Pipeline Girth Weld Inspection and Flaw Acceptance Criteria for Sour Service Applications

2017 ◽  
Author(s):  
Shashi Bhushan Kumar ◽  
Kapil Mohan ◽  
Shaodong Zhang ◽  
Jens P. Tronskar
Keyword(s):  
Best Practice ◽  
Oil And Gas ◽  
Probability Of Detection ◽  
Resistance Testing ◽  
Acceptance Criteria ◽  
Gas Field ◽  
Radiographic Inspection ◽  
Weld Inspection ◽  
Girth Welds ◽  
Sour Service

To establish flaw acceptance criteria for carbon steel pipeline girth welds that are intended to transport sour crude, wet sour gas and condensate it is important to assess the effect of operating environment and strain levels by performing the fracture toughness/ resistance testing as per DNV-OS-F101: 2013 in a representative simulated service environment or under more severe test conditions. None the less many oil and gas field operators still believe that using workmanship criteria and radiographic inspection will be adequate to ensure a safe future operation of the pipeline meeting the design life requirements under sour or severely sour operating environments. Unfortunately, experience shows that this is a dangerous practice as radiography tends to miss out in detecting the most severe planar defects such a lack of fusion, hydrogen induced cracking and weld root centerline cracks, this is specifically so for narrow J-bevel welds. Hence, DNV GL based on experience from many projects advocates inspection of all sour service pipelines using inspection methods such as AUT with a high probability of detection for planar flaws. Further, the AUT acceptance criteria shall be chosen appropriately with due considerations as workmanship type of acceptance criteria without proper verification may result in non-conservatism in the pipeline girth weld inspection and weld sentencing. This present paper presents some recent project experiences from typical sour service subsea pipeline projects and provide advices representing what is considered current best practice for testing and qualification of AUT systems for sour service projects.

Fracture Toughness Testing and Validation of Pipeline Girth Weld Flaw Acceptance Criteria for Sour Service Under Large Strain

2011 ◽  
Author(s):  
You You Wu ◽  
Wen Guo Yuan ◽  
Tse Ven Steven Chong ◽  
Jens P. Tronskar
Keyword(s):  
Fracture Toughness ◽  
Oil And Gas ◽  
Large Strain ◽  
Axial Strain ◽  
Laboratory Data ◽  
Local Buckling ◽  
Acceptance Criteria ◽  
Service Environment ◽  
Girth Welds ◽  
Sour Service

Fracture toughness is one of the most important input parameters for assessment of pipeline girth weld failure capacity. For many new subsea pipeline projects there is a need to develop flaw acceptance criteria for pipeline installation considering the operation phase which may involve the transport of sour oil and gas and where the pipeline is exposed to large axial strain due to local buckling. Engineering Critical Assessment (ECA) performed using laboratory data based on conservative KISSC testing gives small acceptable flaw sizes which may be below the workmanship criteria for pipeline laying. DNV has conducted extensive research based on the requirements of DNV-OS-F101 and DNV-RP-F108, aiming to establish a method to develop J-R curves applicable for ECA of pipeline girth welds in sour service environment and a methodology to validate the ECA by segment testing in a laboratory-simulated sour service environment as per DNV-RP-F108.

Early Engagement of ECA in Offshore Deepwater Pipeline Design

2021 ◽  
Author(s):  
Daowu Zhou ◽  
Lingjun Cao ◽  
T. Sriskandarajah ◽  
Mark Lewis ◽  
Daniel Manso
Keyword(s):  
Oil And Gas ◽  
Fluid Composition ◽  
Acceptance Criteria ◽  
Gas Field ◽  
Detailed Design ◽  
Damage And Fracture ◽  
Weld Material ◽  
Challenging Environment ◽  
Oil And Gas Field ◽  
Pipeline Design

