90 ECT board: what it holds
90 ECT board carries 90 lb per inch of edge in an edge crush test. Built into a 12 × 12 × 12 in AAC triple wall box, the simplified McKee formula puts its compression strength near 2,668 lbf.
Estimated box compression by flute
| Inside size, in | AAC triple wall |
|---|---|
| 8 × 6 × 4 | 2,038 |
| 10 × 8 × 6 | 2,310 |
| 12 × 12 × 12 | 2,668 |
| 14 × 10 × 8 | 2,668 |
| 16 × 12 × 10 | 2,882 |
| 18 × 12 × 12 | 2,983 |
| 18 × 18 × 18 | 3,268 |
| 20 × 16 × 14 | 3,268 |
| 24 × 18 × 18 | 3,529 |
| 24 × 24 × 24 | 3,773 |
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 AAC triple wall box can carry at each age:
| Inside size, in | 0 days | 10 days | 30 days | 90 days | 180 days |
|---|---|---|---|---|---|
| 8 × 6 | 2,038 | 1,284 | 1,223 | 1,121 | 1,019 |
| 10 × 8 | 2,310 | 1,456 | 1,386 | 1,271 | 1,155 |
| 12 × 12 | 2,668 | 1,681 | 1,601 | 1,467 | 1,334 |
| 14 × 10 | 2,668 | 1,681 | 1,601 | 1,467 | 1,334 |
| 16 × 12 | 2,882 | 1,815 | 1,729 | 1,585 | 1,441 |
| 18 × 12 | 2,983 | 1,879 | 1,790 | 1,641 | 1,491 |
Neighbouring grades
| Grade | ECT change | BCT change, same flute and size |
|---|---|---|
| 112 ECT | +22 lb/in | +24% |
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
- TAPPI T 811: Edgewise compressive strength of corrugated fibreboard (short column test)
- McKee, R.C., Gander, J.W. & Wachuta, J.R. (1963). "Compression strength formula for corrugated boxes." Paperboard Packaging 48(8): 149–159
- Flute calipers: Foster (1997), Wiley Encyclopedia of Packaging Technology
Last reviewed . See all sources and how Packgent computes.