Pipeline operations are a varietal complex of underground arteries@ terminals@ compressor and pumping stations@ all of which help to transport natural gas@ crude oil@ refined products@ water@ coal and many other commodities from producing areas to marketing areas. Major oil and gas pipelines criss-cross continental United States with a total of over 750@000 miles of steel tubes@ represent capital expenditures of billions of dollars and a source of work for thousands of skilled craftsmen. Since the oil and gas industries represent a major segment of the pipeline users@ this discussion will center about such pipelines.