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