The water column Branca Water proof 35 is used to perform analysis of resistance to water penetration of fabrics, non-woven fabrics, felts etc.., in accordance with the standard EN 20811.
There are two types of analysis to mention about the instrument:
The analysis of the minimum pressure which causes the passage of water through the specimen;
The analysis of the time of waterproofing given at a certain pressure;
The test determines the resistance of a fabric to water penetration; this kind of test is carried out with the instrument Water proof 35 and it consists of a cylinder of about 200 cm of height, at the base of which is connected to a ring flange on which is placed the sample of fabric.
The cylinder is fed with water at 20 °C ± 5 °C at a speed of 1 cmH2O per second and the pressure level is controlled, according to the principle of communicating vessels, through direct reading of a graduated scale in cm placed on a glass tube, connected with the cylinder, and just next to it.
The pressure of the water column is distributed over a surface area of 100 cm2.
There are two applicable methods: with a constant hydrostatic pressure and with an hydrostatic pressure limit;
a) With a constant hydrostatic pressure:
Where the purpose of the test is to verify the behavior of the test sample subjected, for a period of 24 hours, at a defined pressure that remains constant throughout the test time. After this period of time it shows the result expressing an opinion on the lower face of the specimen.
The lower face of the fabric during the test:
it is kept dry;
it gives rise to water drops or dripping, which before the end of the test are ended;
it gave rise to water drops or dripping, which before the end of the test were not interrupted.
With this test it is possible to determine the degree of effectiveness of the water proof test procedure.
b) With hydrostatic pressure limit
It determines the behaviour of the specimen, subjected to a hydrostatic pressure with a constant increase until it shows clearly the presence of three drops of water on the upper surface. The method used is the one described above: during the test, the water level should rise of 1 cm of water column per every second. The operator observes the sample until the appearance on its outer surface of 3 drops of water. Then it demonstrates the pressure value indicated on the scale and this will be the result of water proof test.
Thanks to its easy operation it is possible to perform the analysis on samples of 100 cm2 of surface, with pressure progressively variable from 0 up to 200 cm of water column.
The pressure increase can be 10 cm / min (UNI and AATCC) or 60 cm / min (DIN and AFNOR).
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