Wednesday, March 11, 2020

YARN COUNT TESTING AND YARN TENSILE STRENGTH TESTING, CSP OF YARN


YARN COUNT, TENSILE STRENGTH ( BUNDLE STRENGTH AND  YARN C.S.P. TESTING


Yarn count testing:

The testing of the yarn count gets completed in below steps:

Preparation of Lea or skein of yarn:

The yarn package is placed on the cone holder in the wrap reel. Now the end of the yarn gets passed through a yarn guide. This end is tied with a screw fitted in the wrap reel.  See below picture:

A counter meter is fitted in this wrap reel. This counter meter helps to count the number of wraps of yarn in the skein. Today's wrap reel is equipped with stop motion. When the number of wraps of yarn reaches to the pre feed number of wraps, the stop motion actuates immediately and stops the wrap reel.  


The diameter of wrap reel gets equal to 1.5 yards. A lea or skein length of 120 yards is required  for count testing. Thus the number of wraps is fixed in the counter meter. That is 80. 

The wrap reel gets driven by a motor. When the set length reaches to feed number, it gets stopped immediately. Now the les gets off loaded manually. The initial end and final end are tied together firmly.

Weighing of Lea or skein of yarn
Now the lea of yarn is weighed in the electronic weighing scale. Make sure there is no error in weighing scale. If there is any error, please reset the weighing scale before weighing of Lea. Please se below picture:




Yarn count calculation:

                              = 2/ 14.76 s

Tensile strength of the yarn:

It is the most important parameter of yarn. The tensile strength of the yarn is the force required to break the yarn. The tensile strength of the yarn is a very important property of yarn. It directly affects the performance of yarn during weaving and another process. Since yarn goes under moderate tension during different processes of weaving and jerk gets applied to the yarn, so that the yarn should have enough strength to wear this tension and jerk. There are two methods used to test the strength of the yarn:
·       Bundle strength
·       Single end strength

Bundle strength:

This method is used in spun yarn only. Bundle strength does not give correct value of yarn strength but it helps to compare two yarns of the same count. If we have to select the best one yarn between two same counts of yarn, bundle strength is very useful.

A skein or lea of 120 yards (having 80 wraps of 1.5 yards) is prepared. It is broken with the help of vertical lea strength tester and breaking force (tensile strength) is recorded in the pound, Kg or Newton. Now count strength product of yarn is calculated as follows:

Loading of Lea on tensile strength tester:

The prepared lea of yarn is loaded on the tensile strength tester as shown in below figure:

You should always check load cell reading. The initial reading of load cell should be zero. If you notice an error in the initial reading, please reset the reading of load cell.


Breaking of Lea or skein

Now the green push button is pushed to start the machine. As the load gets increased gradually, the lea gets broken when the load reaches to breaking point. Now the reading of the load cell is recorded.



C.S.P. Calculation:

Tensile strength = 159.8 kgs
                              = 159.8 X 2.204 lbs
                              = 352.19 lbs

C.S.P. =Yarn count( Ne) X tensile strength (lbs)
           = 7.38 X 352.19

C.S.P. = 2599.16

The yarn having more CSP is better than the yarn of lower CSP for the same count of yarn.

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