Jute fibre is extensively used for the manufacture of sacking, bagging and tarpaulins. It is also used for making of rope, twine, carpet backing cloth, linoleum and artificial leathers. Carpet backing cloths were mainly consumed in the foreign markets. Jute cuttings are also used as one of the raw materials for paper making. It is also used for the manufacture of some other fabric in union with other fibres.
The manufacture of jute products consists of spinning and weaving but the raw fibre has to pass through various operations preparatory to spinning and weaving which commence with opening of the fibre of the bales, subsequent processes being batching, backing, carding etc. to render the fibre throughly split up and combed for spinning. After weaving the operation which is carried out is known as finishing.
PROCESSES
BALE OFENING
The first operation so to say is opening of bales. In our country, opening of bale is not generally performed by machine as kutcha bales are used in the mills mostly. But when pucca bales are opened, it is invariably done by machinery. The jute in such type of bales has been so tightly compressed that machinery is generally necessary to break it. apart. The latest machine cuts the ropes binding the bales and bursts it open by the vertical pressure of three fluted rollers. While the bale is free to expand laterally. The result is that the jute is delivered from the machine in a condition in which it is loose enough to be handled. Another method is to cut the ropes with knives or axes and pass the sections of the bale into a bale opening machine which consists of a heavily weighted upper working over two smaller ones studded with teeth which, combined with the revolving action, tear the compressed fibres apart. Then jute is selected or graded according to the quality.
BATCHING & SOFTENING
Since the jute contains only a very small percentage of natural oil (approximately 0.5%) oil and water has to be added to the fibre in order to make processing possible. An emulsion of mineral oil and water known as batching mixture is prepared, the usual proportions of oil and water respectively the usual proportions of oil and water respectively being 15% and 85%. The operation of batching jute is carried out with the object of softening and lubricating the fibre, so that it may pass more easily through the subsequent processes of carding, drawing and spinning without lapping upon the rollers. Batching consists of introducing into jute hot batching mixture. This is usually done whilst the fibre is passing through the softener, though it is sometimes done before the softening process.
In the softening process, jute having been split up and doubled into what are known as “stricks”, is fed on to an endless feed-sheet and passes through a series of fluted rollers pressed together by springs and is thus softened. The batching process may also be carried out by a jute spreader. The only difference between the softener and the modern spreader is that with the former, the batched jute spreader is that with the former, the batched jute has to lie on batching stalls or barrows for 36 to 43 hours, while with the spreader, the jute comes off in a packed roll which is more easily handled, although there is the same waiting period before the jute can be carded. Jute cuttings, threads, ropes and the like are fed into the testing machine in order to reduce it to the light or open state of two suitable for the normal carding machine.
CARDING
After the conditioning period jute is passed first to a breaker card and then to a finisher card, the purpose being to produce a loose material combed to align the fibre and to clean them by removing pieces of bark or grit. The strikes of jute are laid uniformly on a feed sheet and pass by means of a feeding roller into the breaker card which consists of a large cylinder covered with stout metal pies and revolving inside a metal case. At various points around the cylinder, small rollers also covered with pins revolve in the opposite direction. The jute is red into the breaker card in rolls of silver, the number of rolls varying from eight to ten across the breadth of the cylinder. It passes round the cylinder and is throughly combed before emerging from the machine again in the form of silver, which once more is formed into a role and fed into the finisher card, where the process is repeated and a finer silver produced for the next stage. Finisher carding is merely an extension of the same process, the silvers from the breaker card fed into a machine similar to breaker card but having more rollers, set with pins thus again splitting up more finely the filanents.
It is customary to collect the material coming out from the finisher card in special container known as silver can. The silver is about 5 inches wide and ¼ inch thick and the processes from this stage are designed to reduce this to such a gauge, fineness and condition that spinning is possible.
DRAWING
In the first drawing state, the silver is fed into a drawing frame, where a feeding roller passes it over small pins which further assist in aligning the fibres, and then through a pulling roller which is revolving at a greater speed than the feed. The object of the process is to obtain an equal yarn, the fibre in a number of silvers being drawn out and combined into a single silver which is delivered again into silver cans.
The second drawing process is simply a repeatation of the first, the only difference being that with the former, the pins on the gill bars are finer and closer.
ROVING
After the drawing process, the silver then goes through the roving machine, where it gets its first twist, at the end of which it ceases to be silver and becomes rove. The process is an extension of the drawing process which is affected by the rotation. The jute passes down the flyer over one of its prongs to the bobbin. The flyer revolves at a very high speed and the jute is drawn through the frame and simultaneously given the necessary twist before being wound evenly on to the bobbin. The speed of these bobbin spindles and flyers vary from 2700 to 3000 revolutions per minute. The standard of measurement in the jute industry is a “spindle” which is 13162 metres and consequently the length of yarn on a bobbin will depend on the weight of yarn per spindle being spun.
WASTE RECVOERY (DUST SHAKER)
Considerable amount of wastes are produced in preparatory processes prior to spinning. In view of the relatively high price of the raw materials existing at present, these waste are processed to produce a yarn of inferior quality. As the waste is dirty and contains many impurities, it is passed through a dust shaker before going to a heavy card with a more robust form of pin. The waste is shaken free of dust and other impurities and delivered in the form of clean tow. Thereafter, it is mixed with the already processed waste and carded, and follows the normal course to the spinning frame.
Winding
Winding is done to have maximum yarn length on one single package so as to economic handling and also to clean the yarn of some of the defects. Cop winding is usually done direct from the bobbin. A cop is yarn shaped and wound in the form of a slender cylinder so that it fits into the loom shuttle. It measures about 10 inch x 1 ½ inch diameter. Yarn which are to be used as warp is rewound from the bobbins on cylindrical or conical tag ended spools which contain 8 1b. or more of yarn.
Beaming and Dressing
Yarn to be used for making the warp of jute cloth is normally dressed with some form of starch to give it added strength in the loom and to improve the ultimate appearance of the cloth. For this purpose it is pulled off a bank of spools through a series of guides and wound in parallel layers on a “beam”, which is simply a large bobbin revolving horizontally. When the beam is loaded with the required length of yarn it is removed to the dressing machine where the yarn is passed through a steam heated trough containing a starch preparation and then passed over steam heated rollers, pressed and dried. It is then rewound on another beam for transfer to the loom. The number of spools used to form a warp beam depends on the width of the cloth to be woven and the type of loom on which the weaving is to be done.
Weaving
The lengthwise warp beams are put on looms and by feeding yarn (weft) width-wise by a shuttle, the fabric is woven. There are three types of looms used for jute weaving: flat, circular and jacquard.
The principle for flat looms is similar to that for weaving other forms of yarn, the warp of the cloth being pulled off the beam and the weft laid in from the cop in the shuttle.
Circular looms are used to produce a continuous cylinder of jute cloth destined for making sacks without a side seam. This type of looms are not used in our country.
Jacquard looms are used to produce jute carpets and little different from jacquard looms used for any other type of pattern weaving.
The cloth from the loom requires finishing which includes cropping, damping, mangling, calendering, (by steam heat), lapping, measuring, crisping sack cutting and sewing, printing, packing.
Cropping and Singeing
It consists in shaving the cloth of its loose fibres projecting outside from the surface of the cloth by means of knives rotating at very high speed. The machine used for this purpose has two or four barrels fitted with their steel knives set spirally and turning at approximately 1200 revolutions per minute against fiexed knive as ledger blades.
Singeing is an alternative process to cropping in which these fibres are removed by a gas flame. But this method is rarely used.
Measuring machines are sometimes used for measuring the length of the various pieces or “webs”.
It may be necessary to imprint trade or other marks such as I.S.I. Marketing on the cloth.
Packing of the bales of cloth require the use of hydraulically operated press. Packed burles are bound with hoop vion known as baleing hoops.
Twine Making
Two or three strands of yarn are put though a machine similar to a spinning machine and are twisted into twine.
FIRE HAZARDS OF THE PROCESSES
Jute is the main raw material processed in the jute mills which in any form, being of an inflammable fibrous nature, is a swift fire carrier and fire therefore be an even present hazard.
Waste is the most important factor which is responsible for many large fire losses in Jute Mills. The lighter waste which is known as “Fluff” is the most dangerous in this regard. Most of the waste collects under or around the machinery, but many of the short fibres thrown off by the machinery, are so light that they float in the atmosphere. These short fibres eventually settle on any surface, with the result, they not only cover the floor and machines but also settle on structural members of the buildings, overhand trunking, piping, electrical fittings, and even rough wall surfaces. In jute mills, fluff exists almost in all the sections. Even a small spark due to friction or an electrical fault is sufficient for the fire to spread across the fluff covered surface. As the fluff burns it drops and ignites the stocks on the floor. Jute lint and dust settles to the greatest extent in the preparatory departments such as jute selection, batching, softening, winding, weaving, beaming and finishing departments.
Waste is produced in the mills continuously and such wastes are normally reprocessed by treating it mainly in dust shaker machines. As dust shaker machine is handling only the wastes which is more hazardous than the yarn itself, so the hazard associated with this process is more. The so called waste is created by various means; by the dropping of loose end of the fibre while the machines are being fed; by the machinery itself, either by intent or by inability of the machine to process all of the fibres fed into it as in drawing and spinning; and by friction between the fibres themselves or between the fibres and some part of the machinery as in looms. Removal and collection of these wastes efficiently is related to the standard of house keeping in a risk.
The importance of good house-keeping for elimination of hazards need no emphasis. To ensure good house-keeping both inside the department of the mills and in the compound, not only a good layout of the plant is necessary, but it also becomes a management responsibility. In juts mills, cleanliness inside the department is of prime importance as jute fluff accumulates and settles on machines, shafts and switches, starters, wirings etc. It is, therefore, necessary that a schedule is worked out and record maintained to know when the departments are cleaned. Every department of jute must be cleaned frequently.
Waste which collects on the floor can be constantly swept up, but where it settles overhead or collects on or under machine it presents difficulties. Where sweeping is not practicable, the most satisfactory method of removing overhead waste is to blow it down by jets of compressed air. Since the fibres are clinging virtually in felt form to one another, the felt falls readily to the floor. But compressed air is not generally used in the mills in our country. Compressed air may also be necessary to remove the accumulation on or under the machines where normal cleaning is difficult, and particularly where production is carried on around the clock as is the case with most of the mills. The problem of keeping floors and areas under machines cleared may, however, to a large extent be, overcome by an underground vacuum waste extraction plant by which the waste may be drawn through grills on the floor to a central waste-collecting house. The process gives rise to another problem in that a fire on the factory floor could be drawn into the waste house, by passing any fire break that there might be, but the advantage of such an extraction system for outweigh this one main disadvantage. This type of waste collection system is also not used in our country.
The amount of raw jute as also stock-in process should be kept down to the minimum.
There is practically no chance of self ignition of the batching mixture as it is having a flash point of over 340*F. Also no evidence has been found of spontaneous combustion resulting from its use.
Incidence of fire arising out of the use of jute cards have been reported. The basic reason being that the jute at the beginning of the carding process was still dirty and a small stone going through the machine could strike a fire. Fire hazards in the carding department are also caused due to friction between metallic belts and the pulley. Also electric spark due to
(1) Report all damaged cables and electrical equipment and ensure their early repair.
(2) Ensure the maintenance of double earthing of all motors and switches. Earth wire or plate must be of proper diamension.
(3) Schedule yearly insulation resistance and earth continuity tests.
(4) Insist on periodic checking of all motors for signs of overheating.
(5) See that the terminal boxes of motors and switches and flexible condicts are in sound condition.
(6) Ensure that covers of distribution and motor control switches and starters are in their proper position.
(7) Check distribution panel boards and switches for unnecessary cable entry openings and arrange for them to be plugged off.
(8) Ensure that all electrical equipments are of metal clad construction, dust tight and of adequate capacity.
(9) Arrange for periodical cleaning of switch board, panels, switches, controllers and starters.
(10) Clean the under floor cable trenches at least once in a month or more frequently if
necessary.
(11) Ensure that lighting wirings are of iron conduits or cables.
CONSTRUCTION AND LAYOUT
Generally, the entire manufacturing processes from batching to finishing are carried out under a single shed. Most of mill buildings are constructed of brick walls and jackarched masonary roof. Recently, a few mills have been built up with R.C.C. roofs. Otherwise, all the mills are very old. As all the process sections are located in a single shed the maximum probable loss arising out of a single fire is very high because of accumulation of values. Finished goods godowns are normally located in the same shed but separated from the manufacturing section by means of perfect party walls. It would always be better if there are some sort of separations between the manufacturing departments. Especially the processes prior to spinning being more hazardous should be segregated from the other sections so that any fire occurring in more hazardous sections will not spread to spinning, weaving and other sections. It is also difficult to seggregate the various process sections by means of perfect party walls, since it may interrupt easy flow of materials.
Raw jute godowns are generally built up in rows, but each godown is separated from the other by means of perfect party walls.
At present rope alleys in most of the jute mills are no longer in use because of conversion of shaft drive to individual motors. These rope alleys have been converted into electric substation, repairing shop etc. in a number of mills. Boiler houses are usually located in a detached building or adjoining the mill without any direct communication. Most of the mills have installed diesel generators in order to cope up the acute power failure. These generators are used mostly in detached buildings.
FIRE EXTINGUISHING APPLIANCES
Long experience has proved that water properly applied is still the best medium for extinguishing jute fires. Because of the rapidity with which such fires can spread, prompt and efficient first aid action is very important. Employees are usually on the spot to take the necessary action in the event of fire in the process departments.
Jute mills are invaribly equipped with the hand appliance i.e. extinguishers and buckets. Hand appliances in-fact, play very important roles in preventing the fire from spreading at the inception. Average worker in a jute mill knows the operation of extinguishers and there is a tendency to use sufficient numbers of extinguishers in case of a very small fire.
All the jute mills in our country barring a few are protected by external hydrant system with separate pumps. Discounts from fire insurance premiums are sanctioned if the installation comply with the standards laid down in Fire Protection Manual published by the Tariff Advisory Committee. It is to be mentioned here that the discounts on account of fire protection installation are withdrawn in case of poor maintenance of installations, since, such installation will not be of any use in event of outbreak of a fire.
Apart from hand appliances and hydrant installations, a large majority of the mills are having automatic sprinkler installation for the protection of the manufacturing departments as well as jute godowns. The automatic sprinkler as its name implies is a device for automatically distributing water upon a fire in sufficient quantities in order to extinguish it or hold it in check if the fire is located where it is not possible for the water jets to reach. Structural damage by fire is likely to be relatively slight when sprinklers are in operations.