Equipe Jean PAIN
Image of a branches' chipper

About granulometry of chipped materials

Is the granulometry of chipped material of any importance ?

YES ! Because of the granulometry depends the possibilty -or UNpossibility- to revalorize the wood.

The Jean PAIN chippers have been originally built to ensure an optimum granulometry, as Jean PAIN defined it on the page 48 of his book THE METHODS OF JEAN PAIN.

"... it is better to have a long, thin fragment than a short, thick one ..."

Personal wild imagining ? Not !

It took many years to Jean PAIN to lead to this statement.
At first, Jean PAIN was using a sickle and a fork to make his brushwood compost, but only using twigs with a diameter of 8 mm.
To make his method able to produce large amounts of compost, mechanization was necessary.
First, Jean PAIN used a hammer mill (1973).
Soon, we realized that the crushed product was too diverse to easily make compost. We had to screen or re-grind it to get something good for agricultural application.
The use of a chipper with blades fixed on a rotor shown us the path.

Size grading of chips made with JEAN PAIN chippers
  Screen (in mm) %
1 4,0 mm 71,2 % 86,9% > 2,5 mm
2 3,2 mm 8,0 %
3 2,5 mm 7,7 %
4 2,0 mm 4,8 % 7,5% entre 1,6 et 2 mm
5 1,6 mm 2,7 %
6 1,0 mm 2,7 % 5,5 % < à 1,6 mm
7 0,5 mm 1,7 %
8 < 0,5 mm 1,1 %
Decomposition of the size of the Jean PAIN chips

This granulometry is obtained directly on the output of the chipper, without screening.
Typical size-grading can vary around these values depending on the wood humidity.
Note the high classification : 87 % > at 2,5mm.