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Fracture-cavity carbonate reservoirs provide a large area, fracture development, high productivity, long stable production time, and other characteristics. However, after long-term exploitation, the lack of energy in the formation leads to a rapid decrease in production, and the water content in crude oil steadily increases, thereby disrupting normal production. To recover normal production, it is necessary to connect the cracks and pores that have not been affected during the original production, so as to allow the crude oil inside to enter the production cracks and replenish energy through methods such as hydraulic expansion of fracture-cavity carbonate rock. Accordingly, we propose hydraulic expansion techniques based on the following four processes for implementation: (1) applying high pressure to prevent a nearby fracture network from opening the seam, (2) connecting a distant fracture-cavity body, (3) breaking through the clay filling section of a natural fracture network, and (4) constructing an injection production well pattern for accelerating injection and producing diversion. Hydraulic fracturing involves closing or partially closing the original high-permeability channels, which usually produce a large amount of water, while opening previously unaffected areas through high pressure to increase crude oil production. We also introduce two composite techniques: (1) temporary plugging of the main deep fractures, followed by hydraulic expansion; and (2) capacity expansion and acidification/pressure processes. Hydraulic expansion allowed us to recover and supplement the formation energy and efficiently increase production. We tested various wells, achieving an effective hydraulic expansion rate of up to 85%. In addition, the productivity of conventional water injection and hydraulic expansion after on-site construction was compared for one well, clearly indicating the effectiveness of water injection and the remarkable crude oil increase after hydraulic expansion. [ABSTRACT FROM AUTHOR]

Fracture-cavity carbonate reservoirs provide a large area, fracture development, high productivity, long stable production time, and other characteristics. However, after long-term exploitation, the lack of energy in the formation leads to a rapid decrease in production, and the water content in crude oil steadily increases, thereby disrupting normal production. To recover normal production, it is necessary to connect the cracks and pores that have not been affected during the original production, so as to allow the crude oil inside to enter the production cracks and replenish energy through methods such as hydraulic expansion of fracture-cavity carbonate rock. Accordingly, we propose hydraulic expansion techniques based on the following four processes for implementation: (1) applying high pressure to prevent a nearby fracture network from opening the seam, (2) connecting a distant fracture-cavity body, (3) breaking through the clay filling section of a natural fracture network, and (4) constructing an injection production well pattern for accelerating injection and producing diversion. Hydraulic fracturing involves closing or partially closing the original high-permeability channels, which usually produce a large amount of water, while opening previously unaffected areas through high pressure to increase crude oil production. We also introduce two composite techniques: (1) temporary plugging of the main deep fractures, followed by hydraulic expansion; and (2) capacity expansion and acidification/pressure processes. Hydraulic expansion allowed us to recover and supplement the formation energy and efficiently increase production. We tested various wells, achieving an effective hydraulic expansion rate of up to 85%. In addition, the productivity of conventional water injection and hydraulic expansion after on-site construction was compared for one well, clearly indicating the effectiveness of water injection and the remarkable crude oil increase after hydraulic expansion.

Abstract Hydroformed parts are widely used in industrial automotive parts because of their higher stiffness and fatigue strength and reduced weight relative to their corresponding cast and welded parts. This paper reports a hydraulic-forming experimental platform for rectangular tube fittings that was constructed to conduct an experiment on the hydraulic forming of rectangular tube fittings. A finite element model was established on the basis of the fluid–solid coupling method and simulation analysis. The correctness of the simulation analysis and the feasibility of the fluid–solid coupling method for hydraulic forming simulation analysis were verified by comparing the experimental results with the simulation results. On the basis of the simulation analysis of the hydraulic process of the torsion beam using the fluid–solid coupling method, a sliding mold suitable for the hydroforming of torsion beams was designed for its structural characteristics. The effects of fluid characteristics, shaping pressure, axial feed rate, and friction coefficient on the wall thicknesses of torsions beams during formation were investigated. Fluid movement speed was related to tube deformation. Shaping pressure had a significant effect on rounded corners and straight edges. The axial feed speed was increased, and the uneven distribution of wall thicknesses was effectively improved. Although the friction coefficient had a nonsignificant effect on the wall thickness of the ladder-shaped region, it had a significant influence on a large deformation of wall thickness in the V-shaped area. In this paper, a method of fluid-solid coupling simulation analysis and sliding die is proposed to study the high pressure forming law in torsion beam.

