This device comprises a mounting assembly including an operative subset, a deposit subset, and lateral sets which are assembled on a pipeline so that, without shutting down the pipeline service, the pipeline can be perforated with cutting means, and valve means can be arranged to enable the control of the fluid circulation through the pipeline. The invention also includes an assembly procedure, through which sets and subsets are mounted on the pipeline, the pipeline is perforated, the valve means is positioned, and the valve seats are displaced until the device is in-service.