Tube Lifetime Research Articles

Investigation on corrosion behavior of the atmospheric pressure air cooler tubes caused by multiphase flow

Air coolers are important heat exchangers and widely used in the petroleum and petrochemical industries. The leakage of air cooler tubes due to corrosion frequently happened and seriously affected normal production process leading to unplanned shutdowns, so the corrosion behavior of the air cooler tubes needed to be clarified urgently. In this work, the corrosion behavior of the atmospheric pressure air cooler tubes was investigated by computational fluid dynamics (CFD) simulation and experimental study. It was depicted that the gas–liquid erosion corrosion was the main reason for the leakage of air cooler tubes and the collision angle between the fluid flow and the wall at the inlet of the tubes was the key factor that affects the corrosion behavior of the multiphase flow inside the air cooler tubes. The corrosion was most severe when the collision angle is 30 degree. With the purpose to migrate corrosion, the improvement measure was proposed from the perspective of collision angle elimination. The porous plates were installed and the lifetime of the air cooler tubes was extended to 4 times that of the original conditions, which indicated the installation of porous plates is an effective measure to reduce corrosion.

A breakthrough in creep lifetime prediction: Leveraging machine learning and service data

Improvement of data-driven techniques, specifically machine learning (ML), in material science turned it into a powerful tool for predicting materials behavior. Accordingly, this study provides a ML prediction of empirical creep lifetimes of 9Cr-1Mo ex-service heater tubes that have been used in industry for up to 47 years. Data from over 90,000 h of stress rupture tests shows that the service parameters influence creep lifetime similar to mechanical properties. Employing six different ML algorithms, viz., K Nearest Neighbors (KNN), Support Vector Regressor (SVR), Random Forest (RF), Gradient Boosting (GB), Gaussian Process (GP), and Multi-Layer Perceptron (MLP) demonstrated that the GP and MLP methods performed significantly better in predicting the creep lifetimes rather than other algorithms. Finally, a validation set involving 12 samples was conducted, and the GP algorithm showed better agreement with experimental values than other ML and Larson-Miller Parameter approaches, illustrating the capability of this model to predict creep lifetimes.

Use of Vacuum to Increase the Effectiveness of X-Ray Tube Maintenance

Each device requires redundancy, including the X-ray machine. In an X-ray machine, there is an important component as the location for the creation of X-rays, namely the X-ray tube. This tube needs routine maintenance to increase the tube's lifetime. In addition, maintenance that was originally done manually, with this device can be done automatically and more quickly. In addition, maintenance that was originally done manually can be done automatically and faster with this device. X-ray tube oil vacuum is used as an effective solution for the maintenance of an X-ray tube machine that lasts for days. This device comes with easy use, equipped with two buttons and a display. This device can increase the productivity of both the device and the technician itself. The application of the use of X-ray tube oil vacuum is intended for hospitals and health facilities that have active X-ray machines. This device has been able to be built. Based on the results, it has a 2.5% error for the measurement at minimum and maximum pressure and a 3% error at -15 KPa pressure. The volume of the X-ray tube fully filled is always the same for each measurement. It can be concluded that this device can be effective in time because it only takes minutes to fill the X-ray tube up to full. Still, many parts can be improved and developed, such as the size and the weight.

MCP-PMT quantum efficiency monitoring and operation status of the TOP counter at the Belle II experiment

The Belle II experiment is a high luminosity electron and positron collider experiment at SuperKEKB in Japan. The Time-Of-Propagation counter is a detector for particle identification in the barrel region. Micro-channel-plate photomultipliers are used as photodetectors and measure photon timing with a resolution of 30 ps; this leads to excellent particle identification performance. One of the issues is the photocathode lifetime of the photomultiplier tubes. Monitoring tools have been developed to measure the tube gain, accumulated output charge density and quantum efficiency during physics data taking. The gain was seen to decrease by about 10%. Although the accumulated output charge density is small compared to the tube expected lifetime, a quantum efficiency degradation was found larger than expected for 5% of the tubes after threshold efficiency calibration. Several causes for this degradation are being investigated. They can possibly be related to tube production and noise from the read-out system.

