National Geographic : 1951 Oct
543 National Geographic Photographer B. Anthony Stewart How Much Gas Heats the Oven, Chills the Refrigerator? The Meter Keeps Tab As gas flows through the meter, pressure expands and contracts a bellows made of sheepskin or synthetic rubber. A cam attached to the breathing diaphragm moves the recording pointers. The average gas inspector reads 240 meters a day. One veteran checked more than a million without an error. Gas was sold for a flat charge per burner until the invention of the meter in 1833 (page 562). are machines for digging and filling the ditches, and for bending a section of pipe in a few minutes' time without changing the thickness of its walls (bending being necessary where there is a curve in the line; page 551). There are others for applying protective coatings against corrosion, including paint, enamel, glass-fiber mats, and asbestos felt (page 545); still others for welding the pipe sections to gether and for laying them into place. Most lines are laid three feet or more underground. The contractors on one recent line used 60,000 gallons of primer and 17,000 tons of enamel. It took 20,000 freight cars to de liver the pipe. An unusually vast array of outsize mobile apparatus was required to build Pacific Gas and Electric Company's "Super Inch," a 506 mile link in a 1,600-mile line from Texas and New Mexico to California, both because of the size of the pipe and the desert conditions under which it had to be laid (pages 548, 550, 551). The contracting concern in this case, the Bechtel Corporation, is one of the six groups that built the Hoover Dam and, through an associate organization, Interna tional Bechtel, Inc., constructed the "Tap line," the Trans-Arabian Pipe Line which was completed last year. Super Inch pipe is 34 inches in diameter, largest ever built for such purposes, and reaches to the waist of an average-size man. Before the various protective coatings are applied to the pipe or wrapped about it, all by machinery, it must, naturally, be cleaned. Even in the case of the Super Inch, with all its super machinery, after being cleaned by mechanical apparatus an old-fashioned feather duster was applied by hand to remove any last-minute dust which might have settled on the pipe's exterior. Nowhere has greater progress been made than in welding together the separate lengths, or sections, of pipe, thus speeding up construc tion and doing away with the likelihood of leaks from the older type of mechanical joints, or couplings. One contractor in working across the Mis souri and Mississippi Rivers welded his sections on an LSM and dropped the line in the water as the boat moved along. In a recently completed job, after the sec tions had been put in place in the ground, an inspector was drawn through the pipe in a scooter, to locate defects (page 544). But the ends had to be closed to prevent foxes, rabbits, skunks, rattlesnakes, and copperheads from entering.