May 20, 2005
The digest of articles, methodical materials and standards "The problems of ageing equipment's life assessment and the ways of their solution using the metal magnetic memory method"
The problem of providing the reliable operation of equipment, vessels, gas and oil pipelines and various structures becomes more and more relevant every year as the equipment ageing in many branches of industry significantly surpasses the rates of technical re-equipment. For instance, in power engineering as of January 2005, about 90% of thermoelectric power stations equipment had exhausted its park life and the significant part of it had achieved physical wear. The above-mentioned problem is aggravated by the lack of scientifically grounded concept of technical diagnostics and life determination and by insufficient effectiveness of conventional methods and means of metal non-destructive testing.
It is known that the major part of failures and damages of equipment after long-term operation has unexpected fatigue. "Pre-defect" metal state in many cases is more dangerous, when irreversible changes took place at a microstructural level and the fatigue-assisted damage may occur all of a sudden and, as a rule, in unexpected zones. The sensitivity level of conventional NDT methods does not allow revealing the "pre-defect" state of a metal.
After long-term operation of equipment and structures totals of totals of 100% inspection of all units is required at their life estimation. It is obvious that carrying out such diagnostic works on tens of kilometers of pipelines, on a large park of boilers, vessels using the traditional NDT methods (ultrasound, X-ray, MPI and others) is practically impossible due to large material expenses on metal dressing and other preparatory operations.
It is known that stress concentration zones (SCZs), in which corrosion, creep and fatigue processes flow most actively, are the main sources of equipment damaging. SCZ is a local zone of a product, in which large strain occurred as compared to the entire product volume due to unfavorable combination of the structure features, structural inhomogeneity and working loads. SCZ is a "nucleus" of the developing defect.
The existing methods of strength calculation assume, as a rule, independent flow of corrosion, fatigue and creep processes, though in real practice these processes flow in various combinations and, first of all, in SCZs.
In connection with this the actual tasks at equipment life assessment are: carrying out stress-strained state inspection and detection of SCZs - the main sources of damages development.
For timely detection of susceptible to damaging equipment units methods and means of engineering diagnostics incorporating correlations of informational parameters with mechanical stresses are required.
All leading diagnostic centers of the world are occupied nowadays by the problem of mechanical stresses measurement in operating structures in order to assess their state. However, no effective methods of stress control, suitable for practical application, have been suggested till date.
At present the metal magnetic memory (MMM) method becomes more and more widespread at stress-strained state inspection and early diagnostics of equipment fatigue damages.
A specialized digest of articles, methodical materials and standards on the problem of ageing equipment life assessment was prepared.
- Problems of ageing equipment residual life assessment.
- Metrological problems of equipment stress-strained state assessment and ways of their solution based on the metal magnetic memory method.
- Analysis of the reasons for low effectiveness of materials' stress-strained state (SSS) diagnostics means.
- Methodical guideline for life assessment of potentially dangerous objects based on express methods of engineering diagnostics.
- GD 09-102-95. Methodical guideline for residual life assessment of potentially dangerous objects being under control of Gosgortechnadzor of Russia.
- Method of limiting state determination using the MMM method.
- Power equipment life assessment using the metal magnetic memory method.
- Problems of gas and oil pipelines residual life assessment and ways of their solution based on modern methods and means of engineering diagnostics.
- The experience of gas pipelines stress-strained state inspection using the metal magnetic memory method as compared to traditional methods and means of stress control.
- GOST R 52081-2003. Non-destructive testing. Method of metal magnetic memory. Terms and definitions.
- GOST R 52005-2003. Non-destructive testing. Method of metal magnetic memory. General requirements.
- GOST R 52330-2005. Non-destructive testing. Stress-strained state tests on industrial objects and transport. General requirements.
- Diagnostics of equipment and structures strength using the metal magnetic memory.
- Welding and welding procedures quality inspection problems and their solution based on the metal magnetic memory method.