pft manual

Brookfield Engineering Laboratories, Inc. Page � Manual No. M09-�200

BROOKFIELD POWDER FLOW TESTER

Operating Instructions

Manual No. M09-1200

SPECIALISTS IN THE

MEASUREMENT AND

CONTROL OF VISCOSITY

TEL 508-946-6200FAX 508-946-6262

or 800-628-8139 (USA excluding MA)INTERNET http://www.brookfieldengineering.com

BROOKFIELD ENGINEERING LABORATORIES, INC.11 Commerce Boulevard, Middleboro, MA 02346 USA

with offices in: Boston • Chicago • London • Stuttgart • Guangzhou

Brookfield Engineering Laboratories, Inc. Manual No. M09-�200

Table of Contents

I. INTRODUCTION........................................................................................................................................................3 I.1 Components ............................................................................................................................................. 4 I.2 Utilities ..................................................................................................................................................... 4 I.3Specifications ........................................................................................................................................... 5 I.4 Safety Symbols and Precautions .............................................................................................................. 5 I.5 Back Panel ................................................................................................................................................ 6 I.6 Key Functions .......................................................................................................................................... 7 I.7 Emergency Stop - Reset ........................................................................................................................... 8 I.8 Installation ................................................................................................................................................ 8 I.9 Cleaning ................................................................................................................................................... 9

II. Quick Start................................................................................................................................................................. 10

III. Sample Preparation and Handling............................................................................................................... 13 III.1 Sample Issues ...................................................................................................................................... 13 III.2 Sample Trough .................................................................................................................................... 13 III.3 Lid Selection ........................................................................................................................................ 14 III.4 Outer Catch Tray ................................................................................................................................. 15 III.5 Inner Catch Tray with Shaping Tool ................................................................................................... 16 III.6 Loading the Trough with Sample ........................................................................................................ 16 III.7 Placement of Trough and Lid on the Instrument ................................................................................. 17 III.8 Removal of Trough and Lid from Instrument ..................................................................................... 17 III.9 Cleanup ................................................................................................................................................ 18

IV. Powder Flow Pro Software................................................................................................................................ 19 IV.1 Main Screen and Setup Tab ................................................................................................................ 19 IV.2 Sample Information ............................................................................................................................ 20 IV.3 Test Type ............................................................................................................................................. 21 IV.4 Test Execution..................................................................................................................................... 23 IV.5 How to Stop the Test ........................................................................................................................... 28 IV.6 Analysis Section.................................................................................................................................. 29 .

IV.7 Statistics Page ..................................................................................................................................... 34

Appendix A: Overview of Powder Flow Properties


I. INTRODUCTION

Thereisaneedthroughoutindustrytocharacterizepowderflowpropertiesandflowbehavior.TheBrookfieldPOWDERFLOWTESTER(PFT)isaprecisioninstrumentofrobustdesignthatsatisfiesthisneedandcanbeusedtomeasure,displayandprintoutflowresultsatspecifiedcompaction loads. Potential users include R&D Departments, QC laboratories, IncomingInspectionforrawmaterials,andgovernment/universityorganizations.

The principal of operation of the PFT is to drive a compression lid vertically downward into a powdersamplecontainedinanannularshearcell.Thepowdersamplehasadefinedvolumeandthe weight of the sample is measured before the start of the test. A calibrated beam load cell is used to control the compaction stress applied to the powder. The annular shear cell is then rotated atadefinedspeedandthetorqueresistanceofthepowderintheshearcellmovingagainstthepowderinthestationarylidismeasuredbyacalibratedreactiontorquesensor.Thegeometriesofthelid,shearcell,rotationalspeedofthecell,andthecompressiveloadsappliedtothepowderallcontributetothecalculationswhichdeterminetheflow-abilityofthepowder.

The intended uses for the PFT include: • Pass/failteststocertifymaterialqualitypriortoshipment• Providingmeaningfulnumbersthatguidehowpowderwillhandleinsilos,hoppers,

feeders,fillingmachinesandthelike• Benchmarkingfordailyproductionlotsorforcomparingflowbehaviorofnew

formulations against existing product• Creatingdatabasesforchoiceofproductionlines,sourcing,formulationandsecond

source suppliers• Producingquantitativeresultsthatcanbeusedfordesignofprocessingplantsand

equipment

ThereareseveralpowderflowpropertieswhichthePFTmeasurestocategorizeflow-ability.Notethattheseproperties,whichmayvarywithchangesintemperatureandhumidity,include:• Unconfinedfailurestrength• Major Principal Consolidating Stress• Tensile strength• Angle of internal friction• Angle of wall friction• Cohesive strength• Bulk density

Themostrecognizedindicationofpowderflow-abilityistheunconfinedfailurestrengthwhenviewedasafunctionoftheconsolidatingstress.Wallfriction,internalfriction,andbulkdensityarealsocommonlyusedtorelatemeasurementstoflowbehavior.AppendixAprovidesamoredetailed explanation of these properties and how they are measured.


I.� Components

DESCRIPTION PARTNUMBER

The following items are included with your instrument: Powder Flow TesterPowder Flow Tester 115VAC or PFT115 Powder Flow Tester 230VAC PFT230Powder Flow Pro Software with USB cable PFT-609Power Cord 115 Volt or DVP-65PowerCord230Volt DVP-66

RequiredAccessories which are included with the instrument Standard Accessory Kit PFT-610 (includesPFT-400,PFT-500,PFT-507,PFT-600, PFT-611,PFT-612,CP-23)SampleTroughAluminum230cc(6inchdiameter) PFT-400VaneLid304S/S33cc(6inchdiameter) PFT-500 WallLid304S/S2Bfinish230cc(6inchdiameter) PFT-507 CatchTrays&ShapingBlade(230cc/263cc,6inch) PFT-600Powder Scoop PFT-611Cleaning Brush PFT-612 3/8”Wrench[forleveling] CP-23Operator Manual M09-1200

Optional Accessory items that can be ordered for use with the Powder Flow Testerinclude the following: SampleTroughAluminum230cc(6inchdiameter)PFT-400 SampleTrough[lessscreen](230cc,6inch) PFT-401A PerforatedScreen(230cc,6inch) PFT-440 InnerCatchTraywithShapingTool(230cc,6inch) PFT-6Y OuterCatchTray(230cc,6inch) PFT-8 HumiditySensorwithinterfacecable PFT-607Y RTDTemperatureSensorwithinterfacecable DVP-94Y

I.2 Utilities

Input Voltage: 90-265 VACInputFrequency: 47-63HZPower consumption: 150VAFuse: Two2AMP,5x20mm,FAST-ACTING

PowerCordColorCode: United States Outside United StatesHot(live) Black BrownNeutral White BlueGround(earth) Green Green/Yellow

Mainsupplyvoltagefluctuationsarenottoexceed+/-10%ofthenominalsupplyvoltage.


