Effeci's of Stress on Magnetic Flux Leakage and Magnetic Barkhausen Noise Signals

Pipelines are pressure vessels. Their enviable safety record compares weil with other transportation modes. Typical pipeline fatality rates are about 1% those of rail or air which are, in turn, about 1% of highway fatalities. Pipeline safety is first assured by rigorous inspection during pipe manufacture and line construction. All welds are inspected using radiography to detect voids and ultrasonics to sense cracks. Oil and gas transmission lines are normally buried, so in service inspection must be performed from the inside by pumping an inspection "pig" through the line. Magnetic flux leakage (MFL) pigs are the most cost effective tools for corrosion monitoring. They are propeiled by differential product pressure from one compressor or pumping station to the next, which may be more than 100km away. They are self supporting, demand maximum data storage density and highest energy storage battery power supplies as weil as advanced signal processing to obtain signal discrimination and data compression.