INTRODUCTION
When the bales of cotton arrive at a spinning mill, these are
subjected to the very first process, which is definitely Blow Room.
Basic operations in the blow room:
Ø
Opening
Ø
Cleaning
Ø
Dust removal
Ø Uniform
feed to the carding machine
INPUT OF BLOWROOM
The material input to the blow room was
in the compressed form and full of trashes or impurities i.e. leaves, seed,
chaff, metallic particle and dusts etc.
OUTPUT OF BLOWROOM
After going through the processes of the blow room, the output in
the form of small tufts and it is cleaned and opened.
Principle of action of machines in blow room:
·
Action of
opposite spike:
o
This action reduces
the large tufts of cotton into small ones.
·
Action of
air current
o
The movement of
cotton fibers from machine to machine is done by the effect of continuous air
current,
o
This air current also
helps in separation of trashes
·
Action of
beaters:
o
Beaters are
resposible for removal of all types of impurities
o
Helps in opening of
cotton
·
Action of
regulation motion
o
Gives uniform output
of cotton fiber by help of swing doors
and swing paddels.
A blow
room installed by rieter company is shown in the figure
A blow room installed by Rieter company is shown in
the figure
Details of processes in blow room:
Blow room installations consists of
a sequence of different machines to carry out the above mentioned operations. Moreover Since the tuft
size of cotton becomes smaller and smaller, the required intensities of
processing necessitates different machine configuration.
Opening:
Opening in blow room means opening
into small flocks. Technological operation of opening means the volume of the
flock is increased while the number of fibres remains constant. i.e. the
specific density of the material is reduced.
·
Many types of opener
and beaters are used to open and clean the tufts some of them are given here
Machine used: (Bale Breaker)
The opening process is being done now a days in the
spinning lab of University College of Textile Engineering BZU using Reiter
unifloc machine shown in the figure below
Cleaning:
The process to remove dirt, dust,
broken seeds, broken leafs and other trashes is called cleaning.
Objectives of Opening and Cleaning:
·
To reduce the density
of raw cotton mass
·
To reduce the tuft
size exposing new fiber surfaces, that allows impurities to be removed
·
To reduce the tuft
size in order to improve the mixing of cotton and regularity of the feedstock
delivered to the next process.
·
To achieve these
objectives with a minimum damage to the fibers
Factors influencing cleaning:
·
The larger the dirt
particle , the better they can be removed. Since
almost every blowcroom machine can shatter particles, as far as possible a lot
of impurities should be eliminated at the start of the process.
·
The
higher the degree of opening, the higher the degree of cleaning. A very high
cleaning effect is almost always purchased at
the cost of a high fibre loss. Higher roller speeds give a better cleaning
effect but also more stress on the fibre. If cotton is opened well in the
opening process, cleaning becomes easier because opened cotton has
more surface area, therefore cleaning is more efficient.
·
The cleaning
efficiency is strongly dependent on the TRASH %. It is also affected by the
size of the particle and stickiness of cotton. Therefore cleaning efficiency
can be different for different cottons with the same trash %. There is a new
concept called CLEANING RESISTANCE. Different cottons have different cleaning
resistance.
Cleaning
efficiency may b calculated using formula
·
Due to machine
harvesting , cotton contains more and more impurities, which furthermore are
shattered by hard ginning. Therefore cleaning is always an important basic
operation.
·
In cleaning, it is
necessary to release the adhesion of the impurities to the fibres and to give
the particles an opportunity to separate from the stock. The former is achieved
mostly by picking of flocks, the latter is achieved by leading the flocks over
a grid.
·
In a
beating operation, the flocks are subjected to a sudden strong blow. The
inertia of the impurities accelerated to a high
speed, is substantially greater than that of the opened flocks due to the low
air resistance of the impurities. The latter are hurled against the grid and
because of their small size, pass between the grid bars into the waste box,
while the flocks continue around the periphery of the rotating beater.
·
Air streams are often
used in the latest machine sequence, to separate fibres from trash particles by buoyancy differences rather than beating the material against a
series of grid bars.
Machine used for Cleaning:
Many different types of cleaning
machines with different type of beaters are being used in textile industry, But
in blow room installed in Spinning lab of UCTE BZU uniclean of Rieter is being
used the short description about uniclean is given below
Construction parts:
1.
Cleaning cylinder
2.
Cleaning Grid
3.
Air lock cylinder
4.
