ÎÀÎ "ÍÏÎ ÖÊÒÈ"
Ðîññèÿ, 191167, Ñàíêò-Ïåòåðáóðã, óë. Àòàìàíñêàÿ, ä. 3/6
Òåëåôîí +7 (812) 717 23 79 Ôàêñ +7 (812) 717 43 00
Web http://www.ckti.ru
Material lifetime assessment and testing materials of welded structures of power equipment at fossil and nuclear power plants department

Main activities of the department :

  • Research of main and welding materials of welded structures.
  • Development of welding technologies, including the ones eliminating the need for heat treatment.
  • Participation in design of welded structures consisting in development of weld assemblies from varying domestically produced and imported steel grades which ensure the mandatory service life.
  • Evaluation of various features, such as static and dynamic strength, fatigue strength, brittle strength, fracture resistance, stability loss of welded structures.
  • Modelling of welding processes and evaluation of processing strength to prevent formation of hot and cold cracks during processing and heat treatment. Industrial safety assessment of engineering devices which are supervised by Rostechnadzor (Federal Service for Environmental, Technological, and Nuclear Supervision).
  • Investigation (assessment) of destruction of power-generating equipment elements and units, including the court cases.
  • 3D modelling of welding technologies to optimize the welding technology, streamline the technology development and prevent the formation of crack in the process of welding; forecasting the changes in features of various welding areas.
  • Development of heat treatment technologies.
  • Certification research of welding technologies and issuing of expert reports on compliance of weld metal with the requirements set by the official supervising bodies.
  • Retrofitting of structures by welding, including cast body parts, beams, vessels, etc.

Research of main and welding materials of welded structures

  • Performance of static tests:
    • tensile test at the temperature of negative 100 °C to 900 °C;
    • bending, shearing and torsion test;
    • evaluation of crack resistance of materials and welds at the temperature from negative 100 °C to 400 °C;
    • drift and flattening tests of pipes; impact toughness tests with evaluation of ductile-to-brittle temperature Tk50;
    • research of metal heterogeneity based on the hardness evaluation data;
  • Performance of dynamic tests:
    • evaluation of nil-ductility temperature (NDT);
    • evaluation of crack resistance of metal at dynamic loads (KId);
  • Creep-rupture strength tests:
    • evaluation of stress rupture strength and ductility;
    • evaluation of creep crack resistance (KIcth);
  • Evaluation of crack resistance at stress release (KIrth);
  • Research of corrosion crack resistance (KIscc);
  • Performance of full-scale welds and welding samples;
  • Evaluation of fatique limit and cyclical crack resistance (KItn, KIfc) at cyclical load;
  • Research of macro and microstructure of metal and welds;
  • Fractographic research of fractures occurred due to accidents and element failures – with evaluation of values of loads at the moment of rupture (accident);
  • Research of weld deposition and coatings on metal.

Welding Technology Development

Using the developed welding technology, the laboratory has successfully repaired cast shells of turbines, the shells of emergency regulating valves, LPH, rotors, etc.

Through cracks in cast shells of high pressure cylinders (HPC) before and after welding

before

after

Design of weld assemblies

The laboratory has developed new design principles of turbine units that experience high loads (welded rotors, welded shell parts, diaphragms, welded hollow blades, etc.) using new heat-resistant and highly durable material, as well as combined (dissimilar) welds, that allow significantly streamlining the creation of new products.

Development of welding technology for composite rotors from consisting of various types of steel and alloys

Rotor assembly

The process of narrow-gap welding of the root part

Welding of root parts of rotor welds

Developed and Introduced Technologies

  • The laboratory has developed physical criteria of limits to service life of the equipment made of heat-resistant materials, including dissimilar joints of pearlite-martensitic class.
  • The laboratory has developed an evaluation technology for maximum allowable defect sizes in welds of rotors during their production and repair.
  • The laboratory has developed a method for evaluating crack resistance of welds on power-generating equipment during its production and repair.
  • The laboratory has developed and introduced at domestic factories the rotor welding technology for new-generation nuclear turbines, using state-of-the-art domestically produced and imported materials.
  • The laboratory has developed and introduced at domestic factories a welding technology for composite rotor used in turbines with ultra supercritical steam parameters, using state-of-the-art domestically produced and imported materials.
  • The laboratory has developed and introduced at domestic factories a welding technology for units and elements of turbines used with ultra supercritical steam parameters, using state-of-the-art materials of P91, E911, P92 class.
  • The laboratory has developed and introduced at the domestic factories the low-frequency vibration treatment of welded structures of water turbines – as a replacement for expensive heat treatment.
  • The laboratory has developed and introduced the repair technologies that utilize welding (depositing) of rotors, units and elements of nuclear turbines, as well as turbines used with ultra supercritical steam parameters.
  • The laboratory has determined the destruction parameters of dissimilar (pearlite-martensitic class steels) welds during long service at ultra supercritical steam parameters.
  • The laboratory has determined the limit values of crack resistance at cyclical load (Kth) for welded joints of rotor steels: Ð2ÌÀ + Ð2ÌÀ, Ð2ÌÀ + X12CrMoVWNbN 10-1-1, 26ÕÍ3Ì2FÀ + 26ÕÍ3Ì2FÀ, used for new-generation nuclear turbines, as well as turbines using at ultra supercritical steam parameters.

Evaluation of temperature fields of the rotor at different stages of welding

Temperature fields during aging
(30 hours) of rotor at the girth weld root zone welding

Temperature fields during aging (40 hours) of rotor after welding of the girth weld has been completed

Residual stress field (stress intensity – σi) after depositing, cooling down machining of rotor dummy piston

Temperature field in the composite rotor during heating before welding

Investigation (Assessment) of Destruction of Power-Generating Equipment

The department conducts investigation of destruction of power-generating equipment elements and units.

The accident investigation includes the following tasks:

  • analysis of turbine vibration monitoring data before and during the accident;
  • fractographic research of fractures in the control stage and the flow path of the turbine;
  • research of quality of the base metal and welds of blade assembly;
  • assessment of crack growth kinetics in blades;
  • evaluation of type of loads and the amount of destructive stresses in fractures;
  • damage source analysis, involving the accident emulation.

The source and sequence of destruction are determined by the above mentioned operations.

Display of damaged welded blade assemblies of the control stage after deblading

Strength Evaluation and 3D Modelling

The department performs 3D modelling of welding technologies to optimize the welding technology, streamline the technology development and prevent the formation of crack in the process of welding; forecasting the changes in features of various welding areas.

Distribution of temperature fields in the rotor diaphragm
during heat treatment

The shape of natural oscillations of the LPH shell


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