Hydrostatic Retesting of Existing Pipelines

1984 ◽  
Vol 106 (3) ◽  
pp. 362-368
Author(s):  
J. F. Kiefner ◽  
T. P. Forte
Keyword(s):  
Growth Rate ◽  
Time To Failure ◽  
Operating Pressure ◽  
Pipe Material ◽  
Rate Data ◽  
Time Intervals ◽  
Large Pressure ◽  
Pressure Cycle ◽  
Long Time ◽  
Test Pressure

An analytical model is presented for predicting hydrostatic retest intervals in liquid pipelines which are subjected to frequent large pressure cycles. The model utilizes pressure cycle history, hydrostatic test history, and fatigue crack growth rate data for the pipe material to calculate time to failure for the largest possible defect which could have survived a previous hydrostatic test. An example problem is described which shows the value of maximizing the margin between test pressure and operating pressure in order to achieve long time intervals between tests.

Assessment of the Reliability Level Embedded in Pipeline Design Codes

2014 ◽  
Author(s):  
Sviatoslav Timashev ◽  
Anna Bushinskaya
Keyword(s):  
Limit State ◽  
Random Variables ◽  
State Function ◽  
Operating Pressure ◽  
Pipe Material ◽  
Design Codes ◽  
Statistical Parameters ◽  
Reliability Level ◽  
Long Time ◽  
Pipeline Design

Recently a long time discussion among specialists about the meaning of the probabilities of failure (POF) produced by different reliability analysis methods surfaced in pipeline journals. This paper, which was a long time in the making, is a follow-up on the discussion and analyses the actual reliability level which was empirically embedded in codes for pipeline design [B31G, B31Gmod, Shell92 and Battelle (PCORRC)] and Building Standard (BR) Main Pipelines #2.05.06-85, using a real pipeline as an example. Assessment of the actual reliability level empirically embedded in BR is based on assessing the order of the quintiles of strength parameters (design values of tensile strength and yield strength of the pipe material) and load (internal pressure) on the pipeline. This approach allows direct connection of the deterministic safety coefficients used in the BR with the level of reliability of the pipelines associated with these coefficients. The actual reliability level, empirically embedded in international codes, is calculated as the probability that the limit state function (LSF) of ideal pipeline (without defects) is positive. LSF = Pf − Pop, where Pf is the failure pressure of an ideal pipe, which is estimated by any design code; Pop is the operating pressure. The failure and operating pressure are considered as random variables. The expression for this probability was obtained analytically and in closed form. Recommendations are also presented for choosing probability distributions and statistical parameters for random variables RVs. Extensive calculations permitted revealing the reliability levels which are actually present in the analyzed international pipeline design codes. In a nutshell, the paper proves that the international codes under consideration are very reliable, as they produce very safe designs of pipelines with very low POF, and, hence, provide large safety coefficients, and that the algorithm developed in the paper permits connecting the current level of pipeline degradation (in terms of POF), with its current safety coefficient, which, in this case, is a function of time. All calculating in the paper where performed using MathCAD. Illustrations of these calculations are also presented in the paper.

scholarly journals Optimal Perturbations of an Oceanic Vortex Lens

Fluids ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 63 ◽  
Author(s):  
Thomas Meunier ◽  
Claire Ménesguen ◽  
Xavier Carton ◽  
Sylvie Le Gentil ◽  
Richard Schopp
Keyword(s):  
Normal Mode ◽  
Growth Rates ◽  
Time Interval ◽  
Time Intervals ◽  
Horizontal Structure ◽  
Azimuthal Wave ◽  
Wave Numbers ◽  
Non Linear ◽  
Long Time ◽  
Short Time