I.� Specifications

Load for vertical axis compression: 7kg Accuracy:+/-0.6%FSR

Torque: +/-7.0N•m Accuracy:+/-1.2%FSR

Distance: Accuracy+/-0.3mm

Speeds: Torsionalspeeds:1revolutionperhour(RPH)upto5RPH.Defaultsetting 1 RPH. WhenusingKeypad:10RPH

Axialspeeds:0.1mm/secupto5mm/sec.Defaultsetting1mm/sec WhenusingKeypad:5mm/sec

TemperatureSensing: -20°Cto120°C(Requiresoptionaltemperatureprobe,PartNo.DVP- 94Y)

HumiditySensing: 10%to95%RH+/-5%(Requiresoptionalhumiditysensor,PartNo. PFT-607Y)

Output: USB Port or RS-232 compatible Serial Port

EnvironmentalConditions: 0°Cto40°Ctemperaturerange(32°Fto104°F) 20%-80%relativehumidity,noncondensingatmosphere

Use: Intended for indoor use only. Altitude up to 2000m

Dimensions: 36.2cm(141/4”)Wx39.7cm(155/8”)Dx67.6cm(265/8”)H

Weight: 34kg(751b)

MinimumSystemRequirementsforthePowderFlowProsoftware: Microprocessor: 2GHzprocessor Memory: 512 MB of RAM HardDriveSpace: 30 MB available Video: 1024x768resolution,128MBofgraphicsmemory OperatingSystem: WindowsXP,VistaCommunicationsPort: One USB or RS-232 port

.I.� Safety Symbols and Precautions

Safety Symbols

Refertothemanualforspecificwarningorcautioninformationtoavoidpersonalinjuryor damage to the instrument.

Keephands,fingersandotherbodypartsclearofmovingpartswhenoperatinginstrument.


FunctionalEarthTerminal-Mainpowerentrymodulemusthaveanearthconductor,toensure against electronic failure.

Precautions

Ifthisinstrumentisusedinamanornotspecifiedbythemanufacturer,theprotectionprovided by the instrument may be impaired.

This instrument is not intended for use in a potentially hazardous environment.

Incaseofemergency,turnofftheinstrumentandthendisconnecttheelectricalcordfromthe wall outlet.

Theusershouldensurethatthesubstancesplacedundertestdonotreleasepoisonous,toxic, orflammablegases at the temperaturewhich they are subjected toduring thetest.

Thetorquereactionsensorwillbedamagedifmorethan150%oftheFSRtorque(+/-7.0N•m)isapplied.

I.� Back Panel

Lift.Channel Lift.Channel

Lift.ChannelLift.Channel

jk

lmn

RS232 USBTEMP HUMDPOWER

Figure I-1: Back Panel


1. USB Type B port UsewithUSBCableP/NDVP-202toconnectinstrumenttoacomputer.CableUSB2.0 A Male to B Male.

2. RS-232 Serial Port UsewithRS-232CableP/NDVP-80toconnectinstrumenttoacomputer.

3. Temperature Probe Plug 4-Pinplug.UsewithTemperatureProbeP/NDVP-94Y.

4. Humidity Sensor Plug 3-Pinplug.UsewithP/NPFT-607Y.

5. Power entry module: ON/OFFswitch-fused(seeUtilitiessection)Voltage90-265VAC.

6. Lift Channel positions for handling instrument. Recommend two people for movement of instrument due to heavy weight.

I.� Key Functions

Bubble.Level.Access.Door...

Lift.flap.to.view.Bubble.Level

Figure I-2: Control keys for standalone mode

Standalone mode is used only for positioning of the compression lid assembly and the sample troughdrive.Softwareisrequiredforallotheroperations.

Keypad

«This key is used to move the compression plate assembly UP away from the sample trough drive assembly.

»ThiskeyisusedtomovethecompressionplateassemblyDOWNtowardsthesampletrough drive assembly.


PThis key is used to rotate the sample trough drive assembly clockwise.

QThis key is used to rotate the sample trough drive assembly counter-clockwise.

I.� Emergency Stop - Reset

This button is used to abort a test in case of an emergency condition. All operations will halt whenthebuttonisdepressed.Rotatethebuttontoreset,whichallowstheinstrumenttoreturnto normal operation.

I.� Installation

1. Prepare a clean and level surface.

Note: Thisinstrumentisasensitiveloadmeasuringdevice.Itshouldbeinstalledonaclean,solid,levelbenchsurfacewhichisfreefromexternalvibrations.

2. UnpackthePowderFlowTester(PFT)fromtheshippingcontainer.Todothisremovethetop and front panels of the crate.

3. Remove the instrument from the shipping package.

ThePFTweighs34kg(75lb).Usecautionwhenliftingtheunitoutofthepackaging.

Lift.Here Lift.Here

Lift.Here Lift.Here

Figure I-3: Back View of Lift Points

4. PlacethePFTonasturdy,levelsurface.

5. Position the instrument so the AC power switch is easily accessible.

TheACinputvoltageandfrequencymustbewithintheappropriaterangeasshown onthemodelandserialtagoftheinstrument(locatedonthebackofthePFT).


6. Make sure the AC power switch located in the back of the instrument is in the off position. Connect the power cord to the socket on the instrument and plug it into the appropriate AC line. Turn the power switch on.

7. Remove the "U" shaped foam piece from the area directly above the Compression Plate.

U-ShapedShipping.Foam.

Figure I-4: Shipping Foam Removal

8. Press the Up arrow key to raise the Compression Plate.

9. RemovetheSampleTroughbyliftingitupoffoftheDriveDiscontheinstrument.

10. Remove the foam piece in the Trough.

11. Remove any additional components from the shipping package. Save the shipping container and packaging for future use.

12. Connect the USB cable to the slot designated for the USB in the back of the instrument. If RS-232isusedinsteadofUSB,connectthecabletotheRS-232slot.

13. Connect the other end of the USB RS-232 cable to a computer.

14. The tester must be leveled. Open the bubble level access door. Adjust the four feet until the bubble is centered within the circle of the bubble level; also check to ensure the instrument is stable.Usea3/8"wrench(suppliedintheStandardAccessorykit)ortilttheinstrumenttoadjust the feet by hand.

I.9 CleaningInstrumentandKeypad:Cleanwithadry,nonabrasivecloth.Donotusesolventsorcleaners

Troughs/Lids/Catchtrays:Theseaccessoriesaremadefromavarietyofmaterialsrangingfrommetals(stainlesssteel,Aluminum)toplastics(Tivar88,Teflon).Cleanwithanonabrasiveclothusingsolventsthatare appropriate for both the sample material and the material of the accessory.

Donotapplyexcessiveforcetothecompressionlidassemblyorthesampletroughdriveassemblyontheinstrument.Damagemayoccurtothecomponents.

Some of the accessories have sharp edges.

Brookfield Engineering Laboratories, Inc. Page �0 Manual No. M09-�200

II. QUICK START PROCEDURE

1. Level the instrument.

2. Turn on the power to the instrument. The switch is on the back side.

3. OpenPowderFlowProsoftwareapplicationonPC.Gotosetupmenu.EstablishcommunicationwithinstrumentintheSetupTab.SelectUSBorRS232,whicheverisappropriate.

4. RecordweightofTrough(e.g.702.34grams).

Pin.in.Trough

Figure II-1: Trough

5. Attach the Outer Catch Tray outside the trough. Insert the Inner Catch Tray with Shaping Tool inside the Trough.

Note: Align one hole in the bottom of the Inner Catch Tray to the pin in the Trough.

InnerCatch

Tray

OuterCatch

Tray

Figure II-2: Inner and Outer Catch Tray

6. Fill the Trough with powder and level with the Shaping Tool; use the Shaping Tool with plow bladefortestusingaVaneLid;usetheShapingToolwiththeflatbladefortestusingaWallLid. Remove both catch trays.

Figure II-3: Shaping Blade in Plow Position Figure II-4: Shaping Blade in Flat Position

Brookfield Engineering Laboratories, Inc. Page �� Manual No. M09-�200

7. Record the weight of the powder and the Trough. Subtract the weight of the Trough to determine the weight of the sample.

8. Install the Trough onto the instrument. Outer Catch Tray can be installed on Trough to catch spillage during test.

II-5: Powder Flow Tester

9. Attach the appropriate Lid to the instrument. Use Vane Lid for the Flow Function test and TimeConsolidatedFlowFunctiontest.UsetheWallFrictionLidfortheWallFrictiontestandtheBulkDensitytest.

