Testing and Modeling of an Acoustic Instability in Pilot-Operated Pressure Relief Valves

2015 ◽  
Vol 138 (5) ◽  
Author(s):  
Timothy C. Allison ◽  
Klaus Brun
Keyword(s):  
Dynamic Instability ◽  
Essential Element ◽  
Dynamics Simulation ◽  
Piping System ◽  
Pressure Relief ◽  
Simulation Code ◽  
Acoustic Instability ◽  
Process Gas ◽  
Piping Systems ◽  
Pressure Relief Valves

Pressure relief valves (PRVs) are included as an essential element of many compressor piping systems in order to prevent overpressurization and also to minimize the loss of process gas during relief events. Failure of the valve to operate properly can result in excessive quantities of vented gas and/or catastrophic failure of the piping system. Several mechanisms for chatter and instability have been previously identified for spring-loaded relief valves, but pilot-operated relief valves are widely considered to be stable. In this paper, pilot-operated PRVs are shown to be susceptible to a dynamic instability under certain conditions where valve dynamics couple with upstream piping acoustics. This self-exciting instability can cause severe oscillations of the valve piston, damaging the valve seat, preventing resealing, and possibly causing damage to attached piping. Two case studies are presented, which show damaging unstable oscillations in a field installation and a blowdown rig, and a methodology is presented for modeling the instability by coupling a valve dynamic model with a 1D transient fluid dynamics simulation code. Modeling results are compared with measured stable and unstable operation in a blowdown rig to show that the modeling approach accurately predicts the observed behaviors.

Testing and Modeling of an Acoustic Instability in Pilot-Operated Pressure Relief Valves

2015 ◽  
Author(s):  
Timothy C. Allison ◽  
Klaus Brun
Keyword(s):  
Dynamic Instability ◽  
Essential Element ◽  
Dynamics Simulation ◽  
Piping System ◽  
Pressure Relief ◽  
Simulation Code ◽  
Acoustic Instability ◽  
Process Gas ◽  
Piping Systems ◽  
Pressure Relief Valves

Pressure relief valves are included as an essential element of many compressor piping systems in order to prevent overpressurization and also to minimize the loss of process gas during relief events. Failure of the valve to operate properly can result in excessive quantities of vented gas and/or catastrophic failure of the piping system. Several mechanisms for chatter and instability have been previously identified for spring-loaded relief valves, but pilot-operated relief valves are widely considered to be stable. In this paper, pilot-operated pressure relief valves are shown to be susceptible to a dynamic instability under certain conditions where valve dynamics couple with upstream piping acoustics. This self-exciting instability can cause severe oscillations of the valve piston, damaging the valve seat, preventing resealing and possibly causing damage to attached piping. Two case studies are presented that show damaging unstable oscillations in a field installation and a blowdown rig, and a methodology is presented for modeling the instability by coupling a valve dynamic model with a 1-D transient fluid dynamics simulation code. Modeling results are compared with measured stable and unstable operation in a blowdown rig to show that the modeling approach accurately predicts the observed behaviors.

Design of Discharge Piping for Pressure Relief Systems

1981 ◽  
Vol 103 (3) ◽  
pp. 190-195
Author(s):  
R. H. Ross
Keyword(s):  
Mach Number ◽  
Simple Technique ◽  
Careful Analysis ◽  
Back Pressure ◽  
Piping System ◽  
Flow Function ◽  
Pressure Relief ◽  
Adiabatic Flow ◽  
Pressure Relief Valves ◽  
Relief System

The ASME Boiler and Pressure Vessel Code and publications by many manufacturers caution the design engineer to consider back pressure in discharge piping when sizing and selecting pressure relief valves. Only general guidelines are given, however, because of widely varying installation requirements. This paper addresses manifolded discharge piping system design. The method of analysis provides a simple technique for determining pressure within a discharge piping system. The method is based on adiabatic flow and uses local Mach number to relate expansion of the gas in the pipes to a mass flow function. The paper illustrates that relief valves discharging into lines and headers should not be sized or selected without careful analysis of the entire relief system.

Instability of Pressure Relief Valves in Water Pipes

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
P. Moussou ◽  
R. J. Gibert ◽  
G. Brasseur ◽  
Ch. Teygeman ◽  
J. Ferrari ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Negative Pressure ◽  
Dynamic Instability ◽  
Pressure Sensors ◽  
Displacement Sensor ◽  
Relief Valve ◽  
Pressure Relief ◽  
Water Pipes ◽  
Spring Force ◽  
Pressure Relief Valves

Pressure relief valves in water pipes are known to sometimes chatter when the inlet pressure slightly exceeds the set pressure. While these devices are responsible for numerous fatigue issues in process industries, there is a relatively low number of technical publications covering their performance, especially in heavy fluid applications. The present study is intended as a contribution to the understanding of pressure relief valve dynamics, taking into account fluid-structure interactions. A series of tests were performed with a water relief valve in a test rig. Adjusting the set pressure of the valve to about 30 bars, an upstream pressure varying from 20 bars to 35 bars was imposed, so that the valve opened and the water flow varied from a few m3/h to about 80 m3/h. During the tests, the pipe was equipped upstream and downstream of the valve with static pressure sensors and a flowmeter, the disk lift was measured with a laser displacement sensor, and the spring force was recorded simultaneously. Several fluctuating pressure sensors were also installed in the inlet pipe. Static instability is investigated by comparing the spring force to the hydraulic force. Dynamic instability is observed and it is shown that the resonant behavior of the disk generates an apparent negative pressure drop coefficient at some frequencies. This negative pressure drop coefficient can trigger a dynamic instability in a manner similar to the negative damping effect in leakage-flow vibrations.

Instability of Pressure Relief Valves in Water Pipes

2009 ◽  
Author(s):  
Pierre Moussou ◽  
Rene´ Jean Gibert ◽  
Gilles Brasseur ◽  
Christophe Teygeman ◽  
Je´roˆme Ferrari ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Negative Pressure ◽  
Dynamic Instability ◽  
Pressure Sensors ◽  
Displacement Sensor ◽  
Relief Valve ◽  
Pressure Relief ◽  
Water Pipes ◽  
Spring Force ◽  
Pressure Relief Valves

Pressure relief valves in water pipes are known to sometimes chatter when the inlet pressure slightly exceeds the maximum allowable working pressure (MAWP) value. Though these devices are responsible for numerous fatigue issues in process industries, there is a relatively low number of technical publications describing well-established facts about them, especially for heavy fluids. The present study is intended as a contribution to the understanding of pressure relief valve dynamics, taking into account fluid-structure interactions. A series of tests was performed with a water relief valve upon a test rig. Adjusting the MAWP of the valve to about 30 bars, an upstream pressure varying from 20 to 35 bars was imposed, so that the valve opened and the water flow varied from a few m3/h to about 80 m3/h. During the tests, the pipe was equipped upstream and downstream of the valve with static pressure sensors and a flowmeter, the disc lift was measured with a laser displacement sensor, and the spring force was recorded simultaneously. Several fluctuating pressure sensors were also arranged in the inlet pipe. Static instability is investigated by comparing the spring force to the hydraulic force. Dynamic instability is observed and it is shown that the resonant behavior of the disc generates an apparent negative pressure drop coefficient at some frequencies. This negative pressure drop coefficient can trigger a dynamic instability in a manner similar to the negative damping effect in leakage-flow vibrations.

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.

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