Jul 17, 2023
A blowroom in spinning is a crucial stage in the process of manufacturing yarn. It is responsible for converting raw cotton into a clean, un
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A blowroom in spinning is a crucial stage in the process of manufacturing yarn. It is responsible for converting raw cotton into a clean, un
M FACTOR AND C FACTOR : Developments in Cleaning Ranges at Blowroom
M FACTOR AND C FACTOR
New cleaning ranges have been introduced as compared to those using nipped beating points. Today’s modern ranges of machines have drastically reduced such beating points. Modern harvesting (m/c picked) and ginning (broken seeds) has made cleaning in the preliminary stages much more difficult, even when the trash, by weight itself, is much less. As against this, the demands for today’s cleaning are increasing. Presently, therefore, the modern machines are designed to carry the work of three to four cleaning machines working in tandem of yester years. Cleaning performance of the machine can’t be judged objectively as the cleaning does not merely depend upon the machines alone; but on cotton and its varying properties. In fact influence of the latter is as great as that of former.
In designing modern cleaners, the methods have been developed to differentiate between the various influences and to classify them by numerical values. With these, it has now been possible to give a specific value – Factor M to a machine’s performance i.e. the cleaning effect of that machine.
Cleaning Factors: The quality of cotton factor C is of equal importance to the cleaning effect. It indicates whether a cotton is easy or difficult to clean. Another important factor is the trash content (T). Under the identical mill conditions, the degree of cleaning by a machine is higher, when cotton is dirty than when it is clean. This is factor T & it represents % of trash.
With a low trash content (say 5%), the degree of cleaning (Rg) may be roughly calculated by using the following equation:
Rg = M. C. T
For higher trash content, a more accurate figure can be derived as:
The factor M for different machines has been determined by comparing their performance with present Trutzschler Cleaner RN with nose beater & grid eliminator – M = 1. Likewise, the value for C were found by cleaning tests on standard cleaning machines and comparing the results with mean standard for cotton, valid for some 5 years ago - - C = 1. The factor ‘T’ was directly determined with Shirley Analyzer.
On the basis of these factors, machine influence as well as cotton influence may now be separately determined accurately. This helps in solving specific cleaning problems and developing expedient machines.
The correlation between the various factors is illustrated by the different graphs:
The cotton (with C=1) was passed through at 350 kg/h and degree of cleaning was plotted on Y-axis. This graph shows that for a trash content of 3% (in the material fed to the machine), a cleaning degree of 30% was obtained. Whereas the same machine reaches only 10% cleaning when the trash content is 1%, other conditions being the same. The machine’s rating is then derived as M = 1.The higher the cleaning effect of the machine, the steeper is the characteristic line.
As per this graph, M1 = 1; M2 = 1.5 & M3 = 2.
In this case factor C, when cottons are tested, is 1. Here, the machine factor M = 1 and is kept constant by using one and the same machine. The C factors are found to vary from 0.5 to 2.0 Thus, a value of 0.5 reflects that the cotton is difficult to clean; whereas a value of 2.0 shows that the cotton is easy to clean. Steeper curve means that the cotton is easy to clean.
The values of C obtained under the mill conditions on Saw-Tooth Cleaner RSK for different cottons. The line on the right hand-most characterizes a cotton where C = 0.6. Another line next to it stands for C = 1. Another line to the extreme left is for C = 2.0.This factor C have become worse over last few years and now a days, the value of C = 0.2 (very difficult to clean) is frequently found. The values of C obtained under the mill conditions on Saw-Tooth Cleaner RSK for different cottons. The line on the right hand-most characterizes a cotton where C = 0.6. Another line next to it stands for C = 1. Another line to the extreme left is for C = 2.0. This factor C have become worse over last few years and now a days, the value of C = 0.2 (very difficult to clean) is frequently found.
The cotton with C = 1 contains coarse, little damaged leaf and stem-remainders, all of which are loosely attached to the top surface of the tuft during opening process. Therefore, this cotton is easy to clean, as some of these impurities readily fall-out even when the opening is carried out by hand. The cotton with C = 0.2 contains trash which is crushed into extremely fine fragments. These fragments disperse like wadding-like cotton. The tiny fragments are surrounded by the fibres, thus holding them tenaciously. They very rarely fall-out even when opened by hand. It can be understood that the cleaning effect of a machine can’t be correctly assessed, simply giving a figure for the ‘Degree of Cleaning’. For this, the cotton characteristics & method of preparation need to be taken into account. Factor C depends to a high degree on cotton’s provenance (place of origin), maturity level & its preparation. This (C) factor is also liable to change during the process, especially with different cleaners used in blow room line. These factors will have to be taken into account to arrive at a suitable value of C.
Let the following equation be again looked at.
Rg = 10. M. C. T
With M = 0.5, 1.0, 1.5 & C = 0.5, 1.0, 1.5
Only in extreme cases, C was found to have as low value as 0.2 and as high value of 3.0. The machine factors –M were ranging between 0.5 & 1.0 this shows that the influence of cotton characteristics on its getting cleaned has been far more than machine factor. Using the above equation, cleaning curve for specific cleaning range is plotted. Calculated & measured curves tally reasonably well. The cleaners R1 to R3 are in series. Along with card K, they achieve a degree of cleaning indicated by respective columns. The line indicates a cumulative degree of cleaning obtained at every cleaning stage.
Moisture content and production rate have decided influence also.
All the above discussion is based on production rate of 350 kg/h for cleaners in BR & 40 kg/h for card. Even then, the present methods are suitable for delineating (describe or portray) the cleaning potential and their range.
Comparisons of different Cleaning Machines:
The RN cleaner, with nose beating, achieves cleaning degree of 10% at 1% trash content. Consequently, its machine factor M = 1. The saw tooth cleaner RSK achieves 15% cleaning at 1% trash content; hence its machine factor M = 1.5
Action of RST Cleaner:
This machine is saw-tooth cleaner. It show 33% cleaning with trash content in the cotton as 1%. Evidently, its machine factor M = 3.3. It is obvious that RST is distinctly more efficient than a machine with say, M-factor = 1.65. The total cleaning effect of the two cleaners, working in a series has to be determined. It is usually found that this effect is always lower than the sum of the two machines taken separately. The same applies to the machine factor – M. It follows that the cleaner RST with M = 3.3 is plainly twice as effective as RSK with M = 1.5.
