BS EN ISO 811:2018 pdf download – Textiles – Determination of resistance to water penetration – Hydrostatic pressure test
6 Apparatus
The usual laboratory apparatus and, in particular, the following.
6.1 Fabric clamp.
It should be possible to clamp the specimen of fabric in such a way thata] it is horizontal and is not bulging;
b) an area of the fabric of 10 000 mm2 (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;
d) the specimen does not slip in the clamps;
e) any tendency for penetration to occur at the clamped edge of the specimen is minimized.
With some forms of apparatus, it is recommended that the clamps are faced with a suitable grade ofrubber. It can be helpful to use a sealing wax around the clamps to help prevent water from leaking.
6.2 Mechanism for measuring the increase in water pressure.
The rate of increase of water pressure shall be 10 cm H20/min土0,5 cm H20/min or 60 cm H20/min 土3 cm H20/min (9,8 mbar H20/min土0,5 mbar H20/min or 58,8 mbar H20/min土2,9 mbar H20/min).
Results obtained by different rates may not be the same. The chosen alternative rate shall be stated in the test report.
The higher rate of increase of water pressure is more applicable when testing fabrics with high water resistance.
6.3 Manometer (for manual types of equipment that are not electronic].
The accuracy of the manometer, if used, shall be stated in the test report. If used, the following conditions apply.
a) It is necessary to provide a manometer of suitable range.
1] A manometer which provides for pressures up to 1 m H20 is suitable for fabrics similar in construction to gabardines.
2) For fabrics of closer construction, it is advisable to use a manometer which provides for pressures up to 2 m H20.
b] If more than one testing head is used in conjunction with the manometer, means shall be provided for separately disconnecting them. This is to prevent a high rate of leakage through test specimens already penetrated at three places. With most forms of apparatus, such a leakage can markedly reduce the rate of increase of pressure on the remaining specimens still under test.
7 Atmosphere for conditioning and testing
Conditioning and testing shall be carried out according to ISO 139. If so agreed, conditioning and testing may be carried out in the ambient temperature.
The presence of vapours of volatile organic liquids, such as diethyl ether, in the laboratory when this test is being carried out can affect the results.
8 Test specimen
After receipt, handle the fabric as lttle as possible, avoid folding it sharply and do not treat it in any way (e.g. by ironing it) other than by conditioning.
Take at least five test specimens from different places in the fabric so that they do not contain the same yarns and represent the material as fully as possible. The fabric may be tested without cutting specimens.
Areas with deep creases or fold marks shall not be tested.
9 Test procedure
9.1 Provide freshly distilled water (5.1]) for each specimen tested.
If the instrument used is of the type in which the water to be used for testing is contained in the testing head(s) and rises to come into contact with the specimen, the surface of the water in the testing head(s) may be cleaned in one of the following ways, stated in order of preference.
a] Empty the testing head(S) and refill with sufficient freshly distilled water.
b] Allow the distilled water to overflow from the testing head(s) so that the surface of the water is cleared. Sweep the surface of the water with a glass slide freshly coated with paraffin wax.
c) Allow the distilled water to overflow from the testing head[s) so that the surface of the water is cleared.