In this paper a newly environmental friendly Non-Destructive Testing (NDT) method for underground oil and gas pipeline networks is proposed. A suitable equipment extracts small samples of material from installed buried pipes for mechanical testing. Numerical calculations using Finite Element Analysis (FEM) proves that decreasing wall-thickness pipes is safe for in-field operating conditions. Nevertheless, those locations from where samples are cut should be monitored. For instance by means of Acoustic Testing (AT) system. New way of placing sensors is proposed. Sensors are introduced inside the pipe so that any acoustic wave changes from surrounding medium can be measured. In this type of AT a straightforward procedure must be followed to install sensors on pipe. Therefore, there is no need to uncover tested areas with qualified personnel. The research showed that the signals recorded from internal sensors are comparable to those results extracted from external ones. The study also revealed lower vulnerability to acoustic interference of the sensor placed inside the pipeline.