bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation Method and Analysis on Thermal Compressor Ejection Characteristics
Authors: Xu Huiqiang , Dai Shoubao , Sun Na , Sun Lin , Wang Yanqing
Published: December 2022

Thermal compressor, a similar device like steam driven jet pump, is usually used to keep the vacuum level of condensers in nuclear power plant. Meanwhile, the utilization of thermal compressor is an effective way to recover the heat of exhausted steam from turbines, improving the energy efficiency of secondary circuit in nuclear power plants. The extreme entrainment ration of thermal compressor is a significant parameter to describe its working performance. The present research conducts the theoretical derivation of the related physical process inside the thermal compressor and builds a theoretical model calculating the maximum entrainment ration. The results show that the present model can predict the ejection ability of the thermal compressor with satisfactory accuracy and application scope. The average relative deviation between calculated and experimental result is 9.7% and the maximum deviation does not exceed 23%. Moreover, the results of the model calculation indicate that the ejection ability is enhanced with the increase of primary and suction steam pressure, but weakened by the increase of compressed steam pressure. The entrainment ration increases with the superheat degree of primary steam because of the increasing critical velocity while the superheat degree of suction steam makes no obvious influence.
Development and Verification of Thermal-Hydraulic Constitutive Model for Rectangular Channel
Authors: Feng Yun Fei , Li Lei , Nie Ya Jie , Jiao Xin , Li Jian Yi , Meng Si Jia , Li Ying Hao
Published: December 2022

The plate-shaped fuel element has good heat transfer characteristics, high average power density of the core, and low temperature of the fuel core, which is beneficial to improve the power-to-volume ratio of the core and ensure the safety of the core. Therefore, plate fuels are widely used in compact reactors such as research reactors, integrated reactors, and high-flux reactors. at present, most thermal-hydraulic analysis programs, such as RELAP, RETRAN, THEATRE, are mostly developed for large-scale pressurized water reactors using rod-shaped fuels. It is suitable for narrow rectangular channel of plate type fuel core. Based on this, this paper developed a set of thermal-hydraulic constitutive relation models suitable for narrow rectangular channels, including: flow resistance coefficient calculation model, wall heat transfer Coefficient calculation model, CHF calculation model, etc. The thermal-hydraulic constitutive relational model library of rectangular channel of plate-shaped fuel element is developed by using C++ language. In this paper, the developed constitutive relation model is transplanted into the reactor thermal-hydraulic real-time simulation program, and the IAEA 10MW material test reactor (MTR) benchmark is used to verify the developed rectangular channel thermal-hydraulic constitutive relation model library. Simulation analysis is carried out for two typical accident conditions, reactive introduction (RIA) and loss of flow accident (LOFA) defined in the benchmark problem. correctness.
Study on Fluid-Structure Interaction of Fuel Rod Bundle With Spacer
Authors: Li Shuang , Sun Lanxin
Published: December 2022

In the reactor, the axial flow of the coolant into the core causes the rod bundle to vibrate, and the long-term flow-induced vibration will cause fretting wear. In severe cases, the fuel cladding will be destroyed, jeopardizing the efficiency and safety of the reactor. Therefore, the study of the fluid-induced fluid-structure interaction of fuel bundles is beneficial to ensure the safety of the reactor. In this paper, based on computational fluid dynamics and computational structural dynamics, using Euler-Bernoulli beam theory (Euler-Bernoulli), the numerical calculation of fluid-structure interaction is realized by Fluent. And compared with the 5 × 5 fuel bundle without grid.The influences of the rod bundles with or without grids on the fluid pressure, fluid displacement and vibration under different cross-sections are mainly analyzed, as well as the principle of flow-induced vibration in axial flow. The results show that the influence of the vibration of the rod bundle on the flow field is very weak and can be ignored; The pressure difference between the two radial ends of the fuel rod bundle is one of the factors that cause the flow-induced vibration; The existence of the spacer grid aggravates the disturbance of the flow field, so that a larger pressure difference between the two rod bundles causes a larger vibration, and also affects the position where the larger vibration displacement occurs.
Three-Dimensional Fine-Mesh Coupled Neutronics and Thermal-Hydraulics Calculation for PWR Fuel Pins
Authors: Xie Qiuxia , Liu Xiaojing , Chai Xiang
Published: December 2022