The stability properties of a vortex lens are studied in the quasi geostrophic (QG) framework using the generalized stability theory. Optimal perturbations are obtained using a tangent linear QG model and its adjoint. Their fine-scale spatial structures are studied in details. Growth rates of optimal perturbations are shown to be extremely sensitive to the time interval of optimization: The most unstable perturbations are found for time intervals of about 3 days, while the growth rates continuously decrease towards the most unstable normal mode, which is reached after about 170 days. The horizontal structure of the optimal perturbations consists of an intense counter-shear spiralling. It is also extremely sensitive to time interval: for short time intervals, the optimal perturbations are made of a broad spectrum of high azimuthal wave numbers. As the time interval increases, only low azimuthal wave numbers are found. The vertical structures of optimal perturbations exhibit strong layering associated with high vertical wave numbers whatever the time interval. However, the latter parameter plays an important role in the width of the vertical spectrum of the perturbation: short time interval perturbations have a narrow vertical spectrum while long time interval perturbations show a broad range of vertical scales. Optimal perturbations were set as initial perturbations of the vortex lens in a fully non linear QG model. It appears that for short time intervals, the perturbations decay after an initial transient growth, while for longer time intervals, the optimal perturbation keeps on growing, quickly leading to a non-linear regime or exciting lower azimuthal modes, consistent with normal mode instability. Very long time intervals simply behave like the most unstable normal mode. The possible impact of optimal perturbations on layering is also discussed.

Pressure Cycling Monitoring Helps Ensure the Integrity of Energy Pipelines

2010 ◽  
Author(s):  
Peter Song ◽  
Doug Lawrence ◽  
Sean Keane ◽  
Scott Ironside ◽  
Aaron Sutton
Keyword(s):  
Fatigue Life ◽  
Pipeline System ◽  
Outer Diameter ◽  
Operating Pressure ◽  
Potential Growth ◽  
Integrity Assessment ◽  
Pressure Cycling ◽  
Pressure Cycle ◽  
Primary Focus ◽  
Pump Stations

Liquids pipelines undergo pressure cycling as part of normal operations. The source of these fluctuations can be complex, but can include line start-stop during normal pipeline operations, batch pigs by-passing pump stations, product injection or delivery, and unexpected line shut-down events. One of the factors that govern potential growth of flaws by pressure cycle induced fatigue is operational pressure cycles. The severity of these pressure cycles can affect both the need and timing for an integrity assessment. A Pressure Cycling Monitoring (PCM) program was initiated at Enbridge Pipelines Inc. (Enbridge) to monitor the Pressure Cycling Severity (PCS) change with time during line operations. The PCM program has many purposes, but primary focus is to ensure the continued validity of the integrity assessment interval and for early identification of notable changes in operations resulting in fatigue damage. In conducting the PCM program, an estimated fatigue life based on one month or one quarter period of operations is plotted on the PCM graph. The estimated fatigue life is obtained by conducting fatigue analysis using Paris Law equation, a flaw with dimensions proportional to the pipe wall thickness and the outer diameter, and the operating pressure data queried from Enbridge SCADA system. This standardized estimated fatigue life calculation is a measure of the PCS. Trends in PCS overtime can potentially indicate the crack threat susceptibility the integrity assessment interval should be updated. Two examples observed on pipeline segments within Enbridge pipeline system are provided that show the PCS change over time. Conclusions are drawn for the PCM program thereafter.

Super-Fine Structure in the Critical Flow-Rate of Critical Flow Venturi Nozzles

2002 ◽  
Author(s):  
Masahiro Ishibashi
Keyword(s):  
Fine Structure ◽  
Steady State ◽  
Discharge Coefficient ◽  
Constant Pressure ◽  
Pressure Ratio ◽  
Critical Flow ◽  
Time Intervals ◽  
Critical Flow Rate ◽  
A Value ◽  
Long Time

It is shown that critical flow Venturi nozzles need time intervals, i.e., more than five hours, to achieve steady state conditions. During these intervals, the discharge coefficient varies gradually to reach a value inherent to the pressure ratio applied. When a nozzle is suddenly put in the critical condition, its discharge coefficient is trapped at a certain value then afterwards approaches gradually to the inherent value. Primary calibrations are considered to have measured the trapped discharge coefficient, whereas nozzles in applications, where a constant pressure ratio is applied for a long time, have a discharge coefficient inherent to the pressure ratio; inherent and trapped coefficients can differ by 0.03–0.04%.

