Machines and Apparatuses of Chemical Plants. Machines and Apparatuses of Oil and Gas Industry
DEVELOPMENT OF RECOMMENDATIONS ON THE APPLICATION OF LOCALLY STRENGTHENED VESSEL’S CONNECTING PIPES WITH ENFORCEMENT RIBS
The operational safety of oil and gas chemical facilities depends on the resource of each particular component part of the equipment, that are used in technological process. One of the most urgent tasks for today is to identify potentially dangerous places in the facility and work on forecasting the resource of safe operation and reducing the probability of sudden destruction.
One of these places is welded vessel’s connecting pipes, which, due to different deformation capacity of its parts, causes a concentration of additional stresses and requires special attention in the design and manufacture of apparatus.
In this paper authors consider on the main way to reinforce the hole – the using of reinforcing rings, the advantages and disadvantages of using reinforcing rings are also indicated. The analysis of frequently used pressure vessels hole reinforcing methods showed, that complexities in the design and installation of reinforcing rings are in assembly technology, discovery of weld defects and detection of the defects location.
The possibility of using of locally strengthened vessel’s connecting pipes with enforcement rib is shown in this work, also this units in some cases may be used as an alternative to reinforcing rings, as they are more processible in the manufacture, repair and inspection. The calculations showed that the using of two enforcement ribs oriented along vessel’s generating line for hole reinforcing allows to reduce the level of stresses in the area of welded vessel’s connecting pipes. But the experiments showed that in conditions of cyclic loading the using of locally strengthened vessel’s connecting pipes with enforcement ribs, which are oriented along vessel’s generating line, is not recommended.
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 existing technology of sheet assembling by the method of belt building provides for assembly and welding of the first three belts and their subsequent welding to the edge sheets of the tank. It is assumed that the pressure created by the weight of the three belts will lead to a close fit of the wall and the edge sheets: the gap between them will lie within the allowed limits (0-1 mm).
The analysis of the technology of manufacturing this unit on a real object showed the presence of significant deviations of the assembled rim weld from the regulated values in the wall – edge sheets connection. Also, the deformation (rise) of the margin is revealed due to the influence of residual welding stresses. Both of these defects affect the fatigue life of the welded tank structure.
Authors are invited to use reverse bend of edge sheets, in order to avoid overestimated clearances, as well as compensation of welding stresses and deformations. The analysis carried out using numerical methods of solutions confirmed this possibility.
As a result of practical studies, it has been established that in reservoirs with a volume of up to 10 000 m3, to compensate for welding deformation of the edge, as well as to reduce the gap in the wall – edge sheets joint, it is necessary to reverse the bend of the edge sheet with a maximum value of 3 mm. It is also possible to maintain a back bend up to 1 mm. In this case, the tensile stresses arising from the operation of the reservoir will be compensated by compressive stresses.
During the long-term storage there is a gradual flooding of the fuel oil and the accumulation of mechanical impurities of different nature. Carbenes, karboids and surface-active substances contained in the fuel oil lead to the formation of coarse agglomerates of tarry asphaltene substances which are precipitated. Also polymerization of hydrocarbon components and oxidation ofnon-hydrocarbon ones of the fuel oil cause it.
For cleaning fuel oil from mechanical impurities they use different designs of filters with modes of self-regeneration such as cleaning with the flow reversal of the purified liquid through the mesh, cleaning the mesh with brushes; the scanning method of cleaning.
Existing filter designs are characterized by a low degree of purification of the surface of the filter element, the removed sediment is contaminated by the fuel oil. There is contamination of the filter septum byslurry remnants after its regeneration, resulting in gradually decreasing the free area of the filter septum. For its cleaning they require shutting down the technological equipment and services of personnel to replace the filtering septum that also reduces the productivity of the production line.
The developed design of the drainage filter allows to effectively clean the filter element from mechanical impurities. During the regeneration the mesh drain filter provided for the displacement of fuel oil from the filter and steaming sediment by water vapor as well as blowing sediment into the drainage line.
The filter design allows to increase the cell size of the filter element in the regeneration mode, which facilitates efficient cleaning the mesh element.
The filter design allows to eliminate manual labor and to minimize the loss of time associated with performing maintenance operations of the filter.
The method of calculation of the technical characteristics of the filter septum in various modes of filter operation is given.
This article is devoted to the study of fluid flow in the shellside of shell-and-tube heat exchanger.
Heat transfer in shell-and-tube heat exchangers is a complex process depending on many factors: the fluid properties, the geometric parameters of the flow region, the quality of the heat transfer surface caused by physical properties, surface roughness and fouling rate
Selection of the optimum ratio of geometrical parameters in order to achieve maximum energy efficiency of the heat exchanger must be based on the study of thermal and hydraulic characteristics of the flow.
The most effective method for studying hydrodynamic and heat transfer processes is now the method of computational fluid dynamics implemented in finite element analysis systems. Advantages of CFD is the high speed of calculation, the accuracy and completeness of the result data, which gives an understanding of distribution and flow rates in the apparatus, pressure drop of the interior space as a whole and its individual regions.
The article describes a finite element model of the heat exchanger. Model consists of three domains (tubeside, metal pipe, shell-side) and the domain interfaces.
The simulation results give a complete picture of the distribution of of thermal and hydraulic parameters. Of particular interest is the flow in the shell-side, that has a more complex configuration. Simulation allowed us to estimate the distribution of the fluid flow, to determine the qualitative and quantitative characteristics of the influence of gaps and baffle spacing.
The efficiency of heat transfer in STHE can be increased by restricting dead zones formed near the cross baffles. For this purpose, еру use of the additional baffles, promoting more uniform flow distribution is offered. The results of investigations of the additional baffles influence on efficiency of heat transfer in shellside were carried out in this article.
An analysis of technological peculiarities of execution repair-welding under internal pressure pumped Wednesday for manual arc and semi-automatic welding in protective gas Wednesday.
It is shown that when repair-regenerative welding metal pipeline wall various injuries under internal pressure working Wednesday formed favorable conditions for the formation of high-quality and reliable welds.
Found that when repairing welding electrodes austenite intense pipes from heat-resistant steel 15X5M martensite class comes increased resistance to brittle fracture, the values of which are almost at the level of indicators of base metal and substantially higher than when performing welding operations without pressure.
Metal welding seam under internal pressure in the vessel, has a more homogeneous austenitic-dispersed ferrite structure compared to the seam, made without pressure.
About suture structure of zones is fine-grained equilibrium bejnit structure with distributed relatively evenly dispersed source carbides.
There are virtually no plots overheating martensite acicular nature, hardening and decreases the level of residual welding stresses in dissimilar repair welded connection.
Marked changes in structural-mechanical heterogeneity at welded up intense damage pipes under internal pressure had a beneficial effect on strength and plastic properties have led to increased resistance to cold cracks and brittle fracture after repair-regenerative welding.