Since the beginning of this century,Chinese scientific and technical workers in the field of pres-sure vessels have solved many technical problems brought by production scale upsizing,harsh medium en-vironment and long-term safe operation of process industries,and established the technological methods of design,manufacturing and maintenance based on life-cycle risk control. Based on these achievements,the important pressure vessels in China are no longer depend on importation,and the failure rate per ten thou-sand sets of equipment is decreasing year by year. However,the problem of heavy-duty trend of pressure vessels due to scale upsizing of the process industry plants becomes increasingly prominent,which not only causes large material,energy and labor consumption,and makes processing and manufacturing difficult, but also there may exist certain safety risks. The lightweighting,green design and manufacturing of pres-sure vessels under the premise of ensuring their inherent safety,and the reduction of environmental pollu-tion caused by the failure of pressure vessels subjected to disasters,are two outstanding problems that need to be solved focally during China's "12^th Five-Year Plan" period. At the same time,in recent years,the rapid development of modern information technology,such as Internet of Things,big data etc. and artificial intelligence technology has brought unprecedented opportunities and challenges to the traditional technolo-gy of pressure vessels in China. Another important problem that Chinese pressure vessel technical workers began to explore and solve in the "12^th Five-Year Plan" period,is to deeply integrate with modern infor-mation and artificial intelligence technology so as to promote the development of Chinese pressure vessel technology toward the direction of digitalization,networking and intelligentization. This paper briefly re-views the progress of the green design,manufacturing and maintenance,network-based remote operation and maintenance technology of Chinese pressure vessels since the "12^th Five-Year Plan". In combination with the strategic requirements of " Made in China 2025",this paper also proposes some research sugges-tions during the "13^th Five-Year Plan" period and in the future,including the genome program of pressure vessel materials and additive manufacturing, network-based collaborative manufacturing and intelligent factory,intelligent operation and maintenance,etc.

GB/T 26978—2021 Design and Manufacture of Site Built, Vertical, Cylindrical, Flat-bottomed Steel Tanks for the Storage of Cryogenic Liquefied Gas is the fundamental national standard for the design and construction of cryogenic liquefied gas storage tanks in China.In order to facilitate domestic cryogenic storage tank industry builders to better understand the 2021 version of the standard, starting from the background and significance of the revision, the scope of application, design basis, metal components, concrete components, insulation components and experimental drying replacement cooling of GB/T 26978—2021 were comprehensively interpreted.The differences between the new version of the standard and the original version of the standard and other relevant specifications were compared, and the main changes to the standard in the revision were given, and the reasons and differences for the modifications were analyzed in order to better guide the design and construction of cryogenic liquefied gas storage tanks in China, and promote the implementation of this standard.

Use of hydrogen pipeline is one of the most efficient ways to transport hydrogen in a long distance. However,compared with the mature natural gas pipeline network,the construction of hydrogen pipelines is still relatively small. In recent years,the technology of converting natural gas pipeline into hydrogen pipeline has attracted extensive concern of researchers. The comparative analysis of hydrogen pipeline and natural gas pipeline was conducted in terms of construction status,specifications and standards, material selection,design and manufacture,accident consequences and safety distances,which can provide some references for the construction of hydrogen pipelines and the application of natural gas pipeline transformation technology.

The calculation method of tubesheets of floating-head heat exchanger in Appendix I of JB 4732—1995 did not consider the additional bending moment at cylinder edge, which needs to be improved.The modified calculation formula was given by derivation of the tubesheet calculation method, and the influence of the additional bending moment at the edge of the cylinder not included in JB 4732—1995 on the calculation results of three structures of tubesheet, namely b-type, c-type and d-type, was discussed and analyzed.The results show that the tubesheet calculation results without considering additional bending moment is unsafe under some loading conditions, so the calculation method in JB 4732—1995 needs to be improved.

