Large-scale Piping System Research Articles

Validation of Seismic Performance of Stainless Press-to-Connect Piping System under Cyclic Loadings

Earthquakes with magnitudes over 5.0 occurred near Gyeongju and Pohang in southern Korea in 2016 and 2017, respectively. These earthquakes had both low- and high-frequency components. Due to earthquakes with high-frequency motions, damage to nonstructural systems has been observed to be relatively more than that in structural systems. Consequently, the seismic design or performance evaluation of nonstructural components in critical facilities has emerged as a key research area in Korea. This study presents the results of experimental and numerical analyses using a high-fidelity finite element (FE) simulation in the ABAQUS platform for a press-to-connect piping system as a nonstructural component. Press-to-connect piping systems based on NFPA-13 with two elbows, a flexible coupling, and a T-joint were used. In addition, a cyclic loading protocol was applied using the KBC 2016 and IBC 2015. Based on the component-level experimental test, an FE model of the press-to-connect elbow was developed, and the high-fidelity large-scale piping system with an elbow was validated in this study. In both the experimental and analytical results, no leakage or plastic deformation of the piping system was observed under cyclic loading conditions. The results of the high-fidelity simulation model of the large-scale piping system were identical to those of the experimental test. More specifically, the error of the von-Mises stress at the upper and lower elbows was less than 9%, and the angle between the elbows was less than 2%, corresponding to the limit state of the drift ratio of the building system. Therefore, the high-fidelity simulation model of a large-scale piping system can have high application value. In addition, the design requirements and engineering demands of the piping system, such as the condition of ASME B and PV section III for service level D, were satisfied.

Effect of Variation of Parameters of Large-Scale Piping System Based on Probability Theory on Reliability

Effect of Variation of Parameters of Large-Scale Piping System Based on Probability Theory on Reliability

Fragility Evaluation in Building-Piping Systems: Effect of Piping Interaction With Buildings

Many studies assessing the damage from 1971 San Fernando and 1994 North Ridge earthquakes reported that the failure of nonstructural components like piping systems was one of the significant reasons for shutdown of hospitals immediately after the earthquakes. This paper is focused on evaluating seismic fragility of a large-scale piping system in representative high-rise, midrise, and low-rise buildings using nonlinear time history analyses. The emphasis is on evaluating piping's interaction with building and its effect on piping fragility. The building models include the effects of nonlinearity in the performance of beams and columns. In a 20-story building that is detuned with the piping system, critical locations are on the top two floors for the linear frame building model. For the nonlinear building model, critical locations are on the bottom two floors. In an eight-story building that is nearly tuned with the piping system, the critical locations for both the linear frame and nonlinear models are the third and fourth floors. It is observed that building nonlinearity can reduce fragility due to reduction in the tuning between building and piping systems. In a two-story building, the nonlinear building frequencies are closer to the critical piping system frequencies than the linear building frequency; the nonlinear building is more fragile than the linear building for this case. However, it is observed that the linear building models give excessively conservative estimates of fragility than the nonlinear building models.

버터플라이 밸브의 유량측정 불확도에 대한 영향

For testing large-capacity pumps, the accurate flow rate measurement is needed in the test loop. As a measuring method of flow rate, venturi tube is recommended due to its low pressure loss. However, upstream disturbance of loop component such as a valve has an effect upon the accuracy of flow rate measurement. For controlling flow rate in case of high flow rate and large-scale piping system, a butterfly-type valve is generally used due to its compactness. However, a butterfly valve disturbs downstream flow by generating turbulence, cavities, or abrupt pressure change. In this study, the effect of downstream disturbance of butterfly valve on the flow rate measurement using a venturi tube is investigated. Test loop consists of circulation pump, reservoir, butterfly valve, venturi tube, and reference flow meter. The test is conducted with regard to a different valve opening angle of butterfly valve. According to the valve opening angle, the uncertainty of flow rate measurement is investigated.

Evaluation Methods for Corrosion Damage of Components in Cooling Systems of Nuclear Power Plants by Coupling Analysis of Corrosion and Flow Dynamics (IV) Comparison of Wall Thinning Rates Calculated with the Coupled Model of Static Electrochemical Analysis and Dynamic Double Oxide Layer Analysis and Their Values Measured at a PWR Plant

