The controls of the products of natural stone

The controls to realise on the products of stone have to do  in the phases of manufacture, supply and reception in work and are, on the one hand, responsibility of the manufacturer and, by another, of the Direction Facultativa of the work.

Controls in the phase of manufacture: the Marked CE.

From the year 2003, the manufacturers of products of natural stone are forced to realise a series of controls on his production, related with the marked CE, compulsory requirement for his commercialisation in the European Union.

It is that, the producing companies, have to implant a system of self-supervision in his factory, consistent in realising a series of essays in laboratory, with some frequency, for the knowledge of the physical properties-mechanical of the material and, on the other hand, dimensional and visual control of  his production. 

After implanting this process of control, the manufacturer elaborates two documents: a Statement of provision and a identification label of the Marked CE, that places  on the product.

Previous controls to the supply of the pieces:

Generally, they consider  reason of rejection defects like pieces broken, pieces with open fissures in some face, breaks in the corners of the pieces or flaws of the edges.

Controls of reception in work:

They exist different systems of sampling that can apply to inspect in work, during his reception, the products of natural stone.  One of them is the one who collects  in the norm ISO 2859-1:2012. Procedures of sampling for the inspection by attributes. It splits 1: Plans of sampling for inspect them batch by batch, tabulated according to the limit of quality of acceptance (LCA).

To apply this system, have to take into account, in the first place, several questions that indicate to continuation:

- The product in work has to group in batches, understanding by batch to the group of units of a determinate product, object of control.

- Of each batch will extract a sample, that will compose of a number of representative units of the same.

-The norm ISO of reference establishes a series of levels of inspection, three levels of normal inspection and four special levels of inspection, designated S-1, S-2, S-3 and S-4. The level of inspection that recommends  for natural stone the S-3.

-Limit of Quality of acceptance LCA (%): it is the average of the maximum percentage of no compliances that can tolerate  in a series of batches to consider them satisfactory. In natural stone the LCA that is using  is of 4%.

Knowing all this, to apply this system have to use a series of tables normalised where indicate the criteria of acceptance and rejection of the products in function of the size of our batches in work.

Knowing then the systematic, the controls that recommends  realise on the sample will be, like minimum, the following, taking into account that they have to be a group of proofs that realise  of fast form not to interrupt the normal course of the work: dimensional controls, appearance, essay of absorption of water IN 13755 and essay of resistance to the flexión IN 12372.

In addition to these controls, the managers of the reception of the products in work have to ensure that they come properly documented, with the label CE, if it proceeds, and without defects derived of his manufacture and/or transport.