NewsInformation Center
The test method of Hydrostatic Head Test
2019/04/10
Share:
Scope and field of application:
This International Standard specifies a hydrostatic pressure method for determining the resistance of fabrics to penetration by water. The method is primarily intended for dense fabrics, e.g. ducks, tarpaulins and tentings.
Principle:
The hydrostatic head supported by a fabric is a measure of the opposition to the passage of water through the fabric. A specimen is subjected to a steadily increasing pressure of water on one face, under standard conditions, until penetration occurs in three places. The pressure at which the water penetrates the fabric at the third place is noted. The water pressure may be applied from below or from above the test specimen. The chosen alternative should be stated in the test report.
The result is immediately relevant to the behaviour of fabric articles which are subjected to water pressure for short or moderate periods of time.
Apparatus：
1、The apparatus used for the test should be designed to comply with the following conditions.
1.1 It should be possible to clamp the specimen of fabric in such a way that
a) it is horizontal and is not bulging;
b) an area of the fabric of 100 cm2 * is subjected to steadily increasing water pressure from below or from above the fabric;
c) no leakage of water takes place at the clamps during the test period (see annex, clause A. 1);
d) the specimen does not slip in the clamps;
e) any tendency for penetration to occur at the clamped edge of the specimen is minimised (see annex, clause A.1).
1.2 The water in contact with the test specimen should be distilled or fully deionized water maintained at either 20 + 2 OC or 27 + 2 OC. The chosen alternative shall be stated in the test report. (The use of water at the higher temperature will yield lower values of hydrostatic head; the magnitude of this effect may vary from fabric to fabric.)
1.3 The rate of increase of water pressure shall be 10 + 0,5 cm or 60 ,+ 3 cmH20/min**. Results obtained by the two different rates may not be the same. The chosen alternative shall be stated in the test report.
1.4 A manometer connected to the testing head(s) should allow pressures to be read to an accuracy of 0,5 cmH20 (see annex, clause A.2).
Test procedure:
Provide freshly distilled annex, clause A.3). Wipe all water from the clamping surfaces. Clamp the conditioned specimen in the test head so that the face of the fabric will be in contact with the water. The clamping shall be carried out in such a way that water will not be forced through the specimen prior to the start of the test. Subject the specimen immediately to increasing water pressure. Watch continuously for evidence of penetration by water.
Record the pressure, as conventional centimetres of water, at which water first appears at the third place in the specimen. The accuracy for recording the pressure shall be the following :
until 1 mH20 : 0,5 cm
more than 1 mH20 and until 2 mH20 : 1 cm
more than 2 mH20 : 2 cm
Do not take into account very fine droplets which do not grow after being formed. Do not count subsequent drops which penetrate through the same place in the fabric. Note whether the penetration of water at the third place occurs at the edge of the clamp and reject as unsatisfactory any test in which such penetration occurs at a pressure less than the lowest pressure recorded for the other specimens from the same sample. Test further specimens until the requisite number of satisfactory results is obtained.
Calculation and expression of results:
Calculate the mean of the pressures recorded for the specimens tested according to clause 7. Report the individual results and the mean result in conventional centimetres of water.
Previous: Importance of Textile testing
N e x t : Glow wire test methods
