In this paper, the preliminary study of intervention on puddle iron and cast iron Hydraulic crane, situated in the “Arsenale” of Venice is described. The crane was built by Armstrong, Mitchell & Co. in 1885. It is one of the most important and the last remaining example of XIX century innovation of English engineering, after the disposal of other Armstrong Company cranes. Thanks to the interest of the Superintendency of Venice and The Venice in Peril Fund UNESCO Committee, the crane is now undergoing restoration works. To design and execute the restoring interventions of the crane, a preliminary study was necessary. The first fundamental step consisted on performing a detailed historical research, focused in particular of the past interventions and on identifying the most important causes of damage.