Figure II-6: Vane Lid Figure II-7: Wall Friction Lid


10. GotothePowderFlowProsoftwareapplication.Enterthesampleinformationandtheweightof the powder sample on the main screen.

Figure II-8: Sample Identification and Test Selection

11. Selectthedesiredtestmethod,e.g.FlowFunction.DefaultsettingsfornumberofConsolidationStresses(3)andnumberofOverConsolidationStresses(3)willautomaticallyappear."EvenSpacing" for the Consolidation Stresses is also the default setting.

PushDISPLAYTESTSTRESSESbuttonforadetailedlistoftheteststeps.

Display.Test.Stresses.AppearsHere

Display.Test.Stress.Button

Figure II-9: Flow Function Test

12. Start test by pushing RUN TEST button. Test runs automatically to completion. Save test resultsunderfilenamewhichyouselectedwhenenteringtestsampleinformation.

13. Aftercompletionoftest,usemanualcontrolonfaceofinstrumenttoraiseLid(UPARROW).Remove Lid from instrument. Remove Trough from instrument. Clean off excess powder on instrument.

14. Clean trough and lid.


III. SAMPLE PREPARATION AND HANDLING

Accurateandrepeatabletestresultsrequireattentiontoconditionofthesamplepriortotestingand the use of proper laboratory procedures during sample preparation. This section explains the details.

III.� Sample Issues

TheFlowFunctionandTimeConsolidatedFlowFunctionTestsrequireslightlyover260ccofsamplematerial.Allowingforspillageduringsamplepreparationandtesting,bestpracticesuggests that you start with at least 300cc of sample material. If repeated tests will be performed onthesamesample,then500ccormorearerecommended.

Note the condition of the sample prior to testing. Storage in a bag or sealed container will offer protection,whereasleavingthesampleonthecounterinanopenbagorcontainerwillexposethe sample to the environmental conditions in the test area.

Moisture in the sample is one of the primary factors to be aware of when working with powders because it can have a serious impact in making the powder more cohesive, and thereforelessfree-flowing. Thepotentialfor thepowdertotakeonmoisture(eitherbyadsorptionorabsorption) isafactor thatcanaffect test results. ThePowderFlowTesterhas theoptionalcapabilitytoaccommodateahumiditysensor(PartNoPFT-607Y)whichplugsintothebackof the instrument.

Temperaturemayhavesomeimpact,butcertainlyplayslessofafactorcomparedtohumidity.ThePowderFlowTesterhastheoptionalcapabilitytoaccommodateatemperaturesensor(PartNoDVP-94Y)whichalsoplugsintothebackoftheinstrument.

Consider all environmental issues in your test area before proceeding with your test plan.

III.2 Sample Trough

FigureIII-1showsthestandardSampleTrough(PartNoPFT-400)whichcomeswiththePFT.The Trough is made of aluminum and is of annular shape for containment of sample. In the bottomoftheTroughisaPerforatedScreen(PartNoPFT-440)whichholdsthesampleinplaceso that the powder particles on the bottom do not slide on the smooth metal surface when the Trough rotates.

PerforatedScreen

Figure III-1: Sample Trough


The Trough has a working volume to hold 230cc of sample material when the material is level withthetopsurfaceoftheTrough.WhenusedwiththeVaneLid,theadditionalvolumerequiredfor the Lid increases the total sample size to slightly more than 260cc of material.

III.� Lid Selection

The PFT comes with two types of Lids of annular design as shown in Figure III.2. The bottom side of the Lid is shown in each case; these surfaces make contact with the powder during the test.

Vanes

Figure III-2: Bottom side of Vane Lid and Wall Friction Lid

TheVaneLid(PartNoPFT-500)has18smallcompartmentswhichtrapthepowderparticlesand cause them to shear against the powder particles in the Trough. The Vane Lid is made of 304s/sandhasa15.25cm(6-inch)outerdiameter.

TheWallFrictionLid(PartNoPFT-507)hasasmoothbottomsurfacemadeof304s/swith2Bfinish,whichslidesoverthepowderparticlesintheTroughduringthetest,therebymeasuringthe friction of powder against the surface material of the Lid. The surface can be made of other materials,dependingonyourpreference;316s/sMildsteelandTivar88aretwoothercommonoptions. The choice typically depends on the material of construction that will be used in the storage bin, hopper or containment vessel that stores the powder in your processing plant.ContactBrookfieldoryourauthorizeddealerforalternativechoicesonthesurfacematerialofconstructionfortheWallFrictionLid.

The top sides of the Lids have two pins which engage with the Compression Plate on the instrument during the attachment process. Two release buttons must be pressed in order for the Lid to engage and successfully attach to the Compression Plate.

Engagement..Pin

Engagement..Pin

Figure III-3a: Top Side of Lid Showing Engagement Pins


Release.Button.Hidden

Release.Button

Compression.Plate

Hole.for.EngagementPins

Hole.for.EngagementPins

Figure III-3b: Release Buttons Figure III-3c: Close-up of Compression Plate Holes

III.� Outer Catch Tray

TheOuterCatchTray,showninFigureIII.4,providesaconvenientapronaroundthetroughforcollection of sample material which spills over the edge of the Trough during sample loading andtestexecution.CenteritovertheTroughandobservethatitfitsconvenientlyontheouterlip of the Trough.

Sample.Trough

Outer.Catch.Tray

Figure III-4a: The Outer Catch Tray by Itself Figure III-4b: Outer Catch Tray on the Trough


III.� Inner Catch Tray with Shaping Tool

TheInnerCatchTrayisusedtodistributethesampleevenlyintheTrough.Itfitsintotheannularopening on the Trough. See Figure III.5.

Plow

SampleTrough

Outer.CatchTray

Inner.CatchTray

Figure III-5a: Inner Catch Tray with Figure III-5b: Inner Catch Tray Insterted Into Shaping Blade in Plow Position the Annular Opening of the Trough

TheShapingToolwhichisaffixedtothecenteroftheInnerCatchTrayisrotatedbyhandtodistribute the sample. Note that the Shaping Tool can be removed by unscrewing the thumb screw that secures it to the Inner Catch Tray. This allows the user to choose the type of scraper bladethatisneededforsampledistribution.NotethatonesideoftheShapingToolisflat(forusewithWallLidintheWallFrictionandBulkDensitytests)andtheotheriscurvedwhichpermitsmoundingofthesampleinthetrough(forusewiththeVaneLidintheFlowFunctionandTimeConsolidatedFlowFunctiontests).SeeFigureIII-6.

Plow.Edge

Flat.Edge

Figure III-6a Figure III-6b

Figures III-6a and III-6b Show the Two Positions of the Shaping Blade

III.� Loading the Trough with Sample

WeightheTroughbeforefillingitwithsamplematerial.Recordthevalue.

Place the Outer Catch Tray into position on the Trough. Place the Inner Catch Tray into position ontheTrough.UsethePowderScoop(PartNoPFT-611),whichcomeswiththeinstrument,toplace the powder sample in the Trough. Any spillage is conveniently captured by the Inner and OuterCatchTrays.WhensufficientsamplehasbeenplacedintheTrough,rotatetheShapingTool on the Inner Catch Tray to distribute the sample evenly around the Trough. Rotate in a


clockwise direction until the sample is completely distributed. Then rotate in a counter-clockwise direction to remove excess sample.

Remove the Inner and Outer Catch Trays from the Trough. Return excess sample material in the Catch Trays to the container form which the powder came or throw it away in accordance with your lab policy.

