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Robert E. Gross - One of the best experts on this subject based on the ideXlab platform.

  • effects of seat width on development of adhesions in stainless steel trim spring operated pressure Relief Valves
    ASME 2015 Pressure Vessels and Piping Conference, 2015
    Co-Authors: Robert E. Gross, Stephen P. Harris
    Abstract:

    Previous research has shown that stainless steel (SS) adhesions form in about half of new SS trim spring operated pressure Relief Valves (SOPRV). These adhesions require an additional force (beyond the spring force) to be applied by the process fluid to the disc in order for the valve to lift. This additional force may cause the SOPRV to fail its proof test (FPT) or even to fail to open (FTO) in the presence of excess process pressure. This paper expands on the previous findings to show how seat width relates statistically to whether or not these SS adhesions form and, if they do, whether or not they are of sufficient size to cause FPT or FTO.The findings show it is statistically significant that SOPRV in the study population with seat widths greater than 0.030 inches (in.) formed adhesions more often than SOPRV with seat widths less than or equal to 0.030 in. Furthermore, for this population it is statistically significant that all FPT and FTO occurred on SOPRV with seat widths greater than or equal to 0.030 in. The ramifications of these findings to the safety performance of SS trim SOPRV are discussed.Copyright © 2015 by ASME

  • investigation of adhesion formation in new stainless steel trim spring operated pressure Relief Valves
    Journal of Pressure Vessel Technology-transactions of The Asme, 2014
    Co-Authors: Robert E. Gross
    Abstract:

    Examination of proof test data for new (not previously installed) stainless steel (SS) trim spring operated pressure Relief Valves (SOPRV) reveals that adhesions form between the seat and disk in about 46% of all such SOPRV. The forces needed to overcome these adhesions can be sufficiently large to cause the SOPRV to fail its proof test (FPT) prior to installation. Furthermore, a significant percentage of SOPRV which are found to FPT are also found to “fail to open” (FTO) meaning they would not Relief excess pressure in the event of an overpressure event. The cases where adhesions result in FTO or FPT appear to be confined to SOPRV with diameters less than or equal to 1 in. and set pressures less than 150 pounds per square inch gauge (psig) and the FTO are estimated to occur in 0.31% to 2.00% of this subpopulation of SS trim SOPRV. The reliability and safety implications of these finding for end users who do not perform pre-installation testing of SOPRV are discussed.

  • The Effects of Maintenance Actions on the PFDavg of Spring Operated Pressure Relief Valves
    Volume 6B: Materials and Fabrication, 2014
    Co-Authors: Robert E. Gross, Stephen P. Harris
    Abstract:

    The safety integrity level (SIL) of equipment used in safety instrumented functions is determined by the average probability of failure on demand (PFDavg) computed at the time of periodic inspection and maintenance, i.e., the time of proof testing. The computation of PFDavg is generally based solely on predictions or estimates of the assumed constant failure rate of the equipment. However, PFDavg is also affected by maintenance actions (or lack thereof) taken by the end user. This paper shows how maintenance actions can affect the PFDavg of spring operated pressure Relief Valves (SOPRV) and how these maintenance actions may be accounted for in the computation of the PFDavg metric. The method provides a means for quantifying the effects of changes in maintenance practices and shows how these changes impact plant safety.

  • Statististical Performance Evaluation of Soft Seat Pressure Relief Valves
    Journal of Pressure Vessel Technology, 2014
    Co-Authors: Robert E. Gross, Stephen P. Harris
    Abstract:

    Risk-based inspection methods enable estimation of the probability of failure on demand for spring-operated pressure Relief Valves at the United States Department of Energy's Savannah River Site in Aiken, South Carolina. This paper presents a statistical performance evaluation of soft seat spring operated pressure Relief Valves. These pressure Relief Valves are typically smaller and of lower cost than hard seat (metal to metal) pressure Relief Valves and can provide substantial cost savings in fluid service applications (air, gas, liquid, and steam) providing that probability of failure on demand (the probability that the pressure Relief valve fails to perform its intended safety function during a potentially dangerous over pressurization) is at least as good as that for hard seat Valves. The research in this paper shows that the proportion of soft seat spring operated pressure Relief Valves failing is the same or less than that of hard seat Valves, and that for failed Valves, soft seat Valves typically have failure ratios of proof test pressure to set pressure less than that of hard seat Valves.

