2010-09-10T00:55:05-07:00 http://www.materialsforum.com/ Lussumo Vanilla http://www.materialsforum.com/discussion/69/?Focus=106#Comment_106 2008-02-12T08:37:39-08:00 2008-02-17T07:09:52-08:00 zee http://www.materialsforum.com/account/4/

The investigation of pipe line failures can be very complex, and usually requires multidisciplinary testing and analysis to determine the root cause of failure. The end determination must be able to ...

A typical sequence of failure analysis investigation is as follows:

Photographic documentation of the failed section of line pipe prior to its departure from the accident site and upon its arrival at the testing facility must be available to ensure any damage from mishandling is appropriately noted. Before the shipment of the failed section, proper preservation techniques for the fracture surfaces and the section (including coating), if required, should be identified (such as Visqueen®, SaranWrap®, oils, and other protective covers), and a chain of custody should be established for transfer of the failed section to the testing facility. The internal and external environment of the line pipe must be considered to arrive at the causal factors that may have caused the line pipe to fail. Therefore, the presence of corrosion products inside and outside the line pipe in the area of the failure must be considered and collected for analysis, as appropriate. For example, soil in the immediate area of the failure, dislodged soil adjacent to the ejected pipe, and soil that had adhered to the line pipe may have to be collected for analysis.

A typical sequence of analysis is the following:

• Review of Background information and specifications
• Visual and non-destructive examination
• Physical and dimentional measurements
• Internal and external corrosion examination including review of CP data prior to failure
• Fractography examination and determination of mode of failure
• Metallographic examination
• Mechanical properties

The objective of a metallurgical analysis of a line pipe failure is to assign one or more probable causes for the failure. The failure analysis may identify issues that must be remediated to ensure the integrity of other sections of the failed line pipe as well as other pipeline segments with similar characteristics (i.e. pipe manufacturer, seam type, grade, other specifications, coating type, and environmental conditions). Failure analysis of pipeline appurtenances (such as valves, flanges, bolts, etc.) may use the same methodologies as those outlined herein, but a unique test plan should be developed to handle the unique characteristics of the appurtenance.

The final report should include the root cause and specific recommendations to prevent future failures.]]>