or change of production methods. At this time, "workover rigs" may be used at 

 the site. These are smaller versions of the rigs used in well drilling, and 

 their operation is essentially the same as the larger rigs, though on a smaller 

 scale. 



Pipelines. Pipelines are the usual means of transport of gas and crude 

 oil to purchasers. Pipelines are usually operated by pipeline companies whose 

 interest is the purchase, transport, and sale of petroleum products. Pipelines 

 are designed specifically with the material to be transported and the amount of 

 traffic in mind. 



In most areas, pipelines are buried in the ground. When pipelines cross 

 water bodies such as canals, streams, or bays, problems are encountered with 

 burying the pipe, placing it so as not to disturb navigation, and stabilizing 

 the banks for erosion prevention. 



In areas of marsh, especially difficult problems are encountered in pipe- 

 line placement. Often, the ground is so soft that it will not support heavy 

 equipment. As a result, several different methods have evolved for pipeline 

 placement. In some areas, a ditch wide enough for a pipeline-laying barge is 

 dug across the marsh. Because of environmental problems associated with these 

 wide ditches, other methods using narrow cuts and stationary barges have evolved 



Pipeline operation involves very little actual activity other than the 

 maintenance and checking of equipment. Airplanes are often used to fly the 

 pipeline route and detect leaks. Because pipelines operate under high pressure, 

 pressure-sensing devices are used to monitor pipeline status. Significant 

 changes in pressures activate automatic equipment to close valves, should 

 significant leaks or breaks occur. 



Pipeline life varies depending upon the corrosion and inside wear of the 

 pipe. Corrosion is a problem in most soils, particularly in wet and saline 

 areas. Sacrificial anodes or cathodic protection is often used in conjunction 

 with coating and wrapping pipe for corrosion protection. As the result of 

 corrosion and wear, segments of pipe may be repaired (or replaced if costs are 

 not prohibitive). However, after long service, new lines are put in and old 

 ones are abandoned. With the removal of cathodic protection and the oxidation 

 of sacrificial anodes, old pipe will eventually disintegrate. 



Because of internal friction and changes of elevation, booster pumping 

 stations are required every 64 to 80 km (40 to 50 mi) for oil transport 

 (Davis and Cyrus, 1947). At the booster stations, there are often launchers 

 and traps for entry and removal of pigs, scrapers, or balls. These devices are 

 used to scour and clean the inside of the pipe of paraffin and scale, or to 

 separate materials pumped through the pipeline. 



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