Pipeline In-Service Fillet Weld Inspection Delay Time

2006 ◽  
Author(s):  
A. Dinovitzer ◽  
Vlado Semiga ◽  
L. N. Pusseogda ◽  
Scott Ironside
Keyword(s):  
Delay Time ◽  
Hydrogen Diffusion ◽  
Time Estimate ◽  
Hydrogen Diffusivity ◽  
Hydrogen Cracking ◽  
Time To Peak ◽  
Novel Approach ◽  
Environmental Material ◽  
Delay Times ◽  
Weld Inspection

Traditionally, in-service welding procedures have been developed to minimize the risk of hydrogen cracking by considering the weldment cooling rate and chemistry to control the susceptibility of the resulting microstructure. To further ensure that weld hydrogen cracks do not enter service, weldment inspection is completed. The BMT Hydrogen Diffusion and Cracking Model has been used to develop a means of conservatively estimating the delay time for hydrogen cracking in multi-pass welds. The hydrogen cracking delay time estimate is developed based upon the Time To Peak Hydrogen (TTPH) concept that is evaluated numerically considering the hydrogen diffusivity in the weldment. CSA Z662 indicates that the pipeline operator should delay weld inspection until the risk of cracking is over. This requirement includes a suggested delay time of 48 hours after weld deposition. The BMT Hydrogen Diffusion Model and TTPH concept were used to define conservative inspection delay times for pipeline repair sleeve end circumferential fillet welds deposited in-service. This paper describes the investigation results and the effect of variations in welding, environmental, material and pipeline characteristics on the recommended inspection delay time. These delay times are compared to those recommended by CSA Z662 to illustrate this novel approach to establishing weldment inspection delay times.

Justification for Reducing In-Service Weld Inspection Delay Times for Liquid Pipelines

2018 ◽  
Author(s):  
Matt Boring ◽  
Mike Bongiovi ◽  
David Warman ◽  
Harold Kleeman
Keyword(s):  
Hydrogen Concentration ◽  
Delay Time ◽  
Time Dependent ◽  
Accelerated Cooling ◽  
Hydrogen Cracking ◽  
Inspection Method ◽  
Time To Peak ◽  
Preventative Measures ◽  
Increased Risk ◽  
Delay Times

Welds that are made onto an operating pipeline cool at an accelerated rate as a result of the flowing pipeline contents cooling the weld region. The accelerated cooling rates increase the probability of forming a crack-susceptible microstructure in the heat-affected zone (HAZ) of in-service welds. The increased risk of forming such microstructures makes in-service welds more susceptible to hydrogen cracking compared to welds that do not experience accelerated cooling. It is understood within the pipeline industry that hydrogen cracking is a time-dependent failure mechanism. Due to the time-dependent nature and susceptibility of in-service welds to hydrogen cracking, it is common to delay the final inspection of in-service welds. The intent of the delayed inspection is to allow hydrogen cracks, if they were going to occur, to form so that the inspection method could detect them and the cracks could repaired. Many industry codes provide a single inspection delay time. By providing a single inspection delay time it is implied that the inspection delay time should be applied for all situations independent of the welding conditions or any other preventative measures the company may employee. There are many aspects that should be addressed when determining what should be considered an appropriate inspection delay time and these aspects can vary the inspection delay time considerably. Such factors include the cooling characteristics of the operating pipeline, the welding procedure that is being followed, the chemical composition of the material being welded and if any preventative measures such as post-weld heating are applied. The objective of this work was to provide an engineering justification for realistic minimum inspection delay times for different in-service welding scenarios. The minimum inspection delay time that was determined was based on modelling results from a previously developed two-dimensional hydrogen diffusion model that predicts the time to peak hydrogen concentration at any location within a weld HAZ. The time to peak hydrogen concentration was considered equal to the minimum inspection delay time since the model uses the assumption that if a weld was to crack the cracking would occur prior to or at the time of peak hydrogen concentration. Several factors were varied during the computer model runs to determine the effect they had on the time to peak hydrogen concentration. These factors included different welding procedures, different material thicknesses and different post-weld heating temperatures. The post-weld heating temperatures were varied between 40 F (4 C) and 300 F (149 C). The results of the analysis did provide justification for reducing the inspection delay time to 30 minutes or less depending on the post-weld heating temperature and pipeline wall thickness. This reduction in inspection delay time has the potential to significantly increase productivity and reduce associated costs without increasing the associated risk to pipeline integrity or public safety.

