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48 ECT board: what it holds

48 ECT board carries 48 lb per inch of edge in an edge crush test. Built into a 12 × 12 × 12 in C flute box, the simplified McKee formula puts its compression strength near 772 lbf.

Estimated box compression by flute

Simplified McKee BCT, lbf, empty box
Inside size, inB fluteC fluteE fluteBC double wallEB double wall
8 × 6 × 4527589373791646
10 × 8 × 6598668423897732
12 × 12 × 126907724881,035845
14 × 10 × 86907724881,035845
16 × 12 × 107458335271,118913
18 × 12 × 127728635461,158945
18 × 18 × 188459455981,2681,035
20 × 16 × 148459455981,2681,035
24 × 18 × 189131,0216461,3701,118
24 × 24 × 249761,0916901,4641,195

Working load after storage

McKee gives the strength of a new, dry box. In storage it loses strength. Using Packgent's default storage losses (an assumption, see method), this is the most the bottom C flute box can carry at each age:

Allowed load on the bottom box, lbf (C flute, 48 ECT)
Inside size, in0 days10 days30 days90 days180 days
8 × 6589371354324295
10 × 8668421401368334
12 × 12772486463424386
14 × 10772486463424386
16 × 12833525500458417
18 × 12863544518474431

Neighbouring grades

GradeECT changeBCT change, same flute and size
44 ECT-4 lb/in-8%
55 ECT+7 lb/in+15%

In McKee, BCT scales directly with ECT, so the percentage change in strength equals the change in ECT.

Freight rule limits

NMFC Item 222 ties each grade to a maximum gross weight and size for LTL shipping. Packgent has not published those limits yet because they could not be checked against the current tariff. See the Item 222 page for status.

Sources

  1. TAPPI T 811: Edgewise compressive strength of corrugated fibreboard (short column test)
  2. McKee, R.C., Gander, J.W. & Wachuta, J.R. (1963). "Compression strength formula for corrugated boxes." Paperboard Packaging 48(8): 149–159
  3. Flute calipers: Foster (1997), Wiley Encyclopedia of Packaging Technology

Last reviewed . See all sources and how Packgent computes.