ASTM E3278-21 Standard Test Method for Bubble Point Pressure of Woven Wire Filter Cloth

5.1 Users of industrial woven wire filter cloth as covered by Specification E2814 commonly desire to specify the largest pore size as determined by converting the pressure result of a bubble point test to an absolute filtration rating in micrometres (also known as microns). This test method requires a comprehensive bubble point test method as well as a valid tortuosity or conversion factor for the calculation. This pore size result may be used as a standard rating of a material specification, a performance evaluation or acceptance criteria for material supplied, or a 1st article inspection requirement during the weaving of the cloth. The test is conducted using sample material cut from a woven roll of cloth, and hence should be indicative of the manufactured lot, given the application of appropriate tolerances.

5.2 While some users may desire a bubble point test conducted on some finished, fabricated filter unit, the test conditions for this type of test are outside the scope of this test method. The geometric test parameters for this type of specimen must be explicitly agreed to by the user and producer, and is to be considered a custom test method.

1.1 This test method is based on a capillary flow test that measures the pressure required to force an air bubble through a flat specimen of industrial woven wire filter cloth wetted under a test liquid of known surface tension. An established physical phenomenon, the pressure is inversely proportional to the pore size. This test method details the methodology to determine the bubble point pressure, and the applicable variables to calculate a standardized pressure. The test is recommended for filter cloth with a minimum test pressure of 1.0 inches of water.

1.2 A means for determining a pore size calculation factor (CF) is provided to allow the calculation of a pore size from the resultant pressure (see 15.2).

1.3 This test method uses mixed unit of measures. The values stated in inch-pound units shall be considered standard with regard to the bubble point pressure, test fixture, and procedures. The values stated in SI units shall be considered standard for the test fluid properties and pore size.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.