Abstract Welding acceptance criteria derived through ECA is typically performed after the detailed design. The design loads, together with pipeline and girth weld material testing data, are inputs to ECA and used to evaluate the pipeline girth weld integrity for determining the criticality of potential weld flaws. With ever increasing challenging environment (deepwater, HP/HT, aggressive fluid composition etc) in the oil and gas field, the fatigue damage and fracture failure may become a serious concern, consequently limiting the productivity of the pipeline fabrication. It is therefore essential to integrate ECA into the design loop to remove the uncertainty and risk to achieve a practically workable fabrication solution. In this paper, a strategy to integrate early ECA into pipeline detailed design phase is presented. A case study in a deepwater subsea channel crossing demonstrates that an early ECA engagement effectively mitigates the significant fatigue and fracture risk and obtains workable welding acceptance criteria for fabrication.

Corrosion Fatigue of Welded C-Mn Steel Risers for Deepwater Applications: A State of the Art Review

2005 ◽  
Author(s):  
S. J. Maddox ◽  
R. J. Pargeter ◽  
P. Woollin
Keyword(s):  
Oil And Gas ◽  
Current Knowledge ◽  
Fatigue Loading ◽  
Fatigue Behaviour ◽  
Manganese Steel ◽  
Gas Field ◽  
Internal Surfaces ◽  
Oil And Gas Field ◽  
Offshore Oil And Gas ◽  
Girth Welds

Steel risers for deepwater offshore oil and gas field developments are subject to seawater on the external surfaces, produced fluids on the internal surfaces and to fatigue loading. This paper reviews current knowledge of the fatigue behaviour of welded carbon-manganese steel for risers in relevant environments. A substantial body of data exists relating to the performance of girth welds in seawater with cathodic protection and consequently recent attention has been turned to establishing the fatigue performance in the internal environment, which may contain water, CO2, H2S and chloride and bicarbonate ions.

Inspection Considerations for Deepwater Thick-Walled Riser Systems

2008 ◽  
Author(s):  
Jonathan Bowman ◽  
Hugh Thompson ◽  
Donald Stevens ◽  
James Crane
Keyword(s):  
Fatigue Loading ◽  
Thick Wall ◽  
Inspection System ◽  
Acceptance Criteria ◽  
Adequate Knowledge ◽  
Inspection Process ◽  
Engineering Requirement ◽  
Weld Inspection ◽  
Girth Welds ◽  
The Impact

The fatigue loading on deepwater risers results in the need to impose very tight weld acceptance criteria for pipe alignment and flaw sizes. The production of high-pressure, high-temperature reservoirs calls for increasingly thick-walled riser systems. The combination of thicker wall pipe and the maintenance of tight flaw acceptance criteria challenges automated ultrasonic testing (AUT) which is the primary method of riser weld inspection. An understanding of the limitations of the weld inspection system must be determined and accommodated as part of the engineering process and in conjunction with adequate knowledge of the pipe end dimensions can help optimize the inspection process. This paper discusses the challenges associated with the preparation for and inspection of thick-walled riser system welds and the impact this can have on the system design and engineering requirement. In support of the discussion an overview of a recent study to determine the detect-ability and sizing accuracy of an AUT system with thick-wall pipe girth welds is presented. The qualification program is based upon the AUT inspection of seeded defect welds which are subsequently cut into weld rings, re-inspected with an immersion scan and sectioned to determine the size of the flaws present. All AUT inspections are performed under similar conditions to the inspection of the production welds (i.e., no prior knowledge of the nature of the seeded welds).

