On the Transient Interaction of Centrifugal Compressors and Their Piping Systems

1983 ◽  
Vol 105 (4) ◽  
pp. 891-901 ◽  
Author(s):  
C. R. Sparks
Keyword(s):  
Laboratory Data ◽  
Low Frequency ◽  
Piping System ◽  
Centrifugal Compressors ◽  
Theoretical Concepts ◽  
Acoustic Damping ◽  
Modal Damping ◽  
Impedance Characteristics ◽  
Piping Systems ◽  
Flow Impedance

The problems of surge and other low-frequency pulsation phenomena in centrifugal compressors are described in terms of both machine (head curve) characteristics and the flow impedance characteristics of its attached piping. Flow stability criteria are presented in terms of net modal damping, as the combination of piping acoustic damping and equivalent negative damping of the compressor in the surge region of its performance curve. Surge and instability frequencies are related to acoustic reactance of the piping system. Finally, theoretical concepts are verified both by electrical analog models and by field and laboratory data on real compressors. This paper provides some new and significant findings on the dynamic interaction of centrifugal compressors with piping systems and describes the basic phenomena underlying these interactions. Good agreement is shown between predicted and measured surge frequencies, and for those termed “piping resonance surge” produced by high flow offsets or flat spots in the head curve.

On the Transient Interaction of Centrifugal Compressors and Their Piping Systems

1983 ◽  
Author(s):  
Cecil R. Sparks
Keyword(s):  
Laboratory Data ◽  
Low Frequency ◽  
Piping System ◽  
Centrifugal Compressors ◽  
Theoretical Concepts ◽  
Acoustic Damping ◽  
Modal Damping ◽  
Impedance Characteristics ◽  
Piping Systems ◽  
Flow Impedance

The problems of surge and other low frequency pulsation phenomena in centrifugal compressor are described in terms of both machine (head curve) characteristics and the flow impedance characteristics of its attached piping. Flow stability criteria are presented in terms of net modal damping, as the combination of piping acoustic damping and equivalent negative damping of the compressor in the surge region of its performance curve. Surge and instability frequencies are related to acoustic reactance of the piping system. Finally, theoretical concepts are verified both by electrical analog models and by field and laboratory data on real compressors. This paper provides some new and significant findings on the dynamic interaction of centrifugal compressors with piping systems, and describes the basic phenomena underlying these interactions. Good agreement is shown between predicted and measured surge frequencies, and for those termed “piping resonance surge” produced by high flow offsets or flat spots in the head curve.

Effects on Pipe Vibrations of Cavitation in an Orifice and in Globe-Style Valves

2006 ◽  
Author(s):  
Se´bastien Caillaud ◽  
Rene´-Jean Gibert ◽  
Pierre Moussou ◽  
Joe¨l Cohen ◽  
Fabien Millet
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Low Frequency ◽  
Flow Regimes ◽  
Piping System ◽  
Low Frequencies ◽  
Choked Flow ◽  
Single Hole ◽  
Piping Systems ◽  
Large Amplitude Vibrations

A piping system of French nuclear power plants displays large amplitude vibrations in particular flow regimes. These troubles are attributed to cavitation generated by single-hole orifices in depressurized flow regimes. Real scale experiments on high pressure test rigs and on-site tests are then conducted to explain the observed phenomenon and to find a solution to reduce pipe vibrations. The first objective of the present paper is to analyze cavitation-induced vibrations in the single-hole orifice. It is then shown that the orifice operates in choked flow with supercavitation, which is characterized by a large unstable vapor pocket. One way to reduce pipe vibrations consists in suppressing the orifices and in modifying the control valves. Three technologies involving a standard trim and anti-cavitation trims are tested. The second objective of the paper is to analyze cavitation-induced vibrations in globe-style valves. Cavitating valves operate in choked flow as the orifice. Nevertheless, no vapor pocket appears inside the pipe and no unstable phenomenon is observed. The comparison with an anti-cavitation solution shows that cavitation reduction has no impact on low frequency excitation. The effect of cavitation reduction on pipe vibrations, which involve essentially low frequencies, is then limited and the first solution, which is the standard globe-style valve installed on-site, leads to acceptable pipe vibrations. Finally, this case study may have consequences on the design of piping systems. First, cavitation in orifices must be limited. Choked flow in orifices may lead to supercavitation, which is here a damaging and unstable phenomenon. The second conclusion is that the reduction of cavitation in globe-style valve in choked flow does not reduce pipe vibrations. The issue is then to limit cavitation erosion of valve trims.

