29 мая 2016г.
The article considers the problem of modeling different pipeline failures and determining of the possible points of such failures in pipelines. For this purpose the method of mathematical modeling has been used. Having considered many program packages the authors have determined the least time consuming and the most effective of them. Using the failure parameters as the input data for the program analysis we can determine the exact failure points in pipelines and predict the appearance of the new ones, which leads to great savings in the oil and gas industry.
The value of engineering work in the pipeline transportation becomes relevant with the reduced oil price.
Especially taking into consideration that for each 250 thousand kilometers of Russian gas and oil pipelines the average period of operation has exceeded 30 years.
Since the starting of pipeline operation in the USSR not more than 1,5% of the total pipelines’ length has been annually renewed. With the total length increasing the absolute value of pipelines to change is also rising as well as the amount of pipes for reconstruction [4]. In addition to this regular integrity inspection is also increasing – so in-depth manual investigation of all the risky pipeline parts becomes now impossible, only automatic internal inspection is available.
Being limited in a budget for pipeline renovation capex and inspection opportunities one of our main capabilities is comprehensive analysis of gas and oil pipelines parts to be rebuilt which has also been deeply investigated.
Based on the hypothesis that the main root cause of pipeline failure is overlimited deformation mode our task is to find an opportunity to build a finite element model for all the gas and pipelines. Thus with the help of real input parameters the deformation mode distribution model will be built and, on the basis of the existing regulation documentation, we’ll determine the pipeline points where the risk of designed deformation mode is taking place.
The two main challenges of this approach are the following:
- The finite element analysis is usually a long and complicated process and it can take several days to calculated the deformation mode for a small spare part [3,6,7].
- Creation of the real model, setting up the mesh and placement the input parameters is also a long and complicated process even for simple cylinder [5, 1].
So the creation of a finite element model in such program packages as ANSYS of Autopipe is currently impossible [9, 2]. And, therefore, a special simplified program product, designed especially for deformation long pipelines mode calculation is required.
One of the found program with the described requirements is the Russian program product “START”.
During the testing of this program several problems were solved. One of them is comparison of the maximum deflections of pipeline spans in the conditions of a restraining by real ground and the position in anchorage. In addition - the mathematical model of interaction between the pipeline and a ground has been investigated [8]. It represents the reaction of a nonlinear spring, and it should be noticed that an identical model is used in the package ANSYS.
It has been revealed during the statistical analysis that the values of span deflections under both conditions (restraining in ground and the position in anchorage) depend on many parameters: the working pressure, the pipeline diameter, wall thickness and steel mark. But the ratio between the maximum deflections under these two conditions exponentially depends only on the type of a ground and the span length but remains constants at any internal parameters of the pipeline. This dependence could be established analytically by means of interpolation with a method of the least squares. For this purpose the program package MathCAD has been used.
As a result of this work the special coefficient has been received. It allows us to define a pipeline span deflection in the conditions of restraining in real ground if we know the pipeline span deflection in the position in anchorage.
The given program package essentially simplifies the calculation of a large length pipeline. And therefore it could
be successfully used for the selection of pipeline points for the potential in-depth “manual” inspection and, as a result, to prevent pipeline failures and increase the pipeline reliability assurance
Список литературы
1. Bikmukhametov D.F., Korobkov G.E.,Yanchushka A.P. Features of Aboveground Pipeline Compensation Part Stress-Deformed Study at Permafrost.-Modern Applied Science; Vol. 9, No. 8; 2015. С. 204-212. Published by Canadian Center of Science and Education.
2. Колчин А.В., Янчушка А.П. Математический аппарат нейронных сетей в приложениях. В сборнике: Мировое сообщество: проблемы и пути решения Уфимский государственный нефтяной технический университет. Уфа, 2011. С. 31-32.
3. Коробков Г.Е., Зарипов Р.М., Шаммазов И.А. Численное моделирование напряженно-деформированного состояния и устойчивости трубопроводов и резервуаров в осложненных условиях эксплуатации. Санкт- Петербург. 2009.- 410 с.
4. Коробков Г.Е., Султангареев Р.Х., Исмайлова Н.А. Выявление потенциально опасных участков на трубопроводах в активных геодинамических зонах. Транспорт и хранение нефтепродуктов и углеводородного сырья. 2009. № 1. С. 3-6.
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6. Шаммазов А.М., Зарипов Р.М., Чичелов В.А., Коробков Г.Е. Расчет и обеспечение прочности трубопроводов в сложных инженерно-геологических условиях. Том 1 Численное моделирование напряженно-деформированного состояния и устойчивости трубопроводов. Москва, 2005.- 706 с.
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8. Шаммазов А.М., Зарипов Р.М., Коробков Г.Е. Разработка метода расчета напряженно-деформированного состояния газопроводов, проложенных в сложных инженерно-геологических условиях Нефтегазовое дело. 2004. № 2. С. 119-128.
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