F06: Fibre Length- Almeter

AWTA TEST CODE

:

F06

OTHER NAMES

:

HAUTEUR, BARBE

TEST METHODS

:

IWTO-17

IMAGE

:

AL100 Almeter

APPLICATION

:

This method is primarily applicable to the determination of fibre length distribution parameters of slivers and rovings manufactured from combed wool or combed synthetic fibres. It may also be applied to non-combed slivers, such as, slivers before combing, semi-worsted slivers, woollen slubbings and slivers prepared from scoured wool after carding.

PRINCIPLE

:

An end-aligned numerical fibre sample, prepared by an automatic preparation machine, is fed at constant speed between the plates of a measuring condenser. The capacitance of the condenser, as the sample passes between its places, is proportional to the mass of fibre between those plates at any given time and thus is related to the amount of fibre in any given length group in the sample.

The signal emanating from the measuring condenser is used to plot a cumulative length diagram.

As well, the signal passes to a computer and is used to provide the following parameters:

a) HAUTEUR (H) or cross-section biassed mean length.

b) Coefficient of Variation of HAUTEUR (CVH).

c) BARBE (B) or weight biassed mean length.

d) Coefficient of Variation of BARBE (CVB).

e) Percentage (by cross-section or by weight) of fibres longer or shorter than a given length.

f) Length exceeded by a specified percentage of fibres (biassed by cross-section or by weight).

SAMPLES REQUIRED FOR TESTING

:

A homogeneous portion of a lot being defined as a ball of sliver, a can of drawing sliver or a bobbin of roving and a laboratory sample being defined as a sample of sliver, about 1.2m long, twisted by 30 turns per metre, IT IS RECOMMENDED that the total sample to be submitted for testing consist of at least three (3) laboratory samples taken from three (3) homogeneous portions of sliver or roving selected at random from the lot.

NOTE: THE TWISTING OF THE SLIVER - described in detail in the test method IWTO-17-85(E) - is ABSOLUTELY ESSENTIAL IN ORDER TO OBTAIN ACCURATE RESULTS. The operation of twisting may be omitted only when the ball of sliver or roving is available in the laboratory and testing is to be carried out within four hours of sampling.

INTERPRETATION

:

A knowledge of fibre length and its variation are essential to determination of fibre processing and product end-use, eg short, very variable wools cannot be used for worsted processing.

SERVICE TARGET

:

6 days.

COST

:

See current Fees List.