How long should it last???

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So, I'm reading a story on NPR about that pipeline explosion in San Bruno, CA last september. Seems the feds are finally getting around to hearings so they can fix the blame.Guess who their top scapegoat is?"This week federal investigators prepare to hold hearings into the cause of a gas pipeline explosion in San Bruno, Calif., last September. Preliminary reports from federal investigators cast blame on defective welds in a 60-year-old pipeline."http://www.npr.org/2011/03/01/134138...line-explosionSo, my question is, how can a sixty year old weld that is underground, under serious pressure and in contact with corrosive material be defective if it held just fine for all those years?Is there no reasonable limit on the liability from so called "defective welds"? I admit that I know very little about the codes/regulations for pipelines or anything to do with the petrochemical industry. It just seems a little like a witch hunt to pin the blame on the welder after all this time. How about the inspector or the maintenance company. Or, dare I suggest such a seditious idea, how about the damn regulatory body???Is this typical? The funny thing is, you really don't hear about "defective welds" very often. At least I don't. With all the thousands of miles of fused metal out there. We must be doing something right.Eric
Reply:The company that originally welded the pipeline is probably out of business.  Noone to sue.They pulled that crap with a lot of the EPA super sites in the 80's.Buy American, or don't whine when you end up on the bread line.
Reply:I received second hand information that pipelines typically operate around 80 percent of the pressure that would cause the pipe metal to yield.  In most structures we look at a safety factor of 2 or 3 to one and if it carries people 6 to 1 safety factor.  The argument for so little margin is that the pressure is constant and does not cycle.  Anything over fifty years old made of steel needs frequent inspection.  I keep thinking that there will be more of these failures in the coming years.  We had one happen in Ontario several months ago but fortunately it was in a unpopulated area.
Reply:Welds are typically stronger than the material they are joining.  If it was done properly they should not fail until the pipe itself fails. However the evidence speaks for itself.  If there is evidence of lack of penetration, porosity or cracking in the weld and weld failure is the cause of the event then it is what it is.  Was it just one joint that failed or did the pipe split, not much detail in the story as reported.  Also why were homes allowed to be built so close to the pipeline?  We have had failures on the Trans Canada Pipeline (NG) here but always in rural areas.If it is a welding failure then it is not just the fault of the welder but may also include supervisors, contractors, inspectors, engineers, pipeline owners  and regulators who must share the blame as to what their responsibility regarding this event was so it can be prevented in the future."The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:A metallurgist that examined the pipe said ""The weldment, in fact, only penetrated 55 percent of the pipe," Dauskardt said. "So it had not been welded all the way through&so basically only half of the section side had been filled with the weldment. In addition, it's full of voids, it's got slag inclusions, all sorts of sites that, with operation, would initiate cracks, defects, that would then begin to spread and grow."
Reply:Life of a pipeline is an interesting thing. Here we have pipeline in the ground that were installed in the 30's, so they can last a long time. There were also fewer inspections and welding procedures that were pretty wild back then. There is also a lot of gas welded stuff up through the 70's and 80's. Those lines tend to operate and lower pressures than moderns lines.
Reply:Here's some condensed info in a blog which seems more intent on facts rather than politics along with a pic of a blown out section and a link to a NTSB update. http://blogs.kqed.org/newsfix/2010/1...uno-explosion/"The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:So according to Sandy's link the field welding was not at fault, but there were defects in the seam welding when the pipe was manufactured."The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:Apparently the pipeline was built from leftover pipe from other projects.   They used several very short sections of pipe welded together.The confusion about seamless vs seamed pipe apparently occurred when the data was put into the computer.   The original records showed the pipe to be seamed, which it was.http://www.sfgate.com/cgi-bin/articl...&feed=rss.newsI have no opinion about how long a pipeline should last, but as others have noted, the safety and technical standards associated with pipelines have become more rigorous over the intervening 50 years.RichardSculptures in copper and other metalshttp://www.fergusonsculpture.comSyncrowave 200 Millermatic 211Readywelder spoolgunHypertherm 600 plasma cutterThermal Arc GMS300 Victor OA torchHomemade Blacksmith propane forge
Reply:From the Wall Street Journal on Sandys' link;The Wall Street Jounal said;The board also noted discrepancies between utility records concerning the kind of pipe used and what investigators pulled from the ground after the accident.