San Bruno fracture images

Found some pictures here of the failed San Bruno pipe, along with some experts’ (?) comments.  I can’t draw even superficial conclusions as the pictures aren’t detailed enough and I lack the expertise anyway.  However the zig-zag fracture with long straight edges and a couple of near-90º corners looks distinctly odd, and not at all what one would expect from ductile steel with sound welds.  So suggestions about cracked welds seem plausible.

Any other thoughts?

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4 Responses to San Bruno fracture images

  1. Mark Coates says:


    Some commentary suggests that there could have been a weld issue based on a large number of welds in a localised region. Another thought is location to a more active seismic zones which has steadily strained the pipeline over a numebr of years.

    I was wondering about some type of SCC or brittle failure due to age hardening / strain aging. The pictures are similar to ones I have seen on pressure vessels experiencing brittle failure during a “room temperature” hydrotest. Again, some commentary suggests that this section gave rise to pooling of liquids and/or contaminants in the gas affecting metallurgical properties. External corrosion from moist conditions has also been raised.

    So, no definitive answer from me – and I do not have the expertise to provide a definitive answer. The pictures make me raise the failure issues above, given they have similarities to what I have seen in process plant pipe and equipment failures.


    • petertuft says:

      We’ll just have to await the official report, and hope it comes sooner than the report on the 2004 Belgian incident (still waiting …). It’s in the hands of the National Transportation Safety Board and I think I read somewhere that they expect to report within 12 months.

  2. Kees Hoogesteger says:

    Hi Peter, I have just returned to the pipeline business after some years away. These photos of the blow-out in San Bruno look remarkably like the bits of pipe that came out of the ground at Moomba on the Moomba to Sydney pipeline. The primary cause as we now all should be aware of was Stress Corrosion Cracking. I would not be surprise to learn in one years time that the cause was the same in this case. The edges look rough where the corrosion cracks take place and the tearing is much like we saw. Interesting that it seems to have stopped on a weld. Might be a poor weld that stopped the tear.

  3. petertuft says:

    Kees, welcome back! More comments in the failure in today’s post on the NTSB preliminary report, particularly on the sheer number of welds in this particular pipeline.

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