Propellant tank is the key platform load for satellite and spacecraft propulsion subsystem to store propellant.In order to improve the overall performance of space propulsion system and single machine, and track the development trend abroad, domestic and foreign literature was investigated and analyzed.In view of the research and development technology of aerospace large composite tank, the key technical contents were described from the aspects of material selection, structural design, reliability design, manufacturing process, identification test and product standard.Propellant tank technology is an integrated technology of design, materials, process, test and other technologies.With the improvement of technical level, the comprehensive performance of propellant tank is also constantly improving.Space propellant tanks are developing towards composite structure, low temperature storage, light weight, high strength, high reliability, high safety, long life and strong environmental adaptability.

Steady-state crack growth mechanism and unstable fracture of ductile materials is an important research direction of the fracture mechanics field.In 1973,Anderson first introduced the Crack Tip Opening Angle (CTOA) as a fracture criterion to the finite element simulation of steady-state crack growth,and found that CTOA,as the fracture criterion,can simulate the steady-state crack growth behavior effectively and quantitatively.In the past 50 years,wide and in-depth investigations were carried out in the aspects of crack growth stability,influencing factors,tunneling effect,constraint effect and finite element simulation of fracture process related to CTOA,and relevant standards for CTOA determination were developed.The biggest advantage of CTOA as a fracture criterion lies in that it can accurately simulate the steady-state crack growth behavior of thin-walled structures by using two-dimensional and three-dimensional finite element analysis.It has been widely used in crack growth analysis of aircraft fuselage,complex thin-walled structures and long-distance pipelines.In this paper,the development,standardization and application of CTOA fracture criteria are briefly reviewed,the main problems existing in measurement and application of CTOA are pointed out,and future prospect is also presented.

The low-cycle fatigue tests must be used to evaluate the resistance of metallic materials to fatigue failure.The test standards for low-cycle fatigue of metallic materials have been established in China and foreign countries.By choosing typical standards for low-cycle fatigue tests such as ASTM E606-2012,GB/T 15248-2008,and with reference to GB/T 26077-2010,the differences and characteristics are summarized.It is found that there is little difference between GB/T 15248-2008 and GB/T 26077-2010 in terms of specimen requirements,equipment requirements,test procedure and test report.It is suggested to consider combination of the two standards to form a uniform fatigue test standard for axial strain control.

In order to address the shortage of a 3D two-phase thermal-hydraulic analytical program for secondary side of the steam generator in China's nuclear power plants,in this paper,UDF was adopted in the secondary development of CFD and a 3D two-phase thermal-hydraulic analytical program was successfully developed for secondary side of steam generator based on structural characteristics of the steam generator in pressurized water reactor nuclear power plants and the porous medium model in the large CFD software for commercial use.Based on modeling analysis,a test of the flow and heat transfer was performed in a small-scale tube bundle simulating the primary and secondary side flow field of the steam generator and data of the primary and secondary side flow field of the test body under testing conditions was obtained.Then analysis on the test article was made by building a model using the program developed herein.The results indicate that the program is able to simulate the test article of the steam generator and the predicted result is in good agreement with the measurement result,which proves the reliability of calculation results of this program.

High pressure heater is the important equipment used in back heating system of large thermal power units. Due to its high pressure and heavy weight,it usually needs to be designed by analysis to ensure its safety and economy. In this paper, a method of developing ANSYS-based visual automatic numerical analysis software using Visual Basic (VB) was proposed to solve the problem that the finite element analysis process of high pressure heater is very difficult and the professional requirements for analyzers are relatively high. The software automatically carries out establishment of the finite element model,stress analysis,ex-traction of analytical results and strength evaluation of high pressure heaters through the VB interface for structural design and op-erating parameter input of the high pressure heater in combination with APDL language in ANSYS. By taking a high pressure heat-er as an example,this paper introduced the function and use method of the software in detail. By entering the parameters of the heater into the software and carrying out automatic stress analysis,the purpose of automatic design was successfully achieved, which effectively improves the working efficiency of designers.

On-line monitoring and early warning of oil and gas pipelines is an important measure to ensure their long-term safe op-eration. This paper overviewed the current real-time early-warning technology of oil and gas pipelines based on monitoring data,in-cluding early-warning technology based on signal processing, early-warning technology based on time series and early-warning technology based on artificial intelligence. The common methods in various technologies and their development status were summa-rized and analyzed,and the problems existing in the application of oil and gas pipelines and their prospects were pointed out.