Recent Developments in the Seismic Analysis of Multiply Supported Piping Systems

2004 ◽  
Author(s):  
Abhinav Gupta
Keyword(s):  
System Analysis ◽  
Seismic Analysis ◽  
Coupled System ◽  
Coupled Systems ◽  
Coupled Analysis ◽  
Piping System ◽  
Modal Damping ◽  
Peak Broadening ◽  
Piping Systems ◽  
Recent Developments

This paper presents results from some of the recent studies on seismic analysis of multiply supported piping systems. The seismic responses for an actual feedwater piping system as evaluated from the conventional uncoupled analysis are compared with those obtained from an analysis of the coupled building-piping system. A discussion is also presented on the significance of non-classical damping in such analyses. It is illustrated that the composite modal damping is just another form of classical damping. Consideration of composite modal damping in a coupled analysis can give inaccurate piping responses when the modes of uncoupled systems are nearly tuned. In such systems, the effect of nonclassical damping is quite significant. Since the floor spectra are neither generated nor required in a coupled systems analysis, methods like peak broadening or peak shifting cannot be used directly to account for the effect of uncertainties. Formulations are presented to evaluate the design response from a coupled system analysis by considering the effect of uncertainties in modal properties of uncoupled systems.

Seismic Response Reduction in Piping Systems Using Plastic Deformation of Pipe Support Structures

2012 ◽  
Author(s):  
Tsuneo Takahashi ◽  
Akira Maekawa
Keyword(s):  
Plastic Deformation ◽  
Seismic Response ◽  
Damping Ratio ◽  
Damping Coefficient ◽  
Piping System ◽  
Initial Stiffness ◽  
Support Structure ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Piping Systems

This study describes inelastic seismic design of piping systems considering the effect of plastic deformation of a pipe support structure. The damping coefficient of a piping system is focused on, and the relation between seismic response of the piping system and elastic-plastic behavior of the support structure was studied using nonlinear time history analysis and complex eigenvalue analysis. The analysis results showed that the maximum seismic response acceleration of the piping system decreased largely in the area surrounded by pipe elbows including the support structure which allowed plastic deformation. Furthermore, modal damping coefficient increased a maximum of about seven-fold. The increase ratio of the modal damping coefficient was proportional to the size of the effective mass ratio, when a relatively large increase was seen in the increase ratio of the modal damping coefficient. On the other hand, the amount of the initial stiffness of the support structure made a difference in the increasing tendency of the modal damping ratio. In the case of relatively small initial stiffness, the modal damping ratio of only one vibration mode increased. The increment of the modal damping ratio was proportional to the effective mass ratio in the case of large initial stiffness. In the viewpoint of the inelastic seismic design, the seismic response of the piping system was little affected by the plastic deformation of the support structure with 10% variation of the secondary stiffness to the initial stiffness. The result suggested that the seismic response of the piping system with the support structure can be estimated by using only the support model which has the elastic perfectly plastic property even if there are various shapes of steel type of support structures.

scholarly journals Flow Induced Vibration (FIV) Research of Oil and Gas Process Piping System

2019 ◽  
Vol 8 (2S8) ◽  
pp. 1387-1390
Keyword(s):  
Wall Thickness ◽  
Low Frequency ◽  
Oil Production ◽  
Process Conditions ◽  
Piping System ◽  
Outer Diameter ◽  
Flow Induced Vibration ◽  
Flowing Fluid ◽  
Piping Systems ◽  
Production Facilities

