Patent ID: 8474305

Claim:
A method for detecting presence of target particulates of predetermined size in a fluid comprising both target particulates of the predetermined size and smaller sized non-target particulates, the method comprising: (a) providing at least one pair of serially fluid-connected upstream test and downstream reference filtration elements in a fluid, wherein the upstream test filtration element has a filtration size rating sufficient to remove a predetermined amount of the target particulates of the predetermined size from the fluid and to allow substantially all of the smaller sized non-target particulates to pass therethrough, and wherein the downstream reference filtration element has a filtration size rating sufficient to allow both any remaining portion of the target particulates of the predetermined size not removed by the test filtration element and substantially all of the smaller sized non-target particulates to pass therethrough; (b) providing a primary filtration element in series downstream of the at least one pair of serially fluid-connected filtration elements, wherein the primary filtration element has a filtration size rating that is smaller than the filtration size rating of the test filtration element so as to capture substantially all of any remaining portion of the target particulates and the smaller sized non-target particulates passing through the downstream reference filtration element; (c) measuring differential pressure of the fluid across each of the test and reference filtration elements; and (d) comparing the differential pressure across the test filtration element to the differential pressure across the reference filtration element to thereby detect presence of the target particulates in the fluid by an increase in differential pressure across the test filtration element in comparison to the differential pressure across the reference filtration element.