Удосконалення методу технічної діагностики нафтогазопроводів

Abstract

Дисертація присвячена питанню удосконалення методів технічної діаг ностики нафтогазопроводів. Досліджено та обгрунтовано можливість і доцільність використання показника ударної в’язкості для визначення фактичного технічного стану нафтогазопроводів та розрахунку його залишкового ресурсу. Розроблено новий графоаналітичний метод розрахунку залишкового ресурсу, який полягас у визначенні напруження руйнування дефекту з урахуванням зниження ударної в’язкості металу ділянки трубопроводу. Встановлено наявність та характер залежності між вимірюваними параметрами (твердість та частота електромагнітних коливань) і фактичними значеннями ударної в’язкості матеріалу трубопроводу. На основі встановлених залежностей розроблено новий неруйнівний метод визначення ударної в’язкості матеріалу, який дає можливість розширити кількість вимірюваних інформативних параметрів, що характеризують фактичний напрями реалізації запропонованого методу шляхом розроблення експериментального зразка інформаційно вимірювальної системи для визначення ударної в’язкості матеріалу трубопроводу.

Диссертация посвящена вопросу усовершенствования методов технической диагностики нефтегазопроводов. Исследована и обоснована возможность и целесообразность использования показателя ударной вязкости для определения фактического технического состояния нефтегазопроводов и расчета его остаточного ресурса. Разработан новый графоаналитический метод расчета остаточного ресурса, который заключается в определении напряжения разрушения дефекта с учетом снижения ударной вязкости металла участка трубопровода. Установлено наличие и характер зависимости между измеряемыми параметрами (жесткость и частота электромагнитных колебаний) и фактическими значениями ударной вязкости материала трубопровода. На основании установленных зависимостей разработан новый неразрушающий метод определения ударной вязкости материала, позволяющий расширить количество измеряемых информативных параметров, характеризующих фактическое техническое состояние металлоконструкций долговременной эксплуатации. Определены пути реализации предложенного метода путем разработки экспериментального образца информационно измерительной системы для определения ударной вязкости материала трубопровода.

Dissertation is devoted to the problem of improvement of technical diagnostics method of oil and gas pipelines. It is investigated and substantiated the possibility and feasibility of impact strength parameter to determine the actual technical state of pipelines and assess its remaining life. A lot of experimental studies of Ukrainian and foreign scientists showed a significant change of metal’s impact strength for long term operation. It is determined that thus change is characterized by two intervals - at the first interval the impact strength varies little (10-15 years of operation), the second - is more significant declines. The transition between the first and second intervals in most cases depends on the material, operation conditions and therefore is an individual for a particular pipeline. A descriptive physical model of the effect of metal’s impact strength changes on the pipeline’s actual technical state is developed. This model is based on several factors, namely the reduction of impact strength due to aging, fracture toughness reduction and increasing the ductile-to-brittle transition temperature to a range of operating temperatures. Causes of metal aging lie in structural changes, related primarily to the dynamics of dislocation structure, decomposition cementite component, the redistribution of carbon and nitrogen atoms, microstrains accumulation, increasing of internal stresses in the metal structure. The aging process conditions depend on the structural parameters of material, operating temperature and stress level in the pipe wall. The main problem of this metal is increasing its sensitivity to stress concentrators and defects and to the formation of the metal destruction locations. Based on experimental data and graphical dependencies and given the main provisions of the model, under which, the actual technical state of the pipeline is determined by the number of factors, the function for describing the remaining life of pipeline is proposed. This function represents the general principle of technical state evaluation and remaining life assessment considering the metal’s impact strength change. The developed model allows proposing a new grapho-analytical method for calculating the remaining life of pipelines with a defect. The principle of the new method is to calculate stress, in which the pipe defect will failure. The index of impact strength change over the operation time is inputted in the famous equation NG-18. By the new grapho-analytical method it is possible to determine the time at which defect failure stress (determined using equation NG-18 considering impact strength reduction over operation time) will reach the actual stress of pipe wall. Validation of the method was carried out at crude data from the pipeline with lower impact strength and corrosion. In order to develop a new method for evaluation the actual technical state of gas pipelines considering impact strength reduction the approach based on the management of several informative parameters is developed. The relationships with mechanical characteristics are established for these informative parameters. The complex of experimental investigations was carried out to establish the existence and form of the relationship between the measurable parameters (hardness, coercive force and electromagnetic oscillations frequency of inductive transducer) and the actual values of impact strength of the pipeline material. In order to establish an optimal set of parameters for control and approximation of impact strength as a function of measurable parameters, which helped get its analytical and graphic form, the modem methods of data processing (artificial neural network) was improved and used. On the basis of the dependencies a new non-destructive method for determining the impact strength of the material was developed. This method expands the number of informative measurable parameters that characterize the actual state of long-term operation metalware. To increase the information content of the developed non-destructive method and its applicability for pipe steels the additional tests for impact strength determining were carried out. Samples temperature was around 0 degrees Celsius. Samples were with the V-notch. There was an investigation for the choice of optimal frequency of inductive transducer electromagnetic oscillations. For this purpose the experimental unit was developed. It allows measuring the frequency of electromagnetic oscillations (informative parameter I) with high accuracy. Optimal frequency of electromagnetic oscillations (25 kHz) was chosen as a result of correlation analysis between impact strength and informative parameter values measured at different frequencies. The development of experimental sample of information and measuring system is one of the ways for work results implementation. Work results were approved within the contract of Ivano-Frankivsk National Technical University of Oil and Gas with Main Pipeline Department "Donbastransgas" under the conditions of Novopskov Local Gas Transmission Facility. In particular, it was carried out successful industrial tests of information measuring system. The decreasing of pipeline material impact strength was discovered by non-destructive method. The remaining life of the pipeline considering impact strength change was calculated based on the obtained data. It is recommended to include developed grapho-analytical method in the procedure of safe operation life extension that is laid out in the draft international standard ISO 13623 Petroleum and natural gas industries - Pipeline transportation systems. Recommendations are sent to the ISO Technical Committee 67 “Materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries: In addition, thesis materials were used by the development of Standard of Ukraine 60.3-30019801-067:2009 "Main gas pipelines. Assessment of the actual technical state of critical areas. Methods and techniques" (order by SC Ukrtransgas" № 126 from 27.04.2009) and implemented in the educational process of Syrian Gas Company specialists training (the act of implementation from 18.10.2009).