Piping systems in crude oil production facilities tend to handle high pressure and high velocity flowing fluid at certain flow rate limit resulted in generation of turbulence flow. This turbulence can generate high levels of broad band kinetic energy which can propagate through the system. Even though the energy is distributed across a wide frequency range, most of the excitation is concentrated at low frequency (typically below 100 Hz); the lower the frequency, the higher the level of excitation from turbulence. This leads to excitation of the low frequency vibration modes of the pipe work, in many cases causing visible motion of the pipe and, in some cases, the pipe supports, and this phenomenon is called Flow induced vibration (FIV) and if excessive can result in fatigue failure. This objective of the paper is to identify potential sources of FIV on piping by predicting the Likelihood of failure (LOF) and advising on the necessity for system modifications to minimize or eliminate any FIV induced piping or line failure from Flow Induced Turbulence. These are done by conducting a FIV assessment for piping systems in oil production facilities which are potentially affected by vibration due to both process conditions and mechanically induced pipework vibration. Another scope of this paper is to apply the recommendation action required in order to reduce the likelihood of failure by changing pipe diameter and/or wall thickness by looking at the fluid structure interaction (FSI). By changing the outer diameter and the wall thickness of the pipe, the formation of the excitation in flow regime and the presence of the critical flow disturbance will decrease. These changes are able to reduce the formation of FIV thus increasing the lifespan of the piping system

Numerical Study on Inelastic Seismic Design of Piping Systems Using Damping Effect Based on Elastic–Plastic Property of Pipe Supports

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Akira Maekawa ◽  
Tsuneo Takahashi
Keyword(s):  
Seismic Response ◽  
Seismic Design ◽  
Plastic Property ◽  
Damping Coefficient ◽  
Seismic Load ◽  
Piping System ◽  
Elastic Plastic ◽  
Damping Effect ◽  
Modal Damping ◽  
Piping Systems

This study describes inelastic seismic design of piping systems considering the damping effect caused by elastic–plastic property of a pipe support which is called an elastic–plastic support. Though the elastic–plastic support is proposed as inelastic seismic design framework in the Japan Electric Association code for the seismic design of nuclear power plants (JEAC4601), the seismic responses of the various piping systems with the support are unclear. In this study, the damping coefficient of a piping system is focused on, and the relation between seismic response of the piping system and elastic–plastic behavior of the elastic–plastic support was investigated using nonlinear time history analysis and complex eigenvalue analysis. The analysis results showed that the maximum seismic response acceleration of the piping system decreased largely in the area surrounded by pipe elbows including the elastic–plastic support which allowed plastic deformation. The modal damping coefficient increased a maximum of about sevenfold. Furthermore, the amount of the initial stiffness of the elastic–plastic support made a difference in the increasing tendency of the modal damping coefficient. From the viewpoint of the support model in the inelastic seismic design, the reduction behavior for the seismic response of the piping system was little affected by the 10% variation of the secondary stiffness. These results demonstrated the elastic–plastic support is a useful inelastic seismic design of piping systems on the conditions where the design seismic load is exceeded extremely.

Non-Linear Design Verification of Nuclear Power Piping According to ASME III NB/NC

2008 ◽  
Author(s):  
Lingfu Zeng ◽  
Lennart G. Jansson
Keyword(s):  
Nuclear Power ◽  
Design Evaluation ◽  
Piping System ◽  
Design Verification ◽  
Intensive Study ◽  
Non Linear ◽  
Piping Systems ◽  
Design Requirements

A nuclear piping system which is found to be disqualified, i.e. overstressed, in design evaluation in accordance with ASME III, can still be qualified if further non-linear design requirements can be satisfied in refined non-linear analyses in which material plasticity and other non-linear conditions are taken into account. This paper attempts first to categorize the design verification according to ASME III into the linear design and non-linear design verifications. Thereafter, the corresponding design requirements, in particular, those non-linear design requirements, are reviewed and examined in detail. The emphasis is placed on our view on several formulations and design requirements in ASME III when applied to nuclear power piping systems that are currently under intensive study in Sweden.