III.� Placement of the Trough and Lid on the Instrument

Take the Trough loaded with sample material and weigh it again. Subtract the weight of the Trough to obtain the weight of the sample material. Enter this value into the Sample Information section of the main screen on the Powder Flow Pro software.

Make sure that the Compression Plate on the instrument is in the upmost position. Use the Up arrow on the instrument control panel to reposition the Compression Plate if necessary.

PlacetheTroughontheDriveDiscoftheinstrumentsothatthecenteroftheTroughalignswiththepininthecenteroftheDriveDisc.RotatetheTroughbyhanduntilthepinontheouteredgeoftheDriveDiscengagesoneoftheholesonthebottomoftheTrough’souteredge.Whenthisoccurs,theTroughwillliesecuredinaflatposition,centeredonthedriveplate.

Place the Outer Catch Tray in position around the Trough. This serves to catch any spillage of the sample material when the test is running.

AttachtheappropriatelidtotheCompressionPlateontheinstrument.Youmaychoosetodothis before placing the Trough on the instrument. It is simply a matter of operator preference.

The Lids are sharp. Be careful when installing and removing.

The test is now ready to begin. Refer to the section on Powder Flow Pro Software for details onrunningtestsfromyourPC.WhentheRunTestbuttonispushedonthemainscreen,theLidwillautomaticallydescendontotheTrough,pausingforabriefperiodoftimejustpriortomaking contact with the powder sample in order to perform an autozero check.

III.� Removal of Trough and Lid from Instrument

Whenthetestiscomplete,theLidwillautomaticallyraiseupasmalldistanceoffoftheTrough.This is a visual indication that the test has ended. Push and hold the manual control for the UP arrow on the instrument control panel until the Lid has raised to its upmost position. Then disengage the Lid from the Compression Plate. Clean the excess powder that clings to the Lid.

Remove the Outer Catch Tray from the Trough and dispose of the excess powder in the Tray. Remove the Trough from the instrument and dispose of the powder sample in accordance with lab procedure.CleantheTroughwiththeCleaningBrush(PartNoPFT-612)whichcamewiththeinstrument.Notethattheperforatedscreenmayrequirespecialattentionwithpowderparticlesthat have been trapped in the openings.


III.9 Cleanup

The Cleaning Brush serves to remove excess powder from the Trough and Lid. This may be adequateforrepeatedtestingofthesamepowdertypeswherethepotentialforcross-contaminationbetween samples is not really an issue.

Formorethoroughcleaning,theuseofanairhose,water,oracleaningsolventmaybedesired.Whenusingaliquidforcleaning,makesuretodrytheTroughandLidthoroughlysothatmoisturecontamination does not become an issue with the next sample.


IV. POWDER FLOW PRO SOFTWARE

Software(PartNoPFT-609A)andUSBcableforconnectiontoaPCareprovidedwiththePFTPowderFlowTesterinordertooperatetheinstrument,collectdata,performanalyses,storedatafiles,andexportdatatootherprograms,suchasExcel.ThenameofthesoftwareisPowderFlowProandisoneofseveralprogramslistedontheCDthatcomeswiththePFT.TheotherprogramsontheCDdonotpertaintothePFT.

Connect the USB cable to the PFT and to your PC. Turn on the PFT using the power switch onthebacksideoftheinstrument.LoadtheCDontoyourPCandstartthePowderFlowProprogram.

IV.� Main Screen and Setup Tab

Uponstartup,themainscreencomesupasshowninFigureIV-1.

Figure IV-1: Main Screen

Detailsonsampletypeandtestmethodareenteredonthispage.However,beforeproceeding,make sure that the program is communicating with the PFT by clicking on the Setup Tab. The Setup Screen is shown in Figure IV-2.


Figure IV-2: Setup Screen

Pressthe“Search”button.IftheinstrumentiscorrectlyconnectedtoyourPCwiththeUSB(orRS-232)cable,thegreenlightwillcomeonandthetypeofcommunicationportbeingusedwillbeidentified,inthiscase,USB.

Whileonthispage,itisalsopossibletoadjustthemeasurementunits,axialspeedformovingthelidsupanddown,andtorsionalspeedforrotatingthetrough.Defaultvaluesaresetatthefactoryformeasurementunitsandoperatingspeeds.Ifyoudecidetochangeanyofthesevalues,you must then shut down the Powder Flow Pro program and start it up again in order for the changes to take effect.

Click the Test Tab which brings you back to the Main Screen.

IV.2 Sample Information

The left column on the Main Screen is used to enter information on the sample that you are testing. See Figure IV-3.

Brookfield Engineering Laboratories, Inc. Page 2� Manual No. M09-�200

Figure IV-3: Closeup of Left Column on Main Screen

There are 5 boxes in which to make entries:

a) SampleIdentification e.g.Flourb) ProductName e.g.Lorenzo’sLongGrainBrownRicec) BatchNumber e.g.Listyourcontrolnumberforthesampleor,perhaps,the

datetimeifyoudon’tusecontrolnumbers.d) SampleNumber:Youhavethechoicetoallowthesoftwaretoincrementeachtestwith

asequentialcontrolnumber(thedefaultsetting),oryoucanchoosetosetthisvaluebyclickingthe“SetManually”button.

e) Weight:Entertheweightofthesample.Thedefaultsettingisgrams.

Sample Notes can be entered in the box on the bottom half of the left column on the Main Screen. Thismayprovideinformation,forexample,onhowthesamplewaspreparedorhowlongithasbeen in storage.

Clickonthedisciconabove“SampleIdentification”tosavetheinformationthatyouhavejustentered on your sample.

IV.� Test Type

The middle column on the Main Screen is used to select the type of test that you want to run. See Figure IV-4.


Figure IV-4: Closeup of Middle Column on Main Screen

Chooseoneofthe4teststhatarelistedunder“TestTypes”.ThefirsttwotestsrequiretheuseoftheVaneLid.ThelasttwotestsrequiretheuseoftheWallFrictionLid.Detailsoninformationthat you must enter for each test follow:

a) FlowFunction Theusercansetthenumberofconsolidationstressestotest,whethertospacethe

consolidationstressesevenlyorgeometrically,thenumberofoverconsolidationstressestorunateachconsolidationstress,whethertorepeateachstressmeasurement,andwhethertotestatthetangenttotheUnconfinedMohrCircle.

b) TimeConsolidatedFlowFunction Theusercansettheamountoftimetoconsolidateateachconsolidationstep,whether

touseanewsampleforeachtimeconsolidation,thenumberofconsolidationstressestotest,whethertospacetheconsolidationstressesevenlyorgeometrically,thenumberofoverconsolidationstressestorunateachconsolidationstress,whatstresstoapplyduringtimeconsolidation,whethertorepeateachstressmeasurement,andwhethertotestatthetangenttotheUnconfinedMohrCircle.

c) WallFriction Theusercansetthematerialofthecelllid,thenumberofdisplacementlevelstotest


at,whethertospacethedisplacementlevelsevenlyorinadoublingprogression,thenumberofstressestorunateachdisplacementlevel,andwhatstresstoapplyduringwall displacements.

d) BulkDensityCurve The user can set the number of stress setpoints.

Oncethetestdetailshavebeenfinalized,clickonthe“DisplayTestStresses”buttontoviewthenumberofstepsinyourprogramasshowninFigureIV-5.Inthiscaseaflowfunctionhasbeenselected.Thetwocolumnsontherightshowthesequencefortheconsolidationstressesandthecorresponding overconsolidation stresses that will be applied. Note that the time estimate for the test to run is displayed in the window at the top right of the Main Screen. Units are hours: minutes:seconds.

Figure IV-5: Right Column on Main Screen

Clickonthedisciconabove“TestType”tosavetheinformationthatyouhavejustenteredontest type.

