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Failure Investigation of Internal Girth Weld Coating Surface Preparation: A Case Study

During the construction of a 56km long 16 in. carbon steel sour gas pipeline, repetitive surface
preparation failures were detected during visual inspection of pipeline girth weld internal surface prior to
coating application. Such failures represented 67% of the total pipeline girth welds and were manifested
by excessive sharp-edges at the root pass. To identify the failure causes, an investigation was
performed through reviewing the pipeline, fabrication and coating application specifications and
procedures, quality control records and performing an extensive visual inspection through an advanced
video robotic crawler on all pipeline girth welds made. Upon investigation analysis, the failures were
caused by sharp-edges in the root pass which were attributed to improper practices during
manufacturing, field fabrication and pre-coating quality control. The failure analysis indicated that the
mechanized Gas Metal Arc Welding process, with the parameters used, was not suitable for internal
girth weld coating application. In addition, a more stringent requirement should be applied to the
acceptable pipe-end diameter tolerance and pre-coating quality control to ensure absence of similar
premature surface preparation failures. The pre-coating quality control can be improved through
utilization of robotic laser contour mapping crawler for precise detection and sizing of unsatisfactory
surface weldment defects, including sharp edges.

Product Number: MPWT19-14360
Author: Rashed Alhajri, Yousef Alrayes, Fahad Alhindas, Ghassan Bahamden
Publication Date: 2019
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The integrity of new pipeline projects is critical to Saudi Aramco to avoid any short or long-term impact on the supply of energy. During construction activities, pipeline internal welding inspection is carried out in compliance with international and Saudi Aramco requirements. The visual inspection of internally cladded girth welded pipes requires extra care to avoid any improper field fabrication errors during welding, especially at the root pass area. Such errors can limit the inspection capability and compromise the integrity of pipeline network with possible degradation of corrosion resistance at/near the weld rot, resulting in premature failures. Currently, projects utilize conventional tools such as borescope which is time consuming with limited inspection capabilities (up to 150 meters inside the pipe) and system maneuverability at inspection locations.
The Saudi Aramco Inspection Department enhanced their active inspection technology program and collaborated with a local technology developer. They trialed a wireless crawler robot, which is a high resolution remotely operated robot capable of inspecting internal girth welds with 5000 meters travel capability inside the pipes. The robot can inspect internal girth welds in the field, and inside pipelines with internal diameters of 6 inches and above, and wirelessly transmits the visual inspection results to the outside control room for a timely assessment and critical decision making. The internal visual inspection with wireless crawler robot will help in improving the project progress, reducing repair costs, by identifying defective welds before coating application.

Picture for Role of Metallographic Characterization in Failure Analysis – Case Studies
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Role of Metallographic Characterization in Failure Analysis – Case Studies

Product Number: MPWT19-14379
Author: Syed Ahsan Ali
Publication Date: 2019
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Conducting a materials failure analysis requires a carefully planned series of steps intended to
arrive at the cause of the problem. Consistent with the current trend towards better accountability
and responsibility, failure analysis purpose has been extended in deciding which party may be
liable for losses, be they loss of production, property damage, injury, or fatality [1]. Hence it
increases the importance of proper implementation of characterization tools in failure analysis to
rightly identify the failure mode.
Present work discusses a few case studies to shed light upon the importance of the metallurgical
characterization tools and techniques in identification of correct failure mode. Some typical case
studies where metallography plays a very important role have been discussed, such as improper
welding joints which led to premature failure, sensitization and stress corrosion cracking in S.S.,
improper heat treatment and forging indicated the microstructures which led to the premature
failure. These cases are examples of only a few laboratory based investigations which justify that
without metallography it is not possible to diagnose the causes of premature failures.
Generally, examination of failed components commence with the low-power stereomicroscope
whereas hand-held magnifying lenses are still in wide use by experts to study fractures mostly
limited now for field purpose [2]. Metallographic examination typically is performed after nondestructive
and macroscopic examination procedures while using the light optical microscopy
which helps to assess the failure mode with respect to material defects, shortcomings in
processing, metallurgical changes etc. Since light optical microscopy has limited value for direct
observation of fracture surfaces (more limited for metals than non-metals), with still more factual
information can be gathered by scanning electron microscopy at higher magnification.