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane, and Mixed Mode Bending Under Seismic Load: An Experimental Approach

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Dynamic Behavior ◽  
Failure Modes ◽  
Seismic Load ◽  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Plane Bending

Pressurized piping systems used for an extended period may develop degradations such as wall thinning or cracks due to aging. It is important to estimate the effects of degradation on the dynamic behavior and to ascertain the failure modes and remaining strength of the piping systems with degradation through experiments and analyses to ensure the seismic safety of degraded piping systems under destructive seismic events. In order to investigate the influence of degradation on the dynamic behavior and failure modes of piping systems with local wall thinning, shake table tests using 3D piping system models were conducted. About 50% full circumferential wall thinning at elbows was considered in the test. Three types of models were used in the shake table tests. The difference of the models was the applied bending direction to the thinned-wall elbow. The bending direction considered in the tests was either of the in-plane bending, out-of-plane bending, or mixed bending of the in-plane and out-of-plane. These models were excited under the same input acceleration until failure occurred. Through these tests, the vibration characteristic and failure modes of the piping models with wall thinning under seismic load were obtained. The test results showed that the out-of-plane bending is not significant for a sound elbow, but should be considered for a thinned-wall elbow, because the life of the piping models with wall thinning subjected to out-of-plane bending may reduce significantly.

The Influence of Support Hardware and Piping System Seismic Response on Snubber Support Damping

1997 ◽  
Vol 119 (4) ◽  
pp. 451-456 ◽  
Author(s):  
C. Lay ◽  
O. A. Abu-Yasein ◽  
M. A. Pickett ◽  
J. Madia ◽  
S. K. Sinha
Keyword(s):  
Seismic Response ◽  
Fundamental Frequency ◽  
Damping Ratio ◽  
Damping Coefficient ◽  
Piping System ◽  
Nodal Displacement ◽  
Damping Coefficients ◽  
Fundamental Frequencies ◽  
Piping Systems

The damping coefficients and ratios of piping system snubber supports were found to vary logarithmically with pipe support nodal displacement. For piping systems with fundamental frequencies in the range of 0.6 to 6.6 Hz, the support damping ratio for snubber supports was found to increase with increasing fundamental frequency. For 3-kip snubbers, damping coefficient and damping ratio decreased logarithmically with nodal displacement, indicating that the 3-kip snubbers studied behaved essentially as coulomb dampers; while for the 10-kip snubbers studied, damping coefficient and damping ratio increased logarithmically with nodal displacement.

Sensitivity Analyses for a PWR SCC Case Using the Probabilistic Loss-of-Coolant-Accident (Pro-LOCA) Software

2016 ◽  
Author(s):  
Bruce A. Young ◽  
Sang-Min Lee ◽  
Paul M. Scott
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
The United States ◽  
Design Criterion ◽  
Mitigation Strategies ◽  
Sensitivity Analyses ◽  
Base Case ◽  
Piping System ◽  
Loss Of Coolant Accident ◽  
Piping Systems

As a means of demonstrating compliance with the United States Code of Federal Regulations 10CFR50 Appendix A, General Design Criterion 4 (GDC-4) requirement that primary piping systems for nuclear power plants exhibit an extremely low probability of rupture, probabilistic fracture mechanics (PFM) software has become increasingly popular. One of these PFM codes for nuclear piping is Pro-LOCA which has been under development over the last decade. Currently, Pro-LOCA is being enhanced under an international cooperative program entitled PARTRIDGE-II (Probabilistic Analysis as a Regulatory Tool for Risk-Informed Decision GuidancE - Phase II). This paper focuses on the use of a pre-defined set of base-case inputs along with prescribed variation in some of those inputs to determine a comparative set of sensitivity analyses results. The benchmarking case was a circumferential Primary Water Stress Corrosion Crack (PWSCC) in a typical PWR primary piping system. The effects of normal operating loads, temperature, leak detection, inspection frequency and quality, and mitigation strategies on the rupture probability were studied. The results of this study will be compared to the results of other PFM codes using the same base-case and variations in inputs. This study was conducted using Pro-LOCA version 4.1.9.

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