The steam generator (SG) is one of the important equipments of the nuclear power plant. By analyzing the operating per-formance,structural characteristics,form of expression of degradation and influencing factors of the steam generator and in combina-tion with domestic and foreign research achievements and operating experiences in the field of nuclear power,maintenance measures of the steam generator in service were proposed,including the management of water chemistry during power operation and secondary side sludge rinsing,internal components inspection,maintenance,etc. during refueling outage. The structural integrity of the steam generator was assessed to reduce the risk of SG tube damage and ensure the structural integrity of the steam generator.

The hydrogen barrier performance of the polymer liner material of Type Ⅳ hydrogen storage cylinders used for high-pressure hydrogen storage plays a crucial role in the quality of the cylinders.The polymer liner materials-polyethylene（PE） and polyamide（PA6）,were used as the research objects to conduct molecular dynamics simulations and Monte Carlo simulations of hydrogen transport processes in PE and PA6 to calculate the solubility coefficients, diffusion coefficients and gas permeability coefficients of hydrogen in polymeric materials.The feasibility of molecular dynamics simulation of the barrier properties of the materials was demonstrated by gas permeation experiments.The results show that the dissolution coefficient of gases of PE and PA materials decreases and the gas diffusion coefficient increases as the temperature increases from 288 K to 328 K at 0.1 MPa.And the gas permeability coefficient of the materials increases by 1.0% and 80.3%,respectively, due to the predominance of diffusion.The same trend as above is also obtained for the operating conditions of 41.6 MPa, 52 MPa and 60 MPa.In addition, it is found that graphene and organic montmorillonite modification can reduce the diffusion coefficient of gas in the material by simulation.

The retest,low-temperature toughness test and high-temperature property test had been done to research the properties of 00Cr14Ni14Si4(C4),and to compare the properties with those of S30403 and S31603. The weld ability test and welding procedure qualification for C4 austenitic stainless steel had been done to forecast and verify its weldability and welding performance. The corrosion resistance test had been done for C4,S30403 and S31603 to research their corrosion resistance properties in nitric acid. The understand and master of the properties of C4 goes a step further in its application in manufacturing,in consulting experiences from other manufacturers and in the special evaluation and assessment for material specified in the supervision regulation on safety technology for stationary pressure vessel. The feasibility of C4 passing technical review for new material and becoming a new applicable pressure vessel material in national material standard is discussed.

The transient dynamic analysis was used to analyze the dynamic impact resistance of double-layers metal bellows in ANSYS. The axial and radial load of the bellows were applied in the time domain by the dual sinusoidal wave process. According to finite element analysis, the impact response spectrum of acceleration and displacement of double-layer metal bellows were obtained. Then the impact test on the self-made drop hammer impact test machine was carried out by the prescribed pulse wave-form method,and the axial and radial impact response spectrum of bellows were obtained. The experimental results were basically in agreement with those of the finite element method analysis with the error below 5.5%. The accuracy of the finite element mod-els and the reliability of the numerical analysis were verified by the test method. The anti-impact analysis method and experimental method provide certain reference for anti-impact design of the double-layer bellows.

To investigate the effects of structural parameters and inlet Reynolds number on the performance of the asymmetric airfoil fin printed circuit heat exchanger（PCHE）,a three-dimensional numerical simulation based on computational fluid dynamics（CFD） was carried out, and the results were fitted to obtain the empirical criterion formulas of Nusselt number（Nu） with deviation less than 10% and friction factor（f） with deviation less than 13%.Then, a one-dimensional analysis method was used to calculate the volume, heat transfer rate, and total pressure drop of the full-size PCHE（without simplifying the heat exchanger model）.Finally, a multi-objective optimization design using the NSGA-Ⅱ algorithm was carried out by using the Q/V and Δp as the objective functions, and using the transverse spacing, fin thickness, and inlet Reynolds number as the design variables.The research results show that, compared with the transverse fin spacing of 4.8 mm, when the transverse spacing equals to 3 mm, the values of Q/V can be increased by up to 88.7%,and the values of Δp can be increased by up to 178.6%.Compared with the fin thickness of 0.6 mm, when the fin thickness equals to 2.4 mm, the values of Q/V can be increased by up to 76.5%,and the values of Δp can be increased by up to 93.9%.The NACA8540 airfoil fin PCHE has the best performance compared with the other asymmetric airfoil fin PCHE with different structural parameters.The conclusions obtained herein have certain guiding significance for the application of PCHE with asymmetric airfoil fins.

