Since 2009 the research group managed by the authors promotes the applicability of X-Ray Diffraction technique (NDT) for global stresses measurements in metallic structures for civil engineering and building. There exists standard portable equipments in the market for different applications of those here shown (residual stresses measurements). This paper shows some tests prior the complete calibration for any situation in such a way that can be applied to the quantification of stresses in service. Until now a metallic bar at the Oporto Cathedral, two corrugate bars at laboratory and a small metallic structure at laboratory have been tested. This last experimental work is here shown. The stresses obtained are the sum of the residual stresses and the external applied stresses. Currently the group works in order to remove the effect of the residual stresses by means of tests on small metallic structures specifically built.