A nozzle structure of portable high-pressure hydraulic sandblasting cutting equipment is optimized through simulation analysis and experimental tests in this paper. The hydraulic sandblasting cutting technology uses high speed sand fluid jet for cutting operations, which improves the cutting efficiency. At the beginning, the model of computational fluid dynamics (CFD) was established to simulate different types, cylinder lengths, and cone angles of nozzle. Also, the comparison analyses of the jet characteristics of the nozzles are performed. The results show that the conical straight nozzle has better jet characteristics. Moreover, combined with mathematical methods, the experimental data of conical nozzle are processed and obtained further results, including the effects on cutting depth of working pressure, cutting transverse speed, and cutting target distance. The research models and results in this paper can provide reference for optimizing nozzle structure, improving nozzle cutting efficiency, and developing similar research.

This article investigates numerically welding residual stress distributions of a tube with J-groove weld in control rod drive mechanisms of a pressurized nuclear reactor vessel. Parametric study is performed for the effect of the tube location, tube dimensions, and material's yield strength. It is found that residual stresses increase with increasing the inclination angle of the tube, and the up-hill side is the most critical. For thicker tube, residual stresses decrease. For material's yield strength, both axial and hoop residual stresses tend to increase with increasing the yield strength of Alloy 600. Furthermore, axial stresses tend to increase with increasing yield strength of Alloys 82/182.

Nuclear industry spends enormous time and resources on designing and managing piping nozzles in a plant. Nozzle locations are considered as a potential location for possible failure that can lead to loss of coolant accident. Industry spends enormous time in condition monitoring and margin management at nozzle locations. Margins against seismic loads play a significant role in the overall margin management. Available margins against thermal loads are highly dependent upon seismic margins. In recent years, significant international collaboration has been undertaken through Nuclear Energy Agency (NEA) to study the seismic margin in piping systems and nozzles through experimental and analytical studies. It has been observed that piping nozzles are highly overdesigned and the margins against seismic loads are quite high. While this brings a perspective of sufficient safety, such excessively high margins compete with available margins against thermal loads particularly during the life extension and subsequent license renewal (SLR) studies being conducted by many plants around the world. This paper focuses on identifying and illustrating two key reasons that lead to excessively conservative estimates of nozzle fragilities. First, it compares fragilities based on conventional seismic analysis that ignores piping–equipment–structure interaction on nozzle fragility with the corresponding assessment by considering such interactions. Then, it presents a case that the uncertainties considered in various parameters for calculating nozzle fragility are excessively high. The paper identifies a need to study the various uncertainties in order to achieve a more realistic quantification based on recent developments in our understanding of the seismic behavior of piping systems.

Evacuators are key components of gun barrels, and their main function is to drain the gunpowder gas remaining in the gun bore from the muzzle by ejection. To design an efficient evacuator for the gun barrels, an optimization model with the mathematical expressions describing the working process of the evacuator was established. The four structural parameters that affect the efficiency of the evacuator, including the volume of the gas storage cylinder chamber, the distance of the nozzle from the muzzle end face, the cross-sectional area of the nozzles and the cross-sectional area of the valves, were optimized. The effective working time and reliability indicator of the optimized evacuator were improved. This work describes a framework for improving the design of highly efficient evacuators on gun barrels.

Hydrostatic blasting test can be used to verify the bearing capacity of the pipeline in service. Spiral weld cracks and dents are common defects of pipes, and nozzle repair is a common repair method of perforated pipes. In order to determine the carrying capacity of the X52 pipeline with the above defects and the repaired structure, the corresponding pipe specimens were tested by hydraulic experiment, the yield pressure and burst pressure were recorded for each case. The axial and circumferential strains of the defect and repaired structure were measured in detail, the wall thickness and perimeter of the specimen before and after the experiment were measured, and the failure mechanism was analyzed. According to the relative safety factor in the standard, the bearing capacity of the pipeline was determined.

Pressure safety valves (PSVs) are designed to provide ultimate protection for pressure systems. For design or optimization purpose, it is necessary to study the lift force exerted on the valve disk. Under special valve configuration, the lift force shows discontinuity with the increment of valve opening, which is an undesirable phenomenon because it may be the cause of some serious problems, such as unstable valve operations. To study their characteristics in depth, experimental investigations are conducted in this paper. For lift force measurement, an experimental rig was specially designed and built. A series of force tests were carried out, and the result indicates that two variables, namely, the position of the adjustment ring and the thickness of the valve nozzle, have great influence on lift force; under certain valve configurations, the lift force has a discontinuous performance; for different configurations, degrees and positions of force discontinuities are very different; lift forces are linear functions of the inlet pressures, and the slopes of the force changes are similar for different valve openings.

