Blow room lecture # 3, Blow Room Overview of Preceding Processes, Bale laydown, Fiber feeding, Fiber transportation, Cleaning intensity. Cleaning intensity, pkspiny.

 

         OVERVIEW OF PRECEDING PROCESSES

     Bale laydown

 The effective operation of the UNIclean depends upon the condition of the cotton delivered to it. Bales that have not been allowed to bloom will tend to be fed as lumps rather than tufts and it will be more difficult to remove the trash.

•  Problematic bales should be carefully distributed throughout the laydown
•  Multiple assortments reduce the go/stop ratio of the UNIfloc. This means that the instantaneous material flow rate is much greater than the average rate. The cleaning is performed at the instantaneous rate.

    Fiber feeding

•  The UNIfloc should feed fiber as consistently as possible. Small tufts, uniform density, with a stop/go ratio of 85 to 90%.
•  Small tufts can be cleaned more effectively than large tufts. However, if the opening by the UNIfloc is too fine, the over opened material can create problems in air transportation.
• The UNIfloc “run-in run-out” program should be set to maintain a consistent fiber flow rate throughout the laydown.

    Air requirements

 Fiber transportation, waste and dust control 

	Airflow volume	Pressure	Condition
Material entry	0.6 - 0.8 m3/s	+50 …+150 Pa (+5 ….+15 mm WC)	Continuous
Dust extraction	0.4 - 0.5 m3/s	-400…-700 Pa (-40….-70 mm WC)	Continuous Open Transfer
Waste removal	0.5 m3/s	-700 Pa (- 70 mm WC)	Intermittent
Material exit	0.6 - 1.0 m3/s	-50 …-200 Pa (-5 ….-20 mm WC)	Constant. Including Supplementary Air

    Vario Set cleaning field

 The following illustration graphically shows the amounts of trash and good fiber removed as waste with a range of cleaning settings.

   Definition to be used

 “Degree of Cleaning” - refers to the percentage of trash removed by a cleaning machine. 

Degree of cleaning = Trash in input material – Trash in output material

                               Trash in input material

 

“ Cleaning Efficiency” – Refers to the percentage of trash contained in the waste removed by a cleaning machine. Low fiber content in the waste gives a high cleaning efficiency

 

Cleaning efficiency = Total waste percentage – Fiber content percentage

            Total waste percentage

  

   Results from plant

 Customer in Spain

 A series of cleaning function tests were performed to demonstrate the full range of trash removal and the associated fiber loss. The material used was relatively clean cotton with 1.7 % trash, 1 3/32” staple from a variety of origins.

    Effect of cleaning settings

 To find the optimal machine setting on the UNIclean, the entire range of the VarioSet field was evaluated.

 

 The final adjustment of the VarioSet was;

•  Cleaning intensity          = 0.6
•  Cleaning intensity = 4

 

This setup resulted in a very good cleaning efficiency, together with a superior fiber yield. The Customer realized a

1.52 % increase of the fiber utilization, compared to the conventional blowroom environment.

 

   Undesirable practices

 

§        Bad cleaning settings.

§        VarioSet use not understood by customer.

§        Stop/Go ratio of the UNIfloc too low.

 

   Bale Laydown and Fiber Feeding

 

   General Information

 Fiber feeding from the bales is extremely important. Quality control and process control starts with careful fiber selection for consistent fiber properties and the correct location of bales in the bale laydown.

The removal of the fibers from the bales is the first step in the opening, cleaning, and mixing/blending of the materials. Additionally, the feeding rate must meet spinning plant needs at every processing step. The fiber feeding should not limit the plant’s production capacity.

 

   Bale laydown for cotton

 Spinning plants use cottons of various types and qualities from different regions throughout the world. It is very important to arrange the bales to minimize “Quality Waves” created by fiber variations found between bales. High Volume Instrument (HVI) testing is now widely used and can enable the spinner to better control

consistency of the material in process.

 

Preferred guidelines:

•  Lay down the maximum number of bales.
•  Laydown bales for 24-hour production if space is available.
•  Laydown bales on the first shift.
•  Laydown bales when supervisor is available.
• Arrange bales in small groups (mini – laydown). The average fiber properties of each mini-laydown should be the same as the overall blend average.
•   Problematic bales should be spaced apart and not placed at either end of the laydown.
•  Bales should be opened and allowed to “Bloom” and condition for 24 hours if possible.
•  At the run-out of the bales at one side, new bales should be moved into place and the remaining bale ties removed as soon as possible.
•  The “Rest” of the fiber left from the previous laydown should be picked up and either,
•  Be formed into a mixed bale and the placed in the middle of the next laydown, or                                                                                        
•    Be packed as pieces between the bales of the next laydown.                                    
•  Avoid placing the remaining layers of fiber on the top the bales of the next laydown.
•  When manually leveling the tops of the bales, push the excess material between the bales.
•  Warning! Grouping bales in the laydown by bale height, to avoid manual leveling, can lead to concentrations of fiber properties. This creates quality waves that cannot be eliminated in the subsequent operations and can cause “blow-ups” in spinning.
• Remove most of the bale ties in a preparation area before moving the bales to the laydown position. Carefully remove the last ties and be sure to avoid metallic parts contaminating the fiber. Parts of bale ties are a major cause of fire.

    Bale laydown for man made fibers

 The different fiber types, such as polyester, nylon, viscose /rayon, acrylic, polypropylene and several special technical fibers are produced for specific applications and end uses. The length, denier, crimp, cross-section, strength

/elongation and fiber finish are some of the properties normally controlled by the fiber producer.

•   Care should be taken to follow the producer’s bale laydown recommendations. For example, fibers form different batches and lots should not be mixed for critical end products.
•  Warning! Some plants use low cost “un-branded” fibers for some applications. However, this can lead to problems in high production spinning operations.
•  If the fiber finish does not have sufficient antistatic agent, the fibers will tend to tag and choke in the transportation pipes, chutes and in the blowroom and carding equipment. Additionally laps will increase in the drafting zones resulting in quality problems and a loss of machine efficiency.
•  If the fiber finish has insufficient lubrication, excessive wear can occur in all machines in the process. This can lead to major problems in rotor spinning where opening rolls, rotors and nozzles can be prematurely worn out.