Taking the butt girth welds with unequal thickness of thick wall in the steam medium key system of the nuclear power plant as the research object,this paper comprehensively considers and analyzes the possible defects,structures and the difficulties in the radiographic and ultrasonic inspection of the welds,presents a scheme of defect burying for phased array ultrasonic testing using pre-blind testing and reference blocks,and determines the technical scheme of applying phased array ultrasonic testing technology to solve this kind of non-destructive testing problem.

A heat transfer plate with different diversion structure and its channel model were established, and a new type of curved diversion structure of the heat exchanger plate and its flow channel were put for-ward. The flow and heat transfer of the fluids in the flow channel were numerically simulated by CFD soft-ware,the velocity field,temperature field and pressure field in the flow channel were analyzed. The results show that the fluid distribution between the heat transfer plates with the new type of diversion structure is more evenly, and the pressure loss is significantly reduced under the condition of good heat transfer performance.

The wall thickness of stainless steel spherical tank is 42 mm,the thickness of this specification is the thickest in China. The lofting and pressing process of its spherical plates is different from that of low alloy steel,especially,it is more difficult to cut grooves on thick wall. In this paper,with respect to the main technical difficulties in the manufacture of 2 000 m³ stainless steel spherical shell plates,the processes of sizing,lofting and pressing of blanks were described,and the results completely meet the manufacture requirements of this specification of thick-wall stainless steel spherical tank.

The risk control and management of transportable pressure special equipment are closely related to public safety and social economic development. In order to meet requirements of the safe,efficient stor-age and transportation of new types of energy resources such as natural gas and hydrogen,energy-saving and environmental protection, transportable pressure special equipment trends toward extremity, light-weight and complication. There are series of scientific and technical problems,especially in terms of dam-age and failure modes identification,construction of new equipment such as lightweight equipment and super cryogenic insulation equipment,and dynamic risk monitoring,assessment,warning and emergency. The ob-jective,scheme design, research contents, basic theory and key technology, technical route, expected results,desired economic and social benefits of the National Key R&D Program of China" Research on the Key Technologies of Risk Control and Management of Transportable Pressure Special Equipment" were introduced.

In order to prevent leakage caused by serious corrosion of pipeline in the pipeline production operation,resulting in significant loss of life and property,according to the characteristics of different size of pipe diameter,different straightness and trend and different degree of detachability,the pipeline detec-tion method is refined,and the magnetic flux leakage testing methods for the outside of pipeline are pro-posed for application under different operating conditions,such as the variable diameter magnetization,in-tegral magnetization and local magnetization and DC magnetization etc. based on the principle of magnetic flux leakage testing. Four detectors were designed,such as variable diameter magnetic flux leakage detec-tor applicable to detection of large pipe diameter,the magnetic flux leakage detector for the outside of pipeline applicable to the integral magnetization of straight pipeline,the magnetic flux leakage detector ap-plicable to local magnetization of small diameter pipeline and magnetic flux leakage detector applicable to the electromagnetization of removable pipeline,and the feasibility of these four types of testing methods for detecting corrosion defects in the pipeline on the site was studied. The results show that the method of magnetic flux leakage detection outside of the pipeline can detect and evaluate the pipeline and can also provide the decision basis for pipeline maintenance and management.

