On the definition of the real resource of high-temperature steam pipelines
(Service life prolongation for a period longer than 50 thousand hours)
How much longer will the equipment work? The issue of real resource is on the table when face the prolongation, optimizing maintenance costs, valuation of power plants. We receive the request from the owners, but is the answer of expert organization?
Assessment of pipework metal after exhausting the economic life is carried out according to RD 10-577-03 and SO 153-34.17.470-2003. In general the steam pipe life assessment narrows to assess of the bends’ condition. In the normative documentation the following inspection measures for bends are set:
- search for micro-damages;
-calculation of permanent deformation;
-calculation of residual resource in accordance with SO 153-34.17.470-2003.
It is worth noting that according to current norms analysis of micro-damages should be carried out on 3 bends, selected by the permanent deformation measurements results and calculation of the stress state of a steam pipe.
Based on the positive results of a survey expert organization, following p. 9.5 of Instruction SO 153-34.17.470-2003, could allow further operation of a steam line for a period of not more than 50 thousand hours. However, in certain “justified cases” it is allowed to extend operation of the steam pipe after exhausting of economic life (i.e. the primary extension) for a period of more than 50 thousand hours ». I think you will agree that is profitable to skip a major overhaul and keep the pipeline running for the 8-10 years (i.e. 70-80 thousand hours).
But what kind of case can be called "justified"?
When 100% of a steam pipe elements were controlled.
When more detailed research methods are being used.
Our company obtains a whole range of additional examination methods for inspection of high-temperature steam lines:
-improved method of preparing thin specimen;
-the method of detection of the area most affected by micro-damages
-a methodology for bending life assessment by number of creep micropores;
-developed and patented technique of micro-damages determination by ultrasound velocity;
- life calculation program developed in accordance with SO 153-34.17.470-2003;
-metallographic thin specimen can be inspected directly on the pipeline using a SPM microscope or replicas can be made by using a proprietary Creeplak.
The use of multiple methods is to minimize the random error and assess the life of a bend more precisely. We highlight that in our stock, in addition to convenient proprietary tools, there are three more methods to assess life of the bends' metal (by number of micropores creep, by ultrasonic velocity, calculation of safety factor in accordance with SO 153-34.17.470-2003).