Abstract:
Environment factors are
always important in any type of natural, mechanical, chemical, physical and
industrial process. Environment always influence each and every process
happening in this world either natural or un-natural. Environment factors
(temperature, air, dust, impurities, particles, moisture content, weather,
etc.) effect different processes in different ways.
Industrial processes are
also effected by environment depending upon the type of process, materials and
methods, machines used and end product. Textile industries are also effected by
environmental factors especially by temperature and relative humidity. These
factors effect each department in different way according to its process and
material. Initial step of textile industry so called spinning is also effected
and environmental factors are controlled in each and every stage of spinning,
otherwise quality is deteriorated and results in unbalanced production.
Temperature and
humidity has a great influence on every stage of spinning. Roving section is
also influenced and effects are obvious in end product. Here effects of
temperature and relative humidity on roving section of spinning are explained
with respect to type of material.
1
Introduction:
Temperature and relative
humidity are the two most important environmental factors which has a great
influence on textile processes including spinning processes. These two
parameters effect spinning from bale storage to yarn winding section. Each and
every process from bale storage to winding section is effected by temperature
and humidity. Temperature and relative humidity are explained below:
1.1 What is Temperature?
Temperature has different
definitions according to different fields and contexts. “In an industrial
context, temperature is the
hotness or coldness intensity of air in any environment where process machines and related equipment are kept
and it is called ambient temperature.”
Temperature is measured
by different type of instruments and methods according to environment where it
is measured, mostly thermometer is used for temperature measurement. It is
measured in three units, but the spinning department of textiles measure it in
degree Fahrenheit (oF).
1.2 What
is relative humidity?
Humidity is simply the
amount of water vapors in atmospheric air. “Relative Humidity is a measure of the amount of moisture in the
air compared with the amount of moisture the air can hold.”
Relative humidity is expressed
as a percentage of how much moisture the air could possibly hold at the
temperature it happens when you measure it. It can change when either the
temperature or the amount of water vapor changes. It is inversely proportional
to temperature and measured by psychrometer and hygrograph in percentage.
1.3 What
is roving?
Roving is an intermediate
shape of material between sliver and yarn to easily draft it to yarn. Roving is
made at roving frame also called simplex. It is only used in ring spinning
technique and is effected by environmental factors in different ways due to its
complex structure and feeble material.
2
Influence of temperature and relative
humidity at roving:
Temperature alone does
not have a great effect on the fibers and machine. However the temperature
dictates the amount of moisture the air will hold in suspension and, therefore,
temperature and humidity must be considered together. Effects on machine and
fiber material at roving section are:
2.1 Effects
on machine (Roving frame):
Not only fiber material
but machine is also effected by moisture content and temperature in atmosphere.
Machine is influenced as:
2.1.1 Erosion
of machine parts:
A decrease in temperature
and increase in relative humidity results in rusting and erosion of machine
parts such as gears, driving shafts and bottom drafting rollers. So 50-60%
relative humidity is maintained at roving frame with 75-80OF
temperature.
2.1.2 Dust
and fly Stickiness:
Dust and fly stickiness
increases with increase in moisture content and decrease in temperature. Dust
and small particles present in air stick with machine parts due to high
relative humidity and cause problems in machine operations. This results in
unbalanced process and quality deterioration.
2.1.3 Pneumatically
loaded drafting system:
Modern simplex machines came with pneumatically loaded
top rollers which has a lot of technological advantages. This system needs
continuous air supply while running of machine to put 150-300N pressure on top
rollers of drafting system. It is ensured that the air used for this process is
completely dry having relative humidity nearly zero to put proper pressure with
100-110OF temperature.
2.1.4 Machine
heat-up and wear & tear:
Machine gets heat up in
high temperature and low humidity because of 1500rpm high operating speed. Due
to high temperature atmosphere gets dry, parts are heated up and results in
more wear and tear of machine, which will result in more maintenance costs.
2.1.5 Machine
life:
Increase in wear and
tear, machine heating and dust stickiness at high temperatures and dry air (low
humidity) results in a decrease in machine life. So, optimum level of both
temperature and humidity is required and mostly set in between 50-60% relative
humidity and 75-80OF temperature.