In order to study the buckling stability of large storage tanks under the combined action of uneven settlement of the foundation and wind load,a numerical simulation method for buckling was proposed. The geometric model was established for the storage tank after reasonable simplification of its actual structure,and by applying the boundary conditions such as uneven settle-ment and wind load,the numerical simulation method for the buckling of the storage tank under the combined action of the two was established. A buckling analysis was carried out by taking a 20 000 m³ tank with fixed top as an example. The results show that compared with the storage tank without uneven settlement of the foundation,the wind resistant stability of the storage tank with uneven settlement of foundation was weakened,and the degree of weakening was related to the distribution law of uneven settle-ment of foundation along the circumference of the storage tank;Wind induced buckling tends to occur in the tank wall area corre-sponding to the maximum uplift amplitude. Key words:large-scale storage tanks;uneven

Based on the ISO 13679, leakage tests of premium connection were performed after nine cycles of make-up and break-out of the threads, and the make-up characteristics of premium connection could directly affect its sealing performance and connection strength in service.To explore the feasibility of using finite element method to simulate the process of repeated make-up and break-out, the finite element model of cone-cone premium connection during the process of repeated make-up and break-out was established.The process of make-up and break-out of this joint was simulated nine times.The sealing performance of premium connection was simulated and was verified by experiment.The result show that the sealing performance of the premium connection decreases with the increase of the number of make-ups and break-outs.In the end, its sealing performance decreases to 73% of the first time; the plastic strain on sealing surface is the key factor affecting the sealing performance; with the increase of the number of make-ups, the contact length of sealing surface of the premium connection shows a trend of decreasing first and then increasing; the interference quantity of the sealing surface changes significantly during the make-up and break-out process.The feasibility and accuracy of the finite element method were verified by comparing with the experiment, which provides an effective method to study the influence of the make-up and break-out test on the sealing performance of the premium connection.

The ASME code case 2843 was interpreted in detail and was explained in combination with the cases of high temperature hydrogenating reactor under the interaction of creep and fatigue. The main processes of this creep fatigue analysis include stress intensity check,judgment whether creep is negli-gible,strain and creep verification,creep analysis,fatigue analysis and creep-fatigue interaction curve ver-ification. The materials to which the latest version of the ASME code case 2843 applies is more extensive than the ASME code case 2605-2,and the applicable temperature range and maximum service life of the applicable materials are more explicit. It is concluded that the destruction of creep damage is bigger than that of fatigue damage. Therefore,more attention should be paid to creep damage in practical engineering to carry out sufficient structural strengthening and reduce creep failure.

Equipments operating in elevated temperature environment are often accompanied with obvious creep phenomenon, therefore,how to prevent creep failure is an important subject for ensuring structural integrity of these equipments. The stress-based high-temperature creep design methods in ASME-NH,RCC-MRx and R5 are reviewed and compared with each other from such three aspects as design process,stress limits and design curve. Then,with a nozzle structure on a high temperature tank equipment as an object,creep design and analysis are performed by the above stress-based creep design methods,and the creep design results obtained according to above design criteria are compared with each other.

In order to solve the problems of surfacing at the weld of Q345R+Incoloy 825 alloy composite steel plate and surfacing on the inner wall of the nozzle, the welding process evaluation of electrode arc welding and tungsten argon arc welding was carried out on low alloy steel Q345R by selecting reasonable welding process parameters and welding methods according to the welding characteristics of nickel-based alloy.The types of defects that are easy to occur in the welding process and the welding points that need to be mastered were analyzed, and the quality control measures of the welding process were defined to effectively avoid harmful defects in the welding process and ensure the smooth manufacturing of Q345R+Incoloy 825 alloy composite steel plate pressure vessel, which provides a reference for the subsequent manufacturing of the like material products.

