Status:Closed Asked:Feb 04, 2014 - 09:18 AM
Is there a range of ECT values for each type of corrugated board?
Liner board thickenss and adhesives play a huge role in this, but are there values for the 'most standard' board used?
There have been no published studies that could help answer this question, although inference from unpublished containerboard studies can be helpful. ECT range for a given board combination can be significant, but under certain circumstances the range could be moderate. In a project I was involved with in the early part of the 2000s and confirmed by a more recent FBA member company study, the typical range of Ring Crush values for given “performance” grades of containerboard, including within mill variation and mill-to-mill variation, is around 30% (± 15% from the overall average of the given grade. (The range is slightly larger examining STFI values.).If the two liners and the medium are all at one end of the Ring Crush range at one plant and at the other end of the ring crush range at another plant, the differences in ECT would be similar to the differences in Ring Crush. Statistically, it would be very rare to have all three rolls in the corrugated sandwich at either one end of the distribution or the other, so the real world ECT variation is somewhat less than the theoretical ECT variation. Further, a given plant would have a limited number of suppliers of a given medium and a given “performance” grade of linerboard, perhaps two of the former and one of the later. Limiting the number of containerboard suppliers would also have a tendency to reduce the range of ECT values.
If ECT variation below the carrier minimums (eg Item 222) is a concern of the inquirer, it should be remembered that containerboard mills and box plants understand their raw materials and pick their paper grades with their supply quality in mind, so that they avoid putting together board combinations that won’t meet the carrier minimums for which they are designed to meet (again as long as the combined board is not crushed). More frequently today there are engineered board combinations, some proprietary, that take advantage of unique paper machine characteristics to optimize fiber usage.
Dave Carlson – Fibre Box Association
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