With the great improvement of computer performance, multi-physics and high-fidelity reactor numerical simulation has attracted widespread attention. The development of a three-dimensional fine-mesh coupled neutronics and thermal-hydraulics procedure mainly using the free open source C++ library OpenFOAM is presented in this research. The coupling codes are allowed to solve the coupled neutronic and thermal-hydraulic problem within the same one procedure for both steady-state and transient conditions, avoiding the data transmission between different programs. The coupling strategy among two physical fields is implemented in the same fully three-dimensional and fine mesh system, which eliminates numerical errors caused by the mapping of the grid. For the thermal-hydraulics, the built-in solid-fluid coupling conjugate heat transfer solver is applied for the calculation of the fluid mass, momentum, and energy equations, together with the solid energy equation to obtain the temperature distribution. The neutron diffusion equation is solved iteratively via the developed three-dimensional multi-group multi-region neutron diffusion solver to get the power distribution. The macroscopic cross-sections are pre-generated by the Monte Carlo code OpenMC and fitted as functions of temperature added in the neutron diffusion solver. The temperature distribution obtained by thermal-hydraulics calculation will change the macroscopic cross-sections and then impact the neutron diffusion calculation, while the power distribution gained from the neutronic calculation is transferred to the thermal-hydraulics calculation and is used as the heat source term. This coupling methodology are tested on a 3 × 3 PWR fuel pins model. The results show that all physical fields conform correct distribution regularity, illustrating the feasibility of the coupling methodology.
Analysis of the Thermal Performance of the Passive Containment Cooling System Based on Heat Pipe Technology Under Nuclear Accidents
Authors: Wenying Ji , Changdong Lu , Yangyong Ou , Yichen Chen
Published: December 2022

To evaluate the thermal performance of a closed-loop Passive Containment Cooling System (PCCS) based on hot pipe technology under nuclear accidents, the coupled effect of three systems of reactor primary cooling circuit, containment and the PCCS is analyzed under LB-LOCA with SBO and SB-LOCA with SBO with the PCCS started one hour after the accident. The coupled analysis method is that the heat transfer power of PCCS simulated by the LOCUST model and the mass and energy releasing results obtained from the integrated analysis program for serious accidents are the inputs for containment thermal response analysis code. The results showed that in the 0∼10 hours after the accident, the containment pressure is less than the design limit of 5.20bar.a; in the middle and long term of ten more hours after the accident, the containment pressure is less than 3.50bar.a, the integrity of the containment can be ensured and the feasibility of the design of the PCCS in this paper is validated.
Assessment on Partial Derivatives for Thermal-Physical Properties of Carbon Dioxide
Authors: Wen Shuang , Wen Qinglong
Published: December 2022

To adapt to a requirement of improving the accuracy and efficiency of calculation, a full or partial implicit scheme is usually employed in solving the conservative equations of the supercritical carbon dioxide (S-CO2) Brayton cycle, and partial derivatives of thermal properties such as (∂h/∂ρ)p and (∂h/∂p)ρ are needed in numerical solver. In this paper, the most representative state equations of carbon dioxide are investigated and evaluated by experimental data. The Span-Wagner (SW) equation has a minimal error in all state equations, so the SW equation is chosen as the fundamental equation of thermal properties for partial derivatives. Based on that, the equations of partial derivatives such as (∂h/∂ρ)p and (∂h/∂p)ρ are presented by the Maxwell equation. The paper also evaluates the closure of partial derivatives equations. The deviations of (∂h/∂ρ)p and (∂h/∂p)ρ are within ±0.01% for most points. The maximum closure error of (∂h/∂ρ)p is 0.373%, and the maximum one of (∂h/∂p)ρ is −0.798%. Therefore, the partial derivatives equations obtained in this paper can play a significant role in the safety analysis code.
Research on the Effect of Non-Uniform Inflow on the Cavitation Characteristics of the RCP
Authors: Song Yu , Huang Song , Xu Rui , Yin Junlian , Wang Dezhong
Published: December 2022

In Advanced Passive (AP) series reactors, the reactor coolant pump (RCP) is directly connected to the bottom of the steam generator (SG) rather than a longer pipe for the fully development of inflow, which leads to an unsteady flow at pump inlet. Some scholars have done several study on the cavitation characteristics of RCP. However, the reality is that two pumps are operating at the same time with different inflow. There has been little research about this. Thus, in this paper, a special test loop has been established to simulate this situation. Then numerical and experimental study were carried out with the special system. As a result, cavitation characteristics of parallel pumps were illustrated under the condition of non-uniform inflow, and these results were compared with the uniform condition. The results show some differences in cavitation performance between different conditions. On the one hand the non-uniform incoming flow causes the angle of attack of the impeller changed, and the distribution of cavitation on the blades varies greatly. On the other hand, there are also some difference in cavitation characteristic between the two pumps duo to the distinction of inflow. The cavitation performance has a little change in rated and small flow condition, but for large flow condition has been a dramatic deterioration.
Numerical Simulation of Transient Thermal-Hydraulic Characteristics of Intermediate Heat Exchanger for Sodium Cooled Fast Reactor Under Accident Conditions
Authors: Zeng Xiehu , Wen Qinglong , Bai Genxing
Published: December 2022

In Generation IV nuclear systems, Sodium Cooled Fast Reactor has attracted extensive attention for its particular advantages. Intermediate Heat Exchanger (IHX) is a significant equipment connecting the primary circuit system and secondary circuit system in Sodium Cooled Fast Reactor. Under normal and accident conditions, the temperature fluctuation of the IHX component may cause the alternating change of the local stress, such as sealing weld zones mixing chamber, and the area between inner and outer sleeves. This fluctuation may result in the thermal fatigue of IHX and consequently affect the safety and economy of the reactor operation. Therefore, it is essential to carry out mechanical analysis by experiments or simulations to ensure the structural stability under complex conditions. However, the mechanical analysis must take transient thermal-hydraulic characteristics as boundary and input conditions. Thus, a thorough thermal-hydraulic assessment of IHX is required to guarantee its security under accident conditions.