ECA of Pipeline With Girth Weld Strength Mis-Matching Subjected to Large Strain

2009 ◽  
Author(s):  
Zhengmao Yang ◽  
Shashi Kumar ◽  
Jens P. Tronskar
Keyword(s):  
Base Metal ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Large Strain ◽  
Axial Strain ◽  
Weld Strength ◽  
Assessment Procedure ◽  
Long Distance ◽  
Acceptance Criteria ◽  
Gas Field

In recent years, the strain based design for pipeline has been widely accepted by the industry, but the definition of a rational flaw acceptance criteria for girth welds subjected to axial strain within the context of the existing codified fracture mechanics based assessment procedures is problematic since these are essentially stress based. To extend the FAD method to the large strain conditions, several challenges i.e. weld strength mismatching, fracture toughness, and welding residual stresses have to be understood. With appropriate modifications as per DNV-RP-F108 [1], the assessments procedure detailed in BS7910 document for stress based situations have been used successfully for several projects to develop acceptance criteria for pipeline installation involving plastic straining. But only weld metal strength over-match comparing with base metal is considered in DNV-RP-F108 [1]. High strength line pipes are required to reduce the transmission cost of natural gas in long distance and internal clad with corrosion resistant alloy (CRA) is used for transportation of sour gas. Steel manufactures have developed such line pipes to develop new oil and gas field. The inconel filler metal was selected as weld consumable for the production girth weld in the lay budge. From the all weld tensile tests, it was found that the yield strength of the weld is under-match comparing the base metal, and the pipeline maybe subjected to a strain level up to 1.0% due to the lateral buckling. In this research the effect of weld strength mismatching on the structural integrity of the pipeline subjected to large strain was studied. The Engineering Critical Assessment (ECA) was performed to derive the critical flaw acceptance criteria for the AUT system. The segment tests and numerical analysis were performed to validate the assessment procedure, and the finite element analyses of the pipeline girth weld with surface crack in the weld centre were carried out to investigate the effect of bi-axial loading on the ECA results.

Integration of Welding, NDT, Mechanical Testing and Field Control When Using an ECA Flaw Acceptance Criteria in Pipeline Construction

2018 ◽  
Author(s):  
Junfang Lu ◽  
Bob Huntley ◽  
Luke Ludwig ◽  
Axel Aulin ◽  
Andy Duncan
Keyword(s):  
Mechanical Testing ◽  
Gas Metal Arc Welding ◽  
Probability Of Detection ◽  
Destructive Testing ◽  
Acceptance Criteria ◽  
Pipeline Construction ◽  
High Productivity ◽  
Metal Arc Welding ◽  
Field Control ◽  
Girth Welds

The fracture mechanics based engineering critical assessment (ECA) method has been accepted as a fitness for service (FFS) approach to defining weld flaw acceptance criteria for pipeline girth welds. Mechanized gas metal arc welding (GMAW) processes are commonly used in cross country pipeline girth weld welding because of the advantages in good quality and high productivity. With the technical advancements of non-destructive testing (NDT) techniques, automated ultrasonic testing (AUT) has greatly improved flaw characterization, sizing and probability of detection during weld inspection. Alternative weld flaw acceptance criteria are permitted in pipeline construction code to assess the acceptability of mechanized girth welds using an ECA. The use of an ECA based weld flaw acceptance criteria can significantly reduce the construction cost. Mechanized girth weld acceptance criteria have been progressively transitioned from workmanship standards into using fitness for service based ECAs. To successfully deliver an ECA on a pipeline project, a multidisciplinary approach must be taken during the welding design and construction stages. Welding, NDT, mechanical testing and field control are all integral elements of pipeline construction. All these four elements have to be fully integrated in order to implement the ECA and achieve the overall integrity of a pipeline. The purpose of this paper is to discuss the importance of the integration of these four elements necessary for proper implementation of the ECA weld flaw acceptance criteria.

scholarly journals Reliability of Mechanised UT Systems to Inspect Girth Welds During Pipeline Construction

1998 ◽  
Author(s):  
Jan A. de Raad
Keyword(s):  
High Speed ◽  
Ultrasonic Inspection ◽  
Probability Of Detection ◽  
Inspection System ◽  
Present System ◽  
Immediate Feedback ◽  
Long Distance ◽  
Acceptance Criteria ◽  
Actual Use ◽  
Girth Welds

