scholarly journals The Effects of Maintenance Actions on the PFDavg of Spring Operated Pressure Relief Valves

2014 ◽  
Author(s):  
Julia V. Bukowski ◽  
William M. Goble ◽  
Robert E. Gross ◽  
Stephen P. Harris
Keyword(s):  
End User ◽  
Pressure Relief ◽  
Periodic Inspection ◽  
On Demand ◽  
Plant Safety ◽  
Safety Integrity Level ◽  
Proof Testing ◽  
Average Probability ◽  
Pressure Relief Valves ◽  
Inspection And Maintenance

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.

The Effects of Maintenance Actions on the Average Probability of Failure on Demand of Spring Operated Pressure Relief Valves

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Julia V. Bukowski ◽  
William M. Goble ◽  
Robert E. Gross ◽  
Stephen P. Harris
Keyword(s):  
Probability Of Failure ◽  
Pressure Relief ◽  
Periodic Inspection ◽  
On Demand ◽  
Plant Safety ◽  
Safety Integrity Level ◽  
Proof Testing ◽  
Average Probability ◽  
Pressure Relief Valves ◽  
Inspection And Maintenance

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.

scholarly journals The Operation Modes of E/E/PE System and Their Influence on Determining and Verifying the Safety Integrity Level

2010 ◽  
Vol 13 (1) ◽  
pp. 289-298
Author(s):  
Tomasz Barnert ◽  
Kazimierz Kosmowski ◽  
Marcin Śliwiński
Keyword(s):  
High Demand ◽  
Related Function ◽  
On Demand ◽  
Safety Integrity Level ◽  
Operation Modes ◽  
Mode Of Operation ◽  
Protection Systems ◽  
Average Probability ◽  
Quantitative Verification ◽  
Probabilistic Criteria

The Operation Modes of E/E/PE System and Their Influence on Determining and Verifying the Safety Integrity Level The standard PN-EN 61508 introduces some probabilistic criteria for the E/E/PE systems that can operate in different modes of operation, which are related to the safety integrity level (SIL). For the control and protection systems, operating in a low demand mode, the criterion is the average probability of dangerous failure on demand PFDavg. In case of systems working in a continuous mode of operation or high demand, the criterion is probability of dangerous failure per hour PFH. In practice, the E/E/PE systems implement many safety-related functions (SRFs), which have different requirements for high and low demands. Thus, there is the problem with choosing proper probabilistic criterion for determining required SIL for a safety-related function to be implemented by these systems as well as in the process of quantitative verification of SIL for considered architectures.

The Adhesion Failure Mode in Stainless Steel Trim Spring Operated Pressure Relief Valves

2012 ◽  
Author(s):  
Julia V. Bukowski ◽  
Robert E. Gross ◽  
William M. Goble
Keyword(s):  
Stainless Steel ◽  
Failure Mode ◽  
Failure Rate ◽  
Failure Modes ◽  
Service Failure ◽  
Failure Rates ◽  
Pressure Relief ◽  
Safety Integrity Level ◽  
Adhesion Failure ◽  
Pressure Relief Valves

This paper addresses dangerous failures of stainless steel (SS) trim spring operated pressure relief valves (SOPRV) due to a particular failure mode (SS-to-SS adhesion) which is not currently being included in SOPRV failure rates. As a result, current methods for estimating or predicting failure rates for SS trim SOPRV significantly underestimate these failure rates and, consequently, overestimate the safety provided by the SOPRV as measured by its average probability of failure on demand (PFDavg) or its corresponding safety integrity level (SIL). The paper also illustrates the critical importance of root cause analysis (RCA) of dangerous SOPRV failures in understanding the impacts of various failure modes. Over 1300 proof test results for both new and used SS trim SOPRV from the Savannah River Site (SRS) were identified. RCA was used on the failed valves to classify those failed due to SS-to-SS adhesions. Statistical analysis of the data convincingly demonstrates adhesions, previously assumed to be only an in-storage failure phenomenon, are also an in-service failure mode which needs to be included in SOPRV failure rates. The paper discusses the factors which potentially influence the adhesion failure mode and suggests a possible approach to including this mode in failure rate predictions. An example illustrates how current failure rate models overestimate SS trim SOPRV safety by one or two orders of magnitude.

The Adhesion Failure Mode in Stainless Steel Trim Spring-Operated Pressure Relief Valves

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Julia V. Bukowski ◽  
Robert E. Gross ◽  
William M. Goble
Keyword(s):  
Stainless Steel ◽  
Failure Mode ◽  
Failure Rate ◽  
Failure Modes ◽  
Service Failure ◽  
Failure Rates ◽  
Pressure Relief ◽  
Safety Integrity Level ◽  
Adhesion Failure ◽  
Pressure Relief Valves