In this paper, a thermal-hydraulic simulation of IHX was carried out using system code under steady and transient state conditions. Thermal parameters of steady-state calculation agreed well with the design requirements. Transient-state accident conditions, such as emergency shutdown, Station Blackout (SBO), and Steam Generator Tube Rupture (SGTR), were conducted in this paper. In the emergency shutdown, the wall temperature increased from 703.15 K to 798.41 K in three seconds, and then decreased slowly and stabilized at 626.15K. In the SBO accident, the temperature of the primary and secondary circuit fluids fluctuated violently from 0 to 100 seconds. When the secondary side flow drops to 0, the wall temperature of typical positions changes with the inlet temperature of the primary side, showing a trend of rapid decline and stable. In the SGTR accident, the temperature of the heat transfer tube wall increased rapidly during the early stage of the accident. After that, the primary side flow reduced gradually to 0 with the decrease of the secondary side flow. Because of the trend of flow, the temperature of the tube wall decreased rapidly and then increased slowly. Therefore, the results of various accident conditions in this investigation can contribute to the thermal fatigue analysis of IHX in the near future.
Investigation on a Complete Passive Cooling System Using Large-Scale Separate Heat Pipes in Spent Fuel Pool
Authors: Han Fei , Chen Xiting , Kuang Yiwu , Wang Wen , Ye Cheng
Published: December 2022

Large-scale separate heat pipes used in the complete passive cooling system (PCS) transfer the decay heat in the spent fuel pool (SFP) efficiently through the two-phase natural circulation without any external power. In this study, a lumped mathematical model for the heat pipes are developed and parameters related to the heat transfer ability are discussed to settle the number of the heat pipes under different heat load. For the condensers at the auxiliary building, the effects of the tube pitch and the fin height are discussed, which are key parameters to the heat transfer performance. Different structural designs of the PCS under typical operating conditions are settled. A larger quantity of heat pipes is required for higher decay heat power conditions. To validate the reliability of the PCS, transient three-dimensional simulations of the SFP with immersed evaporators under different heat loads are conducted. Based on the results, detailed thermal-hydraulic characteristics are captured in the pool. Large natural convection circulations are formed at the steady-state. Single flow circulation is formed in the X-Z plane under low heat load cases while a pair of counter-rotate natural convection circulations under high heat load cases. A larger heat load promotes the natural convection intensity and shortens the response time of the PCS. Proper distance between the heat source and heat sink in both vertical and horizontal directions in the SFP is beneficial to the flow organization, improving the heat transfer efficiency of the PCS. The maximum temperature in the SFP is always below the saturation point after the startup of the heat pipes, which could validate the reliability of the PCS and ensure the safety of the plant under emergency conditions.
Large-Eddy Simulation for Dynamical Behavior of Drag and Lift Force on Cylinder Under Critical Reynolds Number Condition
Authors: Hattori Yasuo , Hasebe Yuma , Suto Hitoshi , Nakao Keisuke , Ishihara Shuji
Published: December 2022

We examined performances of LESs by using an open source CFD code, OpenFOAM, which has been widely used all over the world for numerical turbulence simulating, to represent dynamic behavior of drag and lift forces on a cylinder under critical Reynolds number condition. Special attention was paid to effects of numerical set-up of LESs, such as differencing schemes and a wall function for calculating sub-grid scale stresses. The present simulations were based on a LES version with PIMPLEfoam of OpenFOAM, in which the option of RANS scheme was turn off with adding subgrid-scale diffusion estimated by the Smagorinsky model. Two kinds of differencing schemes and wall functions were used, i.e., one was a limited-linear and the other was a liner-upwind scheme with a low-Reynolds number type or a Spaliding type wall function. Effects of numerical set-up on time averaged values of these forces and the Strouhal number, which is a non-dimensional parameter for the frequency of waveform of these forces, were neglectable. On the other hand, the time-series and p.d.f.s of fluctuation components of drag and lift forces clearly showed the upwind scheme with a low Reynolds number type wall function yields attenuations of fluctuating forces. Contrary to these, the LESs by using a limited-linear scheme gave the good agreement of r.m.s. values of fluctuating these forces with previous studies based on DNSs, implying that LESs for examining dynamic behavior of drag and lift forces must require differencing schemes with small numerical diffusions.
Numerical Simulation Study on Anti-Wave Problem of Fluid Storage in Pressurizer Under Marine Conditions
Authors: Yue Jinyu , Wei Tianyi , Xu Sijie , Zhang Biao , Li Dongyang , Tan Sichao
Published: December 2022

