Hydrogen fuel cell vehicle has become the main direction of hydrogen energy utilization because of its advantages of zero emission, short hydrogenation time, long driving range and high efficiency. High pressure hydrogen storage cylinder is one of the key components of hydrogen fuel cell system. Because the temperature of the gas cylinder increases sharply during the rapid hydrogen filling process, and the temperature drops sharply during the hydrogen release process, the drastic temperature change will reduce the fatigue life of the cylinder, which has an important impact on the safety and stability of the whole system. At present, it is necessary to further study the thermodynamic characteristics of gas cylinders in the process of hydrogen filling and discharging. According to the filling and discharging process of high pressure hydrogen cycle, the change and distribution of pressure and temperature and the streamline change in the high pressure cylinder during the process of hydrogen filling and discharging are studied. The pressure and temperature control strategy of high-pressure tank, precooler, test cylinder and low-pressure tank in the process of hydrogen filling and discharging were discussed, and a more safe and effective hydrogen filling and discharging optimization control measure was put forward. This study is of great significance for the stability and safe operation of high pressure hydrogen storage system in the field of hydrogen energy.

Electromagnetic acoustic transducer (EMAT) gradually becomes the main excitation method for surface wave, which is suitably used in periodic inspection or long-term monitoring of pressure equipment. However, the corroded surfaces appearing on the pressure pipes and vessels can cause an increase of background noise and remarkable attenuation of the echo wave, which restrict the improvement of detection accuracy of surface crack. In this paper, a finite element model of EMAT-Generated surface wave inspection for steel plate with rough surface is established based on the constitutive equation of ferromagnetic materials. Considering the Lorentz force and magnetostrictive effect, the influences of rough surface on energy conversion of multiple fields in the excitation and propagation process of electromagnetic acoustic surface wave are separately investigated. The surface wave responses of cracks characterized by rectangular groove on corroded rough surface have been analyzed further. The numerical results indicate that the rough surface of the excitation region below the transducer with a center frequency of 330 kHz has a slight effect on the surface wave energy, while the surface roughness of the propagation region attenuates echo signal of crack significantly. The reflection coefficients of echo signals can be utilized to quantitatively characterize the depth of crack on the corroded surface with roughness less than λ/15 (λ is wavelength of surface wave).

Ultrasonic testing is one of the most common non-destructive testing (NDT) methods for periodic inspection of crude oil storage tanks. Ultrasonic phased array system can effectively and efficiently image different types of defects in the structures through direct contact method. However, the sludge remained on the tank floor gives rise to difficulties on detecting the defects in the floor plate using existing techniques. Therefore, this paper focuses on the development of novel phased array testing methods without requiring complete removal of the sludge. The appropriate experimental apparatus and its parameters used for through-sludge testing are selected based on the acoustic characteristics of the oil sludge composition. Furthermore, a novel phased array full matrix capture method is explored based on firings of multi-element aperture. The total focusing method (TFM) is studied by considering the existence of sludge. The experimental results from the sludge thickness study demonstrate that the TFM imaging technique can more accurately measure the change in thickness of the metal sample at the submillimeter scale. Additionally, high resolution imaging of side drilled holes in size of 1 millimetre can be realized on the samples covered with sludge. Last, the effect of aperture size on the detectability is investigated. Consequently, the results obtained from different sludge experiments show good reliability and measurement consistency of our proposed methods. It delivers great potential to accurately locate and quantitatively evaluate the corrosion defects frequently found in the tank floor.

The analysis of the spectrum features of thermal desorption spectroscopy (TDS) using the desorption-rate profile against temperature is widely applied to investigate the hydrogen kinetics including diffusion and trapping in metallic materials, which is related to hydrogen embrittlement. Recently the TDS spectrum features such as the peak magnitude and the peak area have been used for qualitative assessment of creep damage, although there is still a lack of theoretical understanding on the correlation between TDS spectrum features and creep damage. In this paper, creep voids inducing creep damage are considered as the only kind of hydrogen traps in steels. The relationships between the TDS spectrum features and creep damage of ferritic steels are investigated through parameter analysis of the modified McNabb-Foster model together with the Oriani assumption, which can describe hydrogen evolution during thermal desorption. It is found that the peak area of TDS spectrum is independent of the trap binding energy, and it is proportional to the trap density, demonstrating that it could be a good indicator for creep damage. The creep damage can be characterized as a power-law function of the peak area of TDS spectrum, indicating TDS as a promising semi-destructive characterization method for creep damage of metallic steels.