An Alternative Approach to Time Delay Prior to Inspection for Hydrogen Cracking

2018 ◽  
Author(s):  
William A. Bruce ◽  
Jared Proegler ◽  
Brad Etheridge ◽  
Steve Rapp ◽  
Russell Scoles
Keyword(s):  
Time Delay ◽  
Delay Time ◽  
Good Practice ◽  
Welding Process ◽  
Time Dependent ◽  
Hydrogen Cracking ◽  
Slow Cooling ◽  
Alternative Approach ◽  
Delay Times ◽  
Hydrogen Assisted Cracking

Hydrogen-assisted cracking in welds, which is also referred to as ‘hydrogen cracking’ or ‘delayed cracking,’ often requires time to occur. The reason for this is that time is required for the hydrogen to diffuse to areas with crack susceptible microstructures. Prior to inspection for hydrogen cracking, general good practice indicates that a sufficient delay time should be allowed to elapse — to allow any cracks that are going to form to do so and for the cracks to grow to a detectable size. What is a ‘sufficient’ delay time? Why does a delay time tend to be required for some applications (e.g., installation of a hot tap branch connection) and not for others (e.g., construction of an offshore pipeline from a lay barge)? This paper will address these and other related questions and present the results of recent experimental work on this subject. When determining appropriate delay times prior to inspection, it is important to consider not only the time-dependent nature of hydrogen cracking, but also the expected susceptibility of the weld to cracking. From a time-dependent nature standpoint, longer delay times decrease the chance that cracking can occur after inspection has been completed. From a probability standpoint, if measures can be taken to assure that the probability of cracking is extremely low, then determining an appropriate delay time becomes a moot point. In other words, if the weld is never going to crack, it does not matter when you inspect it. The probability of cracking can be minimized by using more conservative welding procedures (i.e., by designing out the risk of hydrogen cracking during procedure qualification). For example, if hydrogen levels are closely controlled by using low-hydrogen electrodes or a low-hydrogen welding process, or if the hydrogen in a weld made using cellulosic-coated electrodes is allowed to diffuse away after welding by careful application of preheating and slow cooling, or the use of post-weld preheat maintenance (i.e., post-heating), the probability of cracking is significantly reduced, and immediate inspection may be justified. This alternative approach to time delay prior to inspection for hydrogen cracking, which can allow for immediate inspection, will be presented.

Determination of Critical Hydrogen Curves From Slow Bend Tests

2004 ◽  
Author(s):  
L. N. Pusseogda ◽  
A. Dinovitzer ◽  
D. Horsley
Keyword(s):  
Hydrogen Diffusion ◽  
High Strength Steels ◽  
High Strength ◽  
Hydrogen Diffusivity ◽  
Hydrogen Cracking ◽  
Cold Temperatures ◽  
Steel Strength ◽  
Delayed Cracking ◽  
Two Parameters ◽  
Welding Procedure

Recent trends in the pipeline industry are towards the use of high strength steels. As steel strength increases, the delayed hydrogen cracking propensity in the welds also increases. As welding is often completed during winter months, the cold temperatures must be considered in determining joining procedures that will avoid delayed hydrogen cracking. The Graville/BMT Fleet Technology Limited hydrogen diffusion and cracking models have been used successfully in the past to predict delayed cracking and to demonstrate how changes implemented in the welding procedure can minimize the risk of cracking. The two capabilities, hydrogen diffusion and cracking assessment, can be applied to the case of X100 pipe as well, provided the hydrogen diffusivity and the hydrogen cracking susceptibility curves are established for the materials of interest. These two parameters, the hydrogen diffusivity and the hydrogen cracking susceptibility curves are developed to examine the hydrogen cracking susceptibility of SMAW and GMAW welds in X100 pipe, and are the focus of the paper.

scholarly journals Estimation of Delay Times in Coupling Between Autonomic Regulatory Loops of Human Heart Rate and Blood Flow Using Phase Dynamics Analysis

