Why using the INADCO DENSIMETER to determine your Bulk Density
The obligatory European standard EN12580 describes a method to determine the quantity of
your growing media in bulk or as packed product. It consists of two parts:
EN12580 describes in detail how to determine the bulk density of your soil. The method uses screens with different meshes, dependent of the product you want to measure. The purpose of the screen is to prevent the soil from falling from such a height, that the soil which is already in the cylinder will be compressed due to the speed of the falling soil. The screen also regulates the amount of soil which can fall at a specific time as a whole in the cylinder. Due to this method, the cylinder will be filled as homogeneous as possible.
Because the screen has a fixed height of 5 cm above the CEN cylinder the soil will fall in a reproducible way in the 30 cm high cylinder, starting with a drop distance of 35 cm, and ending with one of 5 cm height.
The filling of the CEN cylinder however can never be homogeneous because the lower layers will be compressed by the weight of all the layers above it. As a result of this, every other reliable means of measuring your Bulk Density as a replacement of EN12580 has to take this inhomogeneity into account.
Every method which uses a cross-section on a conveying belt, measuring either by radiation or by contour measurement, without additional methods which assure that the same in homogeneity is achieved as in the standard method, cannot give you a proper result. This although the used equipment and method are perhaps very good ones, but only if used for homogeneous materials. Growing media are not homogeneous materials, so that kind of equipment and measuring Growing Media cannot go together, if you want to do measurements according to EN-12580.
Some of these measuring systems use correction factors in trying to produce the same results as achieved with the standard method. Correction factors however can only be applied when you use them to correct a constant deviation between the standard method and a certain used method. This, however, is not the case because the Growing Media that you have to measure are a natural products that changes from day to day or even within a day.
If you have a mixing line with hoppers for your raw materials, you use a recipe to put the desired amount from each hopper into your mix.
The INADCO Densimeter demonstrates that the mixtures produced by such mixing lines are; often far from homogeneous.
The variations in the flow of the raw materials within a certain batch, some of them caused by changing levels in the hoppers, can be seen
very well. Also big differences in bulk density during the production of virtually equal mixes are shown. Reasons for these phenomena are
differences in moisture, or differences in raw materials.
Even the influence of several different wheel loader drivers can be found. All these variations are every day reality!
The INADCO Densimeter has no correction factor which can be adjusted, just like the standard procedure EN12580 has none. The bulk density according to EN 12580 is simply the net total mass of one full cylinder, divided by the volume of that cylinder.
You can perform a simple test to prove that the measurements of the INADCO Densimeter are correct and that the variations measured during a certain batch are no measuring faults. Take an already measured batch, with all its variations, and take the contents of the lorry in which that batch was loaded and put it in one of your raw-material hoppers. If you now produce a mix consisting of 100% of the material that has already been measured, you will see that all previous differences in measurements are almost gone.
The reproducibility of the INADCO Densimeter is proven by this test.
The principle of the INADCO Densimeter is that the limitation of the height of dropping is not achieved by the use of different screens, but by letting the soil be wiped of a shovel.
The screen which is used in the standard method would need regular cleaning, and therefore is not suitable for a fully automated measurement system.
EN12580 dictates screens with different widths of meshes. So you have to change screens, depending on the particle size of the soil that is to be measured.
INADCO uses a shovel on which a thin layer of material is placed.
This shovel rotates over a weighing measuring cylinder, which is equal to the one used in the standard method. When the shovel is right on top of the cylinder, the soil is stopped by the pre-scraper and drops down from the shovel into the measuring cylinder.
For the filling of the measuring cylinder the screen has been replaced by a shovel and pre-scraper. This guarantees a measuring result comparable with the standard method because the same inhomogeneity in filling is achieved.
When the cylinder is completely full, in approximately 8 layers, the surplus is scraped off by means of the after-scraper; this is the equivalent of the removal of the surplus soil as described in the standard method EN12580.