Erosion Behavior of Stellite-6 and WC-12Co Coatings on SA213-T22 Boiler Steel

At Mae-Moh power plant, Thailand, superheater tubes, which are exposed to a fly ash environment, often degrade due to solid particle erosion. To extend the service lifetime of the superheater tubes, the high velocity oxy-fuel (HVOF) thermal spray technique is used to deposit a protective coating on the material, SA213-T22 steel. In this work, the solid particle erosion of Stellite-6 and WC-12Co coatings was investigated using erodent particle impingement at angles of 30 and 90°. This was carried out with an average particle size of 60 μm. The erosion behavior of SA213-T22 with and without Stellite-6 and WC-12Co coatings was examined using ductile and brittle erosion modes. The erosion testing resulted in the brittle mode for both Stellite-6 and WC-12Co coatings, while the SA213-T22 without coating indicated the ductile mode. On investigation of the surface morphology, the SA213-T22 steel showed ploughing and microcutting. The Stellite-6 coating showed some evidence of ductile erosion such as lips on the coating surface, different from the WC-12Co coating which showed microcracks and deep cavities. The erosion resistance of the Stellite-6 coating was higher than the WC-12Co coating. This was due to the strength and toughness of the metal matrix composite structure and the low porosity of the coating.

Design study for the lifetime of double-sided irradiated absorber tubes

The world is in need of sustainable and cost efficient supply of electrical energy. One important technology could be solar power towers, because of their base load capability. Even though this technology has seen a significant decrease in installation and operation costs, further cost reduction is necessary to reach a higher market share.This study investigates double-sided irradiated absorber tubes to reduce installation costs of molten salt receivers. With a re-arrangement of the tubes towards a star-shaped layout, the required number of the expensive absorber tubes could be halved. This study introduces and uses a vivid methodology, based on linear damage accumulation that allows for the calculation of damage proportions, as well as the expected lifetime of receiver components in years. The calculations show the lifetime of double-sided irradiated tubes to be about ten times higher than for those irradiated from one side. This enables a change in material towards cost efficient austenitic stainless steels, offering an additional option for cost savings. However, it is also outlined that particular attention has to be payed to the aiming point optimization of the heliostat field, because the irradiation has to be quite smooth and uniform on both sides of the tubes to extend the lifetime.

Research on the Effect of Transients of High-Voltage Power Supplies on the Lifetime of High-Power Vacuum Tubes: A Microscopic Assessment

Electron guns are used as the electron sources in high-power electron tubes. The generated electron beam in electric guns passes through an aperture at the center of the anode. Since the electron beam has considerable kinetic energy, any collision between the electron beam and the anode aperture edge damages the electron gun. Therefore, electron guns are designed to meet the compatibility between the diameters of the electron beam and the anode aperture. However, this compatibility is disrupted during the transient time interval of the gun’s power supply. In this article, the cause of failure of the electron gun of high-power electron tubes is investigated for the transient interval of the gun’s power supply. The investigations are carried out on a damaged anode; new experiments and computer simulations are also employed. The microscopic assessment shows the studied anode melted several times, proving the role of power supply transients in the failure of the studied gun. Numerical analyses are presented to verify the result of the microscopic assessments. The numerical analysis is carried out using the finite element method (FEM). The result of this study can provide information for proposing the appropriate transient interval of the vacuum tube’s high-voltage power supplies.