As an alternative to radiography, a field-proven mechanized ultrasonic inspection system is discussed. Called Rotoscan, this system has been developed for inspection of girth welds during construction of long-distance pipelines, both on- and offshore. It is characterized by high inspection speed and instant recording of results. Unlike prevailing radiography, it provides immediate feedback to the welders. Recent technical improvements in flaw sizing and recording have allowed the application of rejection/acceptance criteria for weld defects based on fracture mechanics principles. The development and actual use of such modern acceptance criteria, particularly in Canada, supported the introduction of mechanised ultrasonic inspection. World wide applications proved that, contrary to expectations, ultrasonic inspection does not lead to higher weld repair rates than radiography does. Between early 1989 and now, over 5.000 km of pipeline (300.000 welds) were inspected with Rotoscan and its reliability proven. The introduction of colour enhanced transit distance “C-scan mapping”, producing a coherent picture based on the signal’s transit distance, enabled the system to cope with most existing ultrasonic procedures and acceptance criteria, because of its capability to detect and quantify volumetric defects. Moreover, the integrated simultaneous Time Of Flight Diffraction (TOFD) function enables through-thickness sizing of defect. The present system is capable of achieving a high Probability Of Detection (POD) together with a low False Call Rate (FCR). In the meantime, Rotoscan has been qualified in various countries, for different customers and for a variety of weld processes, pipe diameters and wall thicknesses. Because of its features, the now mature system has demonstrated its capabilities also for use on lay barges as an alternative to high-speed radiography.

Analysis on Bimetallic Lined Pipe for Sour Service in Oil and Gas Field

ICPTT 2013 ◽  
2013 ◽  
Author(s):  
Fagen LI ◽  
Bin Wei ◽  
Xuehui Zhao ◽  
Xiaodong Shao ◽  
Rui Cai
Keyword(s):  
Oil And Gas ◽  
Gas Field ◽  
Oil And Gas Field ◽  
Sour Service

Evaluation of Welding Practices on Sour Service Performance of Carbon Steel Pipeline Girth Welds

2021 ◽  
Author(s):  
Harpreet Sidhar ◽  
Neerav Verma ◽  
Chih-Hsiang Kuo ◽  
Michael Belota ◽  
Andrew J. Wasson
Keyword(s):  
Carbon Steel ◽  
Oil And Gas ◽  
Pipeline Steel ◽  
Oil And Gas Industry ◽  
Welding Parameters ◽  
Line Pipe ◽  
Steel Pipeline ◽  
Weld Root ◽  
Girth Welds ◽  
Sour Service

Abstract In recent past, there have been unforeseen sour service pipeline failures in the oil and gas industry. Sub-optimal microstructure resulting in high hardness (above 250 HV10) in pipeline steel is one of the root causes of such failures. Poor girth weld quality is another leading cause which adversely affects pipeline integrity and safe operations in sour environments. While advancements in welding technologies have led to consistency in production girth welds, effects of welding parameters on performance of carbon steel pipeline girth welds for sour service are not well understood. So, a systematic study is needed to understand the effects of various welding parameters on weld properties and performance. This paper aims at evaluating the effects of various welding parameters on performance of girth welds to provide welding practice guidelines for sour service pipeline applications. In this effort, several welds on X65 grade line pipe girth welds using commercially available welding consumables were made to study the effects of preheat, hot pass tempering, copper backing, root pass heat input, wire consumable chemistry, single vs. dual torch, metal transfer mode, pipe fit-up (root gap, misalignment), on weld root performance. Detailed microhardness mapping and microstructural characterization were conducted. It was evident that the welding parameters studied have a significant impact on root performance. While preheat and pipe fit-up showed most significant impact on weld root performance, other parameters also affected the root performance by varying degree. Based on these results, recommendations for industry are provided to improve reliability of pipeline girth welds in sour service application.

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