RST is the second highly effective machine further to the development of established RSK. It doesn’t require transporting the material through ducts, intermediate storage bins etc. The adjoining graph gives the behavior of the beater in cleaning the cotton. As mentioned earlier, with 1% trash, the cleaning level reached is around 33%
In ingenuity of the action of RST is that for the cylinder, two mote knives are fitted. They are further followed by a carding plate. Up to this the cleaning effect is the same as that of RSK. RST, however has the continuous suction system. This prohibits any possibility of trash and dust back into the material.
Another difference is that there is doffer which transfers the material from cylinder and subsequently; the stripper, which rotates at high speed and which again is equipped with mote knife and suction hood eliminates further trash. The interplay between feed rollers (the lower one has saw-tooth clothing), cylinder, doffer & stripper follows the laws of gentle carding technology. In RST, the mechanics of trash extraction consists of centrifugal force combined with suction in the region of mote knives. This achieved through careful and well-designed stages by determining peripheral speeds& type of clothing. This induces terrific cleaning effect at the last stripper. The width of the aperture in front of mote knife is yet another factor with RST.
With all these arrangements, it is possible to tune RST to different cotton qualities & cleaning requirements by exchanging the covers between knives and cylinder. This is rarely done because it is troublesome.. The latest RST now has lever controlled mote knives wherein the turning is either manual or through servo-motor and this can be done during machine running. With servo-motor, the mechanism is computer controlled. The data for cotton varieties for this setting can be stored (& can be recalled) or integrated through microprocessor, which also controls the speeds & extraction condition in the areas of waste removal & material transfer RST distinguishes itself from other conventional cleaners, not only by its high cleaning effect, but it also extracts only a small amount of useable fibres. It is known that in the beginning of any cleaning range, the waste extracted contains a small proportion of good fibre waste. However, in the last stages, especially with saw-tooth technology, good fibre loss in the waste continuously increases. This is also true for card. The new m/c – RST – giving a high degree of cleaning, gives only 20-25% fibre content which is no longer useable, & therefore, to be eliminated , anyhow. With RST, there is appreciable reduction of waste at card as well, thus improving the yield at that stage. It was thus confirmed that opening & cleaning must be taken as a whole and the various stages need to carefully balance. The first step in opening & cleaning should be removal of coarser impurities. The successive stages should aim at reducing the cotton tufts progressively finer. With properly balanced steps, only a few machines in the range suffice the purpose. People are always apprehensive about the machines with saw-teeth, as they think that it will either damage the fibres or lead to more nep generation. However, this apprehension stems from faulty choice of saw clothing and wrong technology within the machine. (Wrong speeds or not adopting progressive fineness of saw teeth or faulty management of air currents.) Mill tests have shown that like other machine, RST also produces (more) neps. But except carding & combing, the neps do increase in Blow Room. The tensile strength of the yarn & other useful characteristics have remained unchanged. It is necessary to install metal detectors and extractors in the range for protecting saw teeth. Also, it is necessary to replace the clothing, once in two years. The clothing on the main cylinder is very robust to protect from damage & eliminates coarser impurities.
Card as a Cleaning Machine: Apart from individualization, being the main object, the card is also a cleaning machine. There are considerable improvements at the card. The small particles and dust, separated by mote knives and carding segments, are immediately removed by suction. One may be tempted to use two saw tooth cleaners for better results. If the first cleaner is (say) Axi-Flow or RN, both having lower cleaning effect, the new RST still justifies its position, This is because, it easily removes coarse impurities, without crushing them. The smallest and varying particles of trash are of more concern than the total weight of impurities. This is because, the mere weight of impurities does not give correct idea of judging and improving cleaning operations.
There has been constant improvement in the cleaning range used in the blow room line. The graphs shows four cleaners of equal specifications. The degree of cleaning in each successive stage diminished as the material flowed. Beaters being same in the nature, it made extraction of the trash at succeeding stage more difficult. Therefore the total cleaning effect before reaching to card was around 35%. As is known, whatever, blow room leaves, the card tries to complete (at what cost is the question). Therefore, the card showed drastic improvement. This was in 1962.
In 1984, saw-tooth cleaner RSK was introduced. The typical line shown in the earlier curve disappears. In this case, using only three cleaners gave 53% cleaning (+18%), what the earlier four cleaners could not give. In the third graph, using only one cleaner RN, there was second cleaner RST. The graph speaks for itself. It is clear from this graph that RST has almost taken over the function of the card.
Integration of RST into Cleaning Range:
The fig. below, shows the integration of RST into a cleaning range. In this line, the principle of successive opening & cleaning is rigorously followed.
After Blendomat (BD T 019), there is Blending Hopper (BOBS). The material from this is emptied by inclined spike lattice, follows a light beating against the grid and gets fed to RN Cleaner.
Through exhaust condenser cage, the material enters four-chamber blending machine. The material, in quite opened condition, produces a feed, in which, blending size of the tuft, composition & uniformity are indeed ideal. The uniform lap sheet then enters RST. The material from RST meets all the pre-requisites for uniform feeding to the card. The suction from RST is connected to dust extractor DX. Finally, the material is led into chute feed to the card.
CONCLUSIONS A. With RST, ideal conditions are obtained, apart from thorough cleaning of the trash and dust, to feed the card. B. The suction fan provided around RST, allows no lingering of extracted waste. C. The reduction in the tuft size augments much improved functioning of card. D. The flow of the material within any cleaning range has a considerable influence on cleaning performance of the range of machines used in Blow Room. E. The use of microprocessors to constant and continuous flow of the material is very essential for intensive and yet gentle treatment. This means that all the cleaners operate without stopping and adjust themselves by infinitely variable drive to the required feeding rate.
Survey of Blow Room Practices by Pierce-Kelly & Coleman
Survey of Blow Room Practices by Pierce-Kelly & Coleman
Abstracts
Trials were taken in 40 mills; where 100 lbs of cotton passed through Blow Room & Carding.Waste collected separately at every machine & fractionated as – Lint, Chaff (The scales or bracts borne on the receptacle among the small individual flowers of many plants), Dirt & Dust. Survey covers comprehensively different combinations of Blow Room and types of cottons. An assessment of Blow Room is based on (1) Cleaning Efficiency and (2) Good Lint in waste.