Lifetime optimization of solar central receivers via linear actuators

The receiver is a key component of concentrated solar power plants, whose operation can be interrupted by its early failure. In this research, a novel approach to the enhancement of solar receiver lifetime is presented, studying the use of linear actuators in the longitudinal supports of the tubes to induce forced displacements, reducing thermal stresses. Existing analytical models have been improved and joined together, in order to be implemented in a genetic algorithm to optimize the solar receiver lifetime. In a first approach, the maximum equivalent elastic stress, produced by the thermal gradients over the receiver, has been minimized. This approach reduces the maximum thermoelastic stress up to a 9.5%, and increases the lifetime of the receiver to an 8% when a forced displacement of 100 mm (1% of the tube length) is considered. When the rupture time due to creep is optimized, with the same forced displacement of 100 mm, the tube lifetime is enhanced up to a 25%. Small forced displacements (0.1% of the tube length) may lead to a lifetime improvement up to 6%. The small amount of force necessary to carry out the forced displacement of the supports makes feasible the implementation of linear actuators in future solar power plants.

An internal heating mechanism operating in ultra-short-period planets orbiting magnetically active stars

Context. Rocky planets with orbital periods shorter than ~1 day have been discovered by the method of transits and their study can provide information on Earth-like planets not available from bodies on longer period orbits. Aims. A new mechanism for the internal heating of such ultra-short-period planets is proposed based on the gravitational perturbation produced by a non-axisymmetric quadrupole moment of their host stars. Such a quadrupole is due to the magnetic flux tubes in the stellar convection zone, unevenly distributed in longitude and persisting for many stellar rotations as observed in young late-type stars. Methods. The rotation period of the host star evolves from its shortest value on the zero-age main sequence (ZAMS) to longer periods due to the loss of angular momentum through a magnetized wind. If the stellar rotation period comes close to twice the orbital period of the planet, the quadrupole leads to a spin-orbit resonance that excites oscillations of the star-planet separation. As a consequence, a strong tidal dissipation is produced inside the planet that converts the energy of the oscillations into internal heat. The total heat released inside the planet scales as a−8, where a is the orbit semimajor axis, and it is largely independent of the details of the planetary internal dissipation or the lifetime of the stellar magnetic flux tubes. Results. We illustrate the operation of the mechanism by modeling the evolution of the stellar rotation and of the innermost planetary orbit under the action of the stellar wind and the tides in the cases of CoRoT-7, Kepler-78, and K2-141 whose present orbital periods range between 0.28 and 0.85 days. If the spin-orbit resonance occurs, the maximum power dissipated inside the planets ranges between 1018 and 1019 W, while the total dissipated energy is on the order of 1030−1032 J over a time interval as short as (1−4.5) × 104 yr. Conclusions. Our illustrative models suggest that, if their host stars started their evolution on the ZAMS as fast rotators with periods between 0.5 and 1.0 days, the resonance occurred after about 40 Myr since the host stars settled on the ZAMS in all the three cases. This huge heating over such a short time interval produces a complete melting of the planetary interiors and may shut off their hydromagnetic dynamos. These may initiate a successive phase of intense internal heating owing to unipolar magnetic star-planet interactions and affect the composition and the escape of their atmospheres, producing effects that could be observable during the entire lifetime of the planets.

Creep Properties of 9Cr and 14Cr ODS Tubes Tested by Inner Gas Pressure

Oxide-dispersion strengthened steels are promising materials for extreme service conditions including nuclear reactors core. In service conditions, nuclear fuel claddings are exposed to the fission gas pressure at temperatures about 700 °C. This paper presents novel results on ODS creep properties from a round robin of inner gas pressure creep test. A gas pressure creep test, simulating fission gas loading, was designed and achieved by four different European teams. Lifetime and specific behavior of ODS steel tube are prospected. Based on a mechanical clamping achieving gas tightness, short length tubes samples are tested by different laboratories. In situ laser measurements exhibit the radial expansion of ODS steel tubes before failure. Post-mortem, geometrical characterizations are performed to determine hoop strains at failure. A consistent creep lifetime is observed by all the teams even with slightly different testing apparatus and clamping systems. Under inner gas pressure, ODS steels exhibit a typical failure by leakage associated to a very small radial expansion. This behavior results from a brutal failure (burst) without evidence of tertiary creep stage. This failure mode of ODS cladding in creep conditions is consistently observed on all samples of the study. Inner gas pressure creep tests were compared, for the first time, by four European laboratories on ODS steel tube. This technique, simulating the fission gas pressure loading, is applied on small and mechanically clamped samples. This technique shows a remarkable consistency between the different laboratories results and demonstrates to be efficient for ODS steel cladding tube qualification. The results show a correlation between the creep properties and the microstructure.

