216 HYDRAULICS AND ITS APPLICATIONS 



found to be distributed over a length greater than that which they 

 originally occupied. This matter is of some importance in connection 

 with oil transmission pipe lines, through which from time to time 

 different grades of oil are to be pumped, and in which it is desirable to 

 know the probable volume of contaminated oil likely to follow a change 

 over from grade to grade. 



} In experiments on a wooden pipe line conveying water and consisting 

 of a length of 13,200 feet of 10-inch pipe in series with 47,500 feet 

 of 16-inch pipe, 1 aniline dye or bran was admitted for a measured time 

 to the intake, and the discharge from a relief valve on the 10-inch pipe, 

 situated 12,700 feet from the intake, and from the outlet from the 

 