Upgrading Headbox Technology to Improve Quality and Increase Strength on Board Grades, PaperCon 2010 Conference

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In the last few years dilution control technology has been extended to include retrofits that can be applied to existing headboxes. With large slice openings required in many board grade operations, and the diminishing effect of slice lip control as openings increase, dilution profiling is particularly significant. This technology can provide dry weight 2-sigma CD profiles of better than 0.5% irrespective of slice opening. Sheet edges are also improved, giving secondary benefits in sheet runnability, reel building and winding and increased production.

For board grades there may still be substantial additional benefits to replacing an older headbox rather than retrofitting dilution control. Good hydraulic headbox technology can improve CD sheet strength by allowing the papermaker to produce a squarer sheet, with a lower TSI MD:CD ratio, as well as a better CD dry weight spread without low-weight low-test areas. This can translate into higher CD Ring Crush and STFI values, or can be used to reduce the target dry weight and refining levels.