2017 ◽  
Vol 9 (1) ◽  
pp. 16-22 ◽  
Author(s):  
Vladimir S Khorev ◽  
Anatoly S Karavaev ◽  
Elena E Lapsheva ◽  
Tatyana A Galushko ◽  
Mikhail D Prokhorov ◽  
...  
Keyword(s):  
Heart Rate ◽  
Delay Time ◽  
Healthy Subjects ◽  
Low Frequency ◽  
Phase Dynamics ◽  
Oscillatory Systems ◽  
Low Frequency Oscillations ◽  
Delay Times ◽  
The Difference ◽  
Regulatory Loop

Objective: We assessed the delay times in the interaction between the autonomic regulatory loop of Heart Rate Variability (HRV) and autonomic regulatory loop of photoplethysmographic waveform variability (PPGV), showing low-frequency oscillations. Material and Methods: In eight healthy subjects aged 25–30 years (3 male, 5 female), we studied at rest (in a supine position) the simultaneously recorded two-hour signals of RR intervals (RRIs) chain and finger photoplethysmogram (PPG). To extract the low-frequency components of RRIs and PPG signal, associated with the low-frequency oscillations in HRV and PPGV with a frequency of about 0.1 Hz, we filtered RRIs and PPG with a bandpass 0.05-0.15 Hz filter. We used a method for the detection of coupling between oscillatory systems, based on the construction of predictive models of instantaneous phase dynamics, for the estimation of delay times in the interaction between the studied regulatory loops. Results: Averaged value of delay time in coupling from the regulatory loop of HRV to the loop of PPGV was 0.9±0.4 seconds (mean ± standard error of the means) and averaged value of delay time in coupling from PPGV to HRV was 4.1±1.1 seconds. Conclusion: Analysis of two-hour experimental time series of healthy subjects revealed the presence of delay times in the interaction between regulatory loops of HRV and PPGV. Estimated delay time in coupling regulatory loops from HRV to PPGV was about one second or even less, while the delay time in coupling from PPGV to HRV was about several seconds. The difference in delay times is explained by the fact that PPGV to HRV response is mediated through the autonomic nervous system (baroreflex), while the HRV to PPGV response is mediated mechanically via cardiac output.

scholarly journals The Game of Developers and Planners: Ecosystem Services as a (Hidden) Regulation through Planning Delay Times

2020 ◽  
Vol 12 (15) ◽  
pp. 5940
Author(s):  
Dani Broitman
Keyword(s):  
Ecosystem Services ◽  
Social Welfare ◽  
Delay Time ◽  
Open Space ◽  
Simple Game ◽  
Land Development ◽  
Theoretic Model ◽  
Land Use Regulation ◽  
Main Hypothesis ◽  
Delay Times

Planning delay time is a ubiquitous but under-researched land use regulation method. The aim of this study is to link planning delay time with the loss of urban locally provided ecosystem services (ULPES) caused by land development. Our main hypothesis is that the planning delay is an informal tool that ensures social welfare in a given urban area increases even if land is developed and the ULPES associated with the undeveloped land are lost. Whereas the developer’s objective is to maximize his profits, the planner’s target is to achieve the greatest social welfare, as calculated by considering public interest based on the value of open space and the developer’s expected profits. Our results show that, when the ULPES provided by an undeveloped parcel are sufficiently high, planning delay times can be used to prevent the execution of low quality initiatives and to only permit projects that improve general welfare and justify the potential ULPES loss. Planning delay times are interpreted as the expression of continuous negotiation between the interests of the public and those of real-estate developers, regarding the value of ULPES. The implication of the study is that ULPES values are introduced using a simple game-theoretic model allowing interaction between developers and planning authorities. The main significance is an alternative explanation for planning delay times as a consequence of ongoing negotiations between developers and urban planners that represent the general public in the city.

