POROMETRY GRAPH INTERPRETATION
June 1, 2015
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EXPLORING COMMON PROBLEMS IN POROMETRY

WET CURVE HIGHER THAN THE DRY CURVE

Unexpected curves during typical Porometry dry-up wet-up tests often create confusion. Exploring and understanding the slope of the graph is critical in correct analysis and interpretation. Let us discuss some common occurrences & their solutions

  1. DRY AND WET CURVES DO NOT MEET.There are usually two scenarios
    1. In Porometry, the wet specimen becomes dry only after all the wetting fluid has been extruded during the test. Therefore it is normally expected that a wet curve to have contact with the dry curve. However, in some hydrophilic materials, it is difficult to extrude 100% of all the wetting fluid even though enough pressure is applied (without damaging the test specimen).
      TEST RESULTS- Accurate bubble point & mean pore size
      TEST DRAWBACK – Unable to measure smallest pore size/complete pore distribution summary
      RECOMMENDATION- None1
    2. Dry and wet curve completely apart. This usually occurs when sufficient pressure is not applied to extrude all the wetting fluid (dry-up wet up test).TEST RESULT- Accurate B.P, Inaccurate mean poresize/pore distribution.
      RECCOMENDATION – (For a dry-up wet up test) Use a test max pressure high enough to extrude all the wetting fluid.
  2. WET CURVE HIGHER THAN THE DRY CURVEPlease note that the wet curve SHOULD NEVER be higher than the dry curve whatsoever. Such phenomenon are observed usually in a dry- up wet up test, when the test specimen is vulnerable to high test pressure, and the pore stretch/expand/break with a permanent deformation (non-elastic). During the subsequent wet curve, the flow rate is higher and pressure differential is lower, as compared to the dry curve.
    TEST RESULT-Accurate B.P, Inaccurate mean pore size/ pore distribution.
    RECOMMENDATION- It is important to inspect the specimen after the test, and look for unusual stretches/ deformation. A wet up-dry up test will not only be more accurate, but also give you an approximation of the deformation pressure. Using a calculate dry curve for mean pore/pore size distribution will be more accurate .

 

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