The high level of development, fundamental knowledge and engineering experience of our employees allow the company to take part in work on the creation of normative and technical documentation, industry and state standards.
Strength calculations of existing pipelines with defects.
The normative document specifies the calculations for the strength of individual elements of pipeline systems with defects of different types at static load with the definition of their degree of danger.The rules consider 21 types of defects schematized pipelines (loss of metal, cracks, shape defects).
DSTU-N B V.2.3-21:2008.
Determination of residual strength of pipelines with defects
The standard provides for the analysis of material loss defects, axial and circular orientation cracks, local and global corrosion and shape defects as a dent and various types of misalignments of welds.
The normative document regulates the rules of calculations for the strength and durability of direct pipe sections of underground and above ground pipelines, bends and branch pipes with defects detected by means of non-destructive testing.
- limit state criteria;
- system of the safety factors;
- classification and schematization of pipeline defects;
- design characteristics of pipeline loading;
- determines methodology for multilevel quantitative assessment of defects and their diversification according to degree of danger;
- rules to provide conclusions, recommendations, time activity.
The method of calculation of NPP pipelines within "leak before break" conception.
This Method specifies the provisions of sections "Guidelines on the application of "leak before break" conception on NPP. RK-D 0.41.505-10" in terms of data preparation and execution of computational studies to check the applicability of the LBB concept.
The method includes:
- methodology of calculation justification of the concept of LBB;
- method of determining the stress-strain state of pipelines;
- structure integrity assessment of the elements with defects using two-criteria approach;
- approaches to defect growth;
- models of determining the area of opening of through-wall cracks;
- models for determining the rate of leakage from through-wall cracks;
- physical and mechanical characteristics of pipeline steels;
- methods of determining the reference stresses;
- methods for determining the stress intensity factor;
- methods of determining the residual stresses in welds;
- methods of calculation at seismic influences.
For implementation of the "leak before break" conception, experimental and calculations justifications of the ability of NPP systems of control to detect in advance the through defect in pipes before its catastrophic destruction were performed.
Guidance on the application of "Leak Before Break" conception on NPP .
The document establishes the procedure of the applicability "Leak Before Break" (LBB) concept and the requirements for nuclear power plant piping, which can be applied to this concept.
The reactor units with WWER-440 and WWER-1000 designed in the late 70’s of the last century. It fully met the design documentation and operational safety requirements. There were postulated gaps in pipelines, including main circulating pipelines (MCP). The WWER-1000 security systems designed in such a way as to counteract the maximum design accident. For example, the emergency supports has installed for high diameter pipelines (MCP, surge line etc.) as accident prevention measure from reactive forces occurrence due to pipelines rupture. The WWER-440 security systems do not provide such the emergency supports. However, such power units are equipped with main shut-off valves on MCP. It is important to know, the emergency supports are designed first of all for accident effects mitigation. At the same time, “Leak-before-break” concept provide probability reducing of accident occurrence.
The purpose of the LBB implementation is to reduce the probability of a violation of the integrity of the third barrier of deep-seated protection due to the early detection a leak in through defect of the pipeline's metal by diagnostic systems and the timely adoption of measures to prevent the accident.
To justify the LBB an experimental and calculation confirmation is required that the NPP control systems are able to fix a through-wall defect in the metal pipe before catastrophic failure of the pipeline. Also the steadily growth of cracks at plant operation should be confirmed and control methods should detect cracks before their rupture.
This allows detecting them with the help of the control system of the flow much earlier than the catastrophic failure of the pipeline will arise.
Stable growth of the defect during operation must be monitored, and the implemented control methods must be guaranteed to detect the defect before its rupture.
Methodology of hydraulic tests pressure on strength of the main circuit of NPSs with reactor units VVER-1000 and VVER-440 reduction.
The methodology regulates the procedures and types of work to reduce the pressure of hydraulic tests on the strength of equipment and pipelines of the first circuit of the NPP in order to optimize the parameters of hydraulic tests.
The possibility to change the parameters of hydraulic tests is determined by the deterministic and probabilistic analysis based on variation of safety factors of the main parts of reactor unit.
