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Indirect System of Yarn Numbering and Calculation

Indirect System of Yarn Numbering and Calculation
S.M. Bappy Rana
Dept. of Textile Engineering
Bangladesh University of Business & Technology
Cell: +8801781630519



Indirect or Fixed System of Count:
In this system the count of yarn expresses the number of length units in one weight unit. Higher the count finer is the yarn. This system is generally used for cotton, worsted, woolen, linen (wet spun), etc

The indirect system covers the majority of the important types of yarns. The count is based on the number of length units in one weight unit. Thus if 20 length units weigh one weight unit, its\count is 20’s : if 80 length units weigh one weight unit, its count is 80’s and so on. It may be noted that finer or less bulky the yarn, higher is its count number or in other words, the size or bulkiness of the yarn is inversely proportional to the count number and that is why the system is known as indirect system.
count
The disadvantages of this system are that the count number does not express directly the size of the yarn. As explained above a coarse or bulky yarn will have a smaller count number than a finer or less bulky yarn. Secondly when calculating counts of folded yarns, it is more difficult to calculate the resultant count, especially when the component threads are different counts. The advantage of this system is the comparative ease with which the weight of fabrics can be calculated. The twist of yarn, setting of cloth, etc. , can be more easily calculated as they are directly proportional to the square root of the counts of the yarn.

The table shows the different length and weight units used in important indirect systems. 
 
Table
Name of System
Unit of Weight
Unit of Length
English Cotton
1 lb
Hank of 840 yards
French Cotton
1 kg
Hank of 1000 meters.
Bump Cotton
1 oz
1 yard.
Decimal (for all yarns)
1 lb
Hank of 1000 yards.
Metric
1 kg
Hank of 1000 meters.
Spun Silk
1 lb
Hank of 840 yards.
Spun rayon staple fibres
1 lb
Hank of 840 yards.
Worsted
1 lb
Hank of 560 yards.
Linen ( Wet spun)
1 lb
Lea of 300 yards.
Hemp (fine)
1 lb
Lea of 300 yards.
Woolen- Yorkshire Skein
6 lbs
Skein of 1536 yards.
Woolen- American Cut
1 lb
Cut of 300 yards
Woolen- American Run
1 oz
Run of 100 yards
Woolen- Dewsbury
1 oz
1 yard
Woolen- Hawick
26 ozs
Cut of 300 yards
Woolen- Galashiels
24 ozs
Cut of 300 yards
Woolen- Alloa
24 lbs
Spyndle of 11520 yards
Woolen-West of England
1 lb
Snap of 320 yards
Asbestos- British
1 lb
Hank of 50 yards
Asbestos - American
1 lb
Cut of 100 yards
Fiber Glass
1 lb
100 yards

Calculations:

In The indirect system, we have the following:-

Count = Number of length units per weight unit 
 
Or,

                        Length in appropriate length unit
Count= …………………………………………………      ……..(1)
                   Weight in corresponding Weight Unit

By cross multiplication, we have the following:-

                Length in appropriate length unit
Weight = ……………………………………………           …….(2)
                                 Count

Length = Count  X  Weight in appropriate length unit             …….(3)

It will be seen from the above that there are factors, vix., Count, length, weight, of which two must be given to find of the third one.

English Cotton System-

Count = No. of hanks of 840 yards weighing 1 lb.

                Length in Hanks
Count = …………………………                             ……………….. (1)
                 Weight in lbs

Again from the formula,

                 Length in Hanks
Count = ……………………………
                   Weight in lbs
 
We have,

                   Length in yards/840
Count = …………………………………                                  ……..(4)
                Weight in grammes/7000

        7000           Length in yards
= ……………  X   ………………………                              ………(5)
         840           Weight in grains

                              1000
= …………………………………………….                               …..(6)
      Weight in grains of 1 lea of 120 yards

          25               Length in yards
= …………………………………………                       ………..(7)
           3               Weight in grains

                       Length in yards
= 8.33 X   ………………………….                                           ……..(8)
                      Weight in grains

From (5) by cross multiplications, we have,

                                  25                Length in yards
Weight in grains = ………… ……………………                  ..…….(9)
                                   3                      Count

                                                Length in yards
                            =   8.33  X   …………………….                    ……….(10)
                                                    Count

                                     3
Or, Length in yds. = ………  X  Count  X  Weight in grains            ……..(11)
                                    25

The formula (6) is generally used in spinning mills, where a complete lea of 120 yards is reeled out from a bobbin, and tested for count, as well as for tensile strength.

Example: If 240 yards of cotton yarn weight 40 grains, what is the count of the yarn?
 
Solution:
Here,                    
                          240
240 yards = …….……   hanks
                          840

                    40
40 grain = ……….  Lbs
                  7000

                                     Length in hanks
Therefore, Count = …………………………
                                      Weight in lbs

           240 / 840
= ……………………
           40 / 7000

= 50’s Cotton

Also directly applying formula (2),

          Length in appropriate length unit
= …………………………………………
                    Count

                 7000 X 240
Count = ……………………
                  840 X 40

= 50’s Cotton

Again Applying formula (7),

      25             length in yards
= ……… X ……………………
       3             weight in grains

                  25               240
Count = ………  X  ………………
                   3                 40

= 50’s Cotton

Example: Find the weight 270 yards of 60’s cotton yarn.

Solution:
Here,
                        270
270 yds.= …………...   hanks
                        840

                                                            Length in Hanks
Applying Formula , Weight in lbs. = ………………………
                                                                  Count
 
We have,

                            Length in hanks
Weight in lbs. = ………………………
                                Count

       270/840
= …………… lbs.
           60

          270 X 7000
= …………………… grains
          840 X 80

= 37.5 grains

Also directly applying,

                                25                  length in yards
Weight in grains = ………… X ……………………
                                 3                        count

          25              270
= …………  X …………
          3                 60

= 37.5 grains (ANS)

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