Economics of Pumping Oil at Low Friction Losses

Abstract A study of California pipe lines and perusal of many articles in magazines of the oil industry indicate that most trunk-line systems are operated at pressures ranging around 750 lb. per sq. in. These pressures result from high friction losses in 8-in. pipe, which appears to be the predominantly favored size. This paper shows that the greater cost of larger pipe lines for pumping oil at lower friction losses will be returned in a comparatively short time by the saving in power cost. It also indicates the way toward a proper estimate of the power-operating costs for new lines. Application of these principles to the redesign of existing pipe lines is not attempted since the wide variation in the arrangements and characteristics of such lines does not permit generalization. The principles apply nevertheless. A number of California trunk pipe lines are too small in size. This is particularly evident in winter when the oil becomes cold and viscous. Many of these lines were laid before any definite knowledge had been developed concerning the friction losses in oil pipe lines. It is a more or less common occurrence that while holding the pressure at 800 lb. per sq. in. or higher, the pumps will move less and less oil until the line “freezes.” It then becomes necessary to plug it out with light oil. Several means of improving this condition have been under consideration from time to time, such as steam-heating stations and booster stations at intermediate points between pump stations. Electric heaters were tested out on at least two lines. Looping of lines has also been suggested and resorted to more or less. None of these means, however, is entirely satisfactory and most of them cost more than can be justified. The laying of larger lines to improve pumping conditions has also been thought of, having in view the use of standard line pipe. The cost of such heavy large lines has usually been considered prohibitive. Now changes in the art of making and joining pipe of lighter weight have brought the larger sized lines within economic reach.