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Powder flow testing and control
 

Powder flow testing and control

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    Powder flow testing and control Powder flow testing and control Presentation Transcript

    • Introduction:Powder flowability is the ability of a powder to flow in adesired manner in a specific piece of equipment.Flow of powders may be:Free-flowing Non-flowing or CohesiveManufacturing of tablets, capsules, filling of powder in containerinvolves several powder handling steps, including blending,transfer, storage, and feeding to a press or a dosator.The inability to achieve reliable powder flow during these stepscan have a significant adverse effect on the manufacture andrelease of a product to market.
    • Flow Patterns:Two flow patterns developed when powder flow from container:Funnel FlowMass FlowFunnel Flow• Side wall materialstagnant whereas flowof funnel- shapedmaterial take place• First-in-last-out• Chance of powdersegregation• Suitable only for freeflowing powderMass Flow• All of the material is inmotion• First- in-frist-out• Minimize segregationand prevent rat-holing
    • Factors Affecting Powder Flow Properties:The specific properties of a powder that affect its flow are known asflow properties.These flow properties depend upon:Collectiveforces acting onindividual particlesParticle variableEnvironmentalconditionPowder or Particlevariables:• Particle size, Sizedistribution, Shape, Surfacetexture, Cohesively, Surfacecoating, Particleinteraction, Wear or attritioncharacteristic, Propensity toelectro-staticcharge, Hardness, Stiffness, Strength, Fracture toughnessExternal Factorsinfluencing PowderBehaviour:• Flow rate, Compactioncondition, Humidity, Electro-static charge, Aeration,Transportation experience,Container surface effects,Storage time
    • Consideration of critical Factor: Particle Size Particle Nature Porosity Bulk Density Moisture Content Interparticle forceVan der WaalsElectrostaticSurface tensionInterlockingFriction, etcDuring Storage and TransportationCaking and bridgingPackaging conditionHigh to low aerationDe-aerationConsolidation by tapping
    • Powder Flow Problem:1. Rat-holing2. Arching3. Flooding Prevention of flow problem:Increased outlet diameterReduced filling height powderEquipment capacity can be reducedReduced cohesive strength of powderAgitation or mechanical assistance can be utilized
    • Measurement of Flow Properties:1. Angle of repose: The internal angle between the surface of the pile and the horizontalsurface is known as the angle of repose.Angle of repose depends upon: Density Surface area Shapes of the particles The coefficient offriction of the material This angle is in the range0 –90 .Flow Property Angle of repose (Degrees)Excellent 25–30Good 31–35Fair—aid not needed 36–40Passable—may hang up 41–45Poor—must agitate, vibrate 46–55Very poor 56-65Very, very poor ≥ 65
    • Angle of repose method used interparticulate friction or resistanceto movement between particles.Experimental Variable:Segregation of materialConsolidationAerationMethods for determining the static angle of repose :Fixed height methodFixed base diameter methodTilting box methodMethods for determining the dynamic angle of repose:Revolving cylinder method
    • Avalanching Tester:Used to determine dynamic angle ofrepose.MTA (mean time to avalanche)determine and at the time ofavalanching image was captured.Aero-Flow™ AutomatedPowder FlowabilityAnalyzer
    • 2. Carr’s Compressibility Index And Hausner Ratio:Both are determined by measuring the bulk volume and thetapped volume of a powder.CompressibilityIndex (%)Flow Character Hausner Ratio≤10 Excellent 1.00-1.1111-15 Good 1.12-1.1816-20 Fair 1.19-1.2521-25 Passable 1.26-1.3426-31 Poor 1.35-1.4532-37 Very poor 1.46-1.59≥37 Very, very poor ≥1.60
    • 3. Flow Through an Orifice:Useful only for free-flowing materials.Two types of flow rate of powder determined:Mass flow rateVolume flow rateExperimental variable:The type of containerThe size and shape of the orifice usedHeight of the powder bedGeneral guidelines for dimensions of the cylinder are as follows:Diameter of opening > 6 times the diameter of the particlesDiameter of the cylinder > 2 times the diameter of the opening