This research paper is concerned with the mechanical behavior of the cylindrical vessels with hillside nozzles when subjected to both pressure and nozzle bending loads in cyclic forms. The influence of hillside angle on shakedown (SD) limits of the connection under cyclic pressure and combined steady pressure with cyclic nozzle bending is investigated. A shell finite element analysis model is built for the assembly using five different hillside angles ranging from 0 deg to 40 deg. Shakedown limits are determined by a direct technique known as the nonlinear superposition method (NSM). Bree diagrams for cyclic out of plane opening (OPO)/in plane (IP) nozzle moments combined with steady internal pressure are determined. The results show an increase in both OPO and IP shakedown moments as the hillside angle is increased. In addition, the OPO shakedown limit moments for all hillside angles were found to be insensitive to the level of internal pressure; this differs from the IP shakedown moment which starts to decrease with pressure for the high pressures.

In this paper, performance criteria for the seismic design of industrial liquid storage tanks and piping systems are proposed, aimed at introducing those industrial components into a performance-based design (PBD) framework. Considering “loss of containment” as the ultimate damage state, the proposed limit states are quantified in terms of local quantities obtained from a simple and efficient earthquake analysis. Liquid storage tanks and the corresponding principal failure modes (elephant's foot buckling, roof damage, base plate failure, anchorage failure, and nozzle damage) are examined first. Subsequently, limit states for piping systems are presented in terms of local strain at specific piping components (elbows, Tees, and nozzles) against ultimate strain capacity (tensile and compressive) and low-cycle fatigue. Modeling issues for liquid storage tanks and piping systems are also discussed, compared successfully with available experimental data, and simple and efficient analysis tools are proposed, toward reliable estimates of local strain demand. Using the above reliable numerical models, the proposed damage states are examined in two case studies: (a) a liquid storage tank and (b) a piping system, both located in areas of high seismicity.

In this study, a computational fluid dynamics (CFD) analysis of the transient flow field inside the secondary side of a nuclear reactor steam generator (SG) during blowdown following a feedwater line break (FWLB) accident is performed to evaluate the transient hydraulic loading (pressure) on the SG internals and tubes. The nonflashing liquid flow is assumed for a conservative prediction of the transient blowdown loading. The CFD analysis results are illustrated in terms of the transient velocity and pressure disturbances at some selected monitoring points inside the SG secondary side and compared with those predictions obtained from the existing simple analytical model to examine the physical validity of the CFD analysis model. As a result, the existing simple analytical model cannot yield the transient velocity and pressure disturbances and results in underestimation during blowdown as compared to the CFD calculations. Based on the present CFD analysis results, it is seen that an FWLB may result in excessive disastrous transient hydraulic loading on the SG internal structures and tubes near the feedwater inlet nozzle due to the significant pressure changes (pressure wave with very high amplitude) and abruptly increased velocity of water near the feedwater nozzle.

In a related work previously carried out by the authors, finite element analysis of cylindrical vessel–cylindrical nozzle juncture based on the use of thin shell theory, due to the fact that the intersecting nozzle sizes are moderate to large, have been presented. Such analysis becomes invalid in cases when the nozzles are small in sizes which may result in nozzles whose configuration violates the validity of shell assumption. As a result, use of solid elements (based on theory of elasticity) in modeling the cylindrical vessels with small-diameter nozzles is presented in the present paper. Discussions of the numerical experiments and the results achieved are, first, given. The results are then compared with the prediction by other models reported in the literature. In order to arrive at the overall design charts that cover all the possible ranges of nozzle-to-vessel diameter ratio, the charts for the vessels with moderate-to-large-diameter nozzles are augmented with those of cylindrical vessels intersected by small-diameter nozzles developed in this work.

