Ispel practices for heating systems

The components designed in the creep field with time-dependent stress values ​​must be subjected, upon expiry of the theoretical design life (VP), to a series of checks aimed at evaluating the residual life and suitability for further operation , in safe conditions, of the appliance or equipment of which they are part.

The evaluation of the state of the appliance is carried out on the basis of the results of the following actions, to be carried out in order:

• Preliminary analyzes and assessments that take into account the project, the operating history of the appliance, the results of previous inspections and any accidents and/or repairs;
• Preliminary calculation of the theoretical life consumption of components subject to creep degradation;
• Definition of the non-destructive testing plan to be carried out on components subject to viscous flow, taking into account the preliminary calculation;
• Carrying out non-destructive tests and metallographic tests in order to evaluate the structural integrity, in accordance with the above-mentioned control plan;
• Execution (if any) of additional destructive investigations on the material in order to evaluate its state of degradation;
• Calculation of the theoretical life consumption of components subject to degradation by viscous flow, in the real conditions highlighted by the checks carried out (real thicknesses, actual dimensions, corrosion, etc.);
• Final assessments: the state of degradation of the components of the appliance and their fraction of consumed life must be assessed in light of the results of all the analyzes required for each individual situation as none of them, taken individually, can be considered exhaustive or probative. A congruence analysis must be carried out between the results of the calculations and controls: any discrepancies must be highlighted, evaluated and appropriately justified. In light of this analysis, the designer (PR) must propose an interval for further operation of the appliance (ref. UNI/TS 11325-4).