BS ISO 1136:2015 pdf download – Wool — Determination of mean diameter of fibres — Air permeability method
7.1.3 Selection of specimens
The specimens shall be taken from different places in the laboratory sample. In the case of balls of sliver, the laboratory sample shall be made up of pieces of sliver from both inside and outside the ball.
7.1.4 Specimen mass
For the constant flow method, the specimen mass shall be 1,5 g ± 0,002 g. For the constant pressure method, the specimen mass shall be 2,5 g ± 0,004 g.
7.1.5 Preparation For slivers with cut ends, the specimen shall be prepared by cutting off with scissors a length to give as nearly as possible the specimen mass and then making up to the exact mass by adding shorter cut lengths or portions. For slivers with pulled ends, about five hand draws shall be removed and discarded and the specimens weighed out by taking several successive hand draws. These two methods of sampling give the same results if carried out properly.
7.2 Opened sliver
The laboratory sample should weigh not less than 10 g, and if it is known to have an oil content not exceeding 1,0 %, the test specimen may be taken from it without cleaning. Otherwise, the sample should first be degreased by rinsing it well in two baths each of about 200 ml of petroleum ether before conditioning.
Take from the sample 10 g to 20 g of sliver and deparallelize using a Shirley Analyser or another method to give the laboratory sample. Pre-condition (see 6.1) and condition the laboratory sample. For the Shirley Analyser, cut the sliver into lengths of 15 mm to 20 mm before deparallelizing. Other methods may refer to Shirley Analyser. Laboratories can, according to their own conditions, develop their own method.
7.2.3 Number of specimens
Unless otherwise specified, test a minimum of two specimens, and measurements per test specimen two times.
7.2.4 Selection of specimens
Passing the cut sliver through a Shirley Analyser or other methods thoroughly blends the fibres. Test specimens need not, therefore, be made up from pinches of fibre from different parts of the prepared laboratory sample.
7.2.5 Specimen mass
For the constant flow method, the specimen mass shall be 1,5 ± 0,002 g. For the constant pressure method, the specimen mass shall be 2,5 g ± 0,004 g.
8.1 Unopened sliver
8.1.1 Ensure that the meniscus of the manometer (5.2.4) is at the zero mark and, if required, carry out an orifice plate check as detailed in A.3.3. 8.1.2 Pull out the weighed test specimen into a long thin sliver and feed it evenly into the constant volume chamber (5.2.3), packing the fibres down with a smooth rod from time to time. Insert the plunger and screw down the cap to the furthermost extent so that the lip of the plunger is in contact with the base.
8.1.3 Depending on the method to be used, adjust the air valve (5.2.1) as follows:
a) for the constant flow method, adjust the air valve until the top of the float of the flowmeter (5.2.6) coincides with the reference mark R and note the fluid level of the manometer (5.2.4) to the nearest 1 mm or 0,1 μm (see A.3.1);
b) for the constant pressure method, adjust the air valve until the fluid level of the manometer coincides with the 180 mm reference mark P and note the position of the float of the flowmeter to the nearest 1 mm or 0,1 μm (see A.3.2).
8.1.4 Remove the specimen from the constant volume chamber (5.2.3), tease out the fibres by hand, repack in the constant volume chamber without loss of fibre, insert the plunger, and screw down the cap. 8.1.5 Repeat the operation specified in 8.1.4 so that a total of three readings on each test specimen is obtained.
8.2 Opened sliver
8.2.1 Ensure that the meniscus of the manometer (5.2.4) is at the zero mark and, if required, carry out an orifice plate check as detailed in A.3.3.
8.2.2 Pack the specimen evenly into the cylindrical base, a small amount at a time, using forceps, not fingers, to handle the specimen, so as not to contaminate or change the moisture regain of the specimen. Push the fibre into the cylindrical base preferably using the short end of the packing rod and taking particular care to ensure that the fibres are uniformly packed and that the walls and bottom of the chamber are not scratched or marked.
8.2.3 Insert and push down the perforated plunger into the cylindrical base. Secure the plunger cap without rotation of the perforated plunger, ensuring no fibres are trapped between the perforated plunger and the chamber and that the shoulder of the plunger rests firmly on the lip of the chamber.