Transportation, storage, pipelines
In this paper, topical issues of increasing the service life of a rim weld of a steel vertical tank are considered. As shown by numerous studies, the durability of this node largely depends on the accuracy of its manufacture.
The design feature of the unit is the presence of a structural gap between the wall and the edge, which should be within 0-2 mm. The experience of installing the tanks shows that it is not always possible to withstand the necessary clearance. The measurements made on real objects show that the length of such sections reaches up to 7 % of the total area of contact between the wall and the edge.
Analysis of the stressed-deformed state of the rim weld of the vertical steel tank, in the manufacturing of which, due to inaccuracy of the assembly, arises an enlargement of the gap between the wall and the edge showed, that the service life of the rim weld decreases.
Also, the current method is analyzed – raising the edge and the subsequent execution of the rim weld, as a result of which, in the process of loading the tank with the product, the stresses in the zone of thermal influence of the rim weld increase, which can negatively affect the resource of the unit.
To reduce the stress level at the interface between the wall and the edge sheets, the authors propose to make a unit with an overestimated gap with the use of heat treatment operations or vibration treatment of the welded joint during the welding process.
Due to the large dimensions of the tanks, the operation of heat treatment is quite energy-consuming. Therefore, from this point of view, it is more preferable to use a vibrating method for removing residual stresses, which will not only reduce the residual welding stresses, but also increase the strength of the welded joint.
In the oil fields, pipeline networks are used to transport liquid from well clusters to collection points. Oil-gathering pipelines are operated in complicated conditions characterized by high acidity and water-cut oil. A transported liquid containing a large number of reactive components causes intense corrosion of the pipelines leading to emergency rushes, and there is considerable economic damage and environmental damage to the environment.
In the article, based on statistical data, the analysis of the pores of oil gathering pipeline pipelines of one of the Tyumen region deposits was carried out. The territorial location of defects on the terrain is considered, local zones with increased accidents are identified. Based on the results obtained, an original method for visualizing emergency areas in the form of three-dimensional surfaces is proposed.
The reasons for the intensive corrosion of pipelines in local areas of increased accident rate are identified, which are associated with the accumulation of liquid in the lower pipe generatrix. A method for preventive prevention of high corrosion of pipelines in areas of fluid accumulation by the construction of inserts of smaller diameter than the main pipeline is sufficient to ensure the rate of removal of accumulations of liquid from “potentially dangerous” sections of pipelines.
In order to ensure the operative localization of the gust site, it is proposed to reserve sections of pipelines with a high probability of formation of fluid accumulations. To restore the efficiency of emergency pipelines, an effective method is to repair the existing damaged pipes using the “pipe-in-pipe” method. When sanitizing the old pipeline is not dismantled, at the same time, its service life increases several times. Polyethylene pipes have low frictional losses, therefore, a reduction in the capacity of the pipeline, as a rule, does not occur.
The article deals with reliability assessment of gas pumping units of the gas pumping system of Russia by the GTC-10 as example. The park structure of gas pumping unit types is presented. It is shown that the aggregates of this type are of the very large group of gas pumping equipment.
It has been established that a significant part of gas pumping units is worn-out. About 8% of GPA worked more than 100 thousand hours, 45% – 50÷100 thousand hours. By the example of one of the subsidiaries of PJSC “Gazprom” the analysis of quantitative indicators MTBF GTC-10 are done. The empirical reliability function, the density of developments units to failure after major repairs distribution, the failure rate are built.
According to the renovated GPA parameter “the failures distribution density” the kind of the distribution law is determined. It is shown that it is the law of the Weibull distribution.
Analysis of statistical data on the operation of gas pumping units showed that the entire life cycle of work can be divided into three characteristic regions – running, normal operation, the period of wear and aging. For each time period, the Weibull distribution parameters are defined and presented in tabular form.
In the end of the article the conclusions about an increased failure rate of GPA at the equipment running and aging steps are done. The identification of patterns is recommended to be taken into account when planning repairs, vibration surveys and findings of gas pumping units in reserve.
THE LIQUEFIED HYDROCARBONS EVAPORATION MATHEMATICAL MODELING AT THE REZERVOIR THERMAL INSULATION DAMAGE
The paper deals with insulated tanks of liquefied gas operation under normal conditions and in violation of the thermal insulation.
It is shown that the most widely used for double-walled tanks as an insulating material the pearlite filling is used. Over time, the operation undergoes pearlite precipitation, which leads to distortion of insulating performance of the entire system. The resulting voids increase the heat leakage to the tank and accelerates the evaporation process, which inevitably forces the refrigeration compressors working to work with overdrive. The greater the void area formed by precipitation in the heat insulation, the higher the probability of an emergency.
In order to develop a mathematical model of the thermal contact with the vessel environment is made up of the heat transfer interconnected system of equations through the bottom, a side wall, roof and mass transfer equation. The approximation methods for solving differential equations and models built on these thermal processes isothermal storage are analyzed.
A mathematical model to estimate the heat transfer coefficient at draft pearlite by up to 38% of the height of the inner tank is created. The value of the additional heat input, depending on the climatic conditions of the region is established. The analytical ratio to determine the additional evaporation from the surface of the liquid gas in the tank on the depth of precipitated thermal insulation is developed. A comparison with the standard indicators is done.
One of the priority directions of scientific and technical PJSC “Gazprom” is to improve the technology gas trunkline by finding and developing new ways to get added value of natural gas saving.
To maintain the efficiency of gas mains to carry out spot repairs on the results of in-line inspection. In recent years, in PJSC “Gazprom” a significant rate being diagnostics and repair of trunk pipelines.
During repair work on gas pipelines is a very urgent problem of rational use of the gas pipeline section to be disconnected. In general, according to official statistics, emissions of road works 75% of total emissions by the PJSC “Gazprom”.
Development of gas to gas-compressor units are always justified in referring to providing pumping large volumes of gas availability possible the widespread use of this method without additional variable operating costs. The lower the pressure at the outlet the compressor station, the more will reduce the gas pressure shut down for repair of the gas pipeline and therefore achieve the greatest depth of the development of gaz. It should take into account the operating conditions of an opportunity of stable work of gas pumping units in unsteady regime that is in the fall of the inlet pressure to the minimum allowable value of creating the lowest possible outlet pressure gas compressor units.
In this, based on experimental data solved the complex problem of the development of gas and two heterogeneous working “in parallel” aggregates and reduce the emission of methane into the atmosphere.