Survey of Blow Room Practices
Cleanliness was judged by comparing trash content of the product with that of stock fed. Also, these ratios for different stages were expressed in “Logarithmic Form”.The cleanliness of the stock was measured by the logarithms of trash content at that stage (Trash being calculated by fractionation at subsequent stages in the operation).This quantity is expressed as ‘G’ (Weight Grade) and is found to bear close relationship with American grades.The drop of the value of G between any stages is taken as a measure of ‘cleanliness’ achieved during the ‘operation. This drop in the value is denoted as ‘g’ and helps in assessing the performance of individual machine. In the same manner, Wastage of good lint incurred, in the same manner, is expressed in logarithmic value – Lint Deficiency – ‘D’. This was calculated from the yield of ‘good lint’, obtained from the stock fed at each stage. Thus, ‘G’ represents the actual cleanliness and ‘D’ the actual wastage at any particular stage; whereas the values ‘g’ (change in G) and ‘ℓ’ (change in D) show the successive changes. In conclusion, it was shown that, when values of ‘g’ and ‘ℓ’ are roughly equal, the action of the machine (or process) may be considered “Normal”. On the scales adopted, the equality of ‘g’ & ‘ℓ’ means, in fact, that the relative elimination of trash effected by the machine is relative to 100 times the relative loss of lint. By plotting the value of ‘g’ against ‘ℓ’, it is possible to detect any abnormal behavior. Such graphs demonstrate that flocked cotton is responsible for a disproportionate lint loss and that sandy cotton gives abnormal values of ‘g’. Sometimes a low value of ‘g’ is associated with still a lower value of ‘ℓ’. This suggests that air currents are ‘unusually’ strong; however, they favor the recovery of ‘good lint’.
Introduction & Summary
In this general survey, there was found to be random and incalculable variation in the action of the machines. It was also found that the droppings contained both useful lint and unwanted trash.
Cleaning Action & Lint Loss:
The actual weight of the trash in the droppings can’t be taken as measure of its cleaning power. This is because, it obviously depends upon the trash content in the ‘fed’ material (& also on the positioning of the machine in the sequence). That is why a ratio of trash ‘eliminated’ to that ‘fed’, being a better measure, was taken in the study.However, if this were merely taken as the cleaning power of the machine, then again, it would be highly misleading. This is because, then mere removal of the stock in the form of trash would indicate as ‘Cleaning’. Comparing therefore, the trash in delivered material to that fed would be far more ‘sound’. Again, this ratio can’t be taken as ‘Quantitative’ measure of the cleaning action because; the trash content in the feed material (stock-fed) is not proportional to the ratio itself.
The two cleaning actions may reasonably be regarded as equal, if they lower the ‘trash content’ in equal ratio. If the two cleaning actions occur in ‘succession’, it is expected the combined action would lower the trash content by the ‘square’ of the ratio of single action. In such a case, the measure of action being ‘twice’ that of single action, the Logarithms are taken for this purpose. Direct measurement of the trash was not taken; instead, the droppings collected plus the waste in sliver (or lap) was assumed to be the ‘Total Waste %’ in cotton. (Possibly no Shirley m/c available then)
The dust concentration shows a strong correlation with the original trash content in sliver.‘Cleanliness’ of the stock is measured by the log of trash content in the material. The drop in the value of this ‘G’ between any two points is taken as measure of cleaning action of the intermediate process (as mentioned – this value is ‘g’).The yield of Lint in the stock from 100 lbs of bale cotton is also expressed by logarithm. But, to avoid negative values and decimals, this is slightly changed and called as ‘Lint Deficiency’ – “D”. Waste of Lint (Lint Loss ‘ℓ’) is measured by increase in the value of ‘D’. ‘D’ is the ratio of Wt. of cotton processed to Wt of the clean lint present. Lint being lost in the waste, proportion of lint in the stock delivered reduces; hence value of ‘D’ increases
Description of the Test & their Results:
40 tests each of 100 lbs are employed and proceed up to card. The droppings at every machine were separately collected & weighed. They were fractionated into – lint, seeds, chaff, dirt & dust. Fractions are considerable (in large quantity) and only their weights are amenable (responsible) to general statistical survey.
Description of the Test & their Results:
However, the weights do not fully describe the fractions. Hence, some supplementary tests like ‘lint loss’, microscopic examination of trash fraction and dust count of card room air were taken. ‘Stapled tests’ (diagram of lint in the droppings) modify the elimination of ‘waste-fullness’ and they reveal that there is more short fibres in the droppings than in the stock.This excess is more marked in licker-in fly. The trash is all useless and harmful. The fractions of trash are – very easily eliminated smooth seeds and mineral dust. The tenacious part consists – bearded motes & light dust, the chaffs of broken leaves and stalk and all these make-up the bulk of the trash.
The trash remaining in the sliver is very small for accurate fractionation. The trash content in the sliver is roughly constant fraction (about 1/10) of that of card strip.In the whole paper, the quantities are expressed as ‘parts’ per 10,000 parts of bale cotton
Analysis of Action of Opening Machines:
The total cleaning action, involving blow room and licker-in action, till the material reaches the card cylinder varies from g = 303 to g = 951, with mean value of 557 The degree of cleaning (g) or the proportion of original trash is independent of original weigh grade (G0) or grade of bale cotton. Normally Lint Loss, as measured by ‘ℓ’ is roughly equal numerically to the ‘cleaning’ (as measured by ‘g’). In proportional scale, the proportional loss of ‘trash’, is 100 times that of lint.
Cleaning Power
The number & the power of machine also vary, but it is not associated with variation in cleaning. Thus, an easily cleaned cotton is given milder treatment and vice-versa.
On average g = ℓ = 557
Licker-in is twice as long as ‘Crighten’; five times as 3 B.B. and 22 times Exhaust Opener. (Comparatively)
In this case, both ‘g’ and ‘ℓ’ are taken as the measure of opening treatment that the cotton receives in the machines. However, ‘g’ is to be preferred (reasons given later).The treatment given to the cotton in the previous machine is very important in judging the action of any machine.Thus, Porcupine opener fed by the lattice (practically unopened stock) shows more powerful action than the one placed in Scutcher where cotton is far more open. Though the causes for the difference in the power can’t be determined with certainty, the speeds of the beater and the weight of the feed appear to be influential. Flocked cotton is responsible for abnormally high lint loss & sandy cottons for high cleaning.
In some cases, it was found that with low ‘ℓ’ and low ‘g’, strong air currents helped some selective recovery of lint owing to buoyancy. The most striking conclusion was that the present machinery failed generally and consistently to perform such an action of detachment of trash; and the trash, in turn, was carried forward. Thus, there was some definite carry-over of loose trash-&-lint to the subsequent machine (“Re-combination of Lint & Trash”). The action of Dust Trunk following Crighten is an example. The great bulk of trash is vegetable originated and remains substantially constant throughout the process.Sand drops early in the process; seeds are selectively eliminated by scutcher; leaf fragments and bearded motes persist preferentially through all the openers while little dirt enters the ‘dirt boxes’.
No direct relation could be established between ‘lint loss’ and measurable characters of cotton fibres, the influence of the latter being overshadowed by complex variations with varying effects. The variations in the readings of trash and lint for the same machine in different mills are due to variation in setting, load (feeding) and air currents of the machines & their adaptation to cotton; the great difference of the kind & behavior of trash - which may be sand or fuzzy motes – and in the product – which may be fluffy or partially rolled into flocks or strings.
Staple Length of Lint Fraction:
It appears that there is little change in the staple from bale cotton to sliver, if any; there is slight decrease in the length. This is because, all the waste in the lint is much shorter in staple. Therefore, the fibres either carried away in air exhaust or included in trash fraction are predominantly short. It is also evident that if there is fibre breakage, it is probably in the card. The lint in the flat strip is much longer than the one from scutcher droppings. Similarly, lint in scutcher dropping is longer than that in crighten dropping, though the difference is not large & all these are useful in waste spinning.
Staple of Lint & Invisible Loss
Licker-in fly is of different nature and has little spinning value on the whole, the lint fraction may be taken as loss of some useful cotton. This results in loss of sliver quantity, though its quality remains almost unchanged.
Invisible Loss:
Out of 10,000 parts 9379 parts are recovered as ‘finisher lap’; whereas 428 parts are collected as ‘droppings’, thus leaving 193 parts as unaccounted ‘Invisible Loss’.This consists of moisture, lint and dust, all of which escape through air exhaust. A small insignificant amount is lost in handling & collection.
Scale of Cleanliness
The diminution in the trash content decides the cleaning action of the machine. However, the reduction from 10% to 9% can’t be regarded the same as the one from 2% to 1%Therefore, the ratio is the way of comparing. Thus, the reduction from 10% to 5% would be the same as the one from 2% to 1%. The data of lint & trash recovered from 100 lbs of bale cotton are converted into two quantities better suited to general comparison and analysis.The trash content is multiplied by 100 and its logarithm is taken. The value is then multiplied by 1000 to express ‘G’. This is done to avoid negative values and decimals.
Similarly, the ratio of weight of the bale cotton to weight of the lint present is initially found out. It is expressed in logarithm. It is then multiplied by 100,000 to expressed ‘D’As the value of ‘G’ defines the dirtiness of the stock, higher value would indicate dirtier cotton. Further, a given decrease in this value would also indicate, by the same proportion, drop in the trash content. The value of ‘D’ (waste incurred) increases as the pure lint decreases, thus meaning that the Lint Deficiency or extent to which the lint falls short of the full weight of the bale cotton. During the progress of a test, the value of ‘G’ drops, as the trash content of the product is successive stages reduces; whereas the value of ‘D’ rises. Change in ‘D’ is Lint Loss.
The decrease of ‘G’ on passing through a machine is the measure of cleaning done and is denoted by ‘g’.The value of ‘D’ increases (as yield of pure lint from the stock at subsequent stages in comparison to full weight of the bale cotton fed decreases). This is because the material is lost in the form of waste and the proportion of lint in the stock delivered, therefore reduces.‘D is the ratio of ---- (Weight of Bale cotton processed) divided by ---- (Weight of clean lint present).As the denominator is reduced (lint is lost through waste extracion), the ratio (‘D’) increases.
American Grades of Cotton
MF1, SGM2, GM3, SM3, SM4, M5, SLM6, LM7, SGO8 & GO9
Relation between ‘G’ and grades is as follows:
N + 1 = 8 [G/1000 - 2)
With G = 3000, then N = 7 (As per above LM – Low Middling)
Analysis – Cleaning action & Lint Loss
Total action of Blow Room & Licker-in:
The total cleaning varies from G = 303 to 951. In this case the average value is G = 557. The lowest and the highest values of the cotton occur on the same and average grade. Thus, there is no correlation between cleaning & trash content (R = 0.177).The total cleaning may therefore, be regarded as ‘high’ or ‘low’ by comparing it with the value 557, irrespective of the grade of cotton. It shows that the normal practice doesn’t compensate for low grade by extra cleaning i.e. by removing extra proportion of trash
Effect of Grade on Lint Loss:
There is a marked correlation with grade. The dirtier cotton, on the average, loses more lint [R between ‘G0’ & ‘ℓ’ = 0.607]. Independently of the grade, there is also marked tendency for Intense Cleaning associated with ‘High Lint Loss’. (R between ‘g’ & ‘ℓ’ = 0.451]. The correlation of Lint Loss with the grade arises mainly from a group of large lint values, in tests; where two major Openers were used – Willow & Crighten, Two Crighten or Crighten & Buckley (Horizontal) Opener.
Such treatment is given for hard-pressed (difficult to open) cotton.
Analysis – Cleaning action & Lint Loss
This is because, the harder bales and the harder treatment, when they go together, have a tendency to flock the cotton. However, this must be distinguished from a systematic tendency for high trash content to cause extra lint loss.
Cleaning & Lint Loss:
If the flocked cottons are kept aside as abnormal, the grade seems to cease, to be of importance in determining the normal ‘Lint Loss’. Then it (grade) evidently shows closer relation with the cleaning. The majority of the cases show a ‘total cleaning loss’ within 100 units. The larger excesses are due to heavy losses in Licker-in region.The small lint losses may be explained by conservative cleaning of trash which is removed easily.Amount of Treatment: The lowest (g = 303) and the highest (g = 951), both follow the relation g = ℓ, reasonably well. They occur in the same weight grade of cotton. The cleaning and the lint loss, to be normally expected in a Blow Room, depend on the ‘combination’ of the machines actually used.Ratio of lint loss (‘ℓ’) to Cleaning (‘g’) in Machines): The average ratio of g / ℓ is 1.33 and remains more or less the same in Blow Room & Card (Licker-in).If the cotton contains much heavy mineral dirt, a large proportion of this is likely to fall out at the first opportunity without corresponding lint loss. The normal value of g / ℓ is independent of machines or its position in the sequence.
Normal Behavior:
The ratio of g / ℓ is calculated for all the opening machines, except Hopper, Dust Trunk and Exhaust Opener. Licker-in however is included. The large majority of the test show this value is as less than 1.35; medium value is 1.1 and lower one is 0.8. Though the Licker-in has 24 times the action of Exhaust Opener, it does not sieve or select the particles.These beaters only detach these particles under their beating & opening treatment according to own power of adhesion of these particles. The ‘normal’ relation as g = ℓ means that the average probability of a trash particle detaching itself from the stock processed, during an opening process, is 100 times that of ‘Lint’.
Measurement of Action of Machine - (Choice of ‘g’):
Considering the nature of action, essentially these machines are openers; they beat the cotton into small tufts and from the opened part or surface of separation, the dirt or loose lint may fall through the grid into dirt box. This may only occur at the opened part.It is conceivable therefore, that dirt and lint can’t be separated from the center-unopened lumps of cotton.Hence, the cleaning action is essentially the result of opening action & both, the amount of cleaning ’and‘ lint losses may be regarded as a measure of it. On this view and in the light of the results of the above sections, ‘g’ and ‘ℓ’ are equivalent measures of cleaning and opening action of the machine. Also, they are satisfactory measures as they are independent of grade of cotton fed. Both ‘g’ & ‘ℓ’ are subject to rather length-based error.
The former (g) may be exaggerated by the presence of sand or latter (ℓ) by the flocked cotton, both of which again fall-out with abnormal cases. The detached particles of the lint may be selectively recovered by an upward air currents (as in scutcher). If this principle is deliberately exploited and stabilized, the value of ‘ℓ’ would cease to be a valid measure of opening treatment. As the exaggeration of ‘g’ by sand is almost limited to first opener, and if serious, may be discounted. Thus, this quantity (‘g’) may be taken as the most valid measure of opening & cleaning treatment presently available.
M/c g ℓ M/c g ℓ
Licker-in 225 303 P.B. 40 23
Crighten 113 133 P.F. 66 61
Buckley 100 127 Murray O. 55 37
Willow 75 179 Ex. O. 10 14
3 B.B. 45 58 Dust Trunk 24 34
2 B.B. 42 81 Hopper F/O 5 12
K.B. 31 61
[Higher ‘g’ → Higher Cleaning; Higher ‘ℓ’ → Higher Lint Loss]
Action affected by Previous Treatment of Cotton:
This depends upon the value of ‘G’ of the stock fed. Thus, a Porcupine Opener may be much effective in the beginning than the porcupine at the scutcher. Similarly, Buckley at the beginning is much more effective than one that follows Crighten.
Action according to Type of Machine:
The standard of judging the action is to determine the average value of cleaning and lint loss.In Blow Room, the Crighten shows the highest value of ‘g’ (113). Buckley has subnormal efficiency. Kirschner Beater is rather less efficient than other beaters. The large lint loss (‘ℓ’) in K.B. and 2 B.B. is due to flocked cotton (possibly due sheet feed) present at the earlier stage.Thus, both K.B. and 2 B.B. are not responsible for this loss. The low lint loss in P.B. is common to other machines.Though P. Feeder shows higher ‘g’ value, this must be discounted by its position, being at scutcher.Murray Opener has similar effect, considering its position after Crighten.
The small beater at the beginning of Exhaust Opener, which merely acts without nipping a grip is seen to be very ineffective. Its dirt box acts rather as an extension of dust trunk. The dust trunks themselves appear to be effective; but it is not due to their own action. It is merely because they allow dropping of trash and freely drawing the lint through the previous opener by strong draught that is necessitated by the trunk themselves. Hoppers have little action. At the beginning of combination, the droppings are light unless they include lumps. However, the hopper following the opener gives more droppings, which are particles detached but not dropped in the previous machine.
Action of Individual Machine:
To seek the cause of variation, the account must be taken of the position of the machine. The P.O. of the lattice feeder is usually in the beginning and its action is greatly affected by the character of cotton and trash. By the time the scutcher are reached, the variation in the type of trash is much reduced. The scutcher is particularly suited for generation and control of air currents, nicely adjusted to carry the lint while allowing the deposition of trash. This requires effective adjustments of fan speeds, beater speeds, grid bar settings, rate of feed and character of cotton.Mere increase of air currents is likely to carry away both the cotton and the trash through ongoing stream.
When considering the action of any machine followed by a Cage, where cleaning is also done, the credit must be given to the action of the beater preceding it. For, a Cage can only extract particles that have already been detached. The cleaning action of the Crighten is very sensitive to the cotton processed. Here the heavy lint loss is mainly due to flocked cotton; even then sometimes the adjustments of the surrounding bars might prove to be economical. Buckley has normal cleaning power.Dust trunks vary in their action. They offer a further opportunity for the deposition of particles liberated by the beater and carried forward by the air currents. The droppings greatly vary due to bends in the pipes & strength of air currents.
The beater at the beginning of exhaust opener attempts to hit the loose cotton, not held in the nip, nor restrained in any way; but seems merely to spread it on its way.In the sequence of P.O. → C.O. → Dust Trunk → Ex.O, the cotton goes continuously without re-condensation and much loose trash and lint can accompany the cotton in the strong air currents.The droppings are also affected by the efficiency of collection – by the grids, dust box, air currents and by the carry-over from the preceding machine.
