In the wake of the deadly San Bruno natural gas pipeline explosion, government officials have begun to push for stricter gas pipeline safety standards. On September 22, just two weeks after the September 9 explosion that killed eight people and destroyed 37 homes, California senators Diane Feinstein and Barbara Boxer introduced a bill to bolster safety standards. The bill, called the Strengthening Pipeline Safety Enforcement Act, would mandate better inspection devices and tests and would double the number of federal pipeline inspectors to 200 over the next four years. The bill would also require automatic electronic shut-off valves “wherever technically or economically feasible," and would authorize penalties of up to $2.5 million for violations of safety standards.
Representative Jackie Speier, D-SF, also introduced similar legislation called the Pipeline Safety Community Empowerment Act of 2010. Speier’s bill would also mandate the installation of automatic shut-off valves wherever they are technologically feasible. The probe into the deadly San Bruno blast revealed that it took workers almost two hours to shut off the manual valves, time that could have potentially saved lives and homes. The bill would also mandate that gas line operators provide the location information of pipelines as well as emergency response plans to emergency responders and regulators, among other provisions.
As the investigation into the cause of the fatal blast continues, state legislators hope that a similar catastrophe will be avoided in the future. "The pipeline explosion in San Bruno was a tragedy that must never occur again in any American neighborhood," Feinstein said in a statement. "The American people must be assured that the pipelines that crisscross the nation and run beneath their streets are safe."
Could San Bruno Happen In San Antonio?
ReplyDeleteThe conditions that led to the natural gas pipeline explosion in San Bruno, California, in early September could exist in San Antonio or in any metropolitan area where large, high pressure gas pipelines cross old municipal water pipelines. Based on eye witness statements and published accounts of the disaster, this corrosion engineer has a theory on what could have happened. The 30 inch pipeline was installed in 1948 when pipelines were installed without coatings or were often coated by hand over the ditch. Based on the pipeline's age, it is likely that it was protected against corrosion with an impressed current cathodic protection system.
Firefighters on the scene stated that there was no water in the fire hydrants with which to fight the fire. This leads one to speculate that the water main was severed in the explosion. Pictures of the crater showed it to be full of water. Old water mains are often made of cast iron or ductile iron. Newer water pipelines are made of welded steel or non-metallic PVC pipe. If the water pipeline was poorly coated steel, cast iron or ductile iron with its joints bonded across each other, this engineer has an explanation of what could have happened.
Electric current from Impressed current corrosion protection systems on gas pipelines can collect on buried water pipelines. Because electricity follows the path of least resistance, it would typically discharge off the water pipeline and back onto the gas pipeline at the closest point between the two pipelines which would be where they cross each other. When electric current flows off a pipe and into the soil, a corrosion pit is created. Over time the pit can become a hole. Water mains are usually buried very deep to prevent the water in them from freezing during the winter. The gas pipeline was said to be buried about 3 ft. deep.
Assuming that the above conditions existed, a hole in the top of a high pressure water main would have scoured out a larger hole in the pipe from the pressure of the water. This would have had enough force to create a high pressure water jet into the overlying gas pipeline. The force of the water jet could have caused the 62 year old gas pipeline to rupture causing the subsequent explosion.
The answers to the above assumptions will come from maintenance records by the gas company and the water utility. If this theory is found to be correct, there are preventive measures that can be taken to prevent corrosion of water mains by gas pipeline or gas well casing rectifier systems.
Magnesium anodes are often used instead of rectifiers to protect newly installed pipelines with fusion bonded epoxy (FBE) coatings. Magnesium anodes on gas pipelines can not cause corrosion to water mains. One solution in metropolitan areas to protect water mains from gas well or gas pipeline rectifier systems is to use magnesium anodes instead of rectifiers. Another way to prevent damage to water mains is to connect the pipelines together with wires at crossings. These are called bonds. Corrosion engineers are trained in this field of science and are the best source of information on preventing corrosion and fixing problems that could have led to the San Bruno explosion.
Source: http://www.anodesystems.com/Anodes,_Cathodic_Protection_Materials_%26_Surveys/San_Bruno_Discussion.html