Material feed
5.
Material outlet
6.
Exhaust air to filter
7.
Waste removal
But instead of the
material rotating three times inside the machine, it is forced to pass over the
grid five times, always presenting new surface areas to it. The tufts not only
pass over the grid five times, they also pass over a specially arranged
perforated sheet five times. The chamber behind this sheet is
a low-pressure chamber. The air suction through this sheet provides very
efficient dedusting. The waste is collected inside the machine and fed to the
waste transport via an airlock cylinder. Intermittent suction and connection to
continuous suction is possible.
Mixing cotton
Multi mix:
The machine is made up of three parts:
·
a storage
section,
·
an intermediate
chamber
·
a delivery
section.
Flocks are feed simultaneously into
6 J-shaped chambers (2) arranged one behind other in storage section. A
conveyor belt (3) leads the stock
through the intermediate chamber to the take-off unit. The material columns are
diverted out of vertical to horizontal. In addition to a condensing effect,
this 90º bend in the material flow also produces a shift in timing and special
distribution of transport of flocks from first chamber to last chamber. This in
turn results in good long term blending. Therefore as in blending opener,
material is extracted from the middle chamber and subjected to further opening
step between an inclined spiked lattice (5) and an evener roller (7), giving an
additional good short term blending. An optical sensor (6) controls the quantity
of material in the mixing chamber. Behind the spiked lattice there is
a take-off roller and a simple pneumatic suction feed to the next
machine.
DUST REMOVAL:
An often
underestimated task of the blow room line is the removal of dust. However, it
is as important as the removal of impurities. Dedusting in the blow room
happens by air suctioning only, either between the machines, e.g. by dust
cages, dust extractors , etc., or within the machine by normal air separation.
Every blow room machine must be capable of extracting dust, so that special
dedusting machines should be needed. The efficiency depends not only on the
devices but also on the size of the flocks. The smaller the flocks, the higher
is the efficiency.
Using Uniflex:
Uniflex is used for further opening,
cleaning, and dedusting of cotton of staple fibers.
A
fan in the feeding duct helps to supply
the machine with raw material. A specialy designed flip flop feeding device (1)
forms a homogeneous wadding in the lamina chute (2) over the whole length and
width. The dust laden transport air is extraced through the lamina chute. The
adjustable depth of the chute allows for homogeneous filling operation to take
place according to the production requirment. Two drums (3) positioned at the
bottom of the chute extract the material. One of them (4) is perforated and
allow additional dedusting. Feeding roller (5) and the servo motor controlled
adjustable feeding plate passes the fiber onto the opening and cleaning unit where
final cleaning takes place. After the operation of this machine the material is
then feed to carding machine.
TRANSPORTATION OF MATERIAL FROM BLOW ROOM TO CARD
For
the transportation of the fibers from the blow room to the card the chute feed
system is used Spinning Mills. In chute
feed system the ducting pipes and the chute is used. The fibers are taken from
the last roller through the condenser, which creates the suction and then feed
them to the card machine.
The condenser is very important part
of the blow room. Its main function is to take the fibers from the back part
and supply them to the next part. All this operation is down on the bases of
the sucking function of the condenser.
Basically the condenser consists on a
fan, stripping roller and a perforated roller. The fan is connected with a
high-speed motor, which rotates it at a high speed. The grid roller has holes
on its surface, which helps it to suck the fibers from the back machine.
When the fan and the grid roller rotates with the help of
the motor, an air vacuum is generated which sucks the fibers from the back
rollers through the holes of the grid roller. The stripper roller removes the
fibers from the perforated roller and through them into the chute.
General factors which affect the degree of
opening , cleaning and fibre loss are,
·
thickness of the feed
web
·
density of the feed
web
·
fibre coherence
·
fibre alignment
·
size of the flocks in
the feed (flock size may be same but density is different)
·
the type of opening
device
·
speed of the opening
device
·
degree of penetration
·
type of feed (loose
or clamped)
·
distance between feed
and opening device
·
type of opening
device
·
type of clothing
·
point density of
clothing
·
arrangement of pins,
needles, teeth
·
speeds of the opening
devices
·
throughput speed of
material
·
type of grid bars
·
area of the grid
surface
·
grid settings
·
airflow through the
grid
·
condition of pre-opening
·
quantity of material
processed,
·
position of the
machine in the machine sequence
·
feeding quantity
variation to the beater
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