Hydroformed parts are widely used in industrial automotive parts because of their higher stiffness and fatigue strength and reduced weight relative to their corresponding cast and welded parts. This paper reports a hydraulic-forming experimental platform for rectangular tube fittings that was constructed to conduct an experiment on the hydraulic forming of rectangular tube fittings. A finite element model was established on the basis of the fluid–solid coupling method and simulation analysis. The correctness of the simulation analysis and the feasibility of the fluid–solid coupling method for hydraulic forming simulation analysis were verified by comparing the experimental results with the simulation results. On the basis of the simulation analysis of the hydraulic process of the torsion beam using the fluid–solid coupling method, a sliding mold suitable for the hydroforming of torsion beams was designed for its structural characteristics. The effects of fluid characteristics, shaping pressure, axial feed rate, and friction coefficient on the wall thicknesses of torsions beams during formation were investigated. Fluid movement speed was related to tube deformation. Shaping pressure had a significant effect on rounded corners and straight edges. The axial feed speed was increased, and the uneven distribution of wall thicknesses was effectively improved. Although the friction coefficient had a nonsignificant effect on the wall thickness of the ladder-shaped region, it had a significant influence on a large deformation of wall thickness in the V-shaped area. In this paper, a method of fluid-solid coupling simulation analysis and sliding die is proposed to study the high pressure forming law in torsion beam. [ABSTRACT FROM AUTHOR]

The design of hydro-bulge molds, able to provide hollow parts with special-shaped cross-sections, is still a pretty complicated task (especially for what concerns the design of the related hydraulic system and its “synchronization”). In the present work, this task is addressed through the introduction of a new type of overhead cylinder hydraulic synchronization system, able to correct automatically any deviation from the optimal process. Using the AMESim software, the displacement synchronization curve of the piston rods of the two cylinders is obtained and it is verified that the system is able to implement an automatic deviation correction function by adjusting the bidirectional servo valve. A mathematical model for the synchronization system is presented, and the transfer function of the closed-loop control system is determined accordingly. The results show that the system response is generated at about 0.1∼0.2 s with the system reaching an equilibrium state at about 0.2 s. [ABSTRACT FROM AUTHOR]

As a high expansion strength corresponds to a high heat transfer efficiency, this study investigated the expansion strength of an air-conditioning heat exchanger jointed by hydraulic expansion. A device that would be reliable and adaptable to different types of tubes and fins was designed and developed for testing hydraulic expansion. The device was used to perform a non-pulsating hydraulic expansion experiment on samples comprising tubes and fins to determine the hydraulic pressure range. The expansion strength was tested by performing tensile tests to evaluate the pull-out force at different bulging zones of the same sample with the selected hydraulic pressure. A series of pulsating hydraulic expansion experiments were performed on the joints of tubes and fins with different pulsating amplitudes and frequencies. Tensile tests were performed on the pulsating hydraulic expansion samples to study the influence of the pulsation parameters on the pull-out force. When the amplitude was fixed, an increase in frequency led to uniform expansion in the exchanger. This indicates that joint expansion in tubes and fins results in a more reliable heat exchanger performance. [ABSTRACT FROM AUTHOR]

In this paper, the process of hydraulic expansion of a pipe by fluid pressure in the operation of fixing heat exchange pipes in a tube sheet is considered. The features of plastic deformation of a pipe of sufficient thickness and loading conditions are distinguished. A digital model of the pipe hydraulic expansion process is proposed, and the technology for creating a permanent joint with an interference fit is modeled. The calculated oscillograms of the process are obtained. A feature of the increase in high (up to 500 MPa) pressure in a liquid is considered in detail. The residual contact stress and interference in the joint are determined. A comparative analysis of the obtained calculated data with experimental data was carried out and showed a good convergence of the results. [ABSTRACT FROM AUTHOR]

As a high expansion strength corresponds to a high heat transfer efficiency, this study investigated the expansion strength of an air-conditioning heat exchanger jointed by hydraulic expansion. A device that would be reliable and adaptable to different types of tubes and fins was designed and developed for testing hydraulic expansion. The device was used to perform a non-pulsating hydraulic expansion experiment on samples comprising tubes and fins to determine the hydraulic pressure range. The expansion strength was tested by performing tensile tests to evaluate the pull-out force at different bulging zones of the same sample with the selected hydraulic pressure. A series of pulsating hydraulic expansion experiments were performed on the joints of tubes and fins with different pulsating amplitudes and frequencies. Tensile tests were performed on the pulsating hydraulic expansion samples to study the influence of the pulsation parameters on the pull-out force. When the amplitude was fixed, an increase in frequency led to uniform expansion in the exchanger. This indicates that joint expansion in tubes and fins results in a more reliable heat exchanger performance.