Crack defect is one of the most dangerous defects in girth weld.Once pipelines encounter natural disasters, they will bear additional bending load in addition to internal pressure, and the bending deformation easily causes girth weld crack propagation and pipeline rupture, when oil and gas pipelines pass through areas with poor geological conditions.The engineering evaluation formula of stress intensity factor at crack tip was fitted based on a large number of finite element data of girth weld cracks.The submodel analysis method can obtain the finite element result data quickly without losing the accuracy, and it is an efficient method to obtain the fitting data of crack stress intensity factor in full-scale bending pipeline.In combination with the theoretical formula of stress intensity factor for circumferential crack provided in API 579,the basic form of stress intensity factor was given.The crack size range was 0.03＜a/c＜0.2 and 0.27＜a/t＜0.54,and the corresponding maximum error was 4.86%.Through full-scale bending tests, it is verified that the critical displacement accuracy of the corresponding formula during crack propagation can reach 5.49%,and the critical far-field strain accuracy of the formula can reach 4.95%.

Based on the main structural processing parameters of the casing premium connection,the calculation formulas for the connection and sealing performance were derived. The integrity evaluation software for the casing premium connection was de-signed and completed. First,the critical load formulas corresponding to each failure form were derived by analyzing the failure form and mechanism of the casing connection. Then,by analyzing the elastic deformation of a single thread tooth,the mechanical analy-sis model of the casing connection was established,and the solution formula for loading distribution of the connection threads was derived in combination with the deformation coordination equation. Finally,the integrity of the connection was evaluated by compa-ring the critical load with the actual load and the total contact pressure on the sealing surface with the gas pressure in the pipe. The evaluation results show that under the same load,the TM connection casing was most prone to shear failure;the total contact stress of the sealing surface was greater than the pressure inside the pipe,and the sealing performance was good.

Electrofusion (EF) is one of the most common methods for connecting polyethylene(PE) pipes. Proper design of EF joint is crucial for the safety of the piping system. Accurate analysis of the stress distribution at interface of the EF joint is the ba-sis for design of joint. In this paper, the method of combination of theoretical formula calculation and finite element analysis (FEA) was used to study the stress distribution of EF joint under variable internal pressure,axial force and temperature. It was found that the stress distributed at the welding interface was small in the middle and large on both sides. The edge stress concen-tration factor was defined as the ratio of peak stress to average stress of the interface. The relationship between the edge stress con-centration factor and fusion zone length was obtained by analysis. The results can provide a theoretical reference for design of fu-sion zone length of the electrofusion joint based on internal pressure and axial force.

Coercive force method is an effective method for nondestructive testing of residual stress of oil and gas pipelines, which has important engineering value for ensuring the service safety of welded pipe sections.Based on the theory of force magnetic coupling, the influences of stress and strain on the coercive force were analyzed, the calculation formulas of strain and coercive force under plane stress state were deduced, and a force magnetic coupling model suitable for pipes was put forward; The magneto elastic strain coefficient of X80 pipeline steel was calibrated by one-way tensile test.The residual stress in the circumferential weld area of pipeline was measured by coercive force method, and the results were compared with those measured by blind hole method.The experimental results show that there is certain error between the axial residual stress measured by coercive force method and that measured by blind hole method, but their stress distribution laws are consistent, which verifies the feasibility of coercive force method.The research results can provide an effective reference for the nondestructive testing of residual stress of X80 pipeline girth welds.

To address the limited understanding of the static stiffness characteristics of metal hoses in aerospace pipeline systems, axial stiffness tests was carried out on metal hoses.By designing axial stiffness tests, the tensile and compressive conditions under no internal pressure and 0.5 MPa internal pressure were considered, and the stiffness curves of two different specifications of metal hose specimens were obtained.The test results show that the axial stiffness of the hose exhibits high nonlinearity.In the low stiffness stage, the stiffness of the two specimens is 56.82 N/mm and 167.13 N/mm, respectively, while in the high stiffness stage, the stiffness of the two specimens is greater than 3 724.62 N/mm and 4 014.14 N/mm, respectively.Using digital image method, the braiding angle change and outer diameter change information of the net sleeve during axial tension were obtained, and the effects of geometric nonlinearity and boundary nonlinearity factors on the hose stiffness were analyzed.An explanation of nonlinear mechanical behavior based on contact was proposed for metal hoses.Using finite element simulation method, the nonlinear stiffness change of metal hoses during axial tension was reproduced, and the explanation of reliability of the nonlinear mechanical behavior based on contact for metal hoses was verified.The study provides a reference for further analysis of metal hose stiffness nonlinearity.

