Statistical Considerations for Determining Extent of Piping Inspections for RBI or API-570 Driven Inspections

2002 ◽  
Author(s):  
D. Hobbs ◽  
A. P.-D. Ku
Keyword(s):  
Random Field ◽  
Confidence Level ◽  
Confidence Limits ◽  
Damage State ◽  
Statistical Tools ◽  
Process Piping ◽  
Piping Systems ◽  
Inspection Data ◽  
Engineering Practices

This paper outlines a method for calculating the number of inspection locations for process piping inspections. The method determines the number of piping inspection locations required for an inspection to detect a particular damage state within the confidence limits of the premised inspection’s reliability. It is intended to be used for piping inspections per API-570, “Piping Inspection Code” and in the application of risk-based inspection concepts presented in AP1-581, “Risk Based Inspection, Base Resource Document”. This method combines recognized inspection and piping engineering practices and random-field statistical tools to calculate the number of inspection locations in piping systems with probabilistic confidence level. This method has provisions for future applications when inspection data is known, or there is greater uncertainty in the distribution of the degradation or the reliability of the inspection data is different than those premised in this paper.

Computer Based Process Piping Stress Analysis: ASME B31.3 Appendix S — Example S2

2006 ◽  
Author(s):  
Don R. Edwards
Keyword(s):  
Stress Analysis ◽  
Operating Temperature ◽  
Stress Range ◽  
Explicit Equation ◽  
The Past ◽  
Process Piping ◽  
Piping Systems ◽  
Sustained Loads ◽  
Computer Based ◽  
Temperature And Pressure

The American Standards Association (ASA) B31.3-1959 Petroleum Refinery Piping Code [1] grew out of an ASA document that addressed all manner of fluid conveying piping systems. ASA B31.3 was created long before widespread engineering use of computer “mainframes” or even before the inception of piping stress analysis software. Also as B31.3 continued to pass thru standards organizations from ASA, ANSI, to ASME, the B31.3 Process Piping Code [2] (hereafter referred to as the “Code”) has remained ambiguous over the past few decades in several areas. The displacement stress range, SE, has always been explicitly defined by both verbiage and equation. Yet, the sustained condition(s) stress, SL, is mentioned not with an explicit equation but with a statement that the sustained stress shall be limited by the allowable stress at the corresponding operating temperature, Sh. Also one might infer from the vague verbiage in the Code that there is only one sustained condition; this would also be an incorrect inference. Also, assumptions would then have to be made as to which supports are allowed to be included in a sustained analysis based on whether the piping “lifts-off” any of the pipe supports during the corresponding operating condition. This paper describes the subtle yet possibly radical concepts that are included in the (recently approved for inclusion into) ASME B31.3-2006 Appendix S Example S2. This paper discusses: • when and in what manner the most severe set of operating temperature and pressure is to be used; • the concept of “sustained condition” and multiple “anticipated” sustained conditions; • determining the support scenario(s) for each anticipated sustained condition; • establishing the most severe sustained condition to evaluate and determine the stress due to sustained loads, SL; • utilizing an equation with sustained stress indices to evaluate SL; • establishing the least severe sustained condition and its effect in determining the largest displacement stress range, SE.

Comparison of the 87 Rb → 87 Sr ages of the red granite of the Bushveld complex from measurements on the total rock and separated mineral fractions

1958 ◽  
Vol 245 (1240) ◽  
pp. 112-117 ◽  
Keyword(s):  
Confidence Level ◽  
Bushveld Complex ◽  
Crushed Rock ◽  
Confidence Limits ◽  
Single Determination ◽  
The Mean ◽  
Age Determinations

Age determinations on a portion of the total crushed rock, and on the felspar fraction of each of four widely separated samples of the red granite from the Bushveld complex are reported. A single determination from the separated biotite of one sample was made. These nine determinations lead to a mean age of 2.41 x 10 9 years [ t 1/2 = 6.3 x 10 10 years] or 1.92 x 10 9 years [ t 1/2 = 5.0 x 10 10 years]. There are no variations between individual determinations that are significant at the 99% confidence level. For the unweighted mean age the 99% confidence limits are ± 0.13 x 10 9 years. Despite the low enrichment of 87 Sr the ‘total rock ’ method shows 99% confidence limits of ± 0.22 x 10 9 years for the mean of four determinations.