  • Statistical Performance Evaluation of Soft (Elastomer) Seat Pressure Relief Valves
    Volume 6A: Materials and Fabrication, 2013
    Co-Authors: Robert E. Gross, Stephen P. Harris
    Abstract:

    Risk-based inspection methods enable estimation of the probability of failure on demand for spring-operated pressure Relief Valves at the United States Department of Energy’s Savannah River Site in Aiken, South Carolina. This paper presents a statistical performance evaluation of soft seat spring operated pressure Relief Valves. These pressure Relief Valves are typically smaller and of lower cost than hard seat (metal to metal) pressure Relief Valves and can provide substantial cost savings in fluid service applications (air, gas, liquid, and steam) providing that probability of failure on demand (the probability that the pressure Relief valve fails to perform its intended safety function during a potentially dangerous over pressurization) is at least as good as that for hard seat Valves. The research in this paper shows that the proportion of soft seat spring operated pressure Relief Valves failing is the same or less than that of hard seat Valves, and that for failed Valves, soft seat Valves typically have failure ratios of proof test pressure to set pressure less than that of hard seat Valves.

Stephen P. Harris - One of the best experts on this subject based on the ideXlab platform.

  • effects of seat width on development of adhesions in stainless steel trim spring operated pressure Relief Valves
    ASME 2015 Pressure Vessels and Piping Conference, 2015
    Co-Authors: Robert E. Gross, Stephen P. Harris
    Abstract:

    Previous research has shown that stainless steel (SS) adhesions form in about half of new SS trim spring operated pressure Relief Valves (SOPRV). These adhesions require an additional force (beyond the spring force) to be applied by the process fluid to the disc in order for the valve to lift. This additional force may cause the SOPRV to fail its proof test (FPT) or even to fail to open (FTO) in the presence of excess process pressure. This paper expands on the previous findings to show how seat width relates statistically to whether or not these SS adhesions form and, if they do, whether or not they are of sufficient size to cause FPT or FTO.The findings show it is statistically significant that SOPRV in the study population with seat widths greater than 0.030 inches (in.) formed adhesions more often than SOPRV with seat widths less than or equal to 0.030 in. Furthermore, for this population it is statistically significant that all FPT and FTO occurred on SOPRV with seat widths greater than or equal to 0.030 in. The ramifications of these findings to the safety performance of SS trim SOPRV are discussed.Copyright © 2015 by ASME

  • The Effects of Maintenance Actions on the PFDavg of Spring Operated Pressure Relief Valves
    Volume 6B: Materials and Fabrication, 2014
    Co-Authors: Robert E. Gross, Stephen P. Harris
    Abstract:

    The safety integrity level (SIL) of equipment used in safety instrumented functions is determined by the average probability of failure on demand (PFDavg) computed at the time of periodic inspection and maintenance, i.e., the time of proof testing. The computation of PFDavg is generally based solely on predictions or estimates of the assumed constant failure rate of the equipment. However, PFDavg is also affected by maintenance actions (or lack thereof) taken by the end user. This paper shows how maintenance actions can affect the PFDavg of spring operated pressure Relief Valves (SOPRV) and how these maintenance actions may be accounted for in the computation of the PFDavg metric. The method provides a means for quantifying the effects of changes in maintenance practices and shows how these changes impact plant safety.

  • Statististical Performance Evaluation of Soft Seat Pressure Relief Valves
    Journal of Pressure Vessel Technology, 2014
    Co-Authors: Robert E. Gross, Stephen P. Harris
    Abstract:

    Risk-based inspection methods enable estimation of the probability of failure on demand for spring-operated pressure Relief Valves at the United States Department of Energy's Savannah River Site in Aiken, South Carolina. This paper presents a statistical performance evaluation of soft seat spring operated pressure Relief Valves. These pressure Relief Valves are typically smaller and of lower cost than hard seat (metal to metal) pressure Relief Valves and can provide substantial cost savings in fluid service applications (air, gas, liquid, and steam) providing that probability of failure on demand (the probability that the pressure Relief valve fails to perform its intended safety function during a potentially dangerous over pressurization) is at least as good as that for hard seat Valves. The research in this paper shows that the proportion of soft seat spring operated pressure Relief Valves failing is the same or less than that of hard seat Valves, and that for failed Valves, soft seat Valves typically have failure ratios of proof test pressure to set pressure less than that of hard seat Valves.