Under the influence of marine conditions on nuclear powered ships, the liquid storage in the Pressurizer shake violently, which affects the normal operation of the Pressurizer and even causes safety accidents. Therefore, it is extremely urgent to design an anti-wave device for the Pressurizer. This paper studies a Pressurizer model with a ring-shaped plate. Using numerical simulation software, the VOF method is used to couple the k-ε model to simulate the liquid level fluctuation of the two Pressurizers with and without anti-wave device under different external excitation cycles. The phenomenon of internal liquid level fluctuation during movement was analyzed, and the pressure transient change characteristics of the pressure monitoring points arranged on the pressurizer were analyzed, so as to compare the different axial sections and the overall water level shaking amplitude. By comparing the simulation results, it is found that when the external excitation period is T = 2∼2.5s, the ring-shaped plate studied in this study can suppress the shaking of the liquid storage in the Pressurizer significantly.
Simulation of Pseudo-Critical Line Based on Different Equation of State and Definition of Pseudo-Critical Region
Authors: Zhao XueBin , Wang Suhao , Liu Ruilong , Liu Xiuting , Huang Yanping
Published: December 2022

The thermophysical properties of supercritical fluids (SCF) will change drastically in the narrow range of thermodynamic conditions near the pseudo-critical line, and this narrow region of thermodynamic parameters is named the pseudo-critical region. The complex fluctuation of thermophysical properties in the pseudo-critical region makes SCF’s thermal-hydraulic characteristics very different from that of subcritical fluids. Therefore, the normal flow and heat transfer prediction models are no longer applicable among this region. From the perspective of engineering application, it is very necessary to determine the pseudo-critical line and pseudo-critical region as a reference point for adjusting thermodynamic parameters and improving the processing efficiency in the application of SCF. In the paper, supercritical carbon dioxide is taken as the research object. First, the pseudo-critical lines were obtained respectively according to three different equations of state. Then, based on the continuous phase transition theory, the pseudo-critical region was determined by the Ehrenfest equation. Finally, the occurrence area of heat transfer deterioration was in alignment with the proposed pseudo-critical region, and the mechanism that affects the heat transfer deterioration behavior was analyzed.
Pump Station Design II: A Tale of Two Pump Stations
Authors: Horner Jim
Published: December 2022

IPC 2014-33740 [1], Pump Station Design, summarized the work Enbridge had completed on the design and construction of 65 new pump stations and the modification of a further 16 existing stations. The $4.0 billion dollar scope was completed over a 12-year period, with the last stations being completed in 2019. This paper documents the application of this body of work on the Keystone XL Pipeline project for TC Energy. This work included the design of 32 new pump stations.

The Keystone XL project experienced delays due to legal and regulatory challenges which gave TC Energy the opportunity to reevaluate their pump station design. The previous design was piping centric and had a significant footprint. The station design developed for Enbridge was more equipment centric, and owing to the compact layout, presented the potential for cost savings in excess of $140 million for their project. This paper provides a unique perspective with which to evaluate the design philosophies employed by comparing the two station designs developed independently.

While the basic design was proven, new work was completed to validate the new application. This effort demonstrated that these pump stations are a unique piping subset. The operating temperature is relatively modest, but the piping is exposed to high pressure and high flow rates (HPF). Prolonged operation with high turbulence and pressure can result in fatigue related failures. These HPF piping systems require additional tools for their design. These analytical techniques include:

• Erosion studies to validate limiting velocities and pipe sizing

• Dynamic piping analysis to minimize potential vibration due to beat frequencies and pressure pulsations

• Finite Element Analysis (FEA) of small-bore connections to minimize the potential for fatigue related damage.

• Computational Fluid Dynamics (CFD) studies to minimize the impact of pump suction turbulence on pump performance.
Sulfide Stress Cracking Response of X80 Simulated Heat Affected Zone for Offshore Pipeline and Riser Application
Authors: Kuo Chih-Hsiang , Zeng Yifei , Baker David , Huang Weiji , Dunn Geoff , Hoyt Douglas , Ladeuille Laurent , Evin Harold
Published: December 2022

To facilitate development of future deeper water assets, riser and pipeline designs using current X65 carbon steel requires increased wall thicknesses to manage the demand from large tensile loads. This increase in wall thickness is due to the weight of the pipe body and the fatigue performance at the hang-off and the touch-down point for steel catenary risers (SCR) and steel lazy wave risers (SLWR). The increased wall thickness poses challenges for fabrication, design, installation and project execution due to the single side welding of thick pipe. Increasing the steel grade from the current X65 to X80 or higher strength grade could reduce the pipe wall thickness and provide potential cost savings from total tonnage and is therefore considered as a potential alternative for deeper water steel riser applications. However, it is challenging to meet the hardness acceptance criteria (i.e. 250 HV10) as per DNV-ST-F101 for the higher strength steel weldment, particularly for sour service.

