The document discusses the USTER HVI 1000 system for testing cotton quality. It analyzes the key components of the system and how it determines various quality characteristics within seconds. The HVI 1000 measures fiber length, uniformity index, micronaire value, strength, elongation, color, trash count/grade and other factors. It provides a fast, objective replacement for human cotton classers and allows farmers, traders, researchers and spinners to efficiently evaluate cotton quality. The HVI 1000 has become a universal standard in the cotton industry for classifying cotton quality.
6. Introduction
For many decades the quality characteristics of cotton was determined by
human classers
Human classer could
categorize
fiber length
color and
trash content quite
well
Difficult or Impossible
for him to determine
× fiber fineness
× short fiber content
× strength
× elongation
× maturity etc.
4 groups of people who had
considerable interest to
improve the determination of
the quality characteristics of
cotton:cotton farmers
cotton traders
cotton research
institutes
cotton spinners
USDA played an important role to push faster test
methods to determine all the quality characteristics of
a cotton bale within a few seconds.
the testing system which was capable to measure the
most important quality characteristics within a very
short time was named High Volume Instrument (HVI).
8. Fiber length
The most important length to be determined with the USTER® HVI
Systems is the Upper Half Mean Length. This length is equivalent to the “classer’s
staple” and is defined according to Fig.
Fibrogram
Fig. Represents the “Fibrogram”, which is a non-end aligned staple dia-gram.
UHML
ML
The fiber length affects the
Yarn evenness
Yarn strength,
Yarn elongation
and
Yarn spinning
process
50%
9. Uniformity Index
The fiber uniformity index is the ratio between the Mean Length and the
Upper Half Mean Length .This value is expressed in percent
Uniformity Index (UI) %
Bale 1
UHML=x
UI=(y-5)%
Bale 2
UHML=x
UI=y%
Short fiber Short fiber
spinning process
increases the
unevenness
decreases the
strength of yarns
Effect Of Low UI
uniformity index
10. Micronaire Value
The micronaire value is a measure of the fiber fineness and the maturity.
Air Flow
The micronaire value can influence
the yarn evenness
the entire spinning process
Particularly the processing
speed in spinning mills
The measurement of micronaire is based on an airflow principle.
A cotton sample of 4 grams is entered into an airflow chamber.
Fig.airflow chamber.
11. Fiber strength
The fiber strength is determined at the same fiber bundle which is used for
fiber length measurement. The jaws are placed 3 mm (1/8 inch) apart.
The unit for fiber strength is Centinewton per tex (cN/tex).
Jaw 8/1 ” space bet n
clamps
Fiber bundle
Clamps
Fig . Fiber strength measurement
For surviving
subsequent processes
In weaving process,
yarns have to reach a
minimum strength
yarn strength is deter-
mined by the fiber
strength considerably.
12. Comb
Fiber Bundle
Top Pair Jaws
Bottom Pair Jaws
Fiber Breakage
Strength Measurement Principle In USTER HVI Machine
13. Fiber
Length
Short fiber content (%)
½”
Fre quency (%)
25 % 50 % X% 100 %
Short fiber index
The measure of the short fiber index is based on the fiber length distribution
throughout the test specimens. An indication of the amount of fibers that are less
than 0.5 inch in length.
14. Color Grade
The Color Grade is a measure of the reflectance (Rd) and the yellowness (+b)
of cotton fibers. These two quality characteristics can also be measured with the
HVI System.
The determination of the color code is based on the Nickerson-Hunter cotton
colorimeter diagram for Upland cotton.
The color code can be determined at the point where the reflectance Rd and
the yellowness +b intersect on the Nickerson-Hunter scale.
15.
16. Classer’s
designation for
reflectance
White
Light
spotted Spotted
Tinged Yellow
stained
Good middling 11* 12 13 -- --
Strict middling 21* 22 23* 24 25
Middling 31* 32 33* 34* 35
Strict low middling 41* 42 43* 44* --
Low middling 51* 52 53* 55* --
Strict good
ordinary
61* 62 63* -- --
Good ordinary 71* -- -- -- --
Below grade 81 82 83 84 85
N.B.* Physical Standards. All others are descriptive
Table : Color Grades of Upland Cotton
Classer’s designation for yellowness
17. Elongation:
Measurement of the elastic behavior of the fiber in the bundle. The distance of
the fiber extend before they break is called elongation and is expressed is
percentage
Δl
lo
Fig. Determination of Elongation
18. Moisture (moist):
Moisture is the amount of percentage of water which present in the specimen
being tested. Moisture content of the cotton sample at the time of testing
using conductive moisture probe. Moisture in the cotton varies with time
temperature and humidity of which the samples have been exposed.
19. Maturity Index:
The maturity index is a relative value that is calculated using a
sophisticated algorithm including the other HVI spectrum measurement
such as micronaire strength and elongation. Maturity indicate the degree
of cell wall thickness within a cotton sample.
20. Trash count:
Trash is measured on the same glass window as the color measurement.
The sample is illuminated from underneath the glass window and a black
and white CCD camera analyzes the changes pixels. A trash particle is
counted if it exceeds the grayness threshold set in the camera. All particles
that cover the glass window are counted one by one and the results are
expressed in trash particle count per surface area.
Trash Area:
The area that is covered by a trash particle is measured at the same time the
particle is counted. The area that is covered by a single particle is summed up
with all areas of the other particles counted on the surface of the glass
window. The result is expressed in relation to the entire measuring area of the
glass window and is expressed as percentage "% Area".
For example, a small number of trash counts can result in a high "%Area"
value if the particles are large. On the contrary, a high number of particle
counts with a small "%Area” value indicate the trash is smaller size (i.e.
pepper trash).
21. Trash Grade (Tr grade):
This is the trash or leaf grade that is determined by calibrating the HVI
spectrum with known samples. These samples are usually numbered from
1 to 7 with increasing amount of trash as the number gets tangers. The
standards used for calibration can be supplied by USDA or established by
the official cotton standards agency in any cotton producing country
22. The first attempt to increase the test speed of cotton classification was
made by the United States Department of Agriculture in the late Sixties with
the HVI
The quality characteristics deter-mined by USTER® HVI Systems are
known by everybody in the cotton supply chain
Conclusions
This test system has evolved in the meantime to a universal classi-
fication unit which has fulfilled the dreams of the pioneers.
Today, with the USTER® HVI 1000 a test system is available which can
satisfy the needs of the cotton farmer, the cotton trader and the cotton re-
search institutes and the cotton spinners.