  • Statistical Performance Evaluation of Soft (Elastomer) Seat Pressure Relief Valves
    Volume 6A: Materials and Fabrication, 2013
    Co-Authors: Robert E. Gross, Stephen P. Harris
    Abstract:

    Risk-based inspection methods enable estimation of the probability of failure on demand for spring-operated pressure Relief Valves at the United States Department of Energy’s Savannah River Site in Aiken, South Carolina. This paper presents a statistical performance evaluation of soft seat spring operated pressure Relief Valves. These pressure Relief Valves are typically smaller and of lower cost than hard seat (metal to metal) pressure Relief Valves and can provide substantial cost savings in fluid service applications (air, gas, liquid, and steam) providing that probability of failure on demand (the probability that the pressure Relief valve fails to perform its intended safety function during a potentially dangerous over pressurization) is at least as good as that for hard seat Valves. The research in this paper shows that the proportion of soft seat spring operated pressure Relief Valves failing is the same or less than that of hard seat Valves, and that for failed Valves, soft seat Valves typically have failure ratios of proof test pressure to set pressure less than that of hard seat Valves.

  • Evaluating Risk and Safety Integrity Levels for Pressure Relief Valves Through Probabilistic Modeling
    Journal of Pressure Vessel Technology-transactions of The Asme, 2013
    Co-Authors: Emily M. Mitchell, Robert E. Gross, Stephen P. Harris
    Abstract:

    The probability of failure on demand (PFD) for spring-operated pressure Relief Valves (SORVs) is estimated by applying the Fréchet and Weibull probability distributions using proof test data from the United States Department of Energy's Savannah River Site (SRS) in Aiken, South Carolina. The data can be accessed through the Center for Chemical Process Safety (CCPS) Process Equipment Reliability Database (PERD). The probability distributions enable the evaluation of risk, estimation of ANSI/ISA-84.00.01 Safety Integrity Levels (SILs), and the impact of potential modifications of the maintenance plan. Current SRS practices are reviewed, and recommendations are made for risk-based adjustments to the maintenance plan. Subsets of Valves are identified in which maintenance times can be extended and in which increased safety margins may be needed.

Csaba Hős - One of the best experts on this subject based on the ideXlab platform.

  • prediction of quarter wave instability in direct spring operated pressure Relief Valves with upstream piping by means of cfd and reduced order modelling
    Journal of Fluids and Structures, 2017
    Co-Authors: I Erdődi, Csaba Hős
    Abstract:

    Abstract This paper focuses on modelling the dynamic instability (flutter/chatter) of gas-service direct spring operated pressure Relief Valves (DSOPRV) due to the acoustic coupling between the valve body dynamics and the upstream piping. Previous studies have shown through reduced order models that there exists a critical inlet pipe length beyond which self-excited vibrations occur due to the presence of a quarter standing wave in the upstream piping. However, to allow analytical computations and simple design equations, these reduced-order models relied on quasi-steady assumptions for the estimation of the discharge coefficient and the fluid force acting on the valve body. This paper proposes two CFD-based methods for the analysis of the fluid forces and valve stability: firstly, steady-state CFD runs were performed to verify the assumptions of the reduced order models and also to increase their accuracy. Secondly, dynamic CFD simulations using deforming mesh technology were conducted, with which the valve response can be resolved with high fidelity including also transient fluid–structure interactions. Comparing the results of the two approaches verify the use of the reduced-order models for stability predictions.

  • dynamic behaviour of direct spring loaded pressure Relief Valves connected to inlet piping iv review and recommendations
    Journal of Loss Prevention in The Process Industries, 2017
    Co-Authors: Csaba Hős, Alan R Champneys, K Paul, M. Mcneely
    Abstract:

    Abstract Recent progress by a number of different groups and authors is reviewed on the stability properties of direct-spring pressure Relief Valves connected to pressure vessels with or without piping systems. Various different notions of stability and mechanisms for instability are revealed both in the case of gas and liquid service. It is stressed that it is not the valve itself that is stable or unstable, rather the harmful vibrations arise through interactions between the valve and its surroundings — the inlet piping, the reservoir, and any outlet piping. A distinction is drawn between underlying instability mechanisms and how these may be triggered during transient operations. The purpose of the work is to provide a coherent simplified account that will be of practical use for proposing new operational guidelines and mitigation strategies. Among these various mechanisms, oscillatory instability due to the interaction with a quarter-wave acoustic mode in the inlet piping is argued to be the most important to mitigate.