This paper addresses dangerous failures of stainless steel (SS) trim spring-operated pressure relief valves (SOPRV) due to a particular failure mode (SS-to-SS adhesion), which is not currently being included in SOPRV failure rates. As a result, current methods for estimating or predicting failure rates for SS trim SOPRV significantly underestimate these failure rates and, consequently, overestimate the safety provided by the SOPRV as measured by its average probability of failure on demand (PFDavg) or its corresponding safety integrity level (SIL). The paper also illustrates the critical importance of root cause analysis (RCA) of dangerous SOPRV failures in understanding the impacts of various failure modes. Over 1300 proof test results for both new and used SS trim SOPRV from the Savannah River Site (SRS) were identified. RCA was used on the failed valves to classify those failed due to SS-to-SS adhesions. Statistical analysis of the data convincingly demonstrates adhesions, previously assumed to be only an in-storage failure phenomenon, are also an in-service failure mode, which needs to be included in SOPRV failure rates. The paper discusses the factors which potentially influence the adhesion failure mode, and suggests a possible approach to including this mode in failure rate predictions. An example illustrates how current failure rate models overestimate SS trim SOPRV safety by 1 or 2 orders of magnitude.

Effect of Truncated Demand and Capacity Distributions on Reliability of Pipelines

2003 ◽  
Author(s):  
Ziad Nakat ◽  
Robert Bea
Keyword(s):  
Pressure Relief ◽  
Physical Constraints ◽  
Demand Distribution ◽  
On Demand ◽  
Truncated Distributions ◽  
Pressure Relief Valves ◽  
Analysis Of Results ◽  
Management Policies ◽  
Comparison And Analysis ◽  
Demand And Capacity

Reliability of pipelines has been considered assuming different probability continuous distributions of demand and capacities. These distributions in reality can be truncated at the tails by physical constraints such as pressure relief valves (demand truncation), and hydro-testing (capacity truncation). This paper describes the effect of truncations on the reliability of pipelines. The effect of truncation by relief valves on the demand distribution is studied first; the effect of truncation by hydro-testing on the capacity distribution is studied second; and last, the combined effect of truncation on demand and capacity is studied. A comparison and analysis of results is presented to assess the importance of truncated distributions of demand and capacity on the reliability of pipelines. The results show that truncated distributions can have large effects on the reliability and should be accounted for, since they can alter significantly inspection and management policies.

Statistical Performance Evaluation of Soft (Elastomer) Seat Pressure Relief Valves

2013 ◽  
Author(s):  
Robert E. Gross ◽  
Stephen P. Harris
Keyword(s):  
South Carolina ◽  
Performance Evaluation ◽  
The United States ◽  
Probability Of Failure ◽  
United States Department ◽  
Relief Valve ◽  
Pressure Relief ◽  
On Demand ◽  
Pressure Relief Valves ◽  
Statistical Performance Evaluation

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.

A Management Study of Pressure Relief Valves

2007 ◽  
Author(s):  
Chi-Hui Chien ◽  
Chun-Hung Chen ◽  
Yih-Shen Lin
Keyword(s):  
Safety Concern ◽  
Operating Conditions ◽  
Test Results ◽  
Pressure Relief ◽  
Site Survey ◽  
Pressure Relief Valves ◽  
Inspection And Maintenance ◽  
Operation Parameters ◽  
A Site ◽  
Analysis Of Variation

As a safety concern, pressure relief valves play important roles in protecting a pressure vessel or pressurized system. The conditions of the pressure relief valves deteriorate day after day which depend on the operating conditions of process train such as variation of pressure and temperature, containment and frequency of relieving during operation. If the deteriorative relief valves failure to operate normally as required, a catastrophic event may occur while no other protective means provided. So, to prepare a plan of inspection and maintenance with suitable intervals based on the knowledge of the relations between the conditions of pressure relief valves and plant operation parameters, is a safety strategy to plant owner. With practical inspection and maintenance works of pressure relief valves performed in a process train, this paper collects the as-received pressure relief valves test results from current inspection intervals and presents the relationships between as-received test data and operation parameters based on analysis of variation (ANOVA) and analysis of correlation. With these analyses, one can get the relationships between the decay conditions of the pressure relieve valves and their operating parameters. A site survey of as-received test results will be used as a case study and the weighting factors corresponding to the operation parameters are also presented.

Failure Assessment of Spring-Operated Pressure Relief Valve Proof Test Data for Extending Time-in-Service

2020 ◽  
Author(s):  
Julia V. Bukowski ◽  
Robert E. Gross ◽  
Stephen P. Harris ◽  
William M. Goble
Keyword(s):  
Working Fluid ◽  
Relief Valve ◽  
Pressure Relief ◽  
Root Cause ◽  
Proof Testing ◽  
Failure Assessment ◽  
Pressure Relief Valves ◽  
Cause Of Failure ◽  
Active Processes ◽  
Time In Service

Abstract The proof test results of 1669 Spring-Operated Pressure Relief Valves (SOPRV), which were previously installed in active processes, were analyzed with respect to proof test ratio (R), time-in-service (TIS), set pressure (SP), working fluid (WF), material composition of the SOPRV and, if an SOPRV failed-to-open (FTO), the root cause of failure in the FTO failure mode if available. Many of these SOPRV had accumulated TIS in excess of the normal maximum of five years yet proof testing indicated that most would have functioned properly. This paper examines the results of the analysis and provides guidelines under which it is appropriate to consider extending TIS for individual SOPRV.

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