MULTIVARIATE MODELS AND VARIABILITY INTERVALS: A LOCAL RANDOM SET APPROACH

2011 ◽  
Vol 19 (05) ◽  
pp. 799-823 ◽  
Author(s):  
THOMAS FETZ
Keyword(s):  
Confidence Level ◽  
Structural Mechanics ◽  
Random Sets ◽  
Confidence Limits ◽  
Random Set ◽  
Multivariate Functions ◽  
Multivariate Models ◽  
Multivariate Case ◽  
Fréchet Bounds

This article is devoted to the propagation of families of variability intervals through multivariate functions comprising the semantics of confidence limits. At fixed confidence level, local random sets are defined whose aggregation admits the calculation of upper probabilities of events. In the multivariate case, a number of ways of combination is highlighted to encompass independence and unknown interaction using random set independence and Fréchet bounds. For all cases we derive formulas for the corresponding upper probabilities and elaborate how they relate. An example from structural mechanics is used to exemplify the method.

Optimizing the laser parameters to attain maximum hardness in nickel based hardfacing surfaces

2017 ◽  
Vol 26 (3-4) ◽  
pp. 113-125 ◽  
Author(s):  
S. Gnanasekaran ◽  
G. Padmanaban ◽  
V. Balasubramanian ◽  
Hemant Kumar ◽  
Shaju K. Albert
Keyword(s):  
Response Surface Methodology ◽  
Design Of Experiments ◽  
Confidence Level ◽  
Feed Rate ◽  
Empirical Relationship ◽  
Travel Speed ◽  
Maximum Hardness ◽  
Powder Feed Rate ◽  
Statistical Tools ◽  
Contour Plots

AbstractIn this investigation, an attempt has been made to optimize the laser hardfacing (LH) parameters such as power, powder feed rate (PFR), travel speed and defocusing distance to maximize hardness of Ni-based hardfacing surfaces. Statistical tools such as the design of experiments (DoE), analysis of variance (ANOVA) are used to develop the empirical relationship to predict the hardness of the deposits at the 95% confidence level. Response graphs and contour plots are constructed using response surface methodology (RSM) concept. From this investigation, it is found that the maximum hardness of 820.48 HV could be achieved for the deposit made using a power of 1314 W, PFR of 9 g/min, a travel speed of 366 mm/min, and a defocusing distance of 32 mm.

On the application of confidence limits to biostratigraphy: an example from diatoms

2020 ◽  
Author(s):  
Cristina Lopes ◽  
João Velez
Keyword(s):  
Sedimentation Rate ◽  
Confidence Level ◽  
Confidence Limits ◽  
Confidence Levels ◽  
Expedition 346 ◽  
Age Model

<p>For years, diatom-based biostratigraphy has been settings bio-events based on a qualitatively approach. This means that the biostratigraphy would set an age based on the findings or not of a certain species. However, how many species are needed to consider a certain datum as certain? One, ten, 100? Moreover, each biostratigrapher sets its on limits. One might consider one as enough and another 10. Therefore, the scale more often used is the absent, rare, frequent, common, dominant or abundant with an explanation of what of these definitions mean. This is very common in, for example, IODP expeditions.</p><p>However, what would happen to these biostratigraphy levels if one would apply, for example, a concept of 95% confidence level? Moreover, what would happen to an age model if this concept would be applied to all the biostratigraphy microfossil?</p><p>Here we will show Expedition 346 age model differences with and without confidence levels applied to diatoms. The differences can be significant and even considering the existence of a hiatus can be reconsider if confidence limits are applied, turning a possible hiatus into a very slow sedimentation rate having serious implications to the initial paleoceanographic interpretations.</p>

Exact confidence limits for prevalence of a disease with an imperfect diagnostic test

2010 ◽  
Vol 138 (11) ◽  
pp. 1674-1678 ◽  
Author(s):  
J. REICZIGEL ◽  
J. FÖLDI ◽  
L. ÓZSVÁRI
Keyword(s):  
Confidence Intervals ◽  
Diagnostic Test ◽  
Sensitivity And Specificity ◽  
Simulation Study ◽  
Confidence Level ◽  
Asymptotic Methods ◽  
Real Life ◽  
Disease Status ◽  
Confidence Limits ◽  
Extensive Simulation

SUMMARYEstimation of prevalence of disease, including construction of confidence intervals, is essential in surveys for screening as well as in monitoring disease status. In most analyses of survey data it is implicitly assumed that the diagnostic test has a sensitivity and specificity of 100%. However, this assumption is invalid in most cases. Furthermore, asymptotic methods using the normal distribution as an approximation of the true sampling distribution may not preserve the desired nominal confidence level. Here we proposed exact two-sided confidence intervals for the prevalence of disease, taking into account sensitivity and specificity of the diagnostic test. We illustrated the advantage of the methods with results of an extensive simulation study and real-life examples.

