Patent ID: 7413666

Claim:
A method of collecting insoluble particles present in a fluid flow stream, particulate matter being collected only when concentrations of the insoluble particles exceed a predetermined threshold level, comprising: (a) continuously counting, on-line and on the basis of preset size ranges, individual particles in a first portion of the flow stream which traverse a laser beam and cast shadows on a detector when the shadows cast are at least as large as that cast by an opaque particle approximately 2 microns in diameter, numbers of particles so counted for a preset subinterval of time and size range being known as particle counts; (b) simultaneously diverting a second portion of the fluid flow stream from its normal course and passing the second portion through a 0.45 micron filter when the total particle count, in a given subinterval, of the particles in the first portion of the flow stream has risen to the threshold level and maintained this level for an interval of time corresponding to a predetermined event delay value; (c) returning the second portion of the fluid flow stream to its normal course while the total particle count remains above the threshold level, the second portion being so returned only after the particle count reaches a maximum for each excursion above the threshold level in which the second portion is diverted; and (d) computing an average particle count for each such excursion by adding together, for each subinterval of time, the particle counts for particles of all sizes greater than 2 microns so as to obtain a total particle count for the subinterval, integrating the total particle counts for all of the subintervals of the excursion, and dividing the integrated total particle counts by the number of subintervals in the excursion.