×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

How to Determine Fracture Propogation in Pipe?

How to Determine Fracture Propogation in Pipe?

How to Determine Fracture Propogation in Pipe?

(OP)
Does anyone know the method of determining the fracture propogation of pipe?

I am trying to determine the resistance to fracture propogation for various grades of pipe.  For example, if a pipe fractures under high pressure, what is the propensity for the fracture to continue to adjacent pipes?

Thanks for any help!

RE: How to Determine Fracture Propogation in Pipe?

HI SuperG,

You need to look at a primer for fracture mechanics.  Learn about "notch toughness" and critical crack lengths for various materials at various stresses.

Regards, John.

RE: How to Determine Fracture Propogation in Pipe?

I recently did a search on Google for Pipe fracture mechanics and came across several technical papers on failures of pipelines that covered this subject. Try the National Transport Safety Board Website. Sorry I dont have the address.

RE: How to Determine Fracture Propogation in Pipe?

Another consideration for protecting a system against fracture propogation is to build in preventative barriers such as changes in direction. In some circumstances this can limit the fracture to only one length of pipe (remember, when you change the direction only a component of the stress force is directed along the new pipe, the other component can be resisted by elbows, supports, etc.).

Try posting this thread in the structural or mechanical engineering forums.

RE: How to Determine Fracture Propogation in Pipe?

Pat Leavers at Imperial College has done a lot of work on this for gas and water mains pipes.  I'm sure he'll be able to answer all of your questions.

RE: How to Determine Fracture Propogation in Pipe?

Check out any of a number of sources related stress crack corrosion.  I'm in the natural gas industry and pretty much nobody worries about this issue unless you have one of the following:

a) a pipeline above 1000 psig (steel)
b) a pipeline operating above 40% SMYS
c) a pipeline with low toughness steel (i.e., highly "brittle")

The analysis is not trivial.  It is usually done with tons of statistics.  Such as:

1) What is the size and orientation of the maximum defect?  At what confidence interval?
2) How many pressure cycles will the pipeline see in it's lifetime (or time until potential failure)
3) Type of fluid and potential energy when under pressure

Good luck.  I've started on this in the past and found work-arounds so I didn't have to solve it.

RE: How to Determine Fracture Propogation in Pipe?

I know that API 579 "Fitness-For Service" (published January 2000) has an extensive section dealing with Assessment of Crack-Like Flaws.  These assesments include all kinds of formula for determining whether a flaw will propogate in the operating environment.  You might want to get your hands on this document to see if there is anything in there that will help you with your investigation.  Be warned, this is the type of document that you will probably have to sit down and study for quite some time to fully utilize.  I have not personally used the section on cracks, but we have used this document for some interesting purposes such as accepting misfabricated piping components that had extremely long lead times.

Hope this helps.

RE: How to Determine Fracture Propogation in Pipe?

What you have to do is consider the worst possible defect size and where it’s likely to occur.  For example one practice is to assume that one run of weld in a multi run joint has no side fusion.  You then have to decide what the toughness of the material is; an approximate correlation can be gained from impact tests.

You need British Standard BS7910, which will answer your question.

Regards
John   post@gowelding.com  www.gowelding.com


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources