This paper describes the development of a new method for the direct measurement of pore sizes in sand screens.Pivotal in the calibration process is a sonic sieving device that energises the microspheres to efficiently transport them through the filter mesh.From the percentage passing,a calibration graph supplied with the standard is used to determine the filter cut point.The analysis time is only 1 minute.Sampling variations both from a single roll and across several rolls were examined on 3 sand screen grades.The uncertainty of the method was less than 5%.This unique method provides a direct traceability to the International unit of length,both NIST and NPL.
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