Impact of the target material surface layer on neutron yield and target lifetime of the neutron tube

The neutron yield and target lifetime of a neutron tube are affected by the target materials, the oxide layer and the overcoat layer on the target film. Target lifetime can be improved by adopting alloy instead of pure titanium. The neutron yields of pure titanium target and 200 nm oxide titanium target are simulated by SRIM, which are in good agreement with the experimental results. The neutron yield and target lifetime are calculated at different deuterium energy and alloy targets with variable surface layers. The protective overcoat layers include Pd, Ni and Al. The simulated results show that oxide layer reduces the neutron yield, and the thicker the oxide layer is, the less the neutron yield is. The target lifetime is increased by using the alloy targets, in which the scandium-titanium alloys has a higher lifetime. Meanwhile, depositing a protective overcoat on the target film surface can increase the neutron yield and extend the target lifetime of the neutron tube. In order to meet the requirements of long lifetime and high yield neutron tubes in different applications, the target was optimized theoretically.

Effects of secondary electron emission yield properties on gain and timing performance of ALD-coated MCP

The technology of atomic layer deposition has been used to improve the lifetime of the microchannel plate-photomultiplier tube (MCP-PMT) effectively and makes MCP possible to choose to coat different potential emissive materials on the internal surface of the MCP channels in the future. However, it is still an open question to what extent the secondary electron emission (SEE) yield properties of the emissive materials influence the behavior of the ALD-coated MCP. In this work, the dependences of the gain and timing performance on the SEE yield properties were assessed by using the Monte Carlo and particle-in-cell methods. We established the three-dimensional MCP single channel model in Computer Simulation Technology (CST) Particle Studio. Three important secondary electron emissions, the backscattered, rediffused and true SEEs, were discussed numerically based on the probabilistic model. The secondary electron cascade processes in the MCP single channel were simulated. The simulation results indicate that the opportunities for improving the gain of the ALD-coated MCP by improving the SEE yields corresponding to the incident energies of 0 eV–100 eV. The backscattered and rediffused electrons are found to have strong effects on the gain and timing performance of the MCP. Although the higher the SEE yield the higher the MCP gain, the drawback is the extremely high SEE yield will make the MCP saturated prematurely and degrade the time resolution. The simulation results will be used to guide the design and selection of emissive material for ALD-coated MCP development.

Effect of Burner Operation on the Catalyst Tube Lifetime of a Steam Methane Reformer: A Numerical Study

In this paper, the catalyst tube lifetime of a practical steam methane reformer is analyzed numerically. The effect of burner operating mode on the flow development, hydrogen yield, and catalyst tube lifetime is discussed, with the aim of improving the reformer performance. The results of this study reveal that using the periodic boundary conditions, the temperatures and hydrogen yields obtained are much lower than the experimental values and the pressures are much lower than those using the real model. This results in overestimating the catalyst tube lifetime and underestimating the reformer operation risk. The catalyst tubes in the downstream area have longer lifetimes, while those in the upstream area have shorter lifetimes. Turning the upstream burners off is more efficient to the catalyst tube lifetime, while turning off the central groups of burners is less efficient. The main drawback of turning off burners is the decrease of hydrogen yield.

