CIQ Workshop

November 30th – December 1st

2010

Understanding the Nature of HVI Data

• Cotton is a biological fiber with natural variability in its properties

• HVI data has natural variability due to cotton variability plus testing variability or error (normal & abnormal)

• Strive to control and minimize abnormal testing variability

• Accept and manage the normal variability

Cotton Plant

• Matures from bottom to top• Cotton at bottom develops first

and cotton at top develops last• Cotton at top and further from

the trunk exhibits lower properties for micronaire, length, uniformity index and strength due to less time for growing and cell development.

Fiber Distribution of any Property

range

Mean(average)

Individual Comb Data

Individual Comb Data

Understanding the Nature of HVI Data

Example:1 Bale of Cotton tested:

100 times x 1 HVI x 1 day

100 times x 1 HVI x 2 days

100 times x 2 HVI x 2 days

100 times x 9 HVI x 2 days

Understanding the Nature of HVI Data

Example:1 Bale of Cotton tested: CV (Coefficient of Variation)

Mic Length SFI100 x 1 HVI x 1 day 1.75 1.04 5.11100 x 1 HVI x 2 days 1.80 1.10 5.14100 x 2 HVI x 2 days 1.87 1.17 9.16100 x 9 HVI x 2 days 1.99 1.38 16.49

Understanding the Nature of HVI Data

Important Points:- HVI data is statistical in nature - Even the best HVI data has an accepted level of

variability (error)

Fiber Distribution

Precision and BiasNot precise, no bias

Precision and BiasPrecise, with a bias

Precision and Bias

Precise with no bias

FIBER PROPERTIES

101.2

Fiber Properties Measured

• Micronaire • UHM Length • Uniformity Index• Strength• Color Rd• Color +b• Trash Percent Area• Trash Count

FIBER PROPERTIES

Micronaire – air flow system, consisting of a balance & a balanced bridge with a chamber which measures the fineness and maturity of the cotton fibers.

• A sample of known mass is compressed into a fixed volume and subjected to a standard air pressure.

FIBER PROPERTIES

– Length – is the average length of the longer one-half of the fibers (upper half mean length)

• Reported in mm’s, 100ths & 32nds of an inch

• Measured by passing a “beard” of fibers through a sensing point. This beard is formed when a comb grasps fibers from a cotton sample, which then are combed and brushed to straighten & parallel them.

Fibrogram

Am

ount

(L

ight

Att

enua

tion

)

Length (Steps)101.2

FIBER PROPERTIES

– Length Uniformity Index– is the ratio between the mean length and the upper half mean length of the fibers and is expressed as a percentage.

• If all the fibers in the sample were the same length, then the uniformity index would be 100

– Because of this, the index will always be less than 100.

UHM & UI from the Fibrogram

Am

ount

Length

UI = (ML / UHML) x 100 50% SL

100% SL

ML UHML

101.2

FIBER PROPERTIES

– Strength – reported in grams per tex.

• A tex unit is equal to the weight in grams of 1000 meters of fiber. Therefore, the strength reported is the force required to break a bundle of fibers one tex unit in size.

Stress / Strain Curve

Distance

Forc

e

101.2

FIBER PROPERTIES

– Color – determined by the degree of reflectance (Rd) & yellowness (+b) as established by the official standards and measured by the HVI

• Reflectance – how dull or bright (degree of grayness) the sample is

• Yellowness - indicates the degree of yellow color pigmentation

USDA Color Grade Diagrams

FIBER PROPERTIES

• The Rd on a scale of 0 to 90, and the +b on a scale from 0 to 20 are converted to a three digit color code determined by plotting the intersecting points on the USDA color diagram.

FIBER PROPERTIES

– Trash – A surface measure of the amount of non-lint material in a cotton sample measured in terms of the percent area of trash and particle count.

• Determined by scanning a compressed cotton sample through a CCD video camera whose image is converted to a digital picture. The picture elements (pixels) that are below a preset level will be black, and those pixels are counted as trash.

– Percent area of trash is calculated along with a trash particle count.

Cotton Division Locations

Washington Headquarters Memphis Field Headquarters / Classing Office Classing Facilities

Facilities & Equipment• Classing Office Locations (10)

1. Florence, South Carolina2. Macon, Georgia3. Rayville, Louisiana4. Memphis, Tennessee5. Dumas, Arkansas6. Corpus Christi, Texas7. Abilene, Texas8. Lamesa, Texas9. Lubbock, Texas10. Visalia, California

• HVI numbers per location (245)22341744171614124326

Cotton Division Locations2040 sq meters

2500 sq meters

7800 sq meters

1200 sq meters

HVI 1000’s by Year Model in USDA Classification Service

Year #2004 402005 502006 482007 402008 302009 202010 10Total: 238

Mic

rona

ire v

alue

Low to high

Low

to h

igh

Instrument analog measurement value(voltage)

INSTRUMENT CALIBRATIONTwo Points

Colo

r Rd

valu

e (r

eflec

tanc

e)

Low to high

Low

to h

igh

Instrument analog measurement value(voltage)

INSTRUMENT CALIBRATIONFive Points

Colo

r +b

valu

e (y

ello

wne

ss)

Low to high

Low

to h

igh

Instrument analog measurement value(voltage)

INSTRUMENT CALIBRATIONFive Points

• Proper Calibration– Use of correct materials

• Clean materials (No contamination)• Current materials• Follow proper procedures

– Placement of materials into instrument– Handling of materials

Conditioning of Materials for Moisture sensitive measurements» Stored in testing environment» Moisture equilibrium » Consistent environment

CALIBRATION

Overview

• Conditioning• Compressed Air• Conveyance• Removal• HVAC

G R A D IN G P R O C E S S

R E M O VA L& B A L IN G

CO

MPR

ESS

ED

AIR

SY

STE

M

HV

AC

S

YS

TE

M

C O N V E YA N C E

C O N D IT IO N IN G

How Facilities Systems Support the Grading Process

• HVAC System– Ensures proper testing conditions for lab and

receiving areas, and provides conditioned air for Rapid Conditioning Units (RCUs).