Background Chronic kidney disease has become a serious public health problem in China. Our study is to explore effect of hydraulic expansion on arteriovenous fistula (AVF) of hemodialysis patients. Methods A total of 190 patients with end-stage renal disease (ESRD) were randomly divided into hydraulic expansion group (n = 117) and conventional surgery group (n = 73). Age, sex, the cause of ESRD, height, weight, body mass index (BMI), blood pressure, and diameter of artery and vein from ultrasonography before surgery from patients were recorded. Doppler ultrasonography of vessel was performed with a 12-MHz scanning probe for vascular measurements. The time of first cannulation was recorded. Primary and secondary patency rates were compared between the two groups. Results The mean arterial pressure for this cohort of patients was around 98.12 mm Hg. The mean diameters of artery and vein ready for anastomoses measured by ultrasonography before surgery were 1.96 and 2.04 mm, respectively. Age, weight, BMI, sex ratio, the cause of renal failure, history of catheter insertion, mean arterial pressure, frequency of hemodialysis, blood flow of hemodialysis, and the mode of anastomoses of AVF in conventional surgery group were similar to hydraulic expansion group. There were no differences in stroke volume of radius arterial and venous pressure before dilation between the two groups. The stroke volume of radius artery increased significantly after hydraulic expansion than before dilation and control group. The primary patency rates of AVF in patients with hydraulic expansion were higher significantly than conventional surgery group. The secondary patency rates in conventional surgery group were not different from hydraulic expansion group. Conclusion Hydraulic expansion showed no difference from conventional surgery in complication after operation, and could decrease the time reliance on catheters and the risk of catheter-related infection, thrombosis, and decrease the related medical care costs. [ABSTRACT FROM AUTHOR]

Heat exchangers, steam generators and condensers often fail due to improper tube-to-tubesheet joint expansion. Among the multiple parameters affecting the residual contact pressure is the tube expansion order as adjacent tube expansion alters the central tube residual stress field. The expansion of adjacent tubes decreases the contact pressure of the central tube. Hence the none-optimized residual stresses and contact pressure achieved by trial and error during the expansion process make the joint vulnerable and prone to leakage failure. This study analyses the elasto-plastic behaviour of a central tube when the surrounding tubes are subjected to hydraulic expansion in turns in a simulated tube-to-tubesheet joint assembly using the numerical FEM. Neighbouring tube expansion, expansion order sequence and ligament efficiency are found to have a major influence on the residual contact pressure. Such a study provides general guidelines on how to control the expansion process and help optimize the residual contact pressure. [ABSTRACT FROM AUTHOR]

The mechanism of failure of heat exchanger and steam generator tube-to-tubesheet joints is related to the level of residual stresses produced in the tube expansion and transition zones during the expansion process and their variation during operation. The accurate prediction of these stresses based on the plastic and creep properties of the joint materials involved can help to design for better leak tightness and strength. Existing design calculations are based on an elastic perfectly plastic behavior of the expansion joint materials and do not account for creep. The proposed model is based on a linear strain hardening material behavior and considers the joint contact pressure relaxation with time. The interaction of the tube and the tubesheet is simulated during the process of the application of the expansion pressure and operation. The effects of the gap, material strain hardening and creep properties are to be emphasized. The developed model results are validated and confronted against the more accurate numerical FEA models.

• It is the first time to systematically study and explore the failure cases of the accidental fracture of the hydraulic expansion mandrel of the tubesheet O-ring of the nuclear steam generator. • The stress corrosion behavior of the internal bulge defect on the inner wall of the heat transfer tube, which was caused by the fracture of the hydraulic expansion mandrel of the O-ring, was studied. • Characteristic zones of the fatigue fracture morphology were observed from the fracture area. The morphology could be divided into the fatigue source zone, the extension zone with brittle fracture and the transient fracture zone with plastic fracture. • The achievements of this paper could provide theoretical and practical support for preventing similar failure and ensuring the expansion quality of the steam generator tubes for nuclear power plants. Hydraulic expansion is commonly adopted for the tube to tubesheet expansion in the steam generator of nuclear power plants, and its quality greatly influences the stable and reliable operation of the steam generator. In this paper, an unexpected fracture of the hydraulic expansion mandrel occurred during the hydraulic expansion process, which caused the internal bulge defect (IBD) in the expanding area of the heat exchange tube. The corrosion test results showed that the IBD area had higher susceptibility to stress corrosion cracking (SCC) than the original tubes, which might lead to premature failure of the heat exchange tube in practical operation. To find out the root causes of this failure, the fracture morphologies of the hydraulic expansion mandrel were observed under the optical microscope (OM) and the scanning electron microscope (SEM), and the stress distribution during service were analyzed by mechanical calculation, The results indicated that the hydraulic expansion mandrel was repeatedly loaded by high-pressure medium during service, thus its weakest point was fractured due to high strain level and low cyclic number inelastic strain fatigue. Based on the results, the underlying mechanisms were discussed, and the countermeasures were proposed. The achievements of this paper provide theoretical and practical support for preventing similar failure and ensuring the expansion quality of the steam generator tubes for nuclear power plants. [ABSTRACT FROM AUTHOR]