Hydrogen Diffusivity and Solubility in Internally Oxidized Pd0.97Zr0.03 and Pd0.97Nb0.03 Alloys

2010 ◽  
Vol 297-301 ◽  
pp. 715-721
Author(s):  
E.R. Lagreca ◽  
Viviane M. Azambuja ◽  
Dílson S. dos Santos
Keyword(s):  
Diffusion Coefficient ◽  
Grain Boundaries ◽  
Hydrogen Pressure ◽  
Hydrogen Diffusion ◽  
Gas Permeation ◽  
Hydrogen Diffusivity ◽  
Sem Images ◽  
Conventional Furnace ◽  
Hydrogen Diffusion Coefficient ◽  
Preferential Segregation

Internally oxidized (I.O.) Pd0.97Zr0.03 and Pd0.97Nb0.03 alloys were submitted to gas permeation tests with temperatures in the range of 473-873 K. The internal oxidation was kept in a conventional furnace at 1073 K for 24 hours in air contact. The formation of nano-oxides, ZrO2 and Nb2O5, dispersed in the Pd matrix was observed. SEM images showed a preferential segregation of these oxides in the grain boundaries. It was observed that the diffusion coefficient in the sample containing Nb oxide was smaller than that in the Pd-Zr oxide. The effect of hydrogen pressure was investigated in the Pd-Nb samples. It was observed that the hydrogen diffusion coefficient increases with increasing the pressure. The hydrogen solubility is bigger for the Pd-Zr internally oxidized. This effect is attributed to the Zr nanoxides, which are smaller than Pd-Nb precipitates and then offer more interface for trapping the hydrogen.

Investigation of Hydrogen Diffusion Characteristics of the Heat Affected Zone of 2.25Cr-1Mo-0.25V Steel by an Electrochemical Permeation Method

2019 ◽  
Author(s):  
Xin Song ◽  
Zelin Han ◽  
Bin Liu ◽  
Mu Qin ◽  
Yuancai Duo ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Hydrogen Concentration ◽  
Heat Affected Zone ◽  
Hydrogen Diffusion ◽  
Trap Density ◽  
Hydrogen Diffusivity ◽  
Hydrogen Flux ◽  
Hydrogen Trap ◽  
Diffusion Characteristics ◽  
Effective Hydrogen

Abstract The heat affected zone (HAZ) of 2.25Cr-1Mo-0.25V welded joint is a critical part for the safety of hydrogenation reactors. Hydrogen has a significant effect on the HAZ, studying hydrogen diffusion characteristics, such as: hydrogen flux and the effective hydrogen diffusivity has a remarkable value in investigating the hydrogen-induced material degradation mechanisms. In this work, an electrochemical permeation method was applied to study the hydrogen diffusion characteristics of HAZ. Then, the metallographic microscope and a software “Image J” were used to analyze the density of grain boundaries of HAZ. The effect of the post–weld heat treatment (PWHT, i.e. annealing) on the hydrogen diffusion characteristics of HAZ was also been investigated. The results show that after PWHT, the effective hydrogen diffusivity of HAZ increases from 1.63 × 10−7cm2·s−1 to 3.68 × 10−7cm2·s−1, the hydrogen concentration decreases from 1.92 × 10−4mol·cm−3 to 1.09 × 10−4mol·cm−3, and the hydrogen trap density decreases from 3.00 × 1026m−3 to 0.76 × 1026m−3. Thus, PWHT can significantly reduce density of grain boundaries, thereby reducing the hydrogen trap density, enhancing the hydrogen diffusivity and reducing the hydrogen concentration.

Load Rejection Tests and Their Dynamic Simulations With a 150 kW Class Microsteam Turbine

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Susumu Nakano ◽  
Kuniyoshi Tsubouchi ◽  
Hiroyuki Shiraiwa ◽  
Kazutaka Hayashi ◽  
Hiroyuki Yamada
Keyword(s):  
Dynamic Simulation ◽  
Rotational Speed ◽  
Delay Time ◽  
Simulation Method ◽  
Dynamic Simulations ◽  
Machine Reliability ◽  
Delay Times ◽  
Simulation Results ◽  
Generator Output ◽  
Good Agreement

A simulation method for load rejection with a 150 kW class radial inflow steam turbine system was proposed to determine over rotational speed at load rejection. Simulations were carried out for several parameters of valves which are operated in an emergency. In addition, load rejection tests were carried out to confirm the machine reliability and to obtain results for comparison with the simulation results. Simulation results show that operation delay times of the steam release and vacuum break valves greatly affect over rotational speed at load rejection. Load rejection tests were done for generator outputs from 69 kW to 113 kW. Maximum over rotational speed of 54,160 rpm was measured at the generator output of 113 kW. Over rotational speed calculated by the dynamic simulation has relatively good agreement with the result for the operation delay time of 0.21 s. If the operation delay time of the steam release valves are kept as 0.21 s at the load rejection for the rated load of 150 kW, the over rotational speed is suppressed within 55,200 rpm which is less than the allowed rotational speed of 56,100 rpm.