The toroidal bellows are usually subjected to high pressure,but in many applications,the toroidal bellows needs to be designed under multiple operating conditions.The toroidal bellows need to bear the high internal pressure as well as the external pressure or vacuum condition.The EJMA standard provides the calculation method for toroidal bellows under internal pressure,but it clearly states that the toroidal bellows under external pressure are not covered.At present,the other standards or codes for bellows in the world also do not involve the calculation of toroidal bellows under negative pressure.This paper revises and analyses the strength equation of toroidal bellows under external pressure or vacuum condition based on former research,and submitted the proposal to EJMA on calculation of toroidal bellows under negative pressure or vacuum,which has been included in EJMA Standard.

China plans to build new nuclear power plants at a rate of six to eight per year after the year of 2016,and more than 110 nuclear power plants will be operated by the year of 2030. Since there are many water pipes in nuclear power plants,the selected pipe material plays a very important rule for the develop-ment of Chinese nuclear power plants. Compared with metallic pipes,high density polyethylene(HDPE) pipes have the advantages of abrasion resistance,earthquake resistance,easy installation,and low cost. This paper reviews the mechanical performance of welded joint and its influence factors,effects of defects on the structural integrity,defect detection techniques and life prediction methods,and the quality of Chi-nese HDPE resin. Finally,based on the ASME HDPE roadmap,the key problems that need to be solved and the corresponding solutions are listed to attract the attention from industry,government departments, and other scientific and technological persons,promote the development of standards and codes for HDPE pipes as soon as possible,and accelerate the development of HDPE pipe industry and its safe use in nu-clear service.

In this paper, the structural and use characteristics of high-purity gas medium volume seamless cylinder were intro-duced,the failure models of such cylinders and the current inspection technologies were investigated and the validity of various in-spection technologies was also analyzed. By the failure mode analysis of the high-purity gas medium volume seamless cylinder,it was concluded that the current domestic inspection methods for general industrial gas cylinders are not suitable for periodic in-spection of high-purity gas cylinders. Meanwhile,according to the inspection methods adopted in DOT and ISO standards,the in-spection methods based on UT and AE,etc. were proposed. Practice proved that,by using this method,a lot of defects that cannot be found by the conventional inspection techniques can be detected. Through analysis and summary of these inspection cases,sug-gestions were given on guaranteeing the safe operation of this type of cylinders.

The numerical simulation model of an ellipsoidal dimple tube with different parameters was established considering thermal-hydraulic performance.The effect of number,axial spacing and cross distribution of dimples on the flow field characteristics and heat transfer characteristics of an ellipsoidal dimple tube were discussed under Reynolds numbers between 5 000 and 40 000.The numerical results show that compared with the smooth tube,the presence of ellipsoidal dimples on the surface of tube will enhance the convective heat transfer effect,and the larger the Reynolds number is,the more obvious it is,but it will increase flow resistance of the fluid through heat transfer tube.In addition,when Reynolds number Re=40 000,the circular distribution number N=6,axial spacing P=14 mm and cross distribution angle is 0°,the influence on thermal-hydraulic performance was the largest,compared with smooth tube,PEC reached 1.156,1.15 and 1.13,respectively.

In view of the technical requirements of continuous performance upgrading of tandem reactor for the modular installation quality of the towering steel structure of the reactor itself, the manufacturing technology to ensure one-time efficient assembly of the reactor was developed and applied continuously.Based on the practical experience in the reactor localization in the past 30 years in the modular design and manufacturing of large-sized riveted welded structural members according to the precision quality requirements of machined parts, the assembly methods, construction contents and pre-inspection function of the simulated assembly in the design stage of the components or the whole module structure of the reactor were summarized, the assembly characteristics of different levels of various module structures and their interactions were explained, the professional technologies for the main purpose of assembly and quality inspection were listed, and some taboos and the development direction of key links were pointed out.Finally, the practice of fully coordinating the differences of standards and norms in different countries in international engineering project management was affirmed, which has promoted technical progress.