    • 4. Shear Cell Method:In the shear cell method, the force necessary to shear the powderbed by moving the upper ring is determined.Types of shear cell method:Cylindrical shear cellAnnular shear cellPlate-type shear cell4.1 Brookfield PFTChoice of Test Options:Flow FunctionTime ConsolidationTest with Flow FunctionWall FrictionData Output:Flow factor IndexArching DimensionRat-hole DiameterHopper Half AngleWall FrictionBulk Density Curve
    • Flow factor index Flowabilityff<1 Non flowing1<ff<2 Very cohesive2<ff<4 Cohesive4<ff<10 Easy flowingff≥10 Free flowingThe standard classification of powderflowability uses the flow factor index (ff):It is ideal for manufacturers who process powders daily and want tominimize or eliminate downtime and expense that can occur whenhoppers discharge erratically or fail to discharge altogether.Consolidation stress
    • 5. Cohesion Index:Stable Micro Systems TA.XT Plus textureanalyzer used to determine cohesioncoefficient which is determined byintegrating the negative areas underthe force displacement curve.Cohesion Index Flow behaviour≥19 Hardened, extremelycohesive16-19 Very cohesive14-16 Cohesive11-14 Easy flowing≤11 Free flowingA low cohesion index is associated withnon-cohesive free-flowing powders.
    • 6. FT4 Powder Rheometer:This methodologies allow measurement of:Flow energyShear propertiesBulk propertiesThe forces causing the deformation and flow is measured.FT4 flowmeter Downward testing mode Upward testing modeCalibration and Data Analysis:The variables are force, torque, height, and rotational and linearvelocities, flow properties determined via extrapolation.
    • Downward Test Mode:It is used to measure the Basic Flow Energy (BFE)Upward Testing Mode:It is used to measure the Specific Energy (SE) which is the flow energyper gram of powder tested.
    • 7. PTG-S4 Powder Characterization Instrument:Features:Fully USP <1174>, EP <2.9.36> andISO 4324 (12/83) compliantMeasure flow-time, cone angle,flowabilityPTG-ER stirrer includedIntegrated analytical balance cellIntegrated dust protection bonnetBuilt-in printer
    • 8. Penetrometry:The pressure of penetration in Pascal was usedto estimate flow rate.Particle size should be in the range of0.250-0.630 mm.Used for non-consolidated pharmaceuticalpowder excipients: sodium chloride,sodium citrate, boric acid, and sorbitol.A polynomial quadratic equation was generated using the ratio ofpenetration pressure to bulk density, from which the flow rates for thegroup of all tested powders could be estimated.
    • Control of powder flow1. Mucon Iris Diaphragm Valve2. Powry Valve3. Vacuum Assisted Powder Flow Nozzle4. Funken Continuous Auto Feeder5. Fluidizing Hopper Flow Control ValveMucon ValvePowry Valve
    • Importance of Flow Properties in Pharmacy:1. Tablet Manufacturing2. Capsule Manufacturing3. During Drug Delivery4. During Mixing and Sieving5. During Unloading of Packs6. During Transportation Through Conveyers7. During Filling of Powders, Dry Suspension and Dry Syrup
    • Conclusion:Powder flow is a key requirement for pharmaceutical manufacturingprocess.An understanding of the fundamentals of powder flow can steerone in the right direction to achieve reliable powder flow. Continuous and even flow of powder during tablet and capsulemanufacturing reduced weight variation, content uniformity (alsohardness in tablet).Powder flow is also crucial during mixing, packaging, and transportationReduction in process costs and maintaining the quality and consistencyof the final product
    • Reference:1. Jenike, A.W., Storage and Flow of Solids (Bulletin 123 of the UtahEngineering Experimental Station), 53 (26), (1964, revised 1980).2. Prescott, J.K., and Barnum R.A., On powder flowability, PharmaceuticaTechnology, October 2000, pp. 60-84 and 236.3. Prescott, J. K. and Hossfeld, R. J., Maintaining product uniformity anduninterrupted flow to direct compression tablet presses.Pharmaceutical Technology, 18 (6), 1994, pp. 99-114.4. Baxter, Thomas J., “When Powders Flow Like Water: AddressingTwo-Phase Flow Effects in Tablet Press Feed System”, Tablets &Capsules, March 2009, Volume 7, No. 2, pp. 26-32.5. Barnum, Roger, Ebb and Flow: Understanding Powder Flow Behavior,Pharmaceutical Processing, March 2009, pp. 18-21.
    • Thanks: