Study of Bale Stacking Plan of a Spinning Mill

1         What is Bale Stacking?

Staple fibers are low density materials and need to be compressed in bales form to transport from one place to other. Fibers are compressed to bales of a specific length, width, height and density in ginning factory and then transported to spinning mills. Spinning mills buy cotton bales according to their annual requirement during the season and store them in warehouses and godowns. These bales are stacked on one another in godowns and dispatched during the whole year according to requirements. This is called Bale Stacking.

2         Bale Stacking Stability

At most sites, bales are held in a warehouse or similar storage area, waiting for process or dispatch.  The main safety objective in the storage area is to maintain safe and stable stacks, so bales do not fall.

Instability can happen in two ways:

¶        stacks may be unstable from the outset because of poor stacking techniques.

¶        stacks may have been stable originally but have become unstable; possible causes for this could be disturbance as adjacent bales are stacked or de-stacked, or disturbance if struck by a lift truck, slippage of bales.

Safe working procedures for stacking and de-stacking should be drawn up and agreed with all appropriate personnel.  These procedures should consider:

¶        the limitations of storage area such as the floor space and height available.

¶        the physical properties of the various types of bales.

¶        the type of lifting and handling equipment to be used.

3         General Pointers to Safe Storage

¶        Keep gangways/walkways clear within the storage area and between stacks, to allow safe movement of lifting and handling equipment.

¶        The storage space reserved for bales should have adequate space to allow safe movement of equipment and bales in the area, maintaining clear gangways.

¶        Floor surfaces should be firm and level.

¶        Floors should not be overloaded.

¶        Stacking in a pyramid fashion and using binder bales can help to keep stacks stable.

¶        Store damaged or doubtful-looking bales separately, not in the bulk of a stack.

¶        Inspect stacks at least weekly and keep a record of the inspections and any resulting action.

¶        Make sure timber pallets are in good condition if they are used.

¶        Make sure personal protective equipment worn during handling, packing and unpacking of bales is adequate.

¶        Introduce a safe system of work and procedures for bale handling, stacking and de-stacking.

¶        Provide training in bale handling and handling equipment.

To minimize climbing on stacks, attach identification tickets to bales where they can be read easily by a person standing at floor level.

4         Bale Stacking at JK Spinning Mills

In this assignment we studied, bale storage and stacking techniques at JK Spinning Mills, 29-km Sheikhupura road, Faisalabad.

J.K Spinning Mill consumes almost 100,000 cotton bales per year. There are total 43 godowns in J.K Spinning Mill; having storage for up to 94,600 bales. These 43 godowns are used by all the tree units of J.K Spinning Mill.  The bales are carried in the godowns through lifter.

All the bales are not of same specifications. JK Spinning Mills use following types of cotton bales;

Bale type	Length (m)	Height (m)	Width (m)	Weight (kg)	Density (kg/m3)
Pakistani	1.1176	0.4826	0.9652	159	305.41
Indian	0.7874	0.5320	0.9827	161	391.10
W. African	1.3716	0.5588	0.8382	225	350.24

4.1        Godowns Dimension and Capacity

Godown dimension (L x W x H) = 1200” x 480” x 216” = 30.5m x 12.20m x 5.49m

Total volume of godown = 2,042.83m³

4.2        Bale Stacking

Three types of bales are used in JK Spinning Mills with each having different dimensions. So, out of 43 godowns, 24 are used for Pakistani cotton bales, 11 for Indian cotton bales and 8 for West African cotton bales.

Stacking of Pakistani bales in 24 godowns is as;

Length wise 25 bales along the length of godown, width-wise 8 bales along the width of godown and 11 bales from floor to roof along the height of godown. Total bales in a godown are;

No. of bales in godown = 25 x 8 x 11 = 2,200

So volume covered by bales in a godown is as;

(25 x 1.1176) x (8 x 0.9652) x (11 x 0.4826) = 1,145.28m³

Estimated bales according to area with empty space allowance for lifter are;

Estimated no. of bales = 26 x 10 x 10 = 2600

Stacking of Indian bales in 11 godowns is as;

Length wise 32 bales along the length of godown, width-wise 7 bales along the width of godown and 10 bales from floor to roof along the height of godown. Total bales in a godown are;

No. of bales in godown = 32 x 7 x 10 = 2,240

So volume covered by bales in a godown is as;

(32 x 0.7874) x (7 x 0.9827) x (10 x 0.5320) = 922m³

Estimated bales according to area with empty space allowance for lifter are;

Estimated no. of bales = 34 x 8 x 10 = 2720

Stacking of West African Bales in 8 godowns is as;

Length wise 20 bales along the length of godown, width-wise 12 bales along the width of godown and 12 bales from floor to roof along the height of godown. Total bales in a godown are;

No. of bales in godown = 20 x 12 x 9 = 2,160

So volume covered by bales in a godown is as;

(20 x 1.3716) x (12 x 0.8382) x (9 x 0.5588) = 1,388m³

Estimated bales according to area with empty space allowance for lifter are;

Estimated no. of bales = 21 x 13 x 9 = 2,457

Total bales stored at a time = 52,800 + 24,640 + 17,280 = 94,720

Estimated total bales = 62,400 + 29,920 + 19,656 = 111,976

5         Conclusion

According to standards, bales stacking efficiency should be in range of 80 – 90%. JK Spinning Mills have 85% efficiency in this regard, so they are good in their bale stacking plans. Bale stacking plan should utilize as maximum as possible area of godowns.

Different Spinning Techniques, their Spinning Methods and Applications...

1         Spinning:

Spinning could be defined as:

ü  The drafting and, where appropriate, the insertion of twist in natural or staple man-made fibers to form a yarn.

ü  The extrusion of filaments by spiders or silkworms.

ü  The production of filaments from glass, metals, fiber-forming polymers or ceramics.

1.1        Spinning techniques:

Different spinning techniques still used are:

1.       Break Spinning: Sliver feed stock is highly drafted and assembled at end of rotating yarn.

2.       Rotor Spinning: Individual fibers converted to yarn through rotary motion.

3.       Friction Spinning: External surface of two rotating rollers is used twist individual fibers into a yarn.

4.       Air-jet Spinning: Utilizes air to apply the twisting couple to the yarn during its formation.

5.       Centrifugal Spinning: A method of yarn formation involving a rotating cylindrical container.

6.       Dispersion Spinning: Polymers are dispersed in a carrier solution and extruded from carrier.

7.       Draw-Spinning: Orientation is introduced prior to the first forwarding or collecting device.

8.       Dry Spinning: Dissolved polymer is extruded by evaporation of solvent.

9.       Flash Spinning: Polymer is extruded at a temperature well above the boiling point of the solvent.

10.   Flyer Spinning: Yarn passes through a revolving flyer leg guide on to the package.

11.   Melt Spinning: Conversion of a molten polymer into filaments by extrusion and cooling.

12.   Reaction Spinning: Polymerization is achieved during the extrusion of reactants.

13.   Ring Spinning: Twist is inserted in a yarn by using a revolving traveler.

14.   Wet Spinning: Dissolved polymer converted to filaments by extrusion into a coagulating liquid.

1.2        Ring spinning technique:

Fiber material is supplied to the ring-spinning machine in the form of roving. The fiber mass of the roving is reduced by a drafting unit. The twist inserted moves backwards and reaches the fibers leaving the drafting unit. The fibers lay around one another in concentric helical paths.

It is the process of further drawing out roving to the final yarn count needed, inserting twist to the fibers by means of a rotating spindle and winding the yarn on a bobbin. These three stages take place simultaneously and continuously.

A mechanically driven spindle, on which the yarn package firmly sits, is responsible for twist. A stationary ring is around the spindle, which holds the traveler. Yarn from the drafting unit is drawn under the traveler, and then led to the yarn package. In order to wind the twisted yarn on a bobbin tube carried by the spindle, the traveler is required to cooperate with the spindle. The traveler moves on the ring without any physical drive, but is carried along by the yarn it is threaded with. The rotation rate of traveler is lower than the spindle, and this difference in the speeds of traveler and the spindle enables the winding of the yarn on the tube. A controlled up and down movement of the ring determines the shape of the yarn package, called Cop or Bobbin.

1.2.1        Properties:

Yarn properties depend on raw material used, twist, fiber length, fiber density, individual fiber strength and many more basic terminologies but generally ring spun yarn has following properties:

ü  Strongest yarn

ü  Finest yarn

ü  Softest yarn

ü  "Z" and "S" twist

ü  Lowest productivity

ü  Most uneven

ü  Most expensive

ü  More hairy, generally

ü  More torque

ü  Widest range of yarn counts

1.3        Advantages and disadvantages of ring spun:

1.3.1        Advantages of Ring Spun:

ü  Production of high strength yarns.

ü  Spinning of fine count yarns.

ü  Proper for special yarns.

ü  It is universally applicable (any material can be spun).

ü  The know-how for operation of machine is well established accessible to everyone.

ü  It is flexible as regards quantities (blend and lot size).

ü  Since the speeds in drawing section are best controlled, yarn evenness is excellent. But if short fibers are too much, yarn unevenness occurs.

ü  Fine yarns can be produced as compared to open end system

1.3.2        Disadvantages of Ring Spun:

ü  Process stages are more numerous. Roving stage exists as an extra process compared to the other systems.

ü  Yarn breakages are more numerous as a result of ring traveler friction and yarn air friction.

ü  Interrupt ions, broken ends and piecing up problems exist because of the yarn breakages.

ü  The high speed of the traveler damages the fibers.

ü  The capacity of the cops is limited.

ü  Energy cost is very high.

ü  Low production rate.

ü  New spinning processes have difficulty in gaining widespread acceptance. Owing to their individual limitations, the new spinning processes are confined to restricted sectors of the market.

ü  The ring frame can only survive in longer term if further success is achieved in automation of the ring spinning process. Also, spinning costs must be markedly reduced since this machine is significant cost factor in spinning mill.

1.4        End uses:

End uses depend on the raw material used, count, fiber length and such other properties of yarn but generally ring spun yarns are used in T-Shirts, Socks, Sports Wear, Other woven and knitted products, Bed sheets, Underwear, Towels and Bathrobes.

2         Rotor spun yarn:

Rotor spun yarn method uses a rotor to collect individual fibers into a yarn. The fibers on entering a rapidly rotating rotor are distributed around its circumference and temporarily held there by centrifugal force. The yarn is withdrawn from the rotor wall and, because of the rotation, twist is generated. Its process flow chart and spinning technique is as:

2.1        Process flow chart:

Fiber/Bale →    Blow Room →     Lap/Chute

                                       ↓

Lap/Chute    →   Carding   →   Sliver (Carded)

                                       ↓

Carded Sliver → 1st Drawing frame   →   Drawing Sliver

                                       ↓

Drawing Sliver   →   2nd Drawing frame →   Drawing Sliver

                                       ↓

Drawing Sliver   →   Rotor Spinning   → Rotor Yarn

2.2        Rotor spun technique:

In open-end spinning, this flow of fibers is interrupted, the fiber strand being opened into individual fibers at a predetermined position, usually by means of an opening roller, followed by airborne fiber transport. This interruption or break in the fiber flow is physically achieved by increasing fiber speed locally to very high levels (up to 100 m/s), so that according to the equation of continuity, the number of fibers in the cross section drops to such low values that the fibers lose contact with each other.

This enables twist to be imparted merely by rotation of the yarn end, which in turn leads to a significantly higher potential rotation speed. A constant stream of separated, individual fibers is allowed to flow to a rotating yarn end. The brush-like, open yarn end grasps the fibers brought into contact with it and continuously binds them into a yarn with the aid of the continual rolling movement.

2.2.1        Yarn properties:

Generally rotor spun yarns have following properties:

ü  More even

ü  Higher strength uniformity

ü  Higher production rate

ü  Fewer processes

ü  Lower cost

ü  Fewer imperfections

ü  Harsher hand (feel)

ü  Not as strong

ü  Limited counts-coarser yarns

ü  “Z” twist only

2.3        Advantages and disadvantages of rotor spun yarn:

Following are the advantages and drawbacks of rotor spun yarn:

ü  The twist in the yarn being determined by the ratio of the rotational speed of the rotor and the linear speed of the yarn.

ü  The production rates  of  rotor spinning is  6- 8 times  higher than that  of  ring spinning and as the machines are fed directly by sliver and yarn is  wound onto  packages  ready for use in fabric formation.

ü  The yarn is a lot cheaper to produce.

ü  Rotor spun yarns are more even, somewhat weaker and have a harsher feel than ring spun yarns.

ü  Rotor spun yarns are mainly produced in the medium count (30 Ne, 20 Tex) to coarse count (10 Ne, 60 Tex) range.

ü  The use of this system has two basic advantages. It is fed by sliver, not as with the ring frame by roving, and so eliminates the speed frame from the process line. It can also be modified to remove any remaining trash to improve yarn quality.

ü  Open-end yarns tend to be more uniform, lower in strength, more extensible, bulkier, more abrasion resistant and more absorbent.

ü  Open-end spinning operates at a rate up to five times that of ring spinning and can be effectively used for cotton, polyester- cotton blends, as well as other short and medium staple systems.

2.4        End uses of rotor spun yarns:

Open end yarns produce different characteristics in the end product. These yarns may be used to advantage in fabrics where uniformity and a smoother surface are of prime importance. Open end yarns are used in pile fabrics, apparel, household, industrial and technical applications. Uses include heavy weight satin and poplins, corduroy, velveteen, rain wear, denims, drills, sheets, pillow cases, bed spreads, printed fabrics, curtains, window blinds, upholstery, cleaning cloths, dress goods, underwear, rugs, carpet, blankets, terry towel and diapers.

3         Vortex spun yarn:

Vortex spinning technology was introduced by Murata Machinery Ltd in Japan in 1997. This technology is best explained as a development of air jet spinning, making use of air jets for yarn twisting. The main feature of Murata vortex spinning (MVS) is its ability to produce yarn at 400 m/min, which is almost 20 times greater than ring spinning frame production. Other advantages include low maintenance costs, a fully automated piecing system and elimination of roving frame. The yarn and the fabric properties of MVS yarn are claimed by the manufacturer to be comparable to those of ring spun yarn.

3.1        Manufacturing principle:

The sliver is fed to a 4-over-4 (or a four-pair) drafting unit. As the fibers come out of the front rollers, they are sucked into the spiral-shaped opening of the air jet nozzle. The nozzle provides a swirling air current which twists the fibers. A guide needle within the nozzle controls the movement of the fibers towards a hollow spindle. After the fibers have passed through the nozzle, they twine over the hollow spindle. The leading ends of the fiber bundle are drawn into the hollow spindle by the fibers of the preceding portion of the fiber bundle being twisted into a spun yarn. The finished yarn is then wound onto a package.

3.2        Vortex spun yarn properties:

·         More ring-like structure

·         Lower hairiness

·         Dyes darker

·         Good handling properties

·         Highest productivity

·         More torque

·         More waste in spinning

·         Limited count range

3.3        Applications:

The application of vortex spun yarns depends strongly on their quality and particular characteristics. Their initial application in woven fabrics was focused on cotton-rich sheeting. MVS yarns broaden this focus to 100% cotton sheeting as well. Other woven end-uses are twill fabrics and fleece fabrics production.

Application to knitted fabrics is spread over interlock and pique knits as well as jersey outerwear. MVS yarns are good for fleece-wear and single knit jersey as they show less pilling and fuzz formation.

The specific structure of MVS yarns leads to a noticeable decrease of the pilling problem. The result is that MVS yarns produce fabrics suitable for suits, shirts, upholstery and curtains. The low shrinkage levels make the yarns very appropriate for linings and beltings.