PROCESS PARAMETERS IN BLOW ROOM
BASIC FUNCTIONS OF BLOW ROOM
1.Opening &
Cleaning
2.Mixing or Bleanding
3.Micro dust removal
4.Uniform feed to the
Carding
5.Recycling of waste
The larger the dirt particle , the
better they can be removed
Since
almost every blowroom machine can shatter particles, as far as possible a lot
of impurities should be eliminated at the start of the process.Opening should
be followed immediately by cleaning, if possible in the same machine.
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.
Cleaning
is made more difficult if the impurities of dirty cotton are distributed
through a larger quantity of material by mxing with clean cotton.
The
cleaning efficiency is strongly dependent on the TRASH %. It is also affected
by the size of the particle and stickyness 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.
If cotton
is opened well in the opening process, cleaning becomes easier because opened
cotton has more surface area, therefore cleaning is more efficient
If
automatic bale opener is used, the tuft size should be as small as possible and
the machine stop time should be reduced to the minimum level possible
If Manual Bale openers are used,
the tuft size fed to the feed lattice should be as small as possible
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 hte 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.
Using Inclined spiked lattice for opening
cotton in the intial stages is always a better way of
opening
the cotton with minimum damages. Ofcourse the production is less with such type
of machines
But one should bear in mind that if material is recyled more
in the lattice, neps may increase. Traditional methods use more number of
machines to open and clean natural fibres.
Mechanical
action on fibres causes some deterioration on yarn quality, particularly in
terms of neps . Moreover it is true that the staple length of cotton can be
significantly shortened .
Intensive opening in the initial machines
like Bale breaker and blending machines means that shorter overall cleaning
lines are adequate.
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.
By using a
much shorter machine sequence, fibres with better elastic properties and
improved spinnability can be produced.
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.
There are
three types of feeding apparatus in the blowroom opening machines two feed
rollers( clamped)
Two feed roller arrangements gives the best
forwarding motion, but unfortunately results in greatest
clamping
distance between the cylinders and the beating element feed roller and pedal
arrangement gives secure clamping throughout the width and a small clamping
distance, which is very critical for an opening machine In a feed roller and
table arrangement, the clamping distance can be made very small. This gives
intensive opening, but clamping over the whole width is poor, because the
roller presses only on the highest points of the web.
Thin places in the web can be dragged out of
hte web as a clump by the beaters
Honeydew(sugar)
or stickiness in cotton affect the process very badly. Beacause of that
production and quality is affected. Particles stick to metal surfaces, and it
gets aggreavated with heat and pressure
These deposits change the surface
characteristics which directly affects the quality and running behavior.
There are
chemicals which can be sprayed to split up the sugar drops to achieve better
distribution. But this system should use water solutions which is not
recommended due to various reasons.
It is better to control the climate inside
the department when sticky cotton is used. Low temperature
( around 22 degree Celsius) and low humidity
(45% RH). This requires an expensive air conditioning set up.
easiest
way to process sticky cotton is to mix with good cotton and to process through
two blending machines with 6 and 8 doublings and to install machines which will
seggregate a heavier particles by buoyancy differences.
General
factors which affect the degree of opening , cleaning and fibre loss are
1.Thickness
of feed web
2.Densitiy
of the feed web
3.Fibre
coherence
4.Fibre
allignment
5.Speed of
openers
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