The objective of this study was to understand the effect of hardness on sulfide stress cracking (SSC) resistance of X80 line pipe base material and weldment in sour service environments. A 323.9 mm OD × 25.4 mm WT seamless quenched and tempered X80 line pipe was used for this study. Coupons were extracted from the pipe and then heat-treated by welding simulator (Gleeble™). Implementing controlled cooling, hardness values ranging from 270 to 350 HV10 were achieved, and representing the heat affected zone (HAZ) hardness. Four point bend SSC test were performed on coupon halves as per NACE TM-0316, loaded to 80% actual yield strength (AYS) and tested for 30 days in selected NACE Region 2 and 3 environments as specified in NACE MR0175/ISO 15156-2. Coupons showed no indication of SSC cracking for the samples with measured hardness values of ∼320 HV10 in the selected NACE Region 2 and 3 environments.
Risk Based Asset Management Model for a Natural Gas Transmission Pipeline
Authors: Hommes Martin , Jager Eric , Kassenberg Paul , Borisov Oleg , Ribberink Jan
Published: December 2022

Gasunie Transport Services (GTS) operate the Dutch high pressure natural gas transmission system in the Netherlands of roughly 12,000 km, which is almost 60 years old. The demand of natural gas is decreasing, although there will remain a need for natural gas for the next decades. A backbone for transporting hydrogen is developed for the near and far future, where possible using former natural gas pipelines. Therefore, there is a need to determine how efficiently this transmission system can be operated for the near and far future. This requires balancing expenditures (CAPEX and OPEX) and risks of operating this transmission system. For this, GTS applies risk based asset management (RBAM). The goal of RBAM is to efficiently use resources (especially manpower and budget), prevent unacceptable high risks and prevent unacceptable high expenditures. So, there is a need to determine the monetized risk of gas transmission pipelines. This can be used to formulate policies for transmission pipelines in general and assess local bottlenecks. E.g., what is the risk of a pipeline section with low depth of cover or is corrosion acceptable and can it be managed efficiently. For this a pipeline risk model “LRM” has been developed, that calculates failure frequency and consequences and thereby risk for 12,000 km.
Laboratory Testing of a Model for Pipe Buried Into Sand Subjected to a Surface Loading
Authors: Mertz Antoine , Dano Christophe , Fernandez Charles , Jenck Orianne , Lebrun Adrien , Emeriault Fabrice
Published: December 2022

A pipe buried into sand was subjected to a surface loading in order to study its mechanical behaviour. The test was conducted at small scale, in a tank filled with sand, while the pipe was instrumented with strain gauges and inner displacements sensors. The paper presents the soil vertical settlement, and pipe response to the load, in terms of deformations, stresses, and radial displacements. The radial displacements are computed using a specially developed methodology and allow to present the deformed shape of the pipe, with limited direct measurements. Results show that under this loading the vertical diameter of the pipe decreases, while the horizontal one increases, but to a lower degree. The deformed shape is more complex than the ellipse often considered. The pipe deformed shape exhibits a rapid change in curvature near the crown, often referred as “heart shaped deformation” in the literature. The overall values of stresses reached remain far from the elastic limit of the material used, and smaller than the impact of the inner gas pressure for this type of relatively thick pipe of moderate diameter.
Pipe-CLSM Interface Bond Strength From Axial Pullout Testing
Authors: Zulkoski Caroline , Wijewickreme Dharma , Honegger Douglas
Published: December 2022

Buried pipeline systems form the backbone of the oil and gas transportation infrastructure, and the performance of these systems located in areas subject to potential ground movements is a critical consideration in engineering design. In mitigating against future or on-going ground displacement hazards, there are instances where the axial soil restraint (soil anchoring capacity) needs to be increased to avoid transferring loads to adjacent potentially vulnerable components in the pipeline system. One method to increase axial soil restraint is to increase the effective diameter of the pipeline. This can be done by encasing the pipeline in controlled, low-strength material (CLSM). The use of CLSM to increase axial soil restraint on buried pipelines requires that the axial load to produce pipe-CLSM interface bond failure be greater than that required for failure at the CLSM-soil interface. To advance the state of knowledge of the axial failure mechanisms of the soil-CLSM-pipe composite, a systematic full-scale testing program was undertaken using the Advanced Soil Pipe Interaction Research (ASPIRe™) modeling chamber at the University of British Columbia. Research findings from 22 axial pullout tests that were completed to assess the bond strength at the interface between CLSM and NPS 8 steel pipe specimens with various coatings are presented. The tests reveal that the bond strengths as a percentage of compressional strength measured in studies of CLSM cast around cold-formed steel align closely to the values measured from these tests.
Development of an Online Calculation Tool for Safety Evaluation of Pipes Subjected to Ground Movements
Authors: Zheng Qian , Qiu Weichen , Ergezinger Noah , Li Yong , Yoosef-Ghodsi Nader , Fowler Matt , Adeeb Samer
Published: December 2022