The juncture of a small cylindrical nozzle to a large cylindrical vessel is very common in the pressure vessel industry. Upon fabrication, it is required that the whole structure is subjected to pressure testing. The test can be expensive as it necessitates pressurizing the whole structure typically having a large volume. Hence, it is proposed to make a “local test,” which is considerably simpler as it involves capping the small nozzle and testing only a relatively small portion of the structure. This paper investigates the accuracy and reliability of such an alternative test, using the finite-element method. Two different finite-element types are used in the study, specifically a shell-based element and a solid-based element. The verification of the finite-element results for two different cases shows that the models used in the study are valid. It also proves that the two element types yield very similar stress results. In addition, the study includes a numerical investigation of more than 40 different nozzle-to-vessel junctures with a wide range of parameters for the nozzle and vessel. The results indicate that the use of cylindrical caps that are slightly larger than the nozzle is not recommended as it produces stresses that are significantly different from those for the original required pressure test. As such, the study provides an estimate of the smallest size of the cap that may be used in the local test to generate stresses that agree with the full test. For most practical geometries, it is shown that the size of the cap needs to be at least 2–30 times larger than that of the nozzle, depending on the geometrical parameters of the juncture.

Parametric study of the thin shell solution of internally pressurized spherical vessel–cylindrical nozzle juncture is used to develop simplified closed-form formulas of stress concentration factor (SCF) as functions of the key vessel–nozzle geometric parameters known to influence the solution. The SCF values are not based on the vessel stresses alone; nozzle stresses are also analyzed and the corresponding SCF determined. Therefore, for a given vessel–nozzle juncture, the designer will be left with adequate information upon which to decide the controlling SCF. Predictions by the proposed equations are validated using finite element method (FEM). Consequently, design charts are presented based on both the vessel's and nozzle's SCF as predicted by the proposed expressions.

As an industry norm, the nozzle local loads are considered to be local and are not considered in foundation design. Presently, this norm is under debate. One opinion is some percent of these loads are to be considered to be transferred to the foundation. The horizontal forces on the foundation are more critical than vertical forces. Attempt has been made to understand the system and create a model which will represent the system to a good approximation. A mathematical model is developed to demonstrate the actual system. It is a stiffness system consisting of equipment, nozzle junction, and connected piping. The connected pipes are heated sequentially to generate nozzle loads in axial and out plane directions. Steady-state thermal loads are calculated for the given system stiffness. Governing parameters are identified and altered to note the effect. The governing parameters identified are equipment diameter (D), nozzle location on equipment (x), and nozzle diameter (d). The effect is studied for pressure range (20–120 bar) and temperature (100–400 °C). The results of percentage loads transferred with respect to the governing parameters are plotted. It is observed that nozzle loads in axial directions are transferred to the foundation almost 100%, whereas out plane loads are absorbed by the system to a greater extent. Further study is required to investigate combined effects of all such nozzle loads for single equipment. The results may be refined for different materials and effect of nozzle reinforcement.

Primary water stress corrosion cracking (PWSCC) phenomenon in dissimilar metal welds is one of the safety issues in ageing pressurized water reactor (PWR) piping systems. It is well known that analysis accuracy of cracking propagation due to PWSCC depends on welding residual stress conditions. The U.S. Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute (EPRI) carried out an international round robin validation program to evaluate and quantify welding residual stress analysis accuracy and uncertainty. In this paper, participation results of the authors in the round robin program were reported. The three-dimensional (3D) analysis based on a fast weld simulation using an iterative substructure method (ISM), was shown to provide accurate results in a high-speed computation. Furthermore, the influence of different heat source models on analysis results was investigated. It was demonstrated that the residual stress and distortion calculated using the moving heat source model were more accurate.

The assessment for adequacy in managing the effects of fatigue in the ASME Code Class-1 (pressure boundary) components is based on a calculated measure of the projected fatigue damage. This measure is the highest cumulative usage factor (CUF) in a given component under a specified set of cyclic loadings and their expected number of repetitions. The Code based calculation of CUF and its adjustments for potential environmentally assisted fatigue (EAF) damage accumulation utilize a multitude of inputs, and conservative assumptions and applied margins. To support the extended service life beyond the original design, or longer life of new designs, changes in inputs and/or conservative assumptions used in these deterministically calculated CUFs are often made to meet a deterministic performance criterion. This makes the impact of uncertainty in the inputs and/or changes in the conservative adjustments difficult to assess. This paper presents a generic, engineering approach for estimation of the uncertainty distribution of CUF based on the expected statistical characteristics of input variables used in the calculation of EAF-based CUF. The approach does not involve Monte Carlo sampling. The proposed statistical approach analytically combines variances of the inputs leading to an acceptable estimation of the total variance of the CUF. The approach does not require specification of full probability distribution(s) for the input variables, nor is the dependence between variables a critical issue from the analytical point of view. Feasibility and limitations of the approach are discussed in relation to the NB-3200 and NB-3600 procedures of the ASME Code and the current Fen-based augmentation for environmental effects. This approach is further examined in the framework of stress–strength interference methodology to account for the uncertainty in the fatigue performance criterion which can lead to a rational deterministic safety factor interpretation and its relation to a quantifiable measure of the probability of exceeding the fatigue performance criterion.

