 This is the aftermath of poor quality work undertaken 54 years before, unknowingly residents of the Crestmore residential neighbourhood of San Bruno California were sitting on top of a ticking time bomb. Just a few defective worlds were to blame, but like with most stories on this channel, a little bit of carelessness and negligence goes a long way. Today we'll be diving into the San Bruno pipeline explosion. My name is John and welcome to Plainly Difficult. Gas, Gas and Gas Natural gas is important, no prizes for that statement. Be it for power stations or being ripped off at the home meter, gas is a vital component for many. Personally I've only recently had to deal with gas as my previous place I used to live in was a bit of a rarity in the UK being fully electric. This caused us some issues in selling as most people prefer gas central heating. Anyways, UK house buying and selling aside, natural gas requires a network of pipes, gates and pumping stations. In the case of our story today, we're going to focus on the pipeline side. One such network is in the San Francisco Peninsula area and is taking shape in the mid 1940s. Multiple gas lines run north from the Milpitas terminal running a length of roughly 46 miles. But for today we'll be looking at just one of those transmission lines named Line 132. Building work on 132 took place over stages beginning in 1944. The line had varying pipe diameters ranging from 20 to 36 inches. The pipe work was built from different gauges of steel as well as employing different types of joints and welds. Two such welds were seam welds where two halves of a pipe are stuck together like this and girth welds which are around the circumference of the pipe and look like this. The line was built upon in 1948 during the project around 10% of the welds were radiographed for defects. This amount of checks was agreed between PG&E Pacific Gas and Electric Company and the construction contractor. In total 209 radiographs were performed on the pipeline. Of these 19 welds were rejected and 4 were reexamined and deemed okay. In addition to the rejected welds they also had 14 more considered borderline. Some of the pipe work had been logged as damaged during construction needing repair. Once the line was down pressure testing could be undertaken. This involved air pumped in at 100 PSI G and by using soapy water on the outside they looked for any bubbling. Like what you do with a bicycle tyre. Then air was pumped in at 100 PSI G and held in the system for 48 hours to look for more slower leaks. After that the line was filled with gas and once again checked for any more leaks. You see transmission gas lines operate under high pressure in order for the gas to move. But even the smallest hole would cause a catastrophic failure. All would be good until 1956 when a section of line 132's pipe in San Bruno needed to be relocated. So in 1956 some houses were to be built around the Glenview Drive area. The area is rather hilly and as such the pipeline was at a different elevation to the housing. And this required 132 to be moved. The work was to be done in-house by PG&E. The 1851 feet section was known internally as segment 180. The 30 inch pipe work for the relocation job wasn't brand new. It was left overs from other projects dating back around 10 years or so. As such to make required lengths several pieces had to be welded together. One such section was of six short segments known as pups. They ranged from between 3.5 and 4.7 feet each and were seemingly made up of non-API X52 standard steel. Each piece was welded together and records of inspection and radiographs weren't kept. Hinting that maybe they weren't even done in the first place. This section of segment 180 also wasn't recorded to be made up of the different lengths welded together. I'll say remember this dodgy bit as it will be important later on. The relocation project was finished and the pipe work was covered back over. Roll forward 40 or so years and line 132 is seeing some modernization. Pipe work got replaced to the north and south of segment 180 in 1995. So the pipe work is controlled by a system called SCADA or supervisory control and data acquisition. The system is controlled by three controllers during the day and two at night. SCADA has sensors all over the system allowing for real time pressure monitoring as well as control over fixed point valves. On top of that they can liaise with workers on the ground. All controllers monitor the system as such when alarm goes off one could acknowledge it and another can deal with the issue. Now without further ado it's time to jump forward to September 2010 if it is arsed. It's the 9th of September 2010 and some upgrade work is being undertaken on the gas networks uninterruptible power supply. Part of the upgrade involved interrupting the SCADA system as different parts were powered down. A side effect of the temporary loss of power was that some of the valves would fail safe and close. As such some of the valves were manually locked open. During the work technicians began to remove an unlabeled circuit breaker. This resulted in a local control panel unexpectedly losing power. Troubleshooting found two power supplies giving out erratic voltages. The erratic voltage led to the pressure transmitters reading an erroneous low pressure signal to regulating valve controllers causing them to fully open. At 5 22 p.m. due to the regulating valves being fully open and the erratic signals caused by the varying voltages the SCADA center alarm console displayed over 60 alarms within a few seconds. Needless to say this overloaded the controllers with quite a few issues to troubleshoot. Several lines from the Milpitas terminal