Underground pipelines are inevitably installed in unstable geohazard areas associated with the possible development of significant ground deformations. Under ground movement, excessive strains can be generated in the pipe wall, which poses a threat to pipeline integrity. This study aims to develop an industry-oriented calculation tool for safety evaluation of pipes subjected to ground movements induced by a variety of nature and construction-related hazards. The tool, comprised of deterministic and reliability-based analyses, is designed within MecSimCalc which is an innovative online platform for creating and sharing web-based Apps for individuals and groups. Calculation flow behind the tool is developed according to a novel method proposed based upon the finite difference method (FDM). Given grid nodes along the pipe, a large set of simultaneous finite-difference equations are constructed based on nonlinear governing differential equations of the Euler-Bernoulli beam under large deflections. The nonlinearities arising from pipe material, pipe-soil interaction, and geometry of the pipe are considered within the model. As unknowns of the finite-difference equations, the axial and lateral displacement of the pipe at each grid node can be obtained using nonlinear equation solvers. This method is utilized to predict the strain demand in the limit state function for reliability-based assessment. Applying stochastic properties for each basic parameter, the probability of failure can be calculated using Monte Carlo Simulation. Meanwhile, the program is compiled using Numba in Python and then optimized by the parallelization technique to enhance computational efficiency.
Modelling Accidental Impact Threats to Natural Gas Storage Wells
Authors: Smith Shawn , Fraser Alex , Shironishi Mari , Neville Dan , Shapiro Dan
Published: December 2022

API RP 1171, which was recently incorporated by reference in US regulation 49 CFR 192.12, and the recent changes to the California Code of Regulations have mandated risk assessments be performed for underground storage wells. A quantitative risk assessment framework has been developed for SoCalGas’s underground gas storage sites in California. This framework includes quantitative models for accidental impact threats to the wellhead and lateral piping, including damage from excavations, vehicle collisions, lifting operations, and aircraft crashes (for first, second, and third-parties). In an industry survey of underground storage operators conducted by the Gas Research Institute in 2004, 15% of the recorded significant release incidents were due to accidental impact threats. Additionally, since there are likely individuals in the immediate vicinity when the incidents occur, releases due to accidental impact threats may carry more significant consequences. In this work, models were adapted from existing industry models for pipelines, nuclear facilities, and aboveground piping stations by updating the inputs to reflect an underground gas storage context and calibrating the overall results to match historical underground gas storage incident data. The models incorporate well-specific attributes and measurements as well as subject matter expert (SME) experience and judgement, with key variables for each model including:

• Excavation damage: excavation frequency (estimated from site-specific one-call data), material and operational properties of buried lateral piping, depth of cover

• Vehicle collisions: vehicle traffic near the well (estimated from modelling the site road network and all site activities involving vehicles), presence of any barriers, the layout of any aboveground lateral piping

• Lifting operations: lifting operation frequency near the well (estimated from modelling the future workover activities at all nearby wells), material and operational properties of the wellhead, and any aboveground lateral piping

• Aircraft crashes: proximity and orientation relative to nearby airports, amount and type of traffic at the nearby airports, the layout of the lateral piping

This paper illustrates the results for field-wide assessments of these accidental impact threats, showing how the risk is differentiated by the specific well context. In contrast to using a single historical incident rate, the models capture the differences in risk between wells within and across fields and can help estimate the effect of performing mitigation activities on specific wells.
Development of a Hybrid of Semi-Automatic Waveform Controlled GMAW and Mechanized FCAW-G Welding Process and Associated Alternative Weld Flaw Acceptance Criteria For Pipeline Construction
Authors: Lu Junfang , Huntley Bob , Aulin Axel , Duncan Andy , Schamuhn Kirk Peter , Belanger Rory , Zorrilla Claude-Yve , Tetteh-Wayoe Debra
Published: December 2022

Pipelines are widely used in the oil and gas industry for transporting crude oil and natural gas from the field to refineries. It has been a general practice to use alternative weld flaw acceptance criteria to assess the acceptability of mechanized girth welds using an engineering critical assessment (ECA) approach. The ECA concept of defining weld flaw acceptance criteria has been accepted as a fitness for service (FFS) assessment based on fracture mechanics, which requires robust welding procedures. Effective planning of the welding procedure specification (WPS) qualification and mechanical testing of the weld and heat-affected zone (HAZ), and weld inspection are the key factors contributing to robust welding procedures and an effective ECA.

Mechanized gas metal arc welding (GMAW) processes are commonly used in pipeline girth weld welding because of their high quality and productivity. With the technical advancements of non-destructive testing (NDT) techniques, the use of automated ultrasonic testing (AUT) with supplemental time of flight diffraction (ToFD) has further enhanced the accuracy and productivity in weld inspection, weld flaw sizing, and probability of detection. The use of alternative acceptance criteria to assess the acceptability of mechanized girth welds using an FFS approach can significantly reduce the construction cost by focusing weld integrity on significant weld flaws. Consequently, unnecessary weld repairs are minimized, increasing the ability to utilize welding resources to achieve more predictable weld quality and productivity. Mechanized girth weld acceptance criteria have been progressively transitioned from using workmanship standards into FFS-based ECAs.