Average % of Trash (composition)
M/c Seed Chaff Dirt Dust
P.O. 21 54 21 3
C.O. 20 57 18 5
Dust Trunk 21 53 19 7
Ex. O. 21 54 19 6
3 B.B. 30 52 15 3
2 B.B. 24 60 14 2
Bale 18 59 13 10
Taker-in 12 69 15 4
Cotton Character:
A short coarse hair should cling less and should fall more readily. It is evidently seen that short fly in the droppings was abundant. A high value of lint loss is from short coarse cotton, which also happens to belong to low grade. But high lint loss is definitely due to hard tufts of cotton produced by – mechanical action, balling or flocking.Flocks can’t be regarded as the effect of – either the cotton character or its grade. The association is accidental & due to commercial cause. Coarse cotton is cheap and great care in ensuring itsCleanliness is not justified. It also commonly packed very densely. To reduce the transport cost. This obviously requires drastic treatment in its opening - & hence flocking.Therefore, the drastic opening will flock or string fine cottons of low or high grade. The fact appears to be that, the difference, either in clinging power or floatability between the coarse and fine lint, is small compared with difference between either kinds of lint and trash or densely tufts of cotton (Principle used in Air Stream Cleaner)
FACTORS AFFECTING OPENING, CLEANING AND BLENDING IN BLOW ROOM
1. Introduction
Textile mills are generally located quite from away from the field where the cotton is grown. If the cottons are brings to mills in the loose form, it is highly uneconomical due to its risk. Therefore, to facilitate economic transportation, the cotton after ginning is compressed into a compact form called bale.
The hard and compact nature of cotton in the bale form, it becomes necessary to open the cotton. The seeds, and leaves are removed in the ginning process, much of the broken leaf, stalk, seed coat, sand etc., are pressed in the bale. To remove this cleaning is necessary, to clean the cotton fibres in bale form should opened into small tuft this is done by opening in blow process.
The number of machine and their type required for a blow room line are governed by the condition and the class of cotton. To open and clean the fibre the materials will harshly treated with the more number of machines. This treatment will affect the fibers. To reduce the fibre damage the fibre should process in subsequent process. Some of the factors will affect opening and cleaning of fibres, if it is not in proper design and setting fibre will affect, i.e. fibre damage, fibre rupture, improper opening and cleaning.
2. Function of Blow Room
· To open the baled fibres into small tufts
· To clean the fibres by removing the foreign matters like seed coats, leaf, sand, fused fibres etc., from the fibres and prepare the material for easy carding.
· To mix through different component fibres of a mixing so as to give homogeneous blending
· To from a compact and uniform sheet of fibres to carding.
3. Blow Room Machineries
The blow machineries can be divided into five categories based on their design ad function.
· Opening machines
· Mixing machines
· Cleaning machines
· Dust removing equipment
· Axillary equipment
3.1. Principle of Opening and Cleaning
The basic principle of opening and cleaning in the blow room line are as follows
· The action of opposing spikes
· The action of aircurrents
· The action of beaters
3.1.1. The Action of Opposing Spikes
The spikes of the evener lattice pick up the pieces of cotton and carried them to point lattice, where they are met by a series of spikes of the evener roller which move in the opposite direction and oppose any further passage. Rough combing action occurs and the spiked lattice carries a small part of the fed cotton along with it. The tearing action is taking place between the two opposing spikes.
3.1.2. The Action of Aircurrent
Air and cotton enter the chamber of the machine together at the bottom or at the center of the beater chamber where the cotton starts to receive one of the many blows from the strikers of the beater. The cotton is thrown against the grid bars by centrifugal force. This action forces the heavier impurities through the bars into the large duct box under the grid bars.
3.1.3. The Action of Beaters
This involves the holding of the mass of fibres while the beater strikes it. The holding of fibres can be done in three ways.
· Feeding by two rollers
· Feeding by a feed roller and a feed plate
· Feeding by a feed roller and pedals
Two feed roller arrangements gives the best forwarding motion, but unfortunately results in greatestclamping distance between the cylinders and the beating element.
Feed roller and pedal arrangement gives secure clamping throughout the width and a small clampingdistance, 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 intensiveopening, but clamping over the whole width is poor, because the roller presses only on the highest pointsof the web. Thin places in the web can be dragged out of the web as a clump by the beaters.
3.2. Opening Machines
Opening is the first operation it means, tearing apart the compressed and matted cotton until it is very much loosened and separated into small tufts with a gentle treatment, and a fibre loss as small as possible.
Opening is also related to cleaning as where is opening there is also cleaning
The term opening in the technological sense, means while number of fibres is remaining constant volume of the flock is increased i.e. the specific density of the material is reduced.
There are two different level of opening
· Opening into fibre tufts (performed in blow room)
· Opening into individual (performed in carding and rotor spinning)
Two different type of opening
· Breaking up of larger tufts into several tufts to create new surfaces (bale breaker)
· Opening of individual tufts to increase the volume (with weight remaining the same)
Both ways are performed, with different intensities in different processing steps (i) in the opening, the breaking up of tufts is dominant (ii) fine cleaning the opening up of a single tuft is mainly performed.
3.2.1. Degree of Opening
It increases when number of machine increase in process. It depends on,
· Raw material (thickness of feed, fibre alignment and size of flock in the feed)
· Machines (arrangement of the pins, teeth, needle, type of clothing, spacing between the material and opening device)
· Speed
· Condition (humidity, temperature).
3.3. Cleaning
The term cleaning in the technological sense means that it is the process of releasing the imprisoned impurities from the bale cotton. 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 mixing with clean cotton.
If cotton is opened well in the opening process, cleaning becomes easier because opened cotton has more surface area, therefore cleaning is more efficient.
3.3.1. Cleaning Efficiency
Cotton contains up to 18% trash in most cases. To clean the material it is unavoidable to remove as much fibre as much waste. Therefore it is necessary to measure the amount of the waste removed and its composition. As it is of high importance also called efficiency. It depends on trash%, machine performance factor and cotton properties factor.
Cleaning efficiency (η) = 10*M*C*T (%)
Where, M – machine performance factor, it varies between 0.5 – 1.5
C – Cotton properties factor, it varies between 0.5 – 1.5
T – Trash %
4. Factors Affecting the Opening and cleaning
· Type of opening and cleaning device
· Selection of beater design
· Type of feed
· Distance between feed and opening device
· Type, and setting of grid
· Angle of grid bar
· Types of fibre
· Action of air current
· degree of penetration
4.1. Type of Opening and Cleaning Device
All opening & cleaning machines can may be broadly classified following types. Loose feeding and beating technique-free beating pointed led type of feeding by air suction. Opening action is increased by increasing the speed of the beater.