This paper introduces a novel method for effectively mitigating high thermal stresses caused during local postweld heat treatment (PWHT) of welds in pressure vessels on which traditional heating method such as bull's eye heating arrangement has been proven difficult in meeting Code requirements for avoiding “harmful” temperature gradients. The method involves the use of a secondary heat band (SHB) that strategically positioned at some distance away from primary PWHT heat band (HB) in terms of vessel characteristic length parameter Rt, where R is vessel radius and t wall thickness. The basic principles associated with the SHB based technique are first demonstrated on a simple straight pipe girth weld configuration. Then, applications for treating nozzle welds in more complex spherical vessel, cylindrical vessel, and at end of cylindrical vessel are presented. Finally, a set of recommended guidelines are provided for defining both the SHB size and location for performing local PWHT on welds in three major nozzle/vessel weld configurations.

This paper describes a sequence of residual stress measurements made to determine a two-dimensional map of biaxial residual stress in a nozzle mockup having two welds, one a dissimilar metal (DM) weld and the other a stainless steel (SS) weld. The mockup is cylindrical, designed to represent a pressurizer surge nozzle of a nuclear pressurized water reactor (PWR), and was fabricated as part of a weld residual stress measurement and finite-element (FE) modeling round-robin exercise. The mockup has a nickel alloy DM weld joining an SS safe end to a low-alloy steel cylinder and stiffening ring, as well as an SS weld joining the safe end to a section of SS pipe. The biaxial mapping experiments follow an approach described earlier, in PVP2012-78885 and PVP2013-97246, and comprise a series of experimental steps and a computation to determine a two dimensional map of biaxial (axial and hoop) residual stress near the SS and DM welds. Specifically, the biaxial stresses are a combination of a contour measurement of hoop stress in the cylinder, slitting measurements of axial stress in thin slices removed from the cylinder wall, and a computation that determines the axial stress induced by measured hoop stress. At the DM weld, hoop stress is tensile near the OD (240 MPa) and compressive at the ID (−320 MPa), and axial stress is tensile near the OD (370 MPa) and compressive near the midthickness (−230 MPa) and ID (−250 MPa). At the SS weld, hoop stress is tensile near the OD (330 MPa) and compressive near the ID (−210 MPa), and axial stress is tensile at the OD (220 MPa) and compressive near midthickness (−225 MPa) and ID (−30 MPa). The measured stresses are found to be consistent with earlier work in similar configurations.

The linear matching method (LMM), a direct numerical method for determining shakedown and ratchet limits of components, has seen significant development in recent years. Previous verifications of these developments against cyclic nonlinear finite element analysis (FEA) have shown favorable results, and now this verification process is being extended to include comparisons with experimental results. This paper presents a comparison of LMM analysis with experimental tests for limit loads and shakedown limits available in the literature. The limit load and shakedown limits were determined for pipe intersections and nozzle-sphere intersections, respectively, thus testing the accuracy of the LMM when analyzing real plant components. Details of the component geometries, materials and test procedures used in the experiments are given. Following this a description of the LMM analysis is given which includes a description of how these features have been interpreted for numerical analysis. A comparison of the results shows that the LMM is capable of predicting accurate yet conservative limit loads and shakedown limits.

The paper reports on recent progress in numerical shakedown and limit analysis based on Melan's lower bound shakedown theorem. After explaining the theoretical foundations of their approach, the authors describe in detail the numerical scheme, in particular the underlying optimization via interior point methods. Numerous examples mostly related to pressure vessel technology are presented, illustrating the potential of the method.

The objective of this paper is the further investigation of the shell intersection problem. The pad reinforced nozzle connections of the cylindrical vessel under internal and external loads are investigated using elastic–plastic analysis and the stress analysis in intersecting shells (SAIS) special-purpose computer program. The method for determining the plastic limit load based on the maximum criterion of the rate of the change of the relative plastic work and program module LOAD_PL for its realization are presented. The results of comparisons with the twice elastic-slope (TES) method were considered for determining the plastic limit load using known experimental data for models of a pad reinforced cylindrical vessel with a radial nozzle under a transverse force. The results of a parametric study of unreinforced and pad reinforced vessel models with a nozzle under internal pressure, in-plane moment, and out-plane moment loadings are discussed.