What is the volume of a loose solid?
The question is very relevant to peat and off-soil cultivation media. In fact, the farmer knows the overall volume of the containers to be utilized (whether pots, trays, or other) and, therefore, the amount of growing medium needed. In this regard, the Ministerial Decree of 30 December 1986, amending the attachments of Law 748/1984, in effect at the time, required that the labels, packaging, and/or shipping documents of the peat indicate the volume, not the weight as generally required for other fertilisers.
Besides the fact that it is not clear whether said regulation refers also to acidic ameliorant peat, a classification that encompasses almost all peats, the problem of how to measure these volumes persists.
Legislative Decree 075/2010, currently in effect, requires that the commercial volume be indicated for all cultivation media.
Hence the need to measure it, which is not without difficulties. In fact, while there is no ambiguity on how to determine the volume of a liquid or a compact solid (the only uncertainty is the measurement temperature), the problem is more complicated for peat, which is always variably compact or compactable. In fact, there is a volume at the time of bagging, which, however, can decrease due to the weight of stacked bags, which remove the air in the mass to varying degrees depending on the pressure to which they are subjected. Later, the volume increases, considerably in certain cases, when the bag is opened and the medium is emptied in the containers, possibly after mechanical or manual handling. Some time ago, there was no Italian measurement method and the German method (DIN11540) was frequently used. On 17 September 1999 the CEN (European Committee for Standardisation) approved method EN12580, developed by the TC223 (Technical Committee), which governs the determination of the amount of bulk or packaged cultivation ameliorants and media. On 21 July 2002, the Ente Nazionale Italiano di Unificazione [Italian Standardisation Organisation] (UNI) incorporated and ratified said European standard; therefore, from said date, it became an Italian standard identified as UNI-EN 12580:2002. The standard provides two basic definitions:
- the bulk density: is the density of the material as received and reconditioned (e.g. by re-wetting) in accordance with the producer's instructions
- Volume: it is the volume of the soil poured out and measured in accordance with this standard. The measurement principle requires weighing the material (net of the bag, if packaged); the bulk density is determined using the known exact volume of the measurement container; the total volume of the medium is obtained from these two values.
The measurement equipment required by the standard consists of:
- a 20-litre volumetric cylinder having a heigh/diameter ratio between 0.9:1 and 1:1;
- a rigid collar having the same diameter as the volumetric cylinder and 75 mm high;
- a sieve positioned 5 cm away from the collar and equipped with three 20, 40, and 60 mm mesh screens. The mesh size is chosen on the basis of the material to be tested: 20 mm for fine-structure material, 40 mm for medium structure, and 60 mm for coarse structure.
The material to be tested is made to go through the sieve to completely fill the cylinder. The collar is removed and the medium is made level with the upper edge of the cylinder. The material is weighed and the bulk density is determined.
What has changed?
As mentioned above, this standard replaces various national methods, among which the best known is certainly DIN11540. Relative to this latter standard, UNI EN12580 involves a decrease of the measured volume between 8% and 15%, depending on the material considered. These differences between the two standards are due to the fact that application of UNI EN12580 involves a less pronounced disaggregation of the material; the screen mesh was 16 mm with DIN 11540.
On the other hand, now the mesh is larger, namely 20, 40, and 60 mm. This allows: the passage of clumps of larger size and weight; a different stratification due to the larger weight of the aggregates and greater compaction; greater uniformity. Standard DIN 11540 requires a 40 litre parallelepiped-shaped container. The smaller size of the UNI EN 12580 cylinder and, above all, its shape allow a more uniform stratification because there are no corners, where compaction of the mass is generally different.
In conclusion, the same bag which had a volume of 80 litres according to the DIN standard will have a volume of about 70 litres according to the UNI EN standard, even though the amount in the bag is unchanged.
Therefore, any complaints regarding the commercial volume of the products will be considered only if they are based on measurements performed in accordance with the above-mentioned EN measurement standards.
A Customer wishing to verify the validity of the measurements carried out by Nuova Flesan must utilise a suitable regulation cylinder. Therefore, any complaints concerning the product's commercial volume based on measurements of the dimensions of the packaging containing the compressed material, the number of pots filled, or other parameters other than the standards described above are not acceptable under any circumstances.
For more information:
the EN 12580:2002 standard is not available in italian. The english version can be purchased (€ 27,00 + IVA) from UNI, also via internet (www.unicei.it)