· Vertical opener (Bladed beater type)
· Step cleaner ( Pin opener type)
· S.R.R.L opener (Saw tooth opener type)
· Axi flow cleaner/ spiro cleaner (Pin opener type)
· Mono cylinder (Pin opener type)
· Porcupine opener (Bladed beater type)
· 3 or 2 Bladed beater (Bladed beater type)
· Kirschner beater
· E.R.M cleaner
Major and Minor cleaning points
· The machine where heavier trash particles are extracted from cotton by heavier beating action is called Major cleaning Point.
Ex: Vertical opener, Porcupine opener, step cleaner S.R.L.L. Opener, Shirley opener
· The Machines where only fine dust & lighter impurities extracted by giving light beating or combing action on cotton by air current is called minor cleaning point.
EX: Kirschner beater, condensing cages, Dust Trunk, Dust filters, etc.
The single-cylinder opener, which is suitable for ’roller’ cottons (meaning fine and long fibre cottons) which have been subjected to cylinder ginning, and which therefore carries out an intensive but not aggressive action; The three-cylinder opener, designed on the other hand, for ’saw ginned’ cottons (generally medium-short length fibre, with a characteristic high content of vegetal impurities), that carries out an extremely intense but still not aggressive action.
4.2. Section of Beater Design
Proper design of preparatory line and regular condition monitoring of the beaters is key to consistent yarn quality and good fibre yield.
In modern blow room four types of beaters are primarily used – disc beaters, peg beaters, pinned beaters and saw tooth beaters each having its own function and suability to certain requirements and conditions. As disc and peg beaters are used for beating and pre – opening of cotton fibres. The pin has a smooth round surface and a spherical tip, which opens the fibres through a gentle untangling action. The round profile of pins also has another significant advantage that is higher performing life and more consistent quality of opening.
Long stable cotton with low trash would require lesser beating and more opening than short stable, trashy cotton. Synthetic fibres require no beating and only gentle opening. Saw tooth wires can be used for opening polyester or nylon fibres. However they can cause several problems if used for opening soft fibres like viscose since fibres have a tendency to disintegrate under stress.
Design Factors in Beaters
Increase in diameter helps reduce the rpm of the beater and also helps increases production. Opening points density – Projection and angle of points and tip profile they influence intensity of opening and cleaning, operating life, reduction in neps and fibre rupture.
4.3. Type of Feed
There are three types of feeding apparatus in the blow room opening machines
· Two feed rollers (clamped)
· Feed roller and a feed table
· A feed roller and pedals
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 the web as a clump by the beaters.
4.4. Distance between Feed and Opening and Cleaning Device
Distance between the feed and beater is important because if distance is more the opener can’t get the feed material properly this affect in the cleaning process. If the feed is more than the opener will get jammed it led to stop the machine. Setting between beater and feed roller = 3/16 inch
4.5. Type and Setting of Grid
Also wider setting is recommended when a very heavy feed is used, so as not to crush the fibres. Wider setting between stripping rail and beater causes unnecessary reprocessing of fibre in the beater section, because of this over treated cotton or repeatedly beated cotton, curly cotton is produced. Inclination of the grid bars are so arranged that the resistance to the movement of cotton gradual1y decreases, from feeding end to the delivery end. Setting between grid bar and beater will be gradual1y increased from first grid bar to the last grid in gradual stages.
Setting Between Beater Blade and Grid
Too close setting will tend to curl the cotton and pass too much good lint through grid bars. If this setting is wider, the action on the cotton will be less which affects the opening action. The beater can be raised or lowered to alter the setting between the striker tips and the grid bars surrounding the beater.
4.6. Angle of Grid Bar
It should be such that the maximum trash extraction is obtained with minimum lint loss. If the angle is too wide - There will be loss of good fibre. If it is too narrow cleaning efficiency is affected. Hence adjustable grid bars have been introduced in latest models, By means of proper adjustment, the optimum angle can be obtained by trial to suit the particular grade of cotton being processed.
4.7. Types of Fibre
Synthetic fibre need only gently opening does not require beating action because fibre does not contain any trash particles. Natural fibres need both the opening and beating action trash particles is will be more. The stable lengths also determine opening and cleaning actions. Long stable cotton with low trash would require lesser beating and more opening than short stable, trashy cotton. Synthetic fibres require no beating and only gentle opening.
4.8. Action of Air Current
If too strong - Cotton will raise and pass through too and affect the opening and trash extraction. If too weak - Cotton will move slowly and will be over treated. This may give good opening but there is a danger of fibre damage and production of curly cotton.
5. Blending
It is the manufacturing of products containing different fibres of known characteristics in proportions. Fibres of known physical properties have to be blended under controlled conditions so that the resultant blend could be reproduced.
The blending operation is based on exact measuring of all fibre properties and correct proportionate.
The purpose of blending is that raw materials used in the spinning mill are always inhomogeneous in their characteristics. To some extent this is due to the different cultivation of natural fibres and the different production conditions for synthetic fibres this influences the end product.
Blending is done to
· Achieve consistent quality product throughout the year
· Reduce the raw material cost as well as the production cost
· Improve the processing performance
· Meet the functional properties of the end product
5.1. Problems in Blending During Spinning Process
The main aim of spinning is to distribute the different fibres evenly in the yarn. For this purpose, a good blend must be produced at some stage of the process and the blend should be maintained up to the stage of binding into the yarn. Achieving the above two points is very difficult. Fibres of different length, different surface, crimp, etc., also behave differently during movements as individuals.
5.2. Types of Blending
· Bale mixing – done before the blow room process
· Stack bending – done before the blow room process
· Lap blending – done in scutchers
· Web blending or fleece bending – done at the ribbon lap and the blending draw frame
· Sliver blending – done at the draw frame
· Rowing blending – done at the ring spinning machine
In addition, controlled and uncontrolled blending must also be distinguished. In uncontrolled blending, the components are brought together at random and without a mixing system (e.g. often in bale mixing). In controlled blending the individual components are supplied to the machines in an ordered fashion and precisely metered (e.g. in weighing hopper feeders).
