Ranking of defective pipelines
Computer Ranking Method of Defective Main Pipelines on the Base of Numerical Simulation Algorithms and Stochastic Analysis
Tech Area / Field
- ENV-MRA/Modelling and Risk Assessment/Environment
- INF-COM/High Performance Computing and Networking/Information and Communications
- INF-SOF/Software/Information and Communications
- PHY-STM/Structural Mechanics/Physics
3 Approved without Funding
VNIIEF, Russia, N. Novgorod reg., Sarov
- Fraunhofer Institute Zerstörungsfreie Prüfverfahren, Germany, Saarbrücken\nSandia National Laboratories, USA, NM, Albuquerque
Project summaryEnhancing operation safety of the main pipeline systems is an actual problem both for Russia and for all industrialized countries.
The majority of the main pipelines operates over 20-30 years. During long operation there is an intensive ageing of structural parts of the operating pipeline systems. In particular, protective properties’ decrease and wear of the insulating covering results in sharp increase of corrosion intensity of the pipelines and the appearance of numerous surface defects as corrosion cavern at pipe walls. It, in turn, results in increase of failures at the main pipelines entailing serious economic, ecological and social consequences. So, according to "GAZPROM" data, failures caused by the corrosion make up to 60 % of the common number of failures at pipelines of the big diameter for last 30 years.
The timely reconstruction and modernization of main pipelines’ defective segments is required for the operation safety enhancing and failures’ decrease. One of the primary goals arising at carrying out of reconstruction and modernization of pipeline systems is the complex analysis of corroded segment states, ranking of pipelines’ defective segments on hazard level, development of economically effective plans of their repair.
The necessity of the given problem solving at present besides social and ecological factors is caused by excessive expenditures for replacement or repair of pipeline segments. Total updating of the main pipeline system is not a real financial task for any large state or private company all over the world. The practical solving of the given problem is especially actually for Russia where (in conditions of the common investments’ deficiency into industry) one of the biggest fleet of the main pipeline systems is situated. The majority from this fleet is on a side (or already behind a side) of service life.
Now, two various approaches are used for a hazard level analysis of defective pipelines segments as in Russia and abroad. The first approach is based on creation and analysis of stochastic models. At this approach the remaining lifetime of a defective segment (before failure) is presented as a conditional random variable. And probability density function (PDF) of this random variable is created, basically, by results of statistical data processing on actual failures and modeling experiments. Essential lack of this approach is that strong dependence of the stochastic models from not numerous empiric data does not allow to receive practical estimations for particular defective segments of the main pipelines with on today required accuracy.
Other approach to an estimation of defective section hazard is its stress state analysis and calculation of maximum loads (for example, burst internal pressure) with use of the deterministic physical and mathematical models. Now the most widespread practical methods of the pipeline sections’ strength estimation with local corrosion defects are manual of the American Society of Mechanics Engineers (ASME) B31G, which initial variant is accepted as national standard of the USA, and also its numerous modifications. All these methods are semiempirical. Its essence is reduced to calculation of burst pressure of the corroded pipe by the formulas received from the elementary linear theory of strength of materials and introduction of empirical coefficients in these formulas. The common disadvantage of these methods’ application is its excessive conservatism. In overwhelming majority its application gives too low estimations of burst pressure and maximum allowable operating pressure (MAOP) that results in over cull of pipelines defective segment. Besides due to functional limitation of these methods, their use in practice, alongside with mass over cull of pipelines defective segments (and unjustified expense for reconstruction), in some cases can lead to the underestimation of really hazardous corrosion defect (group of defects). Consequences of such mistakes can be disastrous.
On the other hand, the modern level of numerical methods of continuum mechanics and power of computers enable development of new approaches to the main pipeline state analysis. In particular, wide experience of development and practical application of the numerical analysis technologies of the multiaxial nonlinear stress state of the pipelines defective segments that are in conditions of multifactor loading and accounting all technical diagnostics data is accumulated by the ISTC Project participants.” The given approach (at presence of the true initial data) allows obtaining the results essentially surpassing on accuracy the results of traditional method applications.
At the same time, as a rule, all initial data necessary for simulating of particular pipeline segments contain some uncertainties connected with the errors of technical diagnostics’ measuring facilities, scattering of physical properties of pipe steel, nonuniformity of loadings, etc.
Offered ISTC Project is directed on the effective solving the problem of the main pipeline segments’ state analysis with corrosion defects and getting of the most accurate quantitative characteristics of hazard level of each segment. As a result of Project carrying out algorithms and the ranking computer program of the main pipeline defective segments on hazard level will be developed on the basis of simultaneous use of numerical methods of continuum mechanics and stochastic methods of the risk assessment.
Development of algorithms will be based on the numerical analysis results of multiaxial nonlinear stress state of a defective segments with use of modern methods and means of computation continuum mechanics and quantitative estimations of influence on results of numerical simulation of uncertainty in the initial data with use of stochastic simulation.
The following problems solving is provided during ISTC Project carrying out:
· development of computation technology for simulation of multiaxial nonlinear stress state of the main pipeline segments with surface wall defects being under multifactor loading taking all technical diagnostics data into account;
· development of an analysis algorithm of influence of uncertainty in initial data (measurement error of defect geometry, scattering of physical properties of pipe steel, nonuniformity of loads, etc.) on quantitative characteristics of strength of the defective pipeline segment;
· development of the computer program for calculation of quantitative characteristics of hazard level and risk assessment of the pipeline defective segments for ranking of the segments on terms of repair.
Solving the Project problems will allow creating unique tool of main pipelines state analysis not having analogues. Its wide practical application will allow to enhancing operation safety of pipelines, to decrease large failures, to plan effectively the expenses of transmission companies for reconstruction of the main pipelines.
As a result of Project carrying out scientists and the experts earlier connected to creation of the nuclear weapon, receive an opportunity for re-orientation the abilities on peace activity and are included in the international scientific cooperation.
In work of ISTC Project it is supposed a participation of 5 leading experts on development and practical application of stochastic simulation methods and the risk assessment in the field of industrial safety from the Federal State Unitary Enterprise “STC Industrial safety” for increase of practical value.
Carrying out of Project will promote the solution not only Russian national problems, but also stability of international economic relations (uninterrupted reliable deliveries of natural gas, oil, etc.) and ecological safety enhancing in the world (to decrease of ground and water resources pollution).
The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.
ISTC facilitates international science projects and assists the global scientific and business community to source and engage with CIS and Georgian institutes that develop or possess an excellence of scientific know-how.