The justification for changing the parameters of the hydraulic tests is carried out in accordance with the IAEA INSAG-25 guidance on the Integrated Risk-Oriented Decision-Making Approach (IRIDM) methodology adapted to this task.
The introduction of the modification provides for the implementation of a calculation analysis with the application of deterministic and probabilistic approaches for the defining elements of the NPP on the basis of evaluation of changes in parameters of strength, damage and reliability (probability of destruction).
Typical program for assessing the technical condition and reassignment of the lifetime of steam generators.
Typical program for assessing the technical condition and reassignment of the life cycle of the main circulating pumps GTSN-195M RU VVER-1000.
Main gas pipelines. The method of estimation of changes of the stress state by the results of determination of the spatial position during conduction of the inline diagnostic
This standard regulates the methods for determining the stress-strain state of the sections of the linear part of the main gas pipelines based on the results of the inline diagnostics carried out, which includes the data of the spatial position of the pipeline.
The standard specifies the requirements for the: data of inline control and methods of the stress-strain state determining due to changes in the spatial position of the pipeline due to landslides, soil subsidence, etc., as well as the criteria of the limit state and the assessment of the technical condition of the elements of the sections of the linear part of the main gas pipelines.
Determination of the technical state of segments of the linear part of the main gas pipelines is carried out according to the analysis of the results:
- intracranial diagnostics,
- examination of anti corrosion protection and corrosion protection,
- inspection of the pipeline by non-destructive methods of control,
- control of the stress-strain state of the metal pipes of the gas pipeline, which are conducted in accordance with the requirements of the current normative documents.
This standard considers a method for evaluating a tensely deformed state based on the results of the determination of the spatial position during inline diagnostics and a change in the stress-strain state based on the comparison of the spatial position during several inline diagnostic.
This standard presents:
- the procedure for collecting and analyzing data on the factory bends and bends of the cold bending of the main gas pipeline route according to the design and executive documentation;
- the procedure for collecting, analyzing and presenting the data of the coordinates of the spatial position of the main gas pipeline according to the data of the inline diagnostics and measurement of measurement errors;
- requirements for comparing design and measured data and data from several diagnostic surveys;
- determination of the stress-strain state in the elements of the linear part of the main gas pipelines according to the spatial position and the change of the spatial position;
- criteria for selection of sections of main gas pipelines by degree of danger.
A typical program for assessing the technical condition and extending the life of the buildings, upper blocks and main connectors of the VVER-1000 reactors.
Main gas pipelines. The method of evaluation of the stress state of potentially dangerous areas.
The standard establishes the procedure for the determination and methods for assessing the stress-strain state of potentially hazardous sections of gas pipelines based on the results of the real spatial position of the pipelines and taking into account detected during the diagnostic examinations of shape defects of the pipe, imperfections of the axial and ring welds and additional loads.
It regulates the calculation methods and criteria for assessing the global stress state of defective parts of the main gas pipelines taking into account stress categorization as well as assessing the local stress state in the area of shape defects of the pipe, imperfections in welds and additional loads, which is complementary to the provisions of the basic standard for design of pipelines - SNiP 02.05.06.
Main gas pipelines. Methods of estimation of the stress state of overground transitions of main gas pipelines.
This standard regulates the diagnostics of overground transitions of main gas pipelines: beam type, cable type, with compensators, without compensators
This standard also establishes the procedure and methodology of: calculation of the actual technical state of the overground transitions of the main gas pipelines; analysis of working conditions and interaction of pipeline elements with the environment; conducting of diagnostics of above-ground pipelines in general and its individual sites, nodes and elements, with the definition of their stress-strain state under static load caused by changes in ambient temperature, wind loads, transverse loads (own weight of pipes, weight of product (gas), weight snow and ice load).
In addition, the standard considers the effect on the stressed-deformed state of the overground transitions of main gas pipelines to change the geometric position of the supports, which are caused by landslides or soils subsidence.
The requirements of this standard apply to the diagnosis of overground of main gas pipelines and are mandatory for all branches of PJSC "UKRTRANSGAS", as well as third party organizations conducting the survey (diagnosis), the state of the main gas pipelines owned by PJSC "UKRTRANSGAZ".