numero26

S. Bulatovic et alii, Frattura ed Integrità Strutturale, 26 (2013) 41-48; DOI: 10.3221/IGF-ESIS.26.05 42 Figure 1 : Part of the steam line during NDT. T ECHNICAL DIAGNOSTICS uring the operation period, fatigue of steam line components may occur. Degradation of material properties and deformation of elements can be accelerated due to the exploitation and repair errors, that's why periodic or continuous diagnostic measurements, conducting periodic tests and data collection programs defined by [1, 2] are needed. In this way, processes that could lead to the creation of system damage are under systematic control, what is also the legal obligation imposed by the regulations, directives and harmonized standards [3 - 5]. Properly conducted technical diagnostics protects parts of the steam line from accident, and also ensures safer conditions for employees as well as rational techno-economic exploitation and maintenance. Technical diagnostic of steam lines must be based on three basic principles:  volume of tests and measurements shall be in accordance with the program of research [1] and an expert knowledge of steam line structure and working conditions;  tests and measurements must be performed in accordance with special procedures, using appropriate equipment and qualified personnel;  test results should be presented in such way that the conclusions include steam line operating conditions, the availability of the test team and staff with appropriate experience and knowledge in the field of design, construction, installation, operation, maintenance, reliability, fracture mechanics and others. NDT TO DETERMINE CAUSE OF STEAM LINE FAILURE or purpose of determining the causes of failure it is necessary to make steam line 100% visual inspection, magnetic, penetrant, ultrasonic, hardness and method of replica testing. If necessary, other tests that would give us a reliable and useful results to determine causes of steam line failure could be done. Fig. 2 shows the possibility of evaluating some damage using NDT methods in the life of the steam line. Visually optical control (VT) VT is used to detect defects that are visible on the surface of the steam line from the outside or inside of the tube. It applies regardless the method to be applied after it, because it is possible to detect errors, such as in our case, and avoid the use of other, more costly methods of NDT. It is often used for the selection of critical areas of the facility for the application of other NDT testing methods. At the same objects it may be performed multiple times (eg, before and after cleaning, or before and after the execution of corrosion protection, etc.). Control of the inside of the tube (endoscopy) allows optical access to the interior of steam lines. It is performed using an endoscope, and as a result we get control of video or photograph controlled inner surface, Fig. 3. D F