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A Interstate petroleum pipeline has to be internally inspected (Smartpig) every five years. This is a expensive chore at about $500,000 per 100 miles ( all depending on size of pipeline ) . It is not a X-ray machine, but takes readings from feelers, and magnetic resonance. It tracks welds, internal corrosion, external corrosion, dents, and total distance. When we first started running smart pigs, you used to have to chase the pig and set magnetic boxes over the line every mile or so for reference points. Now we have learned that by placing metal plates every half mile on the line, we can reference them and have a permanent marking for the future runs. The pig is a self contained computer recording all information. This information is downloaded and then has to be interpeted. You usually can get the emergency dig points within 30 days, the rest of the information takes about 6 months... ... And then several months, (depending on number of anomalys) to dig up and investigate.
All welds made on petroleum pipelines have to be x-rayed, if a section of pipe is replaced it has to be pressure tested.
There are several types of pigs, cleaning, scrubbers, sizing, and of course Smartpigs. If you want to see a bunch of people panic try loosing a Smartpig in a pipeline and see what happens!
All Pipeline Integrity people would say was " That will be a charge of a $1,500,000. 00 if you can't get it out in 24 hours!"