Abstract: Blast joint assemblies are used for integral prevention of erosion of a production string crossing a production zone and simultaneous protection of hydraulic, electric and/or optical lines which need to cross same zones to operate and retrieve data from downhole operated tools. Each assembly is composed by one or more modular joint bodies having each at least one longitudinal slot on its outer surface; protecting covers shielding the longitudinal slots to house control lines housed in each of the longitudinal slots, with the protecting covers being properly retained on the related tubular joint body. The tubular joint bodies are precision machined to be connected by male and female threads granting an exact alignment of all slots in the blast joint(s) and allowing any combination of lengths for coping with any required assembly.