The semi-automatic waveform controlled GMAW and mechanized flux-cored arc welding (FCAW) processes are not unique to the pipe welding industry, especially tie-in welding. However, ECA-based weld flaw acceptance criteria have not been commonly applied to welds using the above welding process combinations. This paper focuses on the development of the alternative weld flaw acceptance criteria for mainline production girth weld construction using a hybrid of semiautomatic waveform controlled GMAW and mechanized gas-shielded FCAW (FCAW-G) processes. It explains the integration of the intended WPS qualification, mechanical testing, ECA methodology and AUT procedures. The girth weld acceptance criteria were developed based on CSA Z662-19 Annex K using Option 2 methodology. Additional fractography, metallography, and hardness mapping were conducted to characterize test specimens with crack tip opening displacement (CTOD) pop-ins.
Update of Line Pipe Charpy Test Interpretation
Authors: Zhang Fan , Rosenfeld Michael J.
Published: December 2022

The Charpy V-notch (CVN) impact test has been widely used by operators and pipe mills to measure steel pipe resistance to fracture propagation. The tests are generally conducted at multiple temperatures to capture the transition from low impact energy nonductile regime to the high impact energy ductile regime. Due to the limitation of wall thickness and curvature of the pipe cross section, the CVN test for thin-walled line pipe generally can only be conducted with reduced size CVN coupons. The reduced size CVN coupon both decreases the measured impact energy and lowers the apparent transition temperature. Prior work (1996) developed a procedure to interpret the CVN data from various size of coupons. The procedure is also able to estimate the entire transition curve even based on a single test data point. This procedure has been widely used since then and been adopted in Section 9F.2.2 of ASME FFS-1/API 579 (2016). In this procedure, the difference between SATT from a given size CVN and the SATT of full pipe wall thickness drop weight tearing test (DWTT) was described by an equation derived from data fitting. Since the SATT of DWTT is fixed, the relationship between SATT from two different sizes of CVN coupons can be correlated through this equation. However, the wall thickness of the pipe is left in this correlation, which implies an artificial impact of pipe dimensions to the changes of SATT among CVN coupons sizes. In this paper, the equation between SATT of CVN and DWTT is updated, which both removes the pipe wall thickness from the correlation among different CVN sizes and achieves better data fitting. This update maintains all the capability of the prior procedure while improving the accuracy and clarity. Worked examples are provided at the end the paper to demonstrate the application of the updated procedure.
Fatigue Analysis of Pipe Hammering During Construction
Authors: Chen Roger , Anthony Joseph , Farrow Kenny
Published: December 2022

Pneumatic hammering may be used to assist with pipe installation and/or removal of stuck pipe during horizontal directional drilling and straight bore crossing operations. Pipe stresses induced during hammering are often poorly understood or undocumented.

To gain a better understanding of the induced stresses, elastic wave analyses were performed to simulate stress waves which travel from the struck end of the pipe and back via reflection from the other end. Due to the nature of the reflections, even compressive hammering (e.g., for pullback assist) results in tensile stress waves (and potential fatigue damage), which sometimes goes unrecognized.

To predict the damage accumulation at planar circumferential flaws (e.g., girth weld defects) from repeated hammering, flaw growth analyses were performed via Paris Law fracture mechanics formulations. An initial flaw based on NDE detection limits was grown to the maximum permitted by API 1104 weld quality requirements. This assumes that the hammered pipe will be used within the pipeline construction assembly and must therefore meet initial inspection requirements for screening of in-situ welds.

For this study, different combinations of pipe diameter, wall thickness, pneumatic hammer model, input energy and soil type were investigated to discover trends and determine limits on hammering force and hammering hours. Allowable hours for a particular set of parameters are provided, along with recommendations concerning monitoring of hammering operations, constructability considerations, and future work to refine the methodology presented herein.
Risk-Based Data-Driven Optimization of Pipeline Inspection Interval
Authors: SooTot Josiah , Oviedo Fernando , Zheng Guanbo , Yap Keng
Published: December 2022