were alarming at high pressures. One of the Milpitas technicians called the SCADA center to see if they could see any pressure values. The center reported 458 PSI-G but this was incorrect. It was actually 396 PSI-G but the system wasn't working as it should. The lines incoming to Milpitas were lowered to 370 PSI-G but the pressure on line one three two was still way too high. At 6.02 p.m. one operator commented to a SCADA operator at the Brentwood facility we've got a major problem at Milpitas and we're overpressuring the whole peninsula. A technician was asked to get a manual reading on the output at Milpitas. It was reading at 396 PSI-G. Soon enough the high pressure was going to find a release. The pipeline revealed its weakest point and this was the six short pup sections of pipe along segment 180. This part was near Skyline Boulevard and San Bruno Avenue. Gas blew out at 6.11 p.m. causing a massive explosion. The high pressure gas continued to stream out fueling a massive fire. Several houses nearby were completely enveloped in the blaze. The explosion created a crater roughly 167 feet long, 26 feet wide and 40 feet deep. 35 houses were levelled and many more suffered serious damage. By 6.15 p.m. Martin Station seven miles downstream from San Bruno Avenue showed the first low pressure alarm at 150 PSI-G for line one three two. The SCADA operators and just 10 minutes later the pressure was down to 50. 911 calls flooded in and firefighters were dispatched to what looked like hell on earth. The high winds had fanned and spread the flames. Smoke reached hundreds of feet into the sky and around 200 firefighters battled with the blaze. The first PG&E official arrived on the scene at 41 minutes past 6 p.m. followed by two others. However none were qualified to operate mainline valves. One of the SCADA operators remotely closed the valves downstream from the rupture by at 7.29 p.m. which stopped the gas coming from the north. A minute later technicians manually closed the valve upstream finally stopping the gas flow after 91 minutes. However the fire continued to burn all the way until 11.40 the next morning. 8 people were killed in the explosion but it wouldn't take until the 29th of September before the figure was actually confirmed. Pretty much everyone from the Crestmore residential neighborhood had to be evacuated although some were allowed to return a few days later. The aftermath. So in the following months after the explosion P&G reduced its pipe pressures by 20% over its network and the company stock price also reduced by 8% knocking off a billion and a half dollars worth of value. On top of that the company had to re-evaluate its pressures over its 1800 mile network. Scarily the company when asked to provide proof of pressure tests of their network resulted in large sections of the gas line being unaccounted for. It would prompt a modernization project on the system with new pipe work, automatic valves and proper inspection of all remaining lines. Needless to say this would cost a lot of money. The company would also be sued which is a pretty standard affair and would settle with 499 victims a total of $565 million. But what of the cause? Well friends of the channel the NTSB would be tasked with that little problem. The investigation. So you know how I said that PG&E couldn't provide evidence of testing for some of its network? Well surprise surprise segment 180 was one of those evidence-less parts. Upon investigation of the rupture location the six welded pup sections were discovered. On top of that it was also found that three of them had only been welded from the outside thus making the bond improper for high-pressure applications. And to make matters worse all of the pups had seen welds further weakening the pipe. Not only that but it was also found that the pups metalwork varied in thickness and wasn't up to standard. It was discovered during the investigation that residents around the disaster area had smelt natural gas in the days leading up to the explosion. The pressure on the pipeline at the time of its failure was 386.4 psi g 11 higher than the company's maximum operating pressure but it was actually below the 400 psi g that the pipe should have been rated for. But we know why it failed the unregulated and improper gauged and welded pups. The NTSB released its report and put the probable cause as one. Inadequate quality assurance and control in 1956 during its line one three two relocation project which allowed the installation of a substandard and poorly welded pipe section with a visible seam weld floor that over time grew to a critical size causing the pipeline to rupture during a pressure increase stemming from poorly planned electrical work at the Milpitas terminal. And number two inadequate pipeline integrity management program which failed to detect and repair or remove the defective pipe section. They also added in their conclusion contributing to the severity of the accident were the lack of either automatic shutoff valves or remote control valves on the line and PG&E's flawed emergency response procedures and delay in isolating the rupture to stop the flow of gas. So this disaster shows just how close we all are to a potential time bomb and especially in this case it was set almost half a century before. This is a plain default production. All videos on the channel are creative commons actuation share like licensed. Plain different videos are produced by me John in the currently warm but windy corner of southern London UK. I'd like to thank my patrons and YouTube members for your financial support as well as the rest of you for tuning in every week. 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