IV.� Test Execution

Tostartthetest,clickthe“RunTest”buttonontheMainScreen.TheLidwilldescendtoaposition slightly above the sample in the Trough; the instrument will perform an autozero; then the Lid will make contact with the sample and the test begins.


TheRawDataTabontheAnalysisScreenwillautomaticallycomeupandshowtheaxialloadtest data and the torsional load test data. See Figure IV-6. The axial load units are shown on theY-axisontherightofthegraph(greencolor)andthetorsionalloadunitsareshownontheY-axisontheleftofthegraph(redcolor).

Figure IV-6:Image of Test Data on Analysis Screen Showing One Full Cycle of a Consolidation Stress and Two Associated Overconsolidation Stresses

Details on test method execution for each of the 4 test types are shown in the followingfigures.


Loadpowder,starttest

Apply consolidation loadShear to steady state

Re-apply consolidation loadMeasure peak

Apply over-consolidation loadMeasure peak

Re-apply consolidation loadShear to steady state

Calculate tangent load

Apply tangent loadMeasure peak

Re-apply consolidation loadShear to steady state

Re-apply consolidation loadMeasure peak

Endtest,processresults

Loop until allincreasing over-consolidationloads are tested

Loop until allincreasingconsolidationloads are taken

Loop until allrepeat over-consolidation measurementsare taken

(if option chosen)

Figure IV-7: Flow Function Test Algorithm.



Applyconsolidationload,shear to steady state

Re-applyconsolidationload,measure peak

Apply over-consolidation load,measurepeak

Re-apply consolidation load,sheartosteadystate

Calculate tangent load

Applytangentload,measure peak

Re-apply consolidationload,sheartosteadystate

Re-apply consolidation load,measurepeak

Leave for time consolidation periodT,applyloadσ

1

Apply Time over-consolidationload,measure peak

Load fresh powder sample(ifoptionischosen)

(if option chosen)


Loop until all increasing over-consolidation loads are tested

Loop until all repeat over-consolidation measurements are taken

Loop until all increasing consolidation loads have been tested

Figure IV-8: Time Consolidated Flow Function Algorithm



Applycompactionload,measure lid position

Applyconsolidationload,shearto steady state

Re-applyconsolidationload,measure peak

ApplyWallconsolidationload,rotateforrequiredsheardisplacement


Loop until all increasing compaction loads are taken

Loop until all reducing consolidation loads are tested

Loop until all increasing wall displacements are measured

Figure IV-9: Wall Friction Test Algorithm



Applycompactionload,measure lid position


Loop until all increasing compaction loads are taken

Figure IV-10: Bulk Density Test Algorithm

Throughoutthetest,agreenlightwillflashandtheestimatedtimetocompletionwillcontinueto count down and be displayed in the top right window on your screen. The algorithms which measure peak torsional stress and steady state torsional stress have optimization functions built into the realtime data analysis. The net result is that some of the test time may be reduced because thesteadystatevalueisachievedearlierthantheallottedtesttimeforaspecificstep(s).

Atanytimeduringthetest,theusercanreturntotheMainScreentoobservethedetailedteststep display and note which step is in progress.

Whenthetestiscompleted,theflashinggreenlightwilldisappear,the“EstimatedTestTime”windowwillbeblank,andtheLidwillraiseupslightlyoffthesample.

IV.� How to Stop the Test

Atanytimeduringthetest,theusercanabortthetestbyclickingontheStopiconintheupperleftcornerofthemainscreenorbyclickingtheStopTestbutton,whichlightsupontheMainScreen once the test starts. See Figure IV-11.


Figure IV-11: Stop Button on the Analysis Screen

IftheuserpushestheEmergencyStopbuttonontheinstrument,thebuttonmustberesetinorderfor the instrument to communicate with the Powder Flow Pro program. Rotate the button in a clockwisedirectionasfarasitwillgo,thenreleasethebutton.

Whenthetestisstoppedbyoneoftheaboveactions,theLidwillliftupfromtheTrough,whichis no longer rotating. The test cannot be resumed at the step where you stopped the test. The datacannotbesaved.Youmuststartallover.Ifthesamplehadbeencompacted,bestpracticeis to replace the sample with fresh material.

IV.� Analysis Section IV.�.� How to Save Data

Oncethetesthascompleted,youhavethechoicetosavetherawtestdataand/orthecalculatedstressdata(clickontheStessDataTab).Mostuserswillchoosetosaveonlythecalculatedstressdata,sincethisisthebasisforcomputingthedesiredoutputparameters:flowcurve,frictionanglecurve,densitycurveandcriticalhopperdimensions.

Therawtestdataconsistsof100datapointspersecond,whichmeansthatthefilesizecanbelarge,especiallyfortestsoflengthyduration.Forthisreason,mostusersmaychoosenottosave raw data.

Tosavethecalculatedstressdata,clickthediskicononthetoolbar.Tosavetherawdata,clicktheboxcalled“SaveRawData”locatednexttothediskicon,thenclickthediskicon;thiswillsave both the raw data and the calculated stress data.

IV.�.2 Choices for Data Display

FigureIV-12showstheavailablechoicesfordatathatcanbedisplayed(RawData,StressData,FlowDataorFrictionAngle,DensityCurve,HopperDesign)andtheformatfordisplayingthedata(Graph,Results,Data).Clickontheboxesthatyourequireandthecorrespondingdataand/orgraph(s)willbeshown.


Figure IV-12: Options for Data Output Display

NotethatthethirdtabontheAnalysisscreencanbeeither“FlowData”or“FrictionAngle”,depending on the type of test that is run. The former appears when Flow Function and Time ConsolidatedFlowFunctionareselected.ThelatterappearswhenWallFrictionisselected.

Whenthe testforBulkDensityCurveisselected, the tabswhichappear includeRawData,StressData,andDensity.

Detailsontheinformationthatcanbeviewedundereachtabfollows:

a) RawData: Alltesttypesdisplaythespecificfieldschosenfortherawdatagraph.Alltheraw

dataalsoappearsinthe“CustomTab”intabularformat.

b) StressData: AllapplicablePeakandSteadyStatestressesareshown.Inaddition,thefollowingis

displayed for each type of test:

• FlowFunctionTestdatashowsalocuslineforeachConsolidationStresssetpoint,withcorrespondingUnconfinedandOverconsolidatedMohrcircles,andaSteadyStatelocusline.FortheSteadyStatelocus,thegradient,angle,andcohesionarereported. For each Consolidation Failure Locus the Major Principal Consolidation Stress,UnconfinedFailureStrength,AngleofInternalFriction,gradient,angle,cohesion,anddensityarereported.

• Time Consolidated Flow Function Test data shows all the instantaneous locus linesandcircles,plusatimeconsolidatedlocuslineforeachConsolidationStresssetpointwithitscorrespondingUnconfinedMohrcircle.Allinstantaneousflowresultsarereported;eachtimeconsolidatedlocusreportsitsUnconfinedFailureStrength and cohesion.

• WallFrictionTestshowsonelocuslineforeachDisplacementsetpointandoneMaximumWalllocus,includingthegradient,angle,andcohesionforeachlocusline.

• DensityTestdata:Notapplicable.

c) FlowCurve:

• FlowFunctionTestshowsthecurveofUnconfinedFailureStrengthsversus


Major Principal Consolidation stresses and reports the Flow Function gradient and intercept,thecriticalArchingandRat-holestress,andtheFlowIndexforagivenstress.

• Time Consolidated Flow Function Test data shows one instantaneous curve and onetimeconsolidatedcurveandreportsthesameresultsastheFlowTest,butshows one set of results based on the instantaneous Flow Function and one based on the time consolidated Flow Function.