In-line inspection (ILI) is a standard industry practice in managing the safety of buried transmission pipelines. It is important to develop a planning strategy for each ILI program to ensure pipeline safety while maintaining cost-efficiency. Defaulting to the maximum inspection interval allowed by regulations without analyzing time-dependent threats affecting a pipeline segment could lead to loss of containment. An optimal inspection interval serves as another barrier in the defense-in-depth safety concept. In this paper, a risk-based data-driven analysis approach is presented to optimize the inspection interval in terms of operational costs while managing the failure risks. The objective function is formulated to consist of cost components (in present value) and weighted residual risk of failure. The cost components are associated with the periodic inline inspections, as well as the expected mitigation actions. The annual mitigation cost is incurred by the number of features that are sentenced for excavation, field inspection, and repair every year according to the risk of failure. A shorter inspection interval would increase the total ILI cost; however, this would also curtail the rising cost of mitigation due to potential feature growth, as well as the residual risk of failure that depends on the mitigation program. The risk of failure is estimated in terms of the probability and consequence of failure. The residual risk is calculated based on features that are either unmitigated or potentially undetected by the in-line inspection tool run. To demonstrate the application of this approach, numerical examples based on external corrosion are provided to show how various conditions of a pipeline segment affect the optimality of inspection interval. The results support further application of the analysis approach in an industrial scale system-wide analysis, such that optimal inspection intervals can be dynamically updated at segment level using the latest ILI data as they become available in an ILI program.
Reliability Analysis of Dented Pipelines in the Absence of Deformation Profiles
Authors: SooTot Josiah , Killeen Katie , Yap Keng , Hassanien Sherif
Published: December 2022

Dents associated with stress risers contribute to pipeline degradation, as they may increase the likelihood of loss-of-containment incidents. The regulatory-based dent and threat integration integrity management utilizes dent depth and potential interaction with stress risers such as crack, corrosion, and/or welds criteria. However, there have been industry incidents that passed such criteria and still resulted in loss of containment. As part of pushing the boundaries of pipeline integrity assessment towards quantitative risk assessment (QRA), a semi-quantitative analysis of dents (SQuAD) had been recently developed; where a strain-based limit state is used to account for pipe properties, dent geometry, and threat integration uncertainties. SQuAD utilizes deformation surface profile reported by caliper in-line inspection (ILI) tools to estimate the radius of dent curvature. Deformation surface profiles are usually provided by the ILI vendors, but it may not be practical to obtain these profiles on all dent features reported across a pipeline system. In the absence of such data, pipeline operators face a challenge in assessing dent severity using the QRA framework. Herein, a practical surrogate model of dent curvature parameters is proposed to enable the use of SQuAD approach without full knowledge of deformation profiles. The surrogate model is a function of ILI reported dent characteristics (i.e., depth, width, and length) and provides a width and length scaling scheme that makes use of dent shape factors. Based on a set of dent cases, the analysis results obtained from SQuAD approach with the surrogate model using several scaling schemes were compared against those obtained from SQuAD approach with ILI-based deformation surface data. It was concluded that with a proper scaling scheme, SQuAD-based surrogate model approach can produce reasonable results with sufficient conservatism compared to the SQuAD-based ILI deformation approach. The proposed approach is suitable for dent integrity screening decision purpose, which would help pipeline operators to assess, rank, and prioritize resources in dent and threat integration integrity management programs.
Probabilistic Corrosion Assessment for Natural Gas Storage Wells
Authors: Ayton Brent , Dessein Thomas , Fraser Alex , Shironishi Mari , Sera Travis , Shapiro Daniel
Published: December 2022

Regulations for gas storage wells require that operators perform initial and subsequent mechanical integrity evaluations as determined using risk assessment [1], incorporated by reference in 49 CFR 192.12 for U.S. operators [2]. As a well ages, metal loss on the casing can grow, increasing the probability of a failure from corrosion. Inspection and repair programs manage this probability by reducing uncertainty in the casing condition and repairing significant metal loss anomalies. However, performing a casing inspection involves a considerable amount of risk, which can vary depending on the well configuration [3]. The benefit of inspection and repair needs to be balanced with the inspection risk to determine the interval that minimizes the overall risk. This paper demonstrates that if detailed information about a well’s configuration, loading, and existing corrosion population is considered, a probabilistic corrosion analysis can be completed to determine a reinspection date that minimizes the overall risk of a release.

A probabilistic implementation of the Level II analysis found in API 579 Fitness-For-Service is described and recommended for these assessments [4]. The deterministic version of this model is the most accurate for predicting burst pressures of casings with metal loss under a wide range of loading conditions [5].

The measurement error of inspection tools and their reporting thresholds relative to typical corrosion rates presents many challenges in calculating corrosion rates deterministically. Calculating unrealistically high growth rates and apparent negative growth rates using inspection data is common. Using the tool measurement error and the distribution of calculated growth rates across several wells, a Bayesian updating approach is described, grouping anomalies in similar environments to develop credible growth rate distributions specific to each joint on a well.

This paper provides several assessments of realistic storage well configurations and corrosion populations to demonstrate how the probabilistic corrosion assessment can determine an inspection interval that minimizes the overall risk and ultimately inform integrity maintenance plans on a well-by-well basis. The examples span a wide range of well conditions to illustrate that the optimal inspection and repair program depends on each well’s configuration, loading, and existing corrosion population. The effect of a corrosion anomaly’s depth in the well and the cement quality on the expected release rate and the resulting risk is also examined.