The most accurate calibration of the sand screens is the Sonic Challenge Test developed by Whitehouse Scientific, where accuracies and repeatabilities of less than 1% are routinely achieved by the technique. Reproducibility or measurement uncertainty, on the other hand, depends of the ability of the weaver to reproduce the same cut point irrespective of the position selected from the roll of mesh. For the best weavers, this is typically around 5% or less.
Cut points are defined as the 97th percentile of the calibrating beads passing the mesh so there is still 3% of the challenging beads passing the mesh so the question being asked is ‘How should the Maximum Pore Size be defined’? Furthermore, ‘How should the sphericity be defined’?
If Maximum Pore Size is defined as d100% (the Maximum Penetrating Particle (MPP)), then the result depends on the probability of aligning the largest particle present in the challenging particles to the maximum aperture in the filter mesh. Earlier experiments showed the measurement uncertainty to be over 40%, making comparisons between meshes very difficult. However, if d99 is used as the definition of Maximum pore size, the measurement uncertainty drops to less than 4%.
In this more comprehensive analysis, 6 specimens each of 4 grades of sand screens with cut points from 175 to 300 microns were tested by...
Session: F1 - Filter Media - Quality Control and Pore Size Analysis I
Day: 13 March 2018
Time: 13:00 - 14:15 h