• WallFrictionTestdata:Notapplicable.


d) FrictionAngleCurve:

• Flow Function Test data shows one curve based on the Effective Angle of Internal Friction for each Consolidation setpoint and reports the Effective Angle of Internal Friction for the critical Arching stress and critical Rat-hole stress.

• Time Consolidated Flow Function Test data reports the instantaneous Flow Function results along with the Effective Angle of Internal Friction for the Time critical Arching stress and Time critical Rat-hole stress.

• WallFrictionTestdatashowsoneWallfrictionanglecurveforeachdisplacementsettingandonecurvebasedontheMaximumWalllocus.ThedatatablistsallWallFrictionangles,ateachstresssetpointateachdisplacementsetting,includingtheMaximumWallFrictionateachstresssetpoint.


e) DensityCurve:

• FlowFunctionTestdatashowsonecurvebasedontheinitialfilldensityandthedensitiesmeasuredattheSteadyStatestressvalues.TheDensityforthecriticalArching stress and critical Rat-hole stress are also reported.

• Time Consolidated Flow Function Test data reports instantaneous results along withtheDensityfortheTimecriticalArchingstressandTimecriticalRat-holestress.

• WallFrictionTestdatashowsonecurvebasedontheinitialfilldensityandthecompactions at the beginning of the test.

• BulkDensityCurveTestdatashowsonedensitycurveincludinginitialfilldensity.

f) HopperDesign:

• Flow Function Test data shows Arching and Rat-hole dimensions based on critical valuespickedoffoftheaboveFlowTestcurves,withtheoptiontouseaseparatedensityfile.OneHopperhalfangle(userhasselectedwhetheritisaconicalorwedgehopper)iscalculatedusingthisfileandtheMaximumWalllocusfromachosenWallTestfile.

• Time Consolidated Flow Function Test data shows two sets of Arching and Rat-holedimensions,onebasedontheinstantaneousflowfunctioncurve,andonebasedontheapplicabletimeconsolidatedflowfunctioncurves.Thereisanoption


touseaseparatedensityfile.TwoHopperhalfanglesarecalculated,bothusingtheMaximumWalllocusofthechosenWallTestfile,butoneusinginstantaneousflowfunctiondataandoneusingtimeconsolidatedflowfunctiondata.

• WallFrictionTestdatacalculatesseveralHopperhalfangles,oneforeachDisplacementsetpoint,eachusingtheflowcurvesfromthechosenFlowTestfile.Arching and Rat-hole dimensions are not applicable.


IV.�.� How to Compare Data

Comparisonsbetweendatafilesaredoneusingoneconditionfromeachfile.Thereareseveraloutputparameterstoconsider.AvailablechoicesareshowninFigureIV-13.Forexample,onlythe Time consolidated values from a Time Consolidated Flow Function test are compared to otherfiles.TheinstantaneousvaluesfortheTimeConsolidatedFlowFunctiontestarenotusedin the comparison.

Figure IV-13: Parameter Choices for Data Output on Test Files


a) FlowFunctionCurves:

• ForFlowFunctionTestdata,usetheregularFlowFunctionforcomparisons.Thisreportsthegradient,intercept,criticalstresses,andFlowIndexbasedonthisFlowFunction.

• ForTimeConsolidatedFlowFunctionTestdata,usethetimeconsolidatedflowcurveforcomparisons.Thisreportsthegradient,intercept,criticalstresses,andFlow Index based on this Time Consolidated Flow Function. If you want to comparetheinstantaneousandtimecurveswithinasingleTimeTestdataset,youcan do so in the Analysis section.

• WallTestdata:Notapplicable.

• Densitydata:Notapplicable.

Refer to Figure IV-14 for an example of several Flow Functions Tests on Limestone Sand.

Figure IV-14: Comparison of Flow Function data in Limestone Sand

b) FrictionAngleCurves:

• ForFlowFunctionTestdata,usetheInternalAngleforcomparisons.Thisreportsthe Internal Angles at critical stresses based on this curve.

• TimeConsolidatedFlowFunctionTestdata,usetheinstantaneousInternalAnglefor comparisons. This reports the Internal Angles at the Time critical stresses based on this curve. If you want to compare the instantaneous and time critical stresses withinasingleTimeTestdataset,youcandosointheAnalysissection.

• ForWallFrictionTestdata,usetheWallAnglecurvefromtheMaximumWallLocusforcomparisons.IfyouwanttocompareWallAnglecurvesatdifferentdisplacementswithinthesamedataset,youcandosointheAnalysissection.IfaWallTestdatasetispartoftheComparison,noanglesarereportedforcriticalstresses,becausethecriticalstressesfortheWallfileareunknown.



c) BulkDensityCurves:

• ForFlowFunctionTestdata,usethedensitiesmeasuredatthesteadystateofeachlocus line for comparisons. This reports densities at critical stresses for arching and rat-holing.

• ForTimeConsolidatedFlowFunctionTestdata,usetheinstantaneousdensitycurve for comparisons. This reports densities at critical stresses for arching and rat-holing.

• ForWallFrictionTestdata,usethedensitydatafromthecompactionsatthestartofthetestforcomparisons.IfaWallTestdatasetispartoftheComparison,nodensitiesarereportedforcriticalstresses,becausethecriticalstressesfortheWallfileareunknown.

• ForBulkDensityTestdata,usethedensitydatafromthecompactionsforcomparisons.IfaDensityTestdatasetispartoftheComparison,nodensitiesarereportedforcriticalstresses,becausethecriticalstressesfortheDensityfileareunknown.

d) HopperDesign:

• ForFlowFunctionTestdata,usethecriticalvaluesfromtheregularflowfunction,frictionangle,andbulkdensitycurvesforcomparisons.ThereisnoexternalDensityfileoption,valuesaretakenfromwithintheFlowFunctionTestdatafile.

• ForTimeConsolidatedFlowFunctionTestdata,usethecriticalvaluesfromthetimeconsolidatedflowcurveforcomparisons.Usetheinstantaneousfrictionangleanddensitycurves.ThereisnoexternalDensityfileoption.IfyouwanttocompareinstantaneousandtimeconsolidatedoutletsizeswithinoneTimeTestdataset,youcan do so in the Analysis section.

• HopperHalfAnglewouldnotbeincludedintheComparisonsection,becauseeachcalculationrequiresspecifyingtwodatasets,aFlowFunction(orTimeConsolidatedFlowFunction)TestandaWallFrictionTestdataset.

IV.� Statistics Page

Statisticscanbedoneonresultswhichhaveonevalueperdatafile.Forexample,statisticscanbedoneontheSteadyStateLocusgradientof10FlowFunctionTestdatasets,becauseeachdata set has only one Steady State Locus gradient. Statistics could not be done on the Time ConsolidationFlowFunctionFailureLocusgradient,becausethereareseveralConsolidationFailure Loci per data set.

See Figure IV-15 for an example of a Statistical Report.


Figure IV-15: Example of Printout for a Statistical Report

The following statistical reports can be created for the types of test data as indicated:

• StatisticsforFlowFunctionand/orTimeTestdatasets:

Statisticscanbedoneonthefollowingresults:SteadyStateLocusgradient,angle,andcohesion;FlowFunctiongradient,intercept,andFlowIndexatagivenstress;Archingdimensionandcriticalarchingstress,frictionangle,anddensity;Rat-holediameterandcriticalrat-holestress,frictionangle,anddensity;fillbulkdensityand maximum bulk density.

• WallFrictionTestdatasets:

StatisticscanbedoneontheMaximumWalllocusgradient,angle,cohesionandangleatagivenstress,fillbulkdensityandmaximumbulkdensity.

• BulkDensityTestdatasets:

Statisticscanbedonethefillbulkdensityandthemaximumbulkdensity.


Appendix A: OVERVIEW OF POWDER FLOW PROPERTIES

Problems with Powder that relate to Gravity Flow Behavior

Atypicalindustrialpowderprocessinglinewillincludeseveralstoragevessels(e.g.bins,bunkers,silos,hoppers,IntermediateBulkContainersorIBCs,sacksetc),feedingorhandlingsteps(e.g.beltconveyor,screwconveyor,pneumaticconveyor,gravitychutesetc)andprocessingsteps(e.g.milling,mixing,drying,baggingetc).Amajorindustrialproblemisgettingthepowdertodischarge reliably from storage into the next process step. Therefore to understand the application ofpowderflowmeasurements, it isuseful tohavesomebackgroundknowledgeof theflowpatternsandflowobstructionsthatcanoccurinsidethestoragevesselsonaprocessingline.

What are the powder flow patterns that can occur in a process storage vessel?

Principallytherearetwodifferentflowpatternsthatcanoccur:

Core-flow(showninFigureA-1a)canbeconsideredthedefaultflowpatternandischaracterizedbypowderdischargethroughapreferentialflowchannelabovethedrawdownpointoftheoutlet.Powderisdrawnintotheflowchannelfromthetopfreesurfaceoftheinventory.Thisgivesafirst-inlast-outdischargeregimeand,ifoperatedonacontinuous(ratherthanbatch)mode,thepowder around walls in the lower section will remain static in the vessel until the time that it is drained down to empty.

Mass-flow(showninFigureA-1b)isthedesirableflowpatternforpowdersthatarepoorflowingortimesensitive,butmustbespecificallydesignedfor.Heretheentirecontentsofthevesselare‘live’,givingafirst-infirst-outdischargeregime.Toachievethis,thehopperwallsmustbesufficientlysteepandsmooth.Foragivenwallmaterial/convergingangle,thepowderwallfrictionmustbebelowacriticalvalue.Also,theproductdischargemustbecontrolledbyavalveorfeederthatallowspowdertoflowthroughtheentirecrosssectionalareaoftheoutlet.(Itisthisfinalpointthatpreventsmanyvesselsfromoperatinginmass-flow.)

A wall friction test will be able to give an approximate assessment of whether a given hopper geometrywillsupportmass-flow(withtheprovisothattheoutletareaisfullyactive).Foranexactcalculationof themaximummass-flowhopperhalfangle,bothwall frictionandflowfunction tests must be undertaken.

What are the powder obstructions that can occur to prevent flow?

Principallytherearetwodifferentflowobstructionsthatcanoccur:

‘Rat-holing’(showninFigureA-2a)istheprincipleflowobstructioninacore-flowvesselandiswherethepowderintheflow-channelabovetheoutletdischargesleavingastableinternalstructure.

‘Arching’(showninFigureA-2b)istheflowobstructioninamass-flowvessel,whereastablepowder arch forms across the outlet or convergingwalls of the hopper, thereby preventingflow.

For a given powder there is a critical outlet dimension that must be exceeded to ensure reliable dischargeofacore-flowormass-flowvessel.Thesearethecriticalrat-holediameterDrhandthecriticalarchingdiameterD

corD

p (dependingonthehoppergeometry). TheBrookfield

PowderFlowTester(PFT)cancalculate thesecriticaldimensionsfollowingaflowfunction


measurement.Anaccuratedimensionrequiresawallfrictiontestaswell.Notethatforagivenpowdertherat-holediameterissignificantlylargerthanthearchingdiameter.

What are the flow patterns that can occur?

Mass-flow

Flowing.core

Drain.down.angle.of.repose

Static.material

Critical.rat-hole.diameter

Core-flow

Figure A-1a: Core-flow Figure A-1b: Mass-flow

What are the forms of the flow obstructions?

Figure A-2a: 'Rat-hole'

DRH

DC

DRH =

2 x σc x 1000

ρ

B x g

Figure A-2b: Arch

Dc =

2 x σc.x 1000

ρ

B x g

Dp =

σc x 1000

ρ

B x g

(Where3Dρ<L)

Conical.hopper:

Plane.hopper:

ρB. g.V o1

σ3 = 0 σ1 = σcσ1 = σc

Conicalhopper

DC

Figure A-3a: Conical hopper Figure A-3b: Wedge (plane) hopper

DP L

Wedgehopper


Note: Twotypesofhoppershapeareconsidered:conicalhoppersandwedge(orplane)hoppers as shown in Figure A-3a & A-3b.

Key differences between powders and fluids

ForNewtonianfluidstheresistancetoshear(viscosity)isindependentofthenormalpressurebut dependent on the shear rate. In powders the effect of these factors is reversed so that shear stress of a powder is strongly dependent on the normal stress but independent of the shear rate. Hencewhencharacterizingpowders,testareundertakenatasinglespeedbutoverarangeofnormal stresses. The other key difference is that powders are anisotropic so the stresses are not equalinalldirectionsandarefrictionalsothattheycangenerateshearstressesatwallboundaries(seewallfrictionsection).

Flow function test

Theprimarymeasureofpowderflowabilityisthepowderflowfunction–whichgivesameasureof the amount of strength the material retains at a stress free surface following consolidation toagivenstresslevel.Thesimplestwayofexplainingtheflowfunctioniswiththeuniaxialunconfinedfailure testshowninFigureA-4,whichmeasures thestrengthofafreestandingcolumn of powder. This condition is analogous to the condition of the powder arch across a hopper outlet shown in Figure A-2b.

i) Consolidationofsample. Powder is placed in a cylindrical cell and compacted under a known normal stress σ

1.

ii) Unconfined sample. The mould is now carefully removed to reveal a compacted column of powder.

iii)Unconfined failure of sample. The normal stress acting on the column of powder is graduallyincreaseduntilfailureoccurs,andthepeaknormalstressσ

c is recorded.

σ1 σ

3

σ3=0

Figure A-4: Uniaxial unconfined failure test

Theaboveuniaxialunconfinedfailuretestisconductedoverarangeofconsolidationstressesand the flow function is constructed by plotting the unconfined failure strength versus theconsolidationstressasshowninFigureA-5.Thegreatertheflowfactor(ff)value,themorefree-flowingthepowder.


Non flowing Very

cohesiveCohesive

EasyflowingUnconfinedFailure

Stre

ngth

σc

Freeflowing

ff=1 ff=2

ff=4

ff=10

Major Principal Consolidation Stress σ1

Figure A-5: The powder flow function

Thestandardclassificationofpowderflowabilityisasfollows:

ff<1 Nonflowing

1<ff<2 Very cohesive

2<ff<4 Cohesive

4<ff<10 Easyflowing

10<ff Freeflowing

Anticipated uses of the Brookfield Powder Flow Tester:

Benchmarking-Measureflowpropertiesonallrawpowdersandblendstodetermineiftherearedifferencesintheirflow-abilityandwhetherthesecorrespondedwithplantexperience.

Newmaterials -Testnew ingredients/blendsversusexisting ingredients /blends todeterminewhetherthealternativematerialislikelytobeeasier,moredifficultornodifferenttohandle.This potential material handling cost can be factored into the purchasing decision.

Reverseengineering-Ifyouhaveplantexperiencewithpowdersthatfloweasilyorpoorlyonagivenprocessline,youcanusethePFTtodeterminetheflowpropertiesofeachpowderanddetermineovertimeaflowabilitywindowrequiredforflowonagivenline.