In this paper, the hydraulically expanded tube-to-tube sheet joints for shell-and-tube heat exchangers made of three sets of commonly used tube and tunesheet materials i.e. 10# for tube and 16Mn for tubesheet, S30408 stainless steel for both tube and tubesheet, and S32168 stainless steel for the both were experimentally studied with the concentration on the relations between the tube expanding percentage, expansion pressure, pull-out force and push-out force. The tube expanding percentages within the ranges of expanding pressure from 160 MPa to 300 MPa for different materials joints were obtained. Both pull-out and push-out tests were carried out for each joint. Results show that the tube expanding percentage almost increases linearly with increasing the expansion pressures. Pull-out force is less than the push-out force and both of them increase with increasing expansion pressures. However unlimited increase of the tube expanding percentage cannot always enhance the pull-out strength of the joints because of “over-expansion”. Finally, to facilitate the application, the relationships between the tube expanding percentage and expanding pressure are given, and also provided are the equations of the relationship between the pull-out force and the tube expanding percentage. [ABSTRACT FROM AUTHOR]

This article presents research work on the influence of the design characteristics of the joint partner elements and especially of grooving and pocketing on the tensile and torsional strength of tubular joints produced by hydraulic expansion when tubes are made of aluminum EN AW-6060. In general, joining of tubular elements can be performed by different methods, but internal expansion presents an interesting alternative to other methods like welding and mechanical forming processes. Commonly, hydraulic expansion is used for the manufacturing of heat exchangers. As a result, time effective and resistant joints must be produced in particular when applying hydraulic expansion in the manufacturing of lightweight structures. [ABSTRACT FROM AUTHOR]

Abstract: The cold hydraulic expansion of two concentric tubulars is analysed with emphasis on the applications to oil and gas casings. Theories of elasticity and plasticity are used to develop a model relating the hydraulic pressure, the geometric dimensions of the tubulars and the residual contact pressure between the pipes. Nonlinear finite element analysis is used to validate the theoretical results and to investigate the effects of end support conditions. Hydraulic expansion experiments are conducted on tubulars and the measured evolution of the deformation and residual contact pressure are compared with the corresponding theoretical predictions and finite element solutions. There is a good agreement between the experimental results and predictions from the theoretical analysis and numerical simulations. The implications of the results for the design of casing hangers and patch repairs of oil and gas tubulars are discussed. [Copyright &y& Elsevier]

Abstract: Safety in nuclear power plants is one of the main problems in design. Steam generator reliability and performance are serious concerns in the operation of pressurized water reactors. Evidence shows that in the cold collector where tubes are connected to it probability of cracking exists. In this research stress distribution in the collector body at different operation condition of WWER-1000 nuclear power plant was analyzed and the collector stability has been investigated by analytical fracture mechanics and finite element method evaluations. Results show that the stresses in the collector body are in the elastic range and the stress intensity factors are lower than critical values. The analytical calculation shows the stability of semi-elliptical cracks near to expansion region of collector body during operation. [Copyright &y& Elsevier]

Carbon steel pipe lined with a thin layer of a corrosion resistant alloy is an economical product used in offshore pipelines that carry corrosive hydrocarbons. The liner and carrier pipe are mechanically expanded together so that on unloading they end up in interference contact. The contact pressure that develops is essential for keeping the composite pipeline intact under bending and axial loads experienced during offshore installation and operation. The manufacture of lined pipe by hydraulic expansion is analyzed with a custom model, which is used to establish the effect of various geometric, material, and manufacturing parameters on the contact pressure. The analysis incorporates incremental plasticity that accounts for material hardening and the biaxial states of stress that develop. It is demonstrated that plastification of the carrier pipe is beneficial, and that a relatively low yield stress liner with low hardening, coupled with a high yield stress high hardening carrier pipe increases the contact pressure. The analysis presented and the results should prove to be useful in the design of the manufacturing process of lined pipe aimed for offshore applications. [ABSTRACT FROM AUTHOR]