Improving the material properties of vacuum devices electrodes by technology rational improvement

The material of the electrodes of high-current vacuum and plasma electronics is traditionally obtained by powder metallurgy methods (mixing components, pressing blanks, hydrogen sintering in a given mode). However, the material of the cathodes produced according to the adopted technology, has a number of significant limitations. They are caused by the impossibility of a uniform distribution and grinding of the initial powder components by the adopted grinding in globe mills, as well as by abundant gas emission during the sintering time. The nonuniformity of the distribution of the composition in the structure, low density, high porosity, low mechanical strength of the emitting material with a metal matrix give a decrease in the operating properties of the cathodes, which leads to a decrease in the lifetime of electronic tubes. This problem is proposed to be solved by directional changes in the physical and mechanical properties of the electrode material by selecting the gravimetric consist of the base material components and improving the existing production process. The article presents the analysis of research results, changes in the structure of the material by optical and scanning microscopy methods, and also describes a complex of acquired physical and mechanical properties of experimental samples obtained by modernized technology. Thus, the developed innovative techniques allowed to increase the hardness by 36%; density by 19%, and to reduce porosity by 25% in relation to traditional cathodes. Such changes in the physical and mechanical properties make it possible to predict an increase in the service life of produced and developed vacuum tubes operating in current flow regimes up to 100 kA and in highly stressed electromagnetic fields up to 500 kV.

Investigation of the Effect of the Efficiency of Catalysts on Early Destruction of Direct Reduction Reformer Tubes.

The catalysts of the direct reduction unit play a critical key role in producing reducing gases and the lifetime of the reformer tubes. In this paper, the effect of reducing the efficiency of catalysts on the early destruction of direct reduction reformer tubes is investigated. Cold compressive strength test, XRF and BET analysis were performed on intact and used catalysts. Also, the microstructure of the destroyed tube was examined by a scanning electron microscope and the amount of sulfur was measured. The results show that in used catalysts compared to intact catalysts, the specific surface area is reduced, and the amount of access to areas containing nickel is reduced. Access to nickel-rich areas will be drastically decreased and reforming reactions will not be performed well. This lessens the efficiency of the catalysts and breaks them down hence several reformer tubes are exposed to higher temperatures and their service life will be considerably reduced. Due to the presence of precipitations, the sulfur amount available in the destructed tube is equal to 0.1%, which is ten times the allowable sulfur content in the reformer tube alloy.

Thermo-structural fatigue and lifetime analysis of a heat exchanger as a feedwater heater in power plant

Today, the use of shell and tube heat exchangers has become widespread and they are used in various industries under very diverse operating conditions. Specific operating conditions make it possible to consider and simulate the operating terms and failure conditions of these converters. In this study, the design of a shell-and-tube counter-flow heat exchanger in AutoCAD software is first considered, and the system is then meshed and simulated in ANSYS 2019 software. Simulation results of temperature, pressure, heat flux and fluid velocity within the system are reported in order to understand the system performance. Failure conditions are evaluated according to the ASME VIII Boiler and Pressure Vessel Code, and the results of equivalent thermal stress analysis and system lifetime under two extreme loading conditions are reported. The highest equivalent thermal stresses under these extreme load conditions occur at the joints of the tubes and tubes sheet and is equal to 641 and 931 MPa, respectively. Also, the lifetimes of tubes and tube sheets are 105 and 104 cycles respectively for the valley and peak load conditions.

Influence of Surroundings on Radiant Tube Lifetime in Indirect-Fired Vertical Strip Annealing Furnaces

The effects of surrounding radiation—emanating from radiation exchange with neighboring partners in indirect-fired vertical strip annealing furnaces, such as the other radiant tubes, the passing strip, and the enclosing furnace chamber—on the radiant tube lifetime were studied. In-house developed and validated numerical models were used to calculate the thermomechanical behavior, especially creep deformations and the corresponding stresses as lifetime indicating parameters. Different setups of recirculating P-type radiant tubes were investigated, including a reference case of an isolated tube. The investigations could be broadly classified into the study of the effects of different tube arrangements, burner operations (synchronous/asynchronous on/off firing), and changes of strip parameters (width/temperature). Results showed higher creep deformation of the central radiant tube in the setup with three tubes arranged horizontally in a row compared to three tubes stacked in a vertical column, even though the respective characteristic temperature values in a firing cycle were similar. Furthermore, the cases with asynchronous burner firing resulted in lower creep rates than other cases, where the burners were operating in synchronous on/off firing modes. In addition, the change of strip width had a higher impact on radiant tube lifetime compared to locally changing strip temperatures across the furnace. Alternating temperatures, caused by burner operation or process changes, such as change of strip’s speed or cross-section, and local temperature gradients were observed to be the main factors influencing the tube’s service life.