With the development of Materials Genome Initiative (MGI) and data mining technology, machine learning (ML) has emerged as an important tool in the research of materials science. For the heat resistant alloys used in furnace tubes, the rapid prediction of the high-temperature properties is critical but difficult until now. In this work, the ML method based on the deep learning algorithm is developed to establish the direct correlation between microstructure inputs and output stress rupture properties of Fe-Cr-Ni based heat resistant alloys. Two simple convolutional neural networks (CNN) and the complex network with VGG16 architecture are implemented and evaluated. The simple CNN and VGG16 models are trained from scratch and pre-trained, respectively. Due to the relatively few training samples in the dataset, the data augmentation configuration and the improved architecture are effective to mitigate overfitting in simple CNN models. The result also shows that in the case of transfer learning, the features extracted from other datasets can be used directly to this new visual task. It is demonstrated that both the simple CNN and VGG16 models reach the high prediction accuracies (more than 90 %) of high-temperature properties with a wide range of microstructures. In addition, the good prediction performance achieved in the small dataset also reveals the deep learning approaches can be used to construct powerful vision models in engineering practice, where very limited data is the common situation.

Thermocouples are the most common temperature measuring components in petrochemical, metallurgical, aerospace and other fields. However, due to the influence of working environment and its own structural characteristics, the thermocouple is highly susceptible to electromagnetic interference in the environment during its work, which seriously affects its temperature measurement accuracy. In this paper, three different shapes of Au/SnO 2 thermocouples were prepared by screen printing technology, and their microstructure, thermoelectric properties and anti-electromagnetic interference were studied. The results show that the Au/SnO 2 thermocouples with different shapes can crystallize well after sintering at 750 °C and above. When temperature difference is from 50 to 300 °C, thermocouples with different shapes can produce stable thermoelectric potential, and the shape has no effect on the output thermoelectric potential. The Au/SnO 2 thermocouple after 850 °C sintering has the best thermoelectric performance. Au/SnO 2 thermocouples can work normally in electromagnetic fields of 3 V/m or less, while standard PtRh10-Pt thermocouples can not work normally in electromagnetic field of 3 V/m. The Au/SnO 2 thermocouple obtained in this study has the advantages of simple preparation method, small size, stable output thermoelectric potential and strong anti-electromagnetic interference ability.

Composite overwrapped pressure vessel (COPV) is considered to be the most promising storage tank for hydrogen. Filling the COPV to high pressure within 3–5 minutes generates temperature increment due to negative Joule-Thomson coefficient and compression effect of hydrogen. This temperature increment induces a non-uniform temperature distribution in the COPV. The difference between the physical properties of inner metallic liner and outer composite will produce thermal stress. In this work a computational fluid dynamics (CFD) model is built to simulate the temperature increment during fast filling of the COPV. A three-dimensional thermal-mechanical finite element model for COPV is set up. The temperature distribution of the COPV by the CFD model is input into the thermal-mechanical model to analyze the stress distribution during the fast filling. This thermal-mechanical analysis model will provide technical support for the design of COPV.

This paper introduces briefly China’s development plan for intelligent manufacturing, and combining with the present situation of design, manufacture and maintenance of pressure equipment, puts forward the development directions for the digitization, networking and intelligentization of pressure equipment at present and in the next decade from three aspects. The first aspect is digital control of shape and performance of pressure equipment. Taking the furnace tube as an example, the Material Genome technology is recommended for establishing the relationship between the microstructure and macroscopic performance of its material and achieve the target macroscopic performance by the adjustment of composition, phase and microstructure; then the additive manufacturing (3D printing) technology can be used to control the resulting shape of certain special structures so as to achieve the integrated shape and performance and significant improvement of its service life. The second aspect is digitization and network-based interconnection of production factors such as materials, equipment and personnel in the pressure vessel production workshop to realize intelligent manufacturing. Taking the transportable pressure vessel for instance, the real-time identification, diagnosis and control of abnormal conditions can be realized by information and communication technology during the key production processes such as baiting, cutting, forming, welding, heat treatment, and non-destructive testing; and if necessary, the suitable manufacturing resources across different enterprises and regions can be organized to achieve the flexible production and collaborative manufacturing of the components such as heads and flanges, etc. The third aspect is to achieve the real-time online integrity assurance of pressure equipment in process industries (e.g., petrochemical and electric power, etc.) by digitization and networking of risk-based inspection (RBI), fitness-for-service (FFS) assessment technologies and their corresponding database, in combination with real-time monitoring technology based on the characteristic safety parameters. Taking the reactor effluent air cooler (REAC) system as an example, this technology would enable not only the safety warning of critical characteristic parameters, but also the self-limiting and self-prevention of the flow-induced corrosion failure by linking with the distributed control system (DCS).

