To implement the method, UkrN Pi proekt Institute has designed, manufactured and tested successfully a portable complex named CARAT, with its principle of operation being based on the AE method. The complex is intended for detection of leakages in any underground or surface steel pipelines, as well as for detection of defects (like crevices) progressing under the load and of considerable zones of plastic deformation in the areas of pipeline wall thinning (with indication of the defect coordinates). CARAT complex comprises a portable Notebook computer, four sensing elements, a processing unit, simulator, accumulator battery and a set of cables. Steel pipelines, operated in such industries as power engineering, metallurgy, chemistry, oil-chemistry, gas and mining, are objects of the study. Failure Of Such objects in the course of their operation can cause large material losses and other severe consequences. Objective of the Study is to design the equipment for non-destructive tests of conditions of steel pipelines by applying a promising acoustic emission (AE) method. The major characteristic features of non-destructive AE testing method include: the method provides for detection of the defects in progress, thus allowing to classify any defects not by their dimensions but by their danger; the method allows to detect fissures when their dimensions are tenth of millimeters only; the method is comprehensive, since it allows to test the entire object with use of one or several sensing elements; location and orientation of the object has no influence over the detection of defects; To implement the method, UkrN Pi proekt Institute has designed, manufactured and tested successfully a portable complex named CARAT, with its principle of operation being based on the AE method. The complex is intended for detection of leakages in any underground or surface steel pipelines, as well as for detection of defects (like crevices) progressing under the load and of considerable zones of plastic deformation in the areas of pipeline wall thinning (with indication of the defect coordinates). CARAT complex comprises a portable Notebook computer, four sensing elements, a processing unit, simulator, accumulator battery and a set of cables (Fig. 1-3).