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General Specification For Twist Test

The most obvious way to measure the number of twists per unit length of yarn is simply to untwist a known length of the yarn and check visually to see whether the twist has been completely removed. The test instrument that used for to measure the number of twists per unit length of yarn called electronic yarn twist tester.


Twist testing methods depends on the specification, accuracy, demanded, from of the sample etc. In general the following points may be followed for getting reliable result.

Usually twist is not distributed uniformly along a yarn. Speaking technically, the amount of twist in a materials is inversely proportional to its thickness. This from is ‘twist x weight=constant’’. And for to avoiding having bias in twist measurement, twist should be determined at fixed intervals along the yarn that is 1 yard of distance which is suitable.

 Withdrawal of yarn over the end of the package adds twist to a yarn, whereas withdrawal from the side of the package does not. The yarn should be withdrawn from the package in the manner in which it would be normally used in the next stage of processing. The package should be mounted vertically on a peg and free to rotate about the peg as the yarn is withdrawn gently from it.

 The actual test specimen should be handled manually such that the fingers do not touch the length over which the twist is actually measured.

 In the case of plied and cabled spun yarn and continuous filament yarn, at least 20 specimens are to be tested if the length is 500 mm according to BIS (British Standards Institution). In the case of single spun yarn, BSI recommends 50 specimens of 25 mm each.

 The tension is the test specimen must be constant. BSI recommends a yarn tension level of tex/2±10% grams. For example: A 40s Nec count (i.e. about 15 tex) yarn would be maintained at a tension in the range 6.35-8.25 grams.
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