Bolted flange joints (BFJs) are very common in the process industries, and they play an important role in equipment connection. A lot of BFJs are working at high temperature. The temperature and internal pressure will lead to gasket stress redistribution, and then affect time-dependent leakage rate of BFJs. In this paper, the effect of internal pressure on gasket stress and leakage rate of BFJ during the long term service at high temperature was discussed. The time-dependent gasket stresses of BFJ during the long term service at high temperature under two tightness levels and three internal pressures were calculated by using the finite element method. And then, based on the leakage rate prediction model of BFJ during the long term service at high temperature proposed, the corresponding time-dependent leakage rates of BFJ during the long term service at high temperature were acquired. The results showed that the internal pressure had a significant impact on the time-dependent gasket stresses and time-dependent leakage rates of BFJ during the long term service at high temperature. This research will help the engineers and technicians to understand the role of the internal pressure on the time-dependent gasket stresses and time-dependent leakage rates of BFJ during the long term service at high temperature.

In recent years, with the gradual expansion of units scale for energy industries such as oil refining, chemical and natural gas, etc. in China, pressure vessels are developing toward the large and heavy direction with the maximum wall thickness reaching hundreds of millimeters and weight exceeding one thousand tons. It not only causes huge material consumption, difficulty in manufacture and processing (even beyond current capability), but probably also lead to new failure modes and mechanisms, and significant safety risks thereby. Therefore, the lightweight design and manufacture under the premise of inherent safety has become an urgent need to break through the bottleneck of manufacturing capability and realize the material and energy conservation. In this paper, the progress of lightweight design and manufacturing technology of heavy-duty pressure vessels in recent years in China is introduced from the aspects of adjustment of material allowable strength, application of high strength steel and matching of strength and toughness, cold stretch of austenitic stainless steel, structure optimization design with multi-parameter coupling, and application of composite materials. Application cases in the construction of pressure equipments such as large hydrogenating reactors, low-temperature ethylene spherical tanks, austenitic stainless steel cryogenic vessels, butyl octanol heat exchangers, etc. are also included. Finally, some suggestions on the future research are proposed including composite pressure vessels in cryogenic environment, materials genome and additive manufacturing technologies for pressure vessels.

Performance of a bolted flange joint (BFJ) is characterized mainly by its ‘strength’ and ‘sealing capability’. How to keep the ‘strength’ and ‘sealing capability’ for the BFJ serving at elevated temperature is a difficult problem in engineering applications. The variations of bolt stress and gasket contact stress play an important role on the structural integrity and sealing performance of BFJ in the bolt-up, pressurization and heat-up stages. In this paper, a three-dimensional elastic-plastic finite element model has been developed to investigate the performance of joint under combined internal pressure and elevated temperature. The thermal-structural coupling method has been used to analyze the variations of axial bolt force, maximum blot stress and gasket contact stress under steady-state and transient thermal loadings. The effects of internal pressure, temperature as well as the heating rate on the variations of bolt load, bolt stress and gasket contact stress have been evaluated. The results show that the maximum bolt stress increases while average gasket contact stress decreases with increasing the temperature under steady-state thermal loading. Besides, when the transient thermal loading is considered, heating rate has a significant effect on the maximum bolt stress and gasket contact stress. This research will contribute to the design of BFJ subjected to elevated temperature.

Creep properties both in hot hydrogen and in air of a vanadium-modified CrMo steel 2.25Cr1Mo0.25V, widely used in hydroprocessing reactors in petrochemical industry, were investigated to determine the effect of hydrogen on high-temperature creep behavior of the low-alloy ferritic steel. The minimum creep strain rate in hydrogen is higher than that in air, whereas the creep strain at failure in hydrogen is relatively smaller. Many tiny spherical cavities are dispersively distributed in the ruptured specimen under hydrogen, which has relatively higher Vickers hardness. Based on the thermodynamics theory, the pressure of methane generated by the so-called “methane reaction” in the vanadium-modified CrMo steel can be calculated by using corresponding thermodynamic data, assuming that methane can reach its equilibrium state during cavitation. Meanwhile, a creep constitutive model based on continuum damage mechanics (CDM) was proposed, taking methane pressure into consideration. The results show that methane pressure increases nonlinearly with increase of hydrogen pressure while it decreases gradually with increase of temperature. The constitutive model considering the damage induced by methane pressure can be used to predict the effect of hydrogen pressure and temperature on creep life, indicating that the influence of hydrogen at elevated temperatures becomes smaller when increasing temperature or decreasing hydrogen pressure.

Bolted flange joints (BFJs) are widely used in the process industries, and there is a large proportion served in the high temperature environment. During the long term service at high temperature, the creep relaxation of each component of BFJ will cause the decline of the residual gasket stress, which will further affect the sealing effect. So, it is very important to make sure the change rule of the leakage rate of BFJ during the long term service at high temperature. Firstly, according to constructing the relationship between the leakage rate and the service time, the leakage rate calculation method of BFJ during the long term service at high temperature was proposed. Secondly, the stress distributions of the gasket during the long term service at high temperature, which was time-dependent, were calculated at the tightness level T2 and T3 by using the numerical simulation method. Finally, based on the time-dependent average gasket stress and maximum gasket stress, the change rule of the time-dependent leakage rate of BFJ during the long term service at high temperature was obtained. The research results will play an important role in mastering the attenuation rule of the leakage rate of BFJ and supporting the leakage rate control of BFJ during the long term service at high temperature.