In order to confirm applicability and accuracy of FAC evaluation methods based on the coupled FAC model of static electrochemical analysis and dynamic oxide layer growth analysis, wall thinning rates calculated with the proposed methods were compared with those measured for the secondary piping of a PWR plant. Distributions of flow velocity and temperature along the whole system were calculated with 1D and 2D computational flow dynamics (CFD) codes and corrosive conditions were calculated with a N2H4-O2 reaction analysis code. Precise flow turbulence at major parts of the system was analyzed with 3D CFD codes to obtain mass transfer coefficients at structure surfaces. Then, wall thinning rates were calculated with the coupled FAC model by applying the mass transfer coefficients. Comparison of the calculated and measured results led to the following conclusions. 1) Structures with complicated geometry in the plant, e.g., the pair of a bend pipe and a valve, could be simplified as a combination of pipes for the calculation. 2) Flow distribution calculated with 3D CFD codes for a large-scale piping system could be extrapolated to those at the very surface of the piping to obtain a precise distribution of mass transfer coefficients at the region of interest. 3) Wall thinning rates calculated by applying the obtained mass transfer coefficients agreed with the measured rates within a factor of 2. 4) The effects of flow turbulence were transferred through a distance of more than 5 times the pipe diameter from the original turbulent point, but the effects on wall thinning rate were negligibly small.

Evaluation Methods for Corrosion Damage of Components in Cooling Systems of Nuclear Power Plants by Coupling Analysis of Corrosion and Flow Dynamics (IV)

In order to confirm applicability and accuracy of FAC evaluation methods based on the coupled FAC model of static electrochemical analysis and dynamic oxide layer growth analysis, wall thinning rates calculated with the proposed methods were compared with those measured for the secondary piping of a PWR plant. Distributions of flow velocity and temperature along the whole system were calculated with 1D and 2D computational flow dynamics (CFD) codes and corrosive conditions were calculated with a N2H4-O2 reaction analysis code. Precise flow turbulence at major parts of the system was analyzed with 3D CFD codes to obtain mass transfer coefficients at structure surfaces. Then, wall thinning rates were calculated with the coupled FAC model by applying the mass transfer coefficients. Comparison of the calculated and measured results led to the following conclusions. 1) Structures with complicated geometry in the plant, e.g., the pair of a bend pipe and a valve, could be simplified as a combination of pipes for the calculation. 2) Flow distribution calculated with 3D CFD codes for a large-scale piping system could be extrapolated to those at the very surface of the piping to obtain a precise distribution of mass transfer coefficients at the region of interest. 3) Wall thinning rates calculated by applying the obtained mass transfer coefficients agreed with the measured rates within a factor of 2. 4) The effects of flow turbulence were transferred through a distance of more than 5 times the pipe diameter from the original turbulent point, but the effects on wall thinning rate were negligibly small.

大きな地震荷重下での配管系の弾塑性応答と疲労破損についての解析評価(J18-1 解析・設計の高度化・最適化(1),J18 解析・設計の高度化・最適化)

The seismic shaking test of a large-scale piping system with a piping bore of 200A and made from carbon steel material was conducted. Two test models were used, one for the design method confirmation test and one for the ultimate strength test, For the ultimate strength test, a series of tests was initiated at a pseudo-elastic design stress level of about 9 times the current allowable primary stress limit (3Sm) for the "S_2" seismic wave, being repeated until the occurrence of piping failure due to through-wall fatigue cracking with ratcheting deformation was obtained during Run 5, of seismic shaking. Post-test analysis results, which were obtained in two steps, compare well with the ultimate strength test results of elasto-plastic global response, local strain and the number of runs to piping failure. In step 1, the elasto-plastic response analysis of the whole model was performed, using elbow element and linear kinemateic hardening rule. In step 2, the local strain behavior of Elbow2 was calculated by forced displacement analysis, using shell element and non-linear kinemateic hardening rule (AF-OW), and the fatigue damage accumulation coefficient was calculated.

Elastic plastic finite element calculations of a cracked piping system and leak-rate evaluations

Post-calculations are presented of an experiment which was performed in the frame of the HDR (overheated steam reactor)-Safety-Program, Phase 2. In the experiment the failure was studied of a large-scale piping system (inner diameter 400 mm) loaded by steady internal pressure (10·5 MPa) and an increasing opening in-plane bending moment under conditions similar to those of a nuclear pressurized water reactor. The piping system failed with leakage through a 400 mm-long crack in the flank of a 90° pipe elbow. The finite element program ADINA (Automatic Dynamic Incremental Nonlinear Analysis) is used for the nonlinear calculations, including fracture mechanical subroutines for the evaluation of J- integral values. As a three-dimensional analysis of the complete cracked piping system would be very expensive, in a first step of the calculations the complete, as yet uncracked, system was modelled using pipe elements. The resulting global displacements are used in a second step as input for three-dimensional detail models of the cracked pipe bend with adjacent straight pipe ends. After structure mechanics results and J- integral values which are calculated to determine the possible amount of stable crack growth, most attention is given to the calculation of leakage areas with respect to the applied loading, for which values between about 400 mm 2 (pressure loading only) and 2000 mm 2 (pressure and bending) were found. By means of a separate computer program, leak rates were calculated using the leakage areas evaluated by finite elements. Values between 20 kg/s and 80 kg/s were obtained.