Reversal of Increasing Failure Rates When Pooling Failure Data

Technometrics ◽  
1994 ◽  
Vol 36 (4) ◽  
pp. 416 ◽  
Author(s):  
John Gurland ◽  
Jayaram Sethuraman
Keyword(s):  
1995 ◽  
Vol 90 (432) ◽  
pp. 1416-1423 ◽  
Author(s):  
John Gurland ◽  
Jayaram Sethuraman
Keyword(s):  

Author(s):  
Guy Desjardins ◽  
Kar Mun Cheng ◽  
Shahani Kariyawasam ◽  
Boon Ong ◽  
Pauline Kwong

As part of its ongoing continuous improvement efforts, TransCanada has analyzed the system-wide historical failure data to understand trends and benchmark risk algorithms. The analysis of historical in-service and hydrostatic-test failures is a good diagnostic tool to assess threats to the pipeline system. This knowledge and understanding can be used to build risk algorithms. Quantification of failure rates also enables risk values among different threats and along the pipeline to be benchmarked appropriately. This paper focuses on the assessment of the expected failure frequency of the pipeline to SCC and corrosion.


Author(s):  
Vania De Stefani ◽  
Peter Carr

Pipelines are subjected to several threats which can cause failure of the line, such as external impact, mechanical defects, corrosion and natural hazards. In particular, offshore operations present a unique set of environmental conditions and adverse exposure not observed in a land environment. For example, offshore pipelines located near harbor areas and in major shipping lanes are likely to be exposed to the risk of damage from anchor and dropped object impact. Such damage may result in potential risk to people and the environment, and significant repair costs. Quantitative Risk Assessment (QRA) is a method which is often used in the oil and gas industry to predict the level of risk. In QRA calculations the frequency of an incident is often assessed by a generic failure frequency approach. Generic failure frequencies derived from local incident databases are largely used in pipeline risk assessments. As a result, risk assessments for offshore pipelines may not reflect accurately operational experience for a specific pipeline or region of operation. In addition, a better understanding of the causes and characteristics of pipeline failure should provide important information to improve inspection and maintenance activity for existing pipelines and to aid in selection of design criteria for new pipelines. This paper presents an analysis of the failure data from various pipelines databases to see if there is a common trend regarding failure rates, and failure-rate dependence on pipeline parameters. A breakdown of the causes of failure has been carried out. The effect on failure frequency of factors such as pipeline age, location, diameter, wall thickness, steel grade, burial depth, and fluid transported have been investigated and are discussed. The objective of this paper is to provide a guideline for the determination of failure frequency for offshore pipelines and to describe a new model developed for use within BP for this purpose. This model uses historical databases and predictive methods to develop failure frequencies as a function of a range of influencing parameters.


2016 ◽  
Vol 34 (2_suppl) ◽  
pp. 176-176 ◽  
Author(s):  
Sarah E. Wong ◽  
Scott A. North ◽  
Christopher Sweeney ◽  
Martin R. Stockler ◽  
Srikala S. Sridhar

176 Background: Screen failures cost effort, time and resources estimated at about $2000 per patient (Bienkowski RS et al 2008). There is little published data about the frequency or causes of screen failures in genitourinary (GU) cancer clinical trials. Methods: We reviewed published articles and contacted study investigators on 42 key phase 2 and 3 trials in advanced GU cancer run from 1999 to 2015. We sought data on the numbers and causes of screen failures. Screen failures were defined as individuals who underwent screening but were not enrolled in the trial. Results: Among all 11 phase 3 trials in prostate cancer, the mean screen failure rate was 25% (17.9%-30.3%). In 4 recent trials evaluating novel androgen receptor pathway targeted agents, abiraterone and enzalutamide before or after chemotherapy for castration-resistant disease, the mean screen failure rate was 28% (range 22% to 30%). Only 2 of 3 prostate cancer chemotherapy trials completed after 2008 collected screen failure data with screen failure rates of 18 and 21%. The main reason for screen failures among all prostate cancer clinical trials was ineligibility. Among 14 phase 3 trials in kidney cancer, 5 reported rates and the mean screen failure rate was 24% (range 21%-27%). The main reasons again were ineligibility, with a very small percentage due to patient refusal. Among 17 phase 2 or 3 trials in bladder cancer, 6 reported rates and the mean screen failure rate was 13% (range 2.04% - 22.8%). The main reasons were primarily ineligibility and patient refusal to a lesser extent. Only (16/42) 38% of the trials published screen failure rates-73% of those in prostate cancer (all completed after 2008), 29% in kidney cancer, and 24% in bladder cancer. Conclusions: Contemporary trials in GU cancer that collected screen failure data had fairly consistent failure rates of 20-30% in prostate and kidney cancer. Many trials did not collect data on the numbers of and reasons for screen failures. Greater standardization of definitions, methods and reporting are needed to better understand and improve screen failure rates in GU cancer trials.


1974 ◽  
Vol 96 (3) ◽  
pp. 175-180 ◽  
Author(s):  
S. C. Chay ◽  
W. D. Loftus ◽  
M. Mazumdar

This paper presents a method to quantify in terms of probabilistic availability the effects of testing and maintenance schedule on the performance of a standby safety system and it describes the mathematical rationale which lies behind it. The purpose of periodic testing and maintenance is to detect any unannounced failures in the system, repair them, and thus ensure the readiness or availability of the equipment. A scheme is given to model generally any complex system in terms of easily visualized equivalent block diagrams such that the formulas developed in this paper or similarly developed formulas can be easily applied. Also presented is a method for incorporating the field failure data to refine a´ priori assumed failure rates which were used in the initial computations.


Technometrics ◽  
1994 ◽  
Vol 36 (4) ◽  
pp. 416-418
Author(s):  
John Gurland ◽  
Jayaram Sethuraman
Keyword(s):  

1994 ◽  
Author(s):  
John Gurland ◽  
Jayaram Sethuraman
Keyword(s):  

Author(s):  
Sérgio B. Cunha

Failure statistics for onshore pipelines transporting oil, refined products and natural gas from the USA, Canada and Europe are compared. Failure data from Brazilian pipelines are presented and included in the comparison. Failure rates for internal and external corrosion, human action and natural forces are analyzed and the expected failure rate for each failure mechanism is indicated. The effects of relevant construction and environmental factors on the failure rates are studied and mean trends are obtained. Furthermore, the sizes of the holes observed in each type of failure are also compared. Finally, the probability of ignition after a failure in gas and liquid pipelines is evaluated. This study may serve as basis for the estimation of failure frequency, hole size and probability of ignition for hazard liquids and gas pipelines.


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