  • dynamic behaviour of direct spring loaded pressure Relief Valves iii Valves in liquid service
    Journal of Loss Prevention in The Process Industries, 2016
    Co-Authors: Csaba Hős, Alan R Champneys, K Paul, M. Mcneely
    Abstract:

    Abstract Previous studies into direct-spring pressure Relief Valves connected to a tank via a straight pipe are adapted to take account of liquid sonic velocity. Good agreement is found between new experimental data and simulations of a coupled fluid-structure mathematical model. Upon increasing feed mass flow rate, there is a critical pipe length above which a quarter-wave instability occurs. The dependency is shown to be well approximated by a simple analytical formula derived from a reduced-order model. Liquid service Valves are found to be stable for longer inlet pipes than for the gas case. However, the instabilities when they do occur are more violent and the valve is found to jump straight into chatter, in which it impacts repeatedly with its seat. Flutter-type oscillations are never observed. These observations are explained by finding that the quarter-wave Hopf bifurcation is subcritical. Water hammer effects can also be observed, which result in excessive overpressure values during chatter. In addition a new, Helmholtz-like instability — not encountered in gas service — is identified for short pipes with small reservoir volumes. This can also be predicted analytically and is shown to explain a valve-only instability found in previous work that incorporated significant mechanical damping.

M. Mcneely - One of the best experts on this subject based on the ideXlab platform.

  • dynamic behaviour of direct spring loaded pressure Relief Valves connected to inlet piping iv review and recommendations
    Journal of Loss Prevention in The Process Industries, 2017
    Co-Authors: Csaba Hős, Alan R Champneys, K Paul, M. Mcneely
    Abstract:

    Abstract Recent progress by a number of different groups and authors is reviewed on the stability properties of direct-spring pressure Relief Valves connected to pressure vessels with or without piping systems. Various different notions of stability and mechanisms for instability are revealed both in the case of gas and liquid service. It is stressed that it is not the valve itself that is stable or unstable, rather the harmful vibrations arise through interactions between the valve and its surroundings — the inlet piping, the reservoir, and any outlet piping. A distinction is drawn between underlying instability mechanisms and how these may be triggered during transient operations. The purpose of the work is to provide a coherent simplified account that will be of practical use for proposing new operational guidelines and mitigation strategies. Among these various mechanisms, oscillatory instability due to the interaction with a quarter-wave acoustic mode in the inlet piping is argued to be the most important to mitigate.

  • dynamic behaviour of direct spring loaded pressure Relief Valves iii Valves in liquid service
    Journal of Loss Prevention in The Process Industries, 2016
    Co-Authors: Csaba Hős, Alan R Champneys, K Paul, M. Mcneely
    Abstract:

    Abstract Previous studies into direct-spring pressure Relief Valves connected to a tank via a straight pipe are adapted to take account of liquid sonic velocity. Good agreement is found between new experimental data and simulations of a coupled fluid-structure mathematical model. Upon increasing feed mass flow rate, there is a critical pipe length above which a quarter-wave instability occurs. The dependency is shown to be well approximated by a simple analytical formula derived from a reduced-order model. Liquid service Valves are found to be stable for longer inlet pipes than for the gas case. However, the instabilities when they do occur are more violent and the valve is found to jump straight into chatter, in which it impacts repeatedly with its seat. Flutter-type oscillations are never observed. These observations are explained by finding that the quarter-wave Hopf bifurcation is subcritical. Water hammer effects can also be observed, which result in excessive overpressure values during chatter. In addition a new, Helmholtz-like instability — not encountered in gas service — is identified for short pipes with small reservoir volumes. This can also be predicted analytically and is shown to explain a valve-only instability found in previous work that incorporated significant mechanical damping.

  • Dynamic behaviour of direct spring loaded pressure Relief Valves in gas service: II reduced order modelling
    Journal of Loss Prevention in the Process Industries, 2015
    Co-Authors: C. J. Hos, K Paul, Alan R Champneys, M. Mcneely
    Abstract:

    A previous study of gas-service direct-spring pressure Relief Valves connected to a tank via a straight pipe is continued by deriving a reduced-order model for predicting oscillatory instabilities such as valve flutter and chatter. The reduction process uses collocation to take into account a finite number N of acoustic pressure waves within the pipe, resulting in a set of 2. N+3 ordinary differential equations. Following a novel non-dimensionalization, it is shown analytically that the model can exhibit, at experimentally realistic parameter values, instabilities associated with coupling between the valve and acoustic waves in the pipe. The thresholds for each instability are such that for a given flow rate, the first mode to go unstable as the inlet pipe length increases is the quarter-wave mode, then a three-quarter wave, a 5/4-wave etc. Thus the primary mode of instability should always be due to the quarter wave. In the limit of low flow rates, a simple approximate expression is found for the quarter-wave instability threshold in the form of inlet pipe length against mass flow rate. This threshold curve is found to agree well with simulation of the full model. For higher flow rates there is a need to include fluid convection, inlet pressure loss and pipe friction in order to get good agreement. The reduced model enables the dependence of the stability curve on key dimensionless physical parameters to be readily computed.

Sasko Dimitrov - One of the best experts on this subject based on the ideXlab platform.