San Bruno disaster

Date 09-11-2010 18:08

Gentlemen,
my opinion on the reason for San Bruno pipeline explosion is not a weld failure, but corrosion, either internal or external.
Brazilian television and newspapers have said that the natural gas pipeline is a rather old one.
Over the years, it might well happened that the chemical composition of the natural gas coming off the wells has changed a little, becoming a slightly sour gas, and sour gas is corrosive.
It might also happened that over the years the pipeline corrosion proof coating has spoiled in some place, giving way to soil corrosion.
And what about cathodic protection, present on all pípelines? Well, to work satisfactorily, cathodic protection systems need careful maintenance, and chances are that in that case maintenance was not so careful ...............
Giovanni S. Crisi
Sao Paulo - Brazil

By 522029

Date 09-12-2010 14:17

Mr. Crisi,

You are probably correct. I have seen very little news coverage on this and what I have seen has been very sketchy.

This morning, Fox News keeps saying a report is to be aired shortly but I have yet to see this report.

Griff

By OBEWAN

Date 09-12-2010 16:41

They can probably find out pretty quick if they examine some sections of pipe away from the part that exploded.

I feel bad for all the homes that were lost. It looks like they were nothing more than a pile of ash. Everything totally gone.

By jwright650 (*****)

Date 09-13-2010 12:02

Looks like an explosion that was local to me a few years back.....details and pics in the link below:

http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=118154

By Bonniweldor (**)

Date 10-27-2010 19:32

It will be interesting to understand how such a pipeline (large diameter, significant pressure) remained in close proximity to such a high population density and residential construction activity, and if the respective operational classification correctly relfected that proximity. How many resisdents knew what was running outside their front door? Whoofty, literally.

For a pipe that old, unique effects of time and local conditions become significant. The pipe section appears to be at a local low point and condensate water, and associated corrosion, can concentrate there. Proximity to a roadway and residential utilities significantly raises the liklihood of denting or gouging type damage. Superimposed stress caused by geological movement can contribute to conditions supporting or activating stress corrosion cracking. The proximity to siesmic activity is intersting for introducting a fatigue component. One can see on the realtime USGS siesmic maps that low level vibrations can occur with high frequency along a fault line (probably a good thing in the general context).

By Skaggydog (**)

Date 09-13-2010 19:29

They said gas welding back before 1930 just wasn't as strong as today's ark welding. Is that right?

By DaveBoyer (*****)

Date 09-14-2010 02:56

Probably right, as the gas welding process would have been 25 years old or less at that time. Modern standards, testing methods & etc. were developed quite a bit latter.

By 803056

Date 09-14-2010 03:32

The article in the link said the California pipeline was 54 years old. That would indicate the line was installed around 1956.

I find it difficult to believe a 30-inch diameter pipeline was welded with oxy-acetylene. The typical means of welding line pipe has been with the shielded metal arc welding process since the late 30's and early 40's. The electrodes typically utilized were cellulous type covered electrodes.

Best regards - Al

By DaveBoyer (*****)

Date 09-14-2010 03:45

It would be a chore to weld 30" pipe with oxy-acetylene, but they have welded railroad track with it, so I guess it could be done [just not by Me].

With regard to anything welded by any method before 1930, if it has been in service since then, weld strength probably isn't the problem.

I think that by '56 they had a pretty good understanding of arc welding, but as Giovanni suggested a lot of corosion could have taken place since then.

By 3.2 Inspector (***)

Date 09-14-2010 10:42

Ask Henry about welding in 56, if he didnt retire before that :)

10.6

By dbigkahunna (****)

Date 09-14-2010 11:07

Cross country pipelines in the 50's were SMAW. OFG welds on cross country pipelines went out in the late 30's. The OFG welds were really good, the issue was the HAZ due to the high heat inputs. My bet on this failure is either corrosion or un-reported damage or a combination of the two.
However, for those who are involved in pipeline integrity management it looks like this is going to be a golden age. Knowing about smart pigs, coatings, cathotic protection, corrosion, repairs, etc. will pay big dividends. Be sure to put pipeline integrity management on the ole resume for prior projects to catch the eye of the HR mental midgets.

By MBSims

Date 09-15-2010 00:43

I noticed from the photos the section that failed is either under a road bed or directly alongside the edge of the pavement. I have to wonder if some settling of the road bed occurred or if increased traffic played a role in causing a fatigue crack to initiate. Or if the pipe could have been damaged during work on the road and covered back up by the road crew.

By ravi theCobra (**)

Date 09-15-2010 22:42

Just a little something you HAVEN'T been told -

There is a small water pond that has the name Lake San Andreas in the area AND the pipeline is about

30 feet from the San Andreas Fault -

Seismicly this is a VERRRRRY interesting area -

By dbigkahunna (****)

Date 09-16-2010 01:21

And this would affect it how? Pipe can move a bunch without failure and being 30 feet from the San Andreas mean nothing. The fault is not a small line. There are several pipelines that cross the San Andreas and have gone through several earthquakes.
I do not have access to any special information, but again my bet is on past third party damage, corrosion or a combination of the two. It would be interesting to see the dance floor they took out.