User:Degen.13/sandbox

Engineering Critical Assessment (ECA) is a procedure by which the safety of a welded structure with defects or flaws can be determined. ECAs utilize the material properties and expected stress history to determine a flaw acceptance criteria which will ensure that welds will not fail during the construction or service life of the welded structure.  The assessment can be used before the structure is in use, or during in-service inspection, to determine whether a given weld is in need of repair. ECAs are used throughout the energy, manufacturing, and infrastructure industries.  ECAs are based heavily upon fracture mechanics principles, and reflect an improvement over traditional methods of weld quality assurance, which can be arbitrary or overly conservative.

Background

During welding, defects or flaws can develop. In some cases, these flaws could potentially affect the integrity of the weld, resulting in failure by fatigue, creep, brittle fracture, or yielding. Therefore, codes to determine weld quality must be developed. Traditionally, welding codes have been based off workmanship criteria.  These criteria are determined empirically, typically by estimating the level of weld quality expected from a skilled welder.  While these criteria have been reliable historically, improvements made in welding technology and materials science are not taken into account.  As a result, over time, workmanship criteria have become increasingly conservative.  This conservatism results in unnecessary repairs, which can increase construction costs and can yield undesirable residual stresses at the location of the repair weld.

Beginning in the late 1970s to early 1980s, engineering critical assessments began to emerge as an alternative to traditional workmanship criteria.  These ECAs relied heavily on recent developments in the field of fracture mechanics.  Where workmanship criteria were developed with a limited understanding of material characteristics, and considered only the length of a given weld flaw, these ECA-based flaw acceptance criteria considered additional factors such as:

• The stress history of the weld, including all cyclic and static stresses expected throughout the life cycle of the welded structure
• The strength of the base metal and weld material
• The fracture toughness (measured via Crack tip opening displacement testing or Charpy impact testing) of the base metal and the weld material
• The flaw orientation (e.g., measurement of flaw length and flaw height, as opposed to flaw length only)

Together, these additional factors allow for more generous flaw acceptance criteria, resulting in fewer unnecessarily repaired welds.

To comply with the flaw acceptance criteria developed during ECA, non-destructive examination must be utilized. Ultrasonic testing is typically used due to its high accuracy, ability to identify flaw size and orientation, and its ability to provide feedback instantly.

ECA for oil and gas pipelines

ECA-based flaw acceptance criteria are commonly used in the oil and gas industry, particularly with regard to qualification of girth welds on cross-country oil and gas transmission pipelines. This is because girth welds are typically uniform from weld to weld, allowing construction contractors to utilize mechanized welding. Mechanized welding increases productivity over manual welding techniques by allowing for better, more uniform control over weld characteristics. ECA-based flaw acceptance criteria are able to take advantage of the high strength and toughness of the welds produced to develop more generous flaw acceptance criteria. In addition, the flaws created during mechanized welding are typically oriented differently than flaws developed from manual welding. ECA-based flaw acceptance criteria more effectively assess these flaws, by considering flaw orientation, rather than just flaw length.

Standards

Several standards specific to ECAs for oil and gas pipelines have been developed. The most commonly used of these are API 1104 Appendix A, API 579, CSA Z662 Annex K, and BS 7910. The standard used depends primarily on the location of the pipeline being installed. The standards differ in methodology and in extreme cases, can result in significantly different flaw acceptance criteria. However, for typical operating conditions, the criteria are easy enough to follow that practical differences between the standards are small.

Evaluating Articles and Sources

Work Hardening

• • Is everything in the article relevant to the article topic? Is there anything that distracted you?
    • It appears that way. I wasn't distracted by anything.
  • Is the article neutral? Are there any claims, or frames, that appear heavily biased toward a particular position?
    • The article appears to be neutral. Having only come at this topic from its relevance to metalworking, it's possible that I'm overlooking a bias toward those topics, but I'm not the right person to assess that.
  • Are there viewpoints that are overrepresented, or underrepresented?
    • There don't seem to be.
  • Check a few citations. Do the links work? Does the source support the claims in the article?
    • As mentioned in the Talk page, the citation relating to indium's work-hardening capabilities says that it can't be work-hardened at cryogenic temperatures, but the wording of "low temperature" in the actual article is a little ambiguous, as low could be construed to be room or near-room temperatures.
  • Is each fact referenced with an appropriate, reliable reference? Where does the information come from? Are these neutral sources? If biased, is that bias noted?
    • There are very few citations for the length of the piece. No citations in the History section, only one in the Theory section, for example.
  • Is any information out of date? Is anything missing that could be added?
    • Everything here is fairly well-established. There doesn't seem to be anything out of date or that would be changed by new information.
  • Check out the Talk page of the article. What kinds of conversations, if any, are going on behind the scenes about how to represent this topic?
    • A few discussions on the article being too jargon-heavy/difficult to approach. Some discussions on proper terminology being used.
  • How is the article rated? Is it a part of any WikiProjects?
    • Part of the Metalworking WikiProject. It's a C-class in terms of quality, but Top-rated in terms of importance.
  • How does the way Wikipedia discusses this topic differ from the way we've talked about it in class?
    • Article focuses more on the theory and reasons for work hardening, rather than just how to use it.

Potential areas of focus

Engineering Critical Assessment

There’s no article for this beyond the sentence referencing it on the ECA page.  It’s a method used to determine maximum allowable weld flaw length/widths based on material properties, a method of Fitness-for-service.  I’m most familiar with its use for girth welds on pipelines but it can be used in other welding scenarios.  Potential sources would be standards (API, DNV, CSA), some papers.  The major issue would be trying to determine whether scope is too narrow/disconnected (I’m not familiar with ECA in other contexts, so not sure if the article would be lopsided in focus).

Fracture Mechanics

The "Fracture Toughness Tests" section just points to "Fracture Toughness". This section could probably be improved by adding a brief primer of a few different fracture toughness testing methods (probably focused most on Charpy testing) for users who want an overview.

Work Hardening

As mentioned in the article review, there's a large lack of citations in the piece relative to how long it is. While the quality of the piece is good, it could probably be improved by Wikipedia's standards by adding a number of citations. Biggest roadblock for me would be having access to the highest quality citations (textbooks, etc.).

Instructor Comments

An article on Engineering Critical Assessment would be excellent. I think that is is okay to limit it to girth welds in pipelines, and others can add to it in the future.