Using Vault Structure Steels to Improve the Lifetime of Radiant Tubes

In the field of industrial furnace construction, the radiant tubes used for heating are critical components. The radiant tubes, which contain a gas burner, are used for separating the oxidizing gas from the furnace atmosphere. An industrial furnace used e.g. for heat treatment of steel strip consists of several hundreds of radiant tubes. Mechanical stresses reduce the lifetime of radiant tubes considerably. For profitable use, a long lifetime is crucial. Therefore, an expanded lifetime of radiant tubes is one of the most decisive parameters in the design of industrial furnaces.This work deals with the capability of radiant tubes made of structured steel sheets. The objectives are a significant increase in lifetime as well as material savings. In addition, further advantages such as an increase in radiant surface are aimed at. The tubes were deformed in a Zwick/Roell testing machine. A vault structured tube and tube without surface structuring were compared with respect to force compensation effects and creep strength. The experimental results were supported by FEM simulation. The compensation of the maximum stresses and deformation is verified by simulation, which explains the effect of structuring on the lifetime of radiant tubes.

Investigation of the Influence of Proximal Radiation on the Thermal Stresses and Lifetime of Metallic Radiant Tubes in Radiation-Dominated Industrial Furnaces*

Abstract The influence of surrounding (or proximal) radiation on radiant tubes inside a continuous hot-dip galvanizing line was investigated. The furnace chamber, the strip and the neighbouring tubes were considered as the surroundings. A coupled heat transfer model was developed and subsequently validated against experimental measurements. This model was used to calculate the radiation exchange between the tube and its surroundings, and to give the new temperature distribution on the tubes as its output. This result served as an input to an already validated FEM model, which was used to assess the creep behaviour and the corresponding stresses on the tube. Basis of the investigated setups were Alloy 602 p-type tubes operating under burner on/off firing. The results show an increase in creep deformation of the tube when the surroundings were taken into account. Highest creep deformations were observed for setups with a strip, even though these cases showed the lowest maximum tube temperatures. Furthermore, an opposing effect between creep deformation and stresses acting on the tube exists. This is supported by the fact that no definite pattern relating the creep and stresses of a tube was found. Local tube temperature gradients and transient cyclic loading due to burner on/off firing were observed to have a significant influence on the tube's service life.

Creep lifetime prediction of virgin and service-exposed Super304H austenitic stainless steel boiler tubes based on hierarchical multiscale analysis and creep cavitation model

ABSTRACTCreep deformation of Super304H austenitic stainless steel boiler tubes in thermal power plants is evaluated using crystal elasto-viscoplastic finite element analysis (CEV-FEA). The material properties of Super304H at elevated temperatures are obtained from experiments and computations at different scales as follows: anisotropic elastic constants of Super304H at elevated temperatures (500–700°C) are obtained from molecular dynamics simulations; microstructures of virgin and service-exposed Super304H boiler tubes are observed using scanning electron microscopy; and macroscopic stress–strain and creep strain curves at 650°C are measured from tensile and miniature creep tests, respectively. Stress concentration evolution at a triple junction of grains featuring various combinations of crystallographic orientations in polycrystalline Super304H is evaluated using CEV-FEA during creep deformation. The remaining creep lifetime of polycrystalline Super304H austenitic stainless steel boiler tubes is estimated from the creep cavitation model, where the stress concentration at the triple junction is used as a representative stress driving creep cavitation.