Critical Analysis of the New High Cycle Fatigue Assessment Procedure From ASME B31.3—Appendix W

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Nikola Jaćimović ◽  
Sondre Luca Helgesen
Keyword(s):  
High Cycle Fatigue ◽  
Design Procedure ◽  
Piping System ◽  
Assessment Procedure ◽  
Stress Range ◽  
Cycle Fatigue ◽  
Fatigue Design ◽  
Process Piping ◽  
Piping Systems ◽  
Fatigue Evaluation

Abstract ASME B31.3, the leading process piping system design code, has included in its 2018 edition a new procedure for evaluation of high cycle fatigue in process piping systems. As stated in the Appendix W of ASME B31.3-2018, this new procedure is applicable to any load resulting in the stress range in excess of 20.7 MPa (3.0 ksi) and with the total number of cycles exceeding 100,000. However, this new procedure is based on the stress range calculation typical to ASME B31 codes which underestimates the realistic expansion stress range by a factor of ∼2. While the allowable stress range used typically for fatigue evaluation of piping systems is adjusted to take into consideration this fact, the new fatigue design curves seem not to take it into account. Moreover, the applicability of the new design procedure (i.e., welded joint fatigue design curves) to the components which tend to fail away from the bends is questionable. Two examples are presented at the end of the paper in order to substantiate the indicated inconsistencies in the verification philosophy.

Flow Induced Vibration Analysis of Topside Piping at High Pressure

2020 ◽  
Author(s):  
Paul R. Emmerson ◽  
Mike J. Lewis ◽  
Neil A. Barton ◽  
Steinar Orre ◽  
Knud Lunde
Keyword(s):  
High Pressure ◽  
Multiphase Flow ◽  
Low Pressure ◽  
Screening Methods ◽  
Flow Induced Vibration ◽  
Cfd Simulations ◽  
Forcing Function ◽  
Process Piping ◽  
Forcing Functions ◽  
Piping Systems

Abstract Flow induced vibration (FIV) from high velocity multiphase flow is a common source of vibration concern in process piping, potentially leading to fatigue failures and hydrocarbon leaks. FIV screening methods tend to be conservative for multiphase flows and are typically only validated for simple single bends at low pressure. FE can predict the response of a system if a sensible forcing function is provided. CFD can be used to predict realistic forcing functions in complex combinations of bends and tees, typically seen in process piping systems. FIV studies were performed on a topside production system operated by Equinor, carrying multiphase flow at high pressure (∼69 bara) conditions, where significant vibration was measured. The study assessed different vibration simulation methodologies, combining FE analysis with forcing functions based on both correlations and CFD simulations. The aim was to gain a better understanding of the accuracy and limitations of calculation methods typically used to assess fatigue. CFD simulations predicted similar force magnitudes but higher frequency forcing at 69 bara compared to equivalent simulations at atmospheric pressure (at the same liquid and gas superficial velocities). The forcing function correlations used do not predict higher frequency forcing at high pressure, which has a significant impact on the predicted vibration. Care is required when undertaking this type of analysis. It is important to have an accurate FE model of the as-built pipework and supports as well as a forcing function which accurately represents the fluid forces on the bends. For the case simulated here the magnitude and peak frequency of the forcing function had a significant influence on the response of the structure. Forcing functions based on correlated data from tests at low pressure should be used carefully for high pressure systems. In addition, the inclusion of phasing of the forces at each bend can influence the structural response, and simulations performed in the frequency domain do not consider this. A combination of CFD and FE modelling offers a potentially powerful tool for assessing and diagnosing multiphase FIV problems in hydrocarbon production piping systems.

Computer Piping Analysis, ASME B31.3 Appendix S: Example S3 — Moment Reversal

2007 ◽  
Author(s):  
Don R. Edwards
Keyword(s):  
Stress Analysis ◽  
Petroleum Refinery ◽  
Axial Stress ◽  
Piping System ◽  
Stress Range ◽  
Analysis Software ◽  
Process Piping ◽  
Piping Systems ◽  
Operating Stress ◽  
The Impact

The American Standards Association (ASA) B31.3-1959 Petroleum Refinery Piping Code [1] grew out of an ASA document that addressed all manner of fluid conveying piping systems. ASA B31.3 was created long before widespread engineering use of computer “mainframes” or even before the inception of piping stress analysis software. From its inception until recent times, the B31.3 Process Piping Code [2] (hereafter referred to as the “Code”) has remained ambiguous in several areas. This paper describes some of these subtle concepts that are included in the Code 2006 Edition for Appendix S Example S3. This paper discusses: • the effect of moment reversal in determining the largest Displacement Stress Range, • the impact of the average axial stress caused by displacement strains on the Example S3 piping system and the augmenting of the Code Eq. (17) thereto, • a brief comparison of Example S3 results to that of the operating stress range evaluated in accordance with the 2006 Code Appendix P Alternative Requirements.

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