Interpretation of Flow Reactor Based Ignition Delay Measurements

2009 ◽  
Author(s):  
David Beerer ◽  
Vincent McDonell ◽  
Scott Samuelsen ◽  
Leonard Angello
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Residence Time ◽  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Flow Reactor ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Recirculation Zones

Compositional variation of global gas supplies is becoming a growing concern. Both the range and rate-of-change of this variation is expected to increase as global markets for Liquefied Natural Gas (LNG) continue to expand. Greater fuel composition variation poses increased operational risk to gas turbine engines employing lean premixed combustion systems. Information on ignition delay at high pressure and intermediate temperatures is valuable for lean premixed gas turbine design. In order to avoid autoignition of the fuel/air mixture within the premixer, the ignition delay time must be greater than the residence time. Evaluating the residence time is not a straight forward task because of the complex aerodynamics due to recirculation zones, separation regions, and boundary layers effects which may create regions where the local residence times may be longer than the bulk or average residence time. Additionally, reliable experiments on ignition delay at gas turbine conditions are difficult to conduct. Devices for testing include shock tubes, rapid compression machine and flow reactors. In a flow reactor ignition delay data are commonly determined by measuring the distance from the fuel injector to the reaction front (L) and dividing it by the bulk or average flow velocity (U) under steady flow conditions to obtain a bulk residence time which is assumed to be equal to the ignition delay time. However this method is susceptible to the same boundary layer effects or recirculation zones found in premixers. An alternative method for obtaining ignition delay data in a flow reactor is presented herein, where ignition delay times are obtained by measuring the time difference between fuel injection and ignition using high speed instrumentation. Ignition delay times for methane, ethane and propane at gas turbine conditions were in the range of 40–500 ms. The results obtained show excellent agreement with recently proposed chemical mechanisms for hydrocarbons at low temperature/high pressure conditions.

Autoignition Delay Time Measurements of Methane, Ethane, and Propane Pure Fuels and Methane-Based Fuel Blends

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
M. M. Holton ◽  
P. Gokulakrishnan ◽  
M. S. Klassen ◽  
R. J. Roby ◽  
G. S. Jackson
Keyword(s):  
Delay Time ◽  
Flow Reactor ◽  
Activation Energies ◽  
Ternary Mixtures ◽  
Atmospheric Flow ◽  
Fuel Blends ◽  
Delay Times ◽  
Fuel Mixtures ◽  
Detailed Kinetics ◽  
Autoignition Delay

Autoignition delay experiments in air have been performed in an atmospheric flow reactor using typical natural gas components, namely, methane, ethane, and propane. Autoignition delay measurements were also made for binary fuel mixtures of methane/ethane and methane/propane, and ternary mixtures of methane/ethane/propane. The effect of CO2 addition to the methane-based fuel blends on autoignition delay times was also investigated. Equivalence ratios for the experiments ranged between 0.5 and 1.25, and temperatures ranged from 930 K to 1140 K. Consistent with past studies, increasing equivalence ratio and increasing inlet temperatures over these ranges decreased autoignition delay times. Furthermore, addition of 5–10% ethane or propane decreased autoignition delay time of the binary methane-based fuel by 30–50%. Further addition of either ethane or propane showed less significant reduction of autoignition delays. Addition of 5–10% CO2 slightly decreased the autoignition delay times of methane fuel mixtures. Arrhenius correlations were used to derive activation energies for the ignition of the pure fuels and their mixtures. Results show a reduction in activation energies at the higher temperatures studied, which suggests a change in ignition chemistry at very high temperatures. Measurements show relatively good agreement with predictions from a detailed kinetics mechanism, specifically developed to model ignition chemistry of C1-C3 alkanes.

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