Bale plucker
Close up of the grid and blades with plucker spikes
5.3. Fibre Properties to be considered for Blending
Variation in fineness between cotton in mixing should not exceed 0.3 (up to 40s, & 0.2 for above 40s. Variation in fibre strength (g/tex-3mm gauge) between cotton in mixing should not exceed 2 (up to 40s s* 3 for above 40s. Fibre fineness and strength affect the yarn strength directly.
Twist variation and CSP variation in yarn can be controlled by mixing cotton on the basis of closer fibre length and micronaire reading. Where ultimate strength is required. Cotton of high fibre strength is used to get strong yarn and fabric.
5.3.3. Fibre Maturity
Maturity percentage of different cottons should be considered before mixing, because it will enable the smooth processing.
6. Conclusion
The number of machine and their type required for a blow room line are governed by the condition and the class of cotton. To open and clean the fibre the materials will harshly treated with the more number of machines. Thus to reduce the fibre damage the fibre should process in subsequent process to opening and cleaning of fibres, if it is not in proper design and setting fibre will affect.
7. Reference
1. Technology of yarn forming, vol-1, by S.Jayaprakasam, T.Murugan, S.Kannan, S.S.M.Institute of Technology and Polytechnic. Pg.1-65
2. The Indian Textile Journal, May 2007, “Evaluation of cleaning efficiency in blow room carding”. Pg. no. 48-54
3. The Indian Textile Journal, December 2008, “Selection of beater design in fibre preparation” Pg. no.108-112
4. NCUTE Extension Program on Blow Room and Carding, Prof. C.D.Kane and Prof. P.V.Kadole
5. Elements of Raw Cotton and Blow Room, by Dr. A.R.Khare, published by Saibook Center
6. Spinning, “Cotton and Wool Spinning” by Ezio Carissoni, Stefanno Dotti, Franco Fleiss, Luigi Petaccia, Lucia Pieri
7. Modern Blow Room, by Dr. A.R.Khare
Trutzschler's MULTI MIXER: Working Principle
Achievements
· Perfect and Homogeneous blend is achieved
· Simultaneous mixing by doublings' over an extended period of time is achieved.
The cotton bales are opened and premixed by bale opener. This blend is blown by the material transport fan and conveyed into the feed duct above the hopper. The charging of the Multimixer starts with the first hopper at the end of the feed duct. It is filled only to just below the photo cell situated in the adjacent hopper, then the closing flap of the second hopper * is opened by push button operation. Second hopper is charged” to a rather higher than the first. The charging level of the hopper rises uniformly up to the last hopper which is fully charged, when the last hopper is full the Closing flap shuts automatically and charging restarts with first hopper, as soon as the level second hopper has dropped below the Photo Electric cell. Whilst the last hopper is being charged, material transport is switched on and material in the hoppers starts to drop.
When the charging level rises, more and more of the holes in the perforated plate of the upper part of .hopper are blocked with material. This increases the pressure the conveyor air. Once a pre-selected pressure is reached, which corresponds to a particular charging level, an electronic switch closes the flap of this hopper and opens up the flap of the next hopper."
The base of each hopper is closed by a pair of deliver roller which transfers the material gradually and uniformly to an opening roller. The delivery rollers of the entire hopper are two variable speed motor with control range up to 1 : 6 in this way it is possible to adjust the output of Multimixer to the feed requirement of the subsequent machine. Opening rollers gently loosen the material into tufts and deliver them into the blending channel from which they are sucked by the subsequent condenser.
How to Select the Cotton for Mixing
A) Cotton is selected by considering the following points.
i. Fibre length, fineness, strength influences yarn strength & spinning value.
ii. Short fibre content, fineness influences on Regularity of yarn.
iii. Maturity and fineness of cotton determine neps generation at different stages,
iv. Trash % in the cotton -indicate- no of beating point’s treatment necessary in blow room.
v. Fibre quality Index '(FQI) = lu.s.m / f
Where
lu = product of 2.5 % span length in mm and uniformity
Ratio %( u) measured on digital Fibrograph divided by ICC
s = Bundle fibre strength in g/tex at 3mm gauge length. Measured on stelometer.
m = maturity co-efficient determined by sodium hydroxide swelling technique,
f = fibre fineness or micronaire value (micro games/inch) FQI is a measure to assess the quality characteristic of the cotton required for spinning different counts with desired CSP values.
B) CSP (Count Strength Product) = (310-count) √ FQI
C) Maturity Co-efficient= (M + 0.6H + 0.4I)/100
Where, M, H and I are % of mature, half mature and immature fibre respectively (Determined by standard sodium hydroxide swelling technique)
D) Fibre propensity for imperfection = trash % x short fibre % divided by Micronaire value
It is a useful tool in the selection of cotton for minimizing the imperfections in the yarn and it should be maintained below: 16.
Blow room - beater suitable for low, medium and fine cotton.
Suggest a modern blow room fine suitable for spinning 80s yarn or for processing low medium cotton or for fine cotton or for processing sea-island cotton Brief function of each machine in a modern blow room line:
In order to retain adequate mixing three blenders are arranged to feed one single process line. Mono cylinder-open and clean the cotton. Auto mixer mix the material thoroughly. Double ERM cleaner, open and clean the cotton. Two way distributor, distribute the cotton from cleaning line into two automatic scutcher equally.
This modern blow room line is suitable for spinning all range of counts. In the case low grade cotton mixing, (below 40s) all the beaters can be utilized. In case of medium grade cotton mixing (40s - 60s) one ERM cleaner can be bypassed. In the case of fine mixing (above 60s, sea-island cotton) one ERM cleaner and mono cylinder can be bypassed. In the case of staple fibre mixing, the material from the blender is directly fed to scutcher bypassing all the machines in a cleaning line.
Control system in Blow room
Following control systems are used in the blow room line to control the feeding and feed the cotton at uniform rate to the scutcher.
A. Photo electric cell is placed in the following places :
· Reserve feed tower of hopper feeder, step cleaner etc.,
· Reserve trunk of automatic scutcher
· Laminar trunk of ERM cleaner
· Filling trunk of chute feeding system.
B. Piano feed regulating motion, in the scutcher.
C. Front sheet position and swing door of hopper feeder.
D. Pressure switch in feeding trunk of automatic scutcher.
E. Solenoids, micro switch, limit switch and relays.