Total Non-Blanked Area
Net unblocked area that will permit the passage of fluid through a screen. NOTE 1 It is expressed in square metres (square feet). NOTE 2 Some screen designs can eliminate as much as 40 % of the gross screen panel area from fluid flow due to backing-plate and bonding-material blockage.
Source: API RP 13C, Recommended Practice on Drilling Fluids Processing Systems Evaluation, Upstream Segment, Fourth Edition, December 2010. Global Standards