The nozzle fillet weld is a critical part of pressure equipment and a weak link that is susceptible to hazardous defects.Therefore, regular inspection of this vulnerable area is very important.Compared to traditional ultrasonic non-destructive testing (NDT), ultrasonic phased array total focusing has advantages in locating and quantifying internal defects in welds.In this study, a phased array total focusing method for internal defects in welds was proposed, and a multi-mode imaging method was applied for defect detection in small-diameter nozzle fillet welds to achieve effective detection of internal defects.Based on the actual size of the detection object, an intelligent algorithm was used to calculate the incidence parameters of acoustic beam and select the optimal imaging area to obtain an effective region multi-mode fusion imaging method.The experimental results show that this method can detect internal defects in fillet welds with a diameter of 0.53 mm and can effectively improve the accuracy of defect quantification and positioning compared to single-view imaging and ordinary ultrasonic testing.

For high-risk use occasion of road tanker for liquefied gas,especially in transportation occasion,the possible failure modes and influence factors of safety accessories on road tanker were analyzed in the present paper.To avoid the influence of unexpected failures on safety accessories such as safety valve and emergency shutoff valve,the present paper proposed specific optimization methods according to previous analysis so as to decrease the accident rate in case of leakage of the tanker due to failure of safety accessories,and achieve the goal of guaranteeing personal safety and reducing property loss.

A denoising method combining variational mode decomposition (VMD) and Mahalanobis distance (MD) was proposed to address the issue of noise interference in the collected leakage signals during oil and gas pipeline leakage detection, which affects monitoring accuracy.This method first utilizes VMD to decompose the signal and obtain multiple modal components.Then, it calculates the Mahalanobis distance between the probability density of each component and the original collected signal in sequence to distinguish between effective modal components and noisy components.Finally, it selects effective modal components for reconstruction so as to achieve the goal of signal denoising.Compared with other denoising methods in simulation signal experiment and actual pipeline leakage signal experiment, the output signal to noise ratio of this method is the highest, which is 46.774 0 dB, and the mean squared error is the lowest, which is 5.197 2×10^-7, which shows that this method has certain advantages in denoising effect, and lays a good foundation for subsequent oil and gas pipeline leakage identification.

Fluid elastic instability is the most important mechanisms that excite vibration of tube bundles in heat exchangers. The study on fluid elastic instability of concentrically distributed tube bundles can provide valuable guidance for the design,manufac-ture and maintenance of this type of heat exchangers. Based on the geometric characteristics of concentric arrays,three representa-tive physical models were established, including quasi-square arrangement, transitional arrangement and quasi-triangle arrange-ment. Flow field and vibration characteristics were obtained from fluid-structure interaction numerical simulation of ANSYS CFX software. The critical velocity and main vibration direction at different positions of concentric arrays were analyzed. It was found that the main vibration direction changed from stream-wise direction to cross-stream direction as the gap flow velocity increased. In the three arrays,the maximum critical velocity appeared in the quasi-square arrangement area,whereas the minimum one occurred in the transition arrangement area. The simulation results show that the transition arrangement was easiest to appear unstable in the tube bundles of concentric arrays,which high attention should be paid to during the design and engineering application.

The present work aimed at studying the interfacial microstructure and shear properties of low-carbon steel/stainless steel clad plates fabricated by hot-roll bonding. It is very interesting to evaluate the correlation between interfacial microstructure and shear properties,especially,the interfacial fracture be-havior and the credibility of shear strength results. OM,SEM,EDS and TEM were used to observe the mi-crostructure of the interface,and the microhardness and shear tests were carried out in strict accordance with the national standard. It was found that there was a diffusion phenomenon of chemical elements with different diffusion length around the interface and resulted in the special appearance of zonal structures. With the addition of Ni foil at the interface,the diffusion of the interface elements is inhibited,which is beneficial to improve the performance of stainless steel. Shear fracture occured zigzag cracks along the weak interface,and the accuracy and reliability of the shear results can be effectively evaluated by refer-ring to the diffusion of interface elements.