To Determine The Air Permeability Of Fabric

-:Air Permeability:-

OBJECT :- To determine the air permeability of fabric 

AIR  PERMEABILITY :-

     Air permeability of fabric is the amount of air in cm³/sec passing through one cm² area under a pressure of 1 cm water head.

THEORY:-

        The measurement of the air permeability--the rate of air flow passing perpendicularly through a known area under a prescribed differential air pressure between the top and bottom surfaces of a material --of textile fabrics, expressed in SI units as cm³/s/cm² and in English units as ft³/min/ft².

A circular fabric is clamped into the tester and through the use of vacuum, the air pressure is made different on o) ne side of the fabric. Airflow will occur from the topside with higher air pressure, through the fabric, to the side with the lower air pressure. From this rate of air flow, the air permeability of the fabric is determined.

Air permeability is an important factor in the performance of textile materials like gas filter, air bags, clothing, mosquito netting, parachutes, sails, tents, and vacuum cleaners. It can also be used to provide an indication of the breathability of weather-resistant and rainproof fabrics.

Construction factors and finishing techniques can have an effect upon air permeability by causing a change in the length of airflow paths through a fabric. Fabrics with different surface textures on either side can have different air permeability depending upon the direction of air flow.

Specifications of  TESTEX  (Hong Kong ) AIR PERMEABILITY TESTER

Range  of  pressure =  50 – 3600  Pascal

Air  permeability Range = 1- 9999   mm/sec.

Error  =  ± 2 %

Max. Thickness  =  8mm  or  less  than  8 mm

No. Of nozzles                   =  11  (0- 10)

One Imperforated plate      = To find out the air leakage

Definite diameter plates    = 4nos

Definite   value plates        = 4nos

Calibration:

Calibration  values  with  Definite  dia. Plates as per table

Definite  dia. plates	Nozzle to be used	area to be set	Pressure	air permeability  value
7.8mm	3-4	20 cm2	127 pa	220± 2 % mm/sec.
21.6mm	6-7	20 cm2	127 pa	1645± 2 % mm/sec.

CALIBRATION  PROCEDURE :-

          1.     First of  all  press  ↑ key ,  menu will appear.

2.     Use parameters option to enter data for Calibration with Definite dia. Plate 7.8mm  as per table and save the data.

          3.     Place 7.8mm  Definite dia. Plates on the sample chamber.

          4.     Now we calibrate the instrument by pressing START and note down the air        

                permeability values.

          5.     place the next plate 21.6 mm dia. and now enter data for Calibration    with 

                Definite dia. Plate 21.6mm  as per table and save the data.

           6.     Calibrate the instrument by pressing START and note down the air              

                permeability values.

          7.     Calibration is complete.

Testing of Fabric :-

1. To test the sample, according to fabric thickness and  construction

  we select the nozzle and Definite value plate.

2. Now we place the fabric on the sample chamber. Then place the

  pressing ring to fix the fabric.

3. Now place the Definite value plate

4. Now we start the m/c & then  note down the readings on display .

5. Take 5 observations   .

Result :- 

Mean   air  permeability                  =

                Sample pressure            =

  Nozzle used                  =

                          Area set                          =