Numerical simulations were performed on the damage behavior of carbon-fiber-wrapped composite cylinder subjected to impact by a flat-ended impactor. The simulation results were in agreement with the test in terms of both the damage morphology of the cylinder and the impact acceleration-time curve of the impactor. The relationship between the impact acceleration-time curve characteristics and the initiation and propagation process of the various damages was analyzed. The effects of the internal pressure on the damage morphology of the cylinder, the impact acceleration-time curve of the impactor, and the critical perforation energy of the cylinder wall were discussed. Change law of the residual burst pressure of the cylinder with different impact energies was obtained. The conclusions in this paper are helpful for the safety assessment of the composite cylinders subjected to impact by foreign objects.

A three-dimensional computational fluid dynamics (CFD) model has been established for the simulations of supercritical LNG heat transfer in a horizontal tube of an intermediate fluid vaporizer (IFV). The influences of inlet pressure and mass flux on heat transfer have been studied. The predictive capabilities of different heat transfer coefficient (HTC) correlations, which is vital for the economic and reliable design of an IFV, have been evaluated. The results indicate that the Jackson correlation gives more accurate HTC predictions for supercritical LNG at the relatively small mass flux, with a maximum deviation of 10% and an average deviation of 6%; while for the cases with larger mass flux, a modification to the Jackson-Hall correlation works well. Detailed flow and heat transfer characteristics and buoyancy effect have also been analyzed. The reported findings would provide insight into the supercritical LNG vaporization process and give guidance to the design optimization of an IFV.

Coke drum is typical industrial equipment which experiences complex thermal and mechanical cyclic load during its operation, and the thermal stress which is produced by the drastic change of temperature is the main cause of the cracking failure of coke drum. This paper aims at coke drum with 1.25Cr–0.5Mo steel, and is based on iterative algorithm. Then we simulate the process of liquid medium climbing the inner surface of coke drum in the stages of oil filling and water quenching with dynamic thermal boundary, and carry out the numerical calculation of transient temperature field of coke drum in main process stages for one operating cycle. After the comparison of simulated temperature values with the measured temperature data at several locations on the outer surface of coke drum, the appropriate equivalent coefficients of convective heat transfer will be obtained. The variation rules of transient temperature field for the key parts of coke drum are discussed. Based on the simulation results of temperature field, the thermal-structure coupling analysis of coke drum is carried out, and the variation characteristics of thermal stress on coke drum are studied later.

Characteristic safety parameter refers to the parameter that reflects the inherent safety margin of pressure equipments subjected to certain failure mechanism. It has three main characteristics. Firstly, it is sensitive to the change in failure mechanism. Secondly, the safety of pressure equipments can be guaranteed by controlling this parameter. Thirdly, it is easy to measure. By real-time monitoring of this characteristic safety parameter, the quantitative assessment of the structural integrity and furhter the diagnosis and warning on the safety of in-service pressure equipments can be realized. In this paper, the definition of characteristic safety parameter is given first for the pressure equipments subjected to several typical failure modes. After that, the selection principle, measurement technique and determination of its critical value, etc., are then introduced by analyzing typical examples. In combination with the technical concepts of the Internet of Things and Big-Data, some research suggestions are proposed with respect to the remote monitoring and diagnosis techniques based on the characteristic safety parameter, including the sensing measurement, monitoring and analysis of big data, real-time diagnosis and early warning of safety condition, etc.

Creep ductility which is assumed to be constant at a given temperature in many creep constitutive models, actually varies with temperature, stress level and creep strain rate, etc. In this paper, the relationship between creep ductility and stress levels of ferritic steels has been briefly discussed from the perspective of failure mechanisms. It can be generally divided into three regimes, including the upper shelf, lower shelf and the transition regime. The four-parameter logistic model has been adopted to quantitatively describe the stress-dependent creep ductility. Furthermore, a modified mechanism-based continuum damage mechanics (CDM) model for ferrtic steels has been proposed using the stress-dependent creep ductility model. Uniaxial creep tests of 2.25Cr1Mo0.25V steel at three stress levels have been carried out and the experimental data points realistically reflecting the creep behavior have been carefully selected to fit the improved CDM model using genetic algorithm (GA). It is shown that the improved model has the capability to characterize the whole creep process of ferritic steels and the stress-dependent creep ductility over a wide range of applied stress.