scholarly journals A study of hydrogen cracking in metals by the acoustoelasticity method

2017 ◽  
Author(s):  
E. L. Alekseeva ◽  
A. K. Belyaev ◽  
L. A. Pasmanik ◽  
A. M. Polyanskiy ◽  
V. A. Polyanskiy ◽  
...  
Keyword(s):  
Hydrogen Cracking ◽  
Acoustoelasticity Method

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.

Hydrogen Cracking During Service of High Strength Steel Cannon Components

2009 ◽  
pp. 897-897-16
Author(s):  
JH Underwood ◽  
E Troiano ◽  
GN Vigilante ◽  
AA Kapusta ◽  
S Tauscher
Keyword(s):  
High Strength Steel ◽  
High Strength ◽  
Hydrogen Cracking

Time Dependence of Hydrogen Induced Cracking of X70 Pipeline Steel Under Severe and Mild Sour Service Conditions Using Ultrasonic Analysis

2020 ◽  
Author(s):  
S. Gawor ◽  
J. B. Wiskel ◽  
D. G. Ivey ◽  
J. Liu ◽  
H. Henein
Keyword(s):  
Pipeline Steel ◽  
Test Sample ◽  
Test Time ◽  
Hydrogen Cracking ◽  
Signal Ratio ◽  
X Ray ◽  
Surface Corrosion ◽  
High Sulfur Content ◽  
Service Conditions ◽  
Sour Service

Abstract A standard NACE hydrogen induced crack test was used to evaluate the resistance of two compositions of X70 steel (X70-X (Ca/S ratio of 2.5) and X70-B (Ca/S ratio of < 0.5)) under severe (pH = 2.7 and 100% H2S) and mild (pH = 5.5 and 100% H2S) sour service conditions. An ultrasonic technique was developed to quantify the severity of hydrogen cracking in both steels as a function of test conditions, steel type and time. In this procedure, a series of local ultrasonic measurements was taken for each test sample to determine a local crack to backwall signal ratio (LCBR). The LCBR values were integrated over the entire sample to give a global crack to backwall ratio (GCBR). A larger GCBR value corresponds to greater hydrogen cracking severity in the sample. Energy dispersive X-ray (EDX) spectroscopy and glancing angle X-ray diffraction (XRD) were used to characterize the surface corrosion products that formed during testing. For severe sour service conditions, the GCBR value reached an asymptotic value of approximately 33% and 47% for X70-X (after 4 days) and X70-B (after 2 days) steels, respectively. For mild sour service conditions, no cracking was observed for testing of less than 16 days. After 32 days, X70-B showed a GCBR of approximately 18%. The onset of cracking of X70-X steel occurred between 32 and 64 days. Samples tested for 64 days showed a GCBR of 30% and 16% for X70-X and X70-B, respectively. Glancing XRD measurements showed the presence of surface FeS on both steels tested under mild sour service. Quantitative XRD (QXRD) analysis was used to obtain the surface coverage of FeS as a function of test time. EDX mapping confirmed the presence of a high sulfur content over a significant fraction of the surface. XRD measurements of X70-B steel under severe sour service after 8 days did not show a significant amount of FeS. The surface FeS is believed to alter hydrogen ingress into the steel, making it difficult to directly compare measured GCBR values obtained under mild and severe sour service.

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