Interpretation of crystal growth rate data using a modified two-step model

1992 ◽  
Vol 123 (1-2) ◽  
pp. 236-246 ◽  
Author(s):  
Clifford Y. Tai ◽  
Chuen-Song Cheng ◽  
Yuen-Chen Huang
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Crystal Growth Rate ◽  
Rate Data ◽  
Step Model

scholarly journals The Forecasting Residual Life of Corroding Pipeline based on Semi-Probabilistic Method

2010 ◽  
Vol 1 (2) ◽  
pp. 1-6 ◽  
Author(s):  
Noor N.M. ◽  
Yahaya N. ◽  
Ozman N.A.N ◽  
Othman S.R.
Keyword(s):  
Standard Deviation ◽  
Residual Life ◽  
Probabilistic Method ◽  
Time To Failure ◽  
Operating Pressure ◽  
Safety Factors ◽  
Internal Corrosion ◽  
Maintenance Schedule ◽  
Operating Strategies ◽  
Pipeline Failures

In general, the prediction of pipeline residual life can effectively assist pipeline operators to evaluate future safe operating strategies including re-inspection and appropriate maintenance schedule. As a result it can minimize the possibility of pipeline failures until it reaches its designed lifetime. A semi-probabilistic methodology for predicting the remaining strength of submarine pipelines subjected to internal corrosion based on Recommended Practice RP-F101 by Det Norske Veritas (DNV) is described in this paper. It is used to estimate the maximum allowable operating pressure of the corroding pipelines based on series of pigging data, which represents corrosion pit location and dimension. The introduction of partial safety factors in the DNV code to minimise the effect of uncertainties due to the defect sizing has improved the reliability of pipeline assessment methodology. Nevertheless, the code is still regarded as a fully deterministic approach due to its incapability of predicting the remaining life of corroded pipeline. Thus, we have added prediction capabilities to the capacity equation by introducing a standard deviation model of future defect depth. By doing so, the variation of safety factors of the capacity equation can be fully manipulated in which prediction of future pipeline residual life becomes feasible. The paper demonstrates calculation and prediction of pipeline residual life subjects to internal corrosion. The results shows the standard deviation of corrosion parameter affected the value of partial safety factor as corrosion progressing, hence amplify the conservatism of time to failure.

scholarly journals GROWTH PERFORMANCE AND HISTOLOGICAL APPEARANCE OF THE HUMPBACK GROUPER JUVENILE (CROMILEPTESALTIVELIS) AFTER TREATED WITH RECOMBINANT GROWTH HORMONE

2015 ◽  
Vol 2 (1) ◽  
pp. 191
Author(s):  
Suci Antoro ◽  
M Zairin Junior ◽  
A Alimuddin ◽  
Agus Suprayudi ◽  
Irvan Faizal
Keyword(s):  
Growth Hormone ◽  
Growth Rate ◽  
Growth Stimulation ◽  
Oral Route ◽  
High Price ◽  
Recombinant Growth Hormone ◽  
Commercial Diet ◽  
Long Time ◽  
Kidney Liver ◽  
Daily Application

Despite as high price consumption fish, humpback grouper grow out take very long time so its culture considered not efficient. Therefore to accelerate its growth rate and make grow out culture more efficient, recombinant Epinepheluslanceolatus growth hormone (rElGH) was applied by oral route. Daily application of rough rElGH at a dose of 5 mg/100 g commercial diet for 42 days resulted significance increase in growth rate compared to control groups. No specific histological damage on kidney, liver and spleen which was attributable to rElGH administration. These results strongly suggested that growth stimulation following oral administration was due to a specific action of rElGH and recombinant GH as mentioned above save for fish consumption. Keywords: growth, histology, humpback grouper, recombinant growth hormone 

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