2.1.6 Condensation
of moisture:
Increase of relative humidity
in the post carding stages up to the spindle point should be gradual. Any
sudden increase of relative humidity may lead to condensation of moisture on
the drafting rollers, cots and aprons, which will prove counterproductive.
2.2 Effects
on processing material:
Major impact of relative
humidity and temperature is on fiber material which is processed to convert
from sliver to roving. Natural and man-made fibers are differently affected by
environment. So temperature and relative humidity influences on material
depends upon material type. Fiber materials at roving frame are affected by
environment as:
2.2.1 Fiber
Cohesion:
Fiber cohesion in roving
increases with increase in humidity and decrease in temperature for both cotton
and man-made fibers. Due to more cohesion in fibers, roving strength increases
and ultimately results in low ends down rate.
2.2.2 Fibers
stickiness:
In a high relative
humidity atmosphere, fibers start to stick with drafting rollers and number of
fibers in roving cross section are decreases due to which mass variation
increases. This results in poor drafting and quality deterioration. Both cotton
and man-made behave same in this case.
2.2.3 Moisture
regain of fibers:
Moisture regain of cotton
fibers increases in high relative humidity environment with low temperature.
Due to more moisture regain, cotton fibers could swell and directly deteriorate
the quality. Man-made fibers such as polyester has very low moisture regain and
thus the impact of temperature and relative humidity on moisture regain of man-made
fibers is very low.
2.2.4 Fibers
pliability:
In order to facilitate
drafting on the roving frames fibers must be pliable which requires increase of
moisture content of fibers for which, temperature is gradually reduced in these
preparatory stages and relative humidity gradually increased.
2.2.5 Static
Electricity:
Dry materials create more
friction and are more prone to static electricity. Higher humidity reduces
static problems and makes materials more manageable enabling more efficient
production.
Static electricity arises
in low relative humidity when fibers and different simplex parts (drafting
rollers, flyer cap, hollow leg, presser arm) rub together, creating an
electrical charge within or on the material. Such electrical charges (static
electric shock) typically leak away to earth (electrical conducting material),
resulting in spark.
Static electricity is
produced according to material charge as cotton is neutral but man-made
polyester has negative charge.
2.2.6 Roving
strength:
Rovings with low moisture
content are weaker, thinner, more brittle and less elastic. These all problems
originate from high atmospheric temperature and low relative humidity.
Cotton strength increases
with increase in relative humidity. Polyester is nearly unaffected. But in
man-made fibers viscose strength goes down with increase in relative humidity.
2.2.7 Elongation:
Elongation percentage
goes up with increased relative humidity for almost all textile fibers. With
increase in relative humidity and low temperature, the resultant roving is more
flexible, elastic and less prone to breakage.
2.2.8 Hairiness:
Friction of fibers with
machine surfaces is reduced in high relative humidity due to which hairiness of
roving is reduced and fibers stick together. Man-made fibers already show low
hairiness because of long length of fibers and they are nearly unaffected in
this case.
2.2.9 Weight,
cost & Production:
Moisture content of
natural fibers (cotton) is gradually increased from blow room to winding
section to increase yarn weight and balance the costs and expenses. So an
optimum moisture content should be gained by fibers at roving to reach 8.5%
standard of cotton. At roving, about 6.5% moisture regain of cotton is achieved
by providing enough relative humidity.
In case of man-made
fibers except viscose and rayon, weight of all the man-made fibers is
unaffected because of low moisture regain.
5 Conclusion:
After all above
discussion and explanation, we concluded that ambient conditions are much
important in spinning and these should be controlled to an optimum level in
each section of spinning. Temperature and relative humidity has a great
influence on simplex machine and roving material. So atmospheric conditions especially
temperature and relative humidity should be controlled according to type of
material and end product properties.
The natural fibers are
highly sensitive to the conditions of the ambient air; they are hydroscopic, so
that the moisture present, whether expressed as moisture content or regain
depends to temperature. The mechanical properties of fibers and roving depend
upon the humidity and temperature.
Man-made fibers are
less sensitive to the ambient air conditions except a few types.
Nice Info....
ReplyDelete