In-plane permeability measurements: a nordic round-robin study

Three methods to measure the in-plane permeability are compared. The method s are based on the wetting and saturated parallel flow techniques and the w etting radial flow technique. It is found that the stability of all three m ethods is very good. The best repeatability in the results is obtained with the wetting parallel flow technique. A main drawback of this method is, ho wever, that the samples are not saturated hence, the saturated parallel flo w method is suggested for continued evaluation. The standard deviation from repeatable measurements of this method is 14 and 20% for the two fabrics t ested. By a round-robin comparison at three laboratories it is found that t he reproducibility of the saturated parallel flow technique is in the same range as the repeatability of the method. Furthermore, it is shown that the liquid tested and the pressure applied have very small influence on the re sults. It is clear that most of the scatter is due to the sample preparatio n and variations in the material. Accordingly, a continued work should be c oncentrated on improvements of the sample preparation, and development of m ethods to reduce the influence, from small errors, in sample preparation on the results. (C) 1999 Elsevier Science Ltd. All rights reserved.