Fracture control resources

One of the difficulties in coming to grips with the finer points of pipeline fracture control is finding the information and tools required to properly prepare a fracture control plan.  AS 2885 contains a great deal of useful guidance material, both in the body of the standard and in appendices, but in itself that is not sufficient for a full understanding.  Unfortunately it could give the impression that it might be sufficient, so it is easy to end up not knowing what you don’t know (by which I don’t mean to be tautological, but that you don’t know the extent of your ignorance).

Appendix L of AS 2885.1-2007 has a list of references at the end but several of them would be hard to find.  Comments on two of these:

1.  Fracture Control in Gas Pipelines, Proceedings of the WTIA/APIA/CRC for Materials Welding and Joining Int’l Seminar, Edited by A B Rothwell, WTIA, Sydney 1997.   Probably not available to anyone who wasn’t at the seminar (but I was there so I have it).  It does not appear to be in the APIA online knowledgebase.  The aim of the seminar was to present the state of the art at the time and hence the proceedings are not so useful as a general reference on the fundamentals.  However several of the papers provide cautions about various pitfalls such as scaling Charpy values from test specimens smaller than the standard 10 mm thickness and the questions over validation of fracture control methods for pipelines of smaller diameter.

3.  Eiber R J, Bubenik T J and Maxey W A, Fracture Control Technology for Natural Gas Pipelines, American Gas Association NG18, Report No. 208, December 1993.  AS 2885 follows this reference with a note that it contains many errors, including in the equations.  The document is commonly known as AGA Report 208 but that won’t help you track it down.  If you really want it the PRCI catalog number is L51691e, which also includes the now-superseded GASDECOM software for calculating decompression velocity.

Much more useful is the revised and corrected document that superseded AGA Report 208:  Fracture Control Technology for Natural Gas Pipelines circa 2001, by Bob Eiber and Brian Leis (PRCI catalog number L51846e).  This is perhaps the single most helpful resource.  But note that while its table of contents lists seven appendices they are not included in the PDF file.  If you do happen to want these they appear to be the same seven appendices as were included in the original 1993 AGA Report 208.

Another potentially useful document is First Major Improvements to the Two-Curve Ductile Fracture Model (PRCI catalog number L52245e).  I say “potentially useful” because it is long and complicated and I don’t pretend to have read all of it let alone absorbed it.  There was extensive experimental work to improve modelling of the effects of backfill as well as other improvements to the prediction of fracture propagation velocity.  The work included development of the PIPE-DFRAC software that accompanies the report and appears to be a particularly straightforward tool.  PIPE-DFRAC solves the whole two-curve problem in one step by calculating both fracture propagation velocity and decompression wave velocity then finding the tangent point, all with negligible serious thought required by the engineer (which may be good or bad depending on who is using the software).

Beyond these resources, the Energy Pipelines CRC is actively working in this area and hopes to release additional tools in the next year or so.  Work has already been completed on a new program for improved calculation of decompression velocity in smaller pipelines; it makes allowanced for the increased frictional resistance as diameter decreases.  Although complete this software will probably not be released until it is combined with a new model for fracture propagation, producing an integrated tool like PIPE-DFRAC but with further improvements to both sides of the two-curve model.

Advertisements
This entry was posted in Pipeline design, Research, Standards. Bookmark the permalink.

2 Responses to Fracture control resources

  1. Anonymous says:

    I purchased a copy of the “Fracture Control in Gas Pipelines” reference from WTIA several years ago. It is a good reference, especially for helping to predict gas behaviours. WTIA can sell these types of conference proceedings to the public. I purchased this in 2002 – 5 years after the event.

    In the past I have also made good use of some of the Fitness for Purpose standards published – BS7910 and API 579. I used BS7910 when developing a fracture control plan for an upstream gathering pipeline.

    Another good reference – and maybe one which the EPCRC could try and obtain – is a specific fracture control plan developed by any of the upstream O&G companies. They need to go beyond the guidance of AS2885 because they are piping raw “gas-field” gases with higher levels of CO2, etc. I know Santos devleoped one for their Baryulah pipeline back in 2000 / 2001, and the persons invovled went well beyond the AS2885 methods.

    Thanks

    Mark C.

  2. Pingback: Fracture initiation control | Pipelines OZ

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s