LABORATORY SCREENING OF PULP (MASTERSCREEN - TYPE INSTRUMENT)

A general purpose practice for screening pulp using a specific screening device is described, which separates from a slurry of pulp fibers a contaminant fraction with size dimensions which are significantly greater than the diameter of a pulp fiber.

Separated contaminants include, but are not limited to, shives in virgin fibers, or macro stickies that are captured by the barrier screen plate, scleroids, dirt, stone cells, plastics, pitch, white pitch, and other contaminants in virgin and recycled fibers.

There are numerous screening instruments used for separation, classification, or quantitation of contaminants from pulp fibers, including T 278 "Pulp Screening (Valley-Type Screening Device)" and T 275 "Screening of Pulp (Sommerville-Type Equipment)." This procedure covers a specific screening procedure to concentrate contaminants by fiber removal, and does not cover use of screens for pulp size classification.

While this Practice does not describe the specific procedure required to quantitatively measure the contaminant fraction separated, it should be noted that where this is done by the user of this practice, slightly different quantitative results may be found among or between results calculated using the device described in this Practice and the various devices in 1.3.