarser or heavier particles) to discharge first. For decades, Industrial Vibrators and Air Blasters have helped restore flow to bulk solid materials. Cohesive Arching Ratholing (Piping) B. m. Some of these conditions include:. Ratholing occurs when material empties out through a flow channel above an outlet. The orifice flow behaviours had thus corroborated with the powders' flow properties. The powder flow is measured using an X-ray-based mass flow meter (SETXvue XP-300, Enurga, Inc. g = gravity constant. If the coarser particles stick to the sides of the hopper they can get rancid and contaminate the next batch. (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. to 2:15 p. Particle size distribution (PSD) estimation by sieving of the two powders was performed according to Ph. There are two main reasons why no-flow conditions happen: arching and ratholing. Keep in mind that the mass-flow bin design process is iterative. Bridging or arching. The flow properties of a bulk solid can have a significant impact on process efficiency and the success of the end product. Magazine Events News & Notes Videos Podcasts Webinars White Papers Breakthrough Products Awards. Figure 3: Stagnant, cohesive powders can form a stable rathole in funnel flow. Robert Sedlock. Generally, flow is limited to a central flow pattern. Tired of hammering on equipment, engineers thus began the development of flow aids for bulk solids. A mass flow screw feeder prevents preferential flow which can lead to ratholing and arching problems. Full size image. The nozzle releases highly pressurized air pulses to promote on-demand, first in and first out flow. "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. Erratic flow results when ratholes collapse, causing the powder to arch as it impacts the out-let. 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. A powder flow analysis is an indicator of how well formulation will release from the hopper during the tableting. Gravity Flow. The Circle Feeder can be used as a material feeder, large industrial feeder, laboratory feeder, powder. g. Ratholing is a flow obstruction is a no-flow condition obstruction that can cause erratic that prevents material discharge discharge. Despite being a simple test of compressibility, it can be useful for identification of powder flow behavior. Material hang-up (arching and/or ratholing) problems are generally caused by one of four things: cohesive forces between powder particles or granules, external forces, inter-particle locking, or elastic constraint issues. 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. 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 (Figure 28. Conducting studies. 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.