Paper has numerous characteristics including Short Span Compression Test (SCT), tensile strength, burst, moisture to name but a few.
Paper attributes are based on a variety of factors including the inclusion of specific additives to stiffen paper, the orientation of fibres within the sheet and the quality of machinery manufacturing the paper.
Paper quality values can be used to calculate board and box compression resistance, which is therefore the case stacking strength.
Typically the McKee Formula is used to link these values and generate a theoretical (Box Compression Test) BCT performance.
It assumes that the boxes are square, but modification for the effect of aspect ratio exists. It predicts maximum load, but not deformation.
On the corrugated board level, several methods have been developed and standardised. To a great extent corrugated board properties can be predicted from paper properties.
When calculating a theoretical box performance, BCT is mostly used with safety factors to take requirements during transport and storage into account. These safety factors are based on experience and have large uncertainties. Safety factors are used in many different ways and combinations with unpredictable results. To summarise, it could be said that the uncertainty results in use of safety factors in many different ways, which creates even more uncertainty.
Stackability during transport and collapse cannot easily be predicted. Therefore many companies use very large safety factors.
Although the SCT, ECT and BCT are intrinsically linked and when placed through the appropriate formula can indicate the box performance within a supply chain. However, due to the unknown climatic or environmental elements affecting a supply chain, safety factors are used to establish theoretical box performance values.
The information sheet associated with this is called Case Size Ratios and can be found: Clicking here