Design-Designthegeometry(convergingangleandoutletsize)ofnewhoppers/silosforreliableflow.

Alternative methods of displaying the flow function test results

Todemonstratepowderflow-ability,theflowfunctioncanbepresentedgraphically(asinFigureA-5)todescribebehavioroverthestressrangeofapproximately0.6kPato10kPa.Thisstressrange is representative of that experienced by the powder in small to intermediate sized silos. However,describingflowabilitywithafunctionmaycomplicatetheanalysisasitissometimesfoundthat theflowfunctionsof twodifferentmaterialscrossoveroneanother,sothat their


relativerankingchangeswithstresslevels.Alternatively,flowabilityrankingsforspecificstresslevels can be determined by calculating the following parameters:

• EstimatedCriticalArchingdiameter[m]: The minimum silo outlet size for reliable gravity dischargeinmass-flow,calculatedusingthearchingequationinFigureA-2b.Thestressvalueistheinterceptoftheflowfunctionwithanff=1.4line*.

• EstimatedCritical‘Rat-hole’diameterin[m]:The minimum outlet diameter to prevent the formationofastable‘rat-hole’inacore-flowvessel.Theoutletdiameteriscalculatedusingtherat-holingequationinFigureA-2a.Thestressvalueistheinterceptoftheflowfunctionwithanff=2.5line**.

• Flowindex:Thegradientofalinefromtheorigintothelastpointontheflowfunction(bydefault**),typicallyintherangeof0.1to1.0.Thisindexwillgiveacomparisonofmaterialsbehavior at intermediate compaction stresses greater than one meter depth of powder.

• Flowintercept:TheinterceptofthebestfitlinearfailurefunctionwiththeunconfinedfailurestrengthaxisgivinganumberinkPa.Thisgivesanumberthatreflectsthepowdersflowabilityat compaction stresses typically less than 0.15m depth of powder.

Note: A timeconsolidatedflowfunction testallows theuser to investigatewhether thematerial gains strength during long term storage.

* Thesearethedefaultflowfactorsettingsbuttheycanbeadjustedbytheuserwithina1.0to 10.0 range for silo design applications.

**Canbeusersettoanystresslevel.

Wall friction test

Thefrictionactingatthewall/powderinterfacehasasignificantinfluenceonthestressdistributionwithinprocessingvessels,silosandhoppers.

Thehigherthewallfriction,themoreofthepowderweightistransferreddownthroughthesilo/vessel/containerwalls,ratherthancompactingthebulksolidbelow.Thelowerthefriction,themoretheself-weightistransmittedthroughthebulksolid.This‘Jasseneffect’isillustratedinFigureA-6,whichdemonstrateshowtheverticalpressuresintheverticalsectionofasilowouldvary if the wall friction were increased from zero to a large value of 40º. The presence of the wallfrictionhasanegativefeed-backeffectonthepressureincreasewithdepth,sogenerallythe stresses approach constant values at a depth of approximately 4 vessel diameters.


Dep

th.o

f.ves

sel.i

n.di

amet

ers.

Z

Major.Principal.Consolidation.Stress.σ1

Hydrostatic.pressure.increase(pgh)

wall friction = 0 degwall friction = 20 deg

wall friction = 40 deg

0

0.5

1

1.5

2

2.5

3

3.5

4

Figure A-6: Stress distributions in vertical walled vessels Software can be used to estimate pressures in a container based on measurements of the bulk density ρ,wallfrictionϕ

w,internalfrictionδ

jandcontainerdiameterD.Theprincipalconsolidation

pressure σ1atdepthZisgivenbythefollowingequation.

σ1.=.. ρ.·.g.·.D... 4.·.λ.·.tanϕW

·..(1–.e..4.·..λ.·.tanϑw·Z).

D

Where: λ = 1.–.sinδ.j 1+sinδ

j

The wall friction angle represents the angle to which a wall surface must be inclined as shown in Figure A-7 to cause powder to slip. The wall friction angle is typically in the range of 10 to 45 degrees.

The wall friction angle is also called the chute angle.

Powder slip

w

Figure A-7: Wall friction


Outputs of the wall friction test

WhiletheresultsofthewallfrictiontestcanbedisplayedgraphicallyintheformofawallfailurelocusasshowninFigureA-8a(representingthelimitingshearstressthepowdercansupportatawall),ortheformofawallfrictionanglefunctionasshowninFigureA-8b(representinghowthewallfrictionanglechangeswithreducingstress),oneofthefollowingfourflowindicesderivedfromthemaximumwallfrictionlocusareusuallyadequate.Thesewallfailurepropertiesare:

• θc,θ

pThemaximummass-flowhopperhalfangle(measuredtothevertical)forconicalor

planar hoppers.• ϕ

wThe maximum wall friction angle to determine the minimum chute angle for gravity

flow(seeFigureA-8b).• GradThemaximumwallfrictionangledisplayedasacoefficient.• c

w The wall cohesion shear stress in kPa that can be supported at the wall under zero

normalstress(seeFigure8a).Thisdeterminesthe‘stickiness’,i.e.whetherpowderislikely to stick to wall surface under close to zero stress. i.e. will powder build up on the wallsofthechutesarounddischarge/transferpoints.

Normal.Stress.σN

Wall.Friction.Locus.(WFL)

Shea

r.str

ess.

8

τ

cw

Wal

l.fric

tion.

angl

e.ϕ

w

Normal.Stress.σN

ϕw.Maximum.wall.friction.angle

90

0

Figure A-8a: Wall friction locus Figure A-8b: Wall friction function

An extended wall friction test allows the wall sample to be subject to large shear displacements (ontheorderof30meters)toestablishwhetherlongtermpowderbuilduponthewallwouldbe expected.

Bulk density test

Itistheself-weightofthepowder,itsbulkdensity,thatcontrolsthestressesactingonthepowderwhenflowingorwhenstaticinprocessinglines/silosetc.Thebulkdensityismeasuredduringthecourseoftheflowfunctiontest(andisrequiredtocalculatethecriticaloutletdimensions)andthewallfrictiontest,butitcanalsobemeasuredinaseparatesingletestforbulkdensityalone.

Compacted bulkdensity(ρcomp)


Incompressible.material

Compressible.material

Full.bulk.density(ρfill)

Major.Principal.Consolidation.Stress.σ1Bu

lk.D

ensi

ty.ρ

Figure A-9: Bulk density curve

Thebulkdensityiscommonlydisplayedasabulkdensitycurve(FigureA-9).Generallyafreeflowingmaterialwillbeincompressible-sowillshowonlyasmallincreaseindensitywithstress.Averycohesivepoorlyflowingbulksolidbycomparisonwillshowalargeincreaseinbulk density with increasing stress. ρfillThefillbulkdensitytoexpectedwhenthepowderispouredintoacontainerρcomp The compacted bulk density will give an indication of the bulk density to expect if the material is poured and compacted to high stress.

Summary

Tosummarize,theBrookfieldPowderFlowTesteroffersfourstandardtests,

1. Flowfunctiontest-Measuresinternalstrength,flowfunction,internalfrictionfunctionandbulkdensityfunction-usedforcharacterizingtheflowstrengthandarching/rat-holingpotentialofpowders.

2. Time consolidated flow function test–Sameasabovebutfollowingstaticstorageforauserdefinedtimeperiod.

3. Wallfrictiontest - Measures friction between the powder and a given wall surface andthebulkdensityfunction–usedforassessingmass-flowhopperhalfanglesandgravityflowchuteangles.

4. Bulkdensitytest–Measuresbulkdensitycurveofthepowder.

Note: Toundertakeafullsilodesignrequirestheusertorunandcombinetheresultsoftests1,2and3.

pft manual

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