• Conditioning System– Brings cotton to proper testing levels.

• Compressed Air System– Supplies air for High Volume Instruments (HVIs)

and Conveyance Systems• Conveyance System

– Brings samples into the grading process.• Loose Removal System

– Removes completed samples from the grading process.

Monitoring Conditions

• Sensors in ceiling-mounted boxes monitor temperature and humidity levels.

• Wall displays show temperature and humidity levels.

• Sling or electronic psychrometers provide a manual check of conditions.

Sample Moisture

• Moisture content monitored with moisture measurement probe such as following:– Strandburg Moisture Meter

101.6

Conditioning Systems

Testing Conditions

• To ensure proper testing level, all cotton samples must have a moisture content of between 6.75 and 8.25 percent (dry weight basis).

• To achieve this moisture content, classing and receiving areas are kept at specified temperature and relative humidity levels:– Temperature: 21 C, +/-1– Relative Humidity: 65% RH, +/-2

Passive Conditioning (Rack)• Background

– Only method of conditioning prior to RCU

– Large conditioning space required

– Providing such space is costly– Samples are placed in single

layers– Samples must be exposed to

conditioned space until the specified moisture level is reached (minimum of 48-hours )

Active Conditioning (RCU)• Background

– RCU developed in 1993– Conditioned air is drawn

through the samples – Air is discharged back into

return to be reconditioned– Conditioning time is

approximately 10 minutes– Smaller conditioning space is

needed

Moisture Affect on Measurements

101.5

55

27

28

25

26

60

24

65 70 75 80

Relative Humidity (% RH)

Fibe

r Str

engt

h (g

/ te

x)

Effect of Moisture on Fiber Properties

• 1% Moisture Content ~ 10% unit change in Relative Humidity(RH)

• Strength – 1% MC change ~ 5% change • Length - 1% MC change ~ 2% change• Micronaire-1% MC change ~ 2% change

101.6

Effect of Moisture on Fiber Properties

• Example

RH MC Mic Str Len 60% 6.5% 4.00 30.0 1.00 70% 7.5% 4.08 31.5 1.02

101.6

American Society for Testing and Materials International

ASTM-I

• Designation: D 7410 – 07Standard Practice for Qualification of Cotton

Classification Instruments for Cotton Marketing

Scope1.1 This practice provides two options for the qualification

of cotton classification instruments: option 1, newly installedcotton classification instrumentation, or option 2, annual verification

of cotton classification instrumentation using evaluationcottons, trash evaluation images, and color evaluation fibersamples for the fiber measurements of micronaire reading,upper half mean length, uniformity index, breaking tenacity

(strength), Rd (color reflectance), +b (color yellowness), percentarea (trash), and particle count (trash).

Qualification Materials and Procedures

ConditioningCondition the cotton samples a minimum of 48 hours according to the temperature and relative humidity levels as specified in Practice D 1776 (21°C plus or minus 1°C) and (65 +/- 2 %).

CalibrationThe cotton classification instrument shall be calibratedusing USDA calibration materials as specified according to theinstrument manufacturer instructions.

Evaluation Cottons

Color Evaluation Fiber Samples

Trash Evaluation Images

Qualification Materials and Procedures

Procedures

1. Materials to test2. Number of test repetitions3. Data captured and required precision4. Data analysis5. Mean (Average)6. Standard deviation7. Criteria required for Pass / Fail

Qualification Materials and Procedures

Difference and Standard Deviation Tolerances for Micronaire Reading, Upper Half Mean Length, Uniformity Index and Breaking Tenacity

Measurements Difference Standard DeviationTolerances Tolerances

Upper Half Mean Length (in.) +/- 0.018 in. 0.0124 in.

Uniformity Index (%) +/- 1.2 % 0.84 %

Breaking strength (g/tex) +/- 1.5 g per tex 1.04 g per tex

Micronaire reading +/- 0.15 reading 0.104 reading

Qualification Tolerances

TABLE 2 Difference and Standard Deviation Tolerances for Micronaire

Measurements Difference Standard DeviationTolerances Tolerances

Micronaire reading +/- 0.10 reading 0.07 reading

Qualification Tolerances

TABLE 3 Difference and Standard Deviation Tolerances for Rd and +b Measurements

Measurements Difference Standard DeviationTolerances Tolerances

Rd (color reflectance) +/- 1.0 % 0.74 %

+b (color yellowness) +/- 0.5 unit 0.34 unit

Qualification Tolerances

Qualification TolerancesTABLE 4 Difference Tolerances for Percent Area (Trash)

Percent Area Image DifferenceMeasurement Levels Tolerances

0.00 to 0.14 +/- 0.02 %

0.15 to 0.34 +/- 0.03 %

0.35 to 0.54 +/- 0.05 %

0.55 to 0.84 +/- 0.07 %

0.85 to 1.14 +/- 0.09 %

1.15 to 1.74 +/- 0.11 %

1.75 to 2.24 +/- 0.14 %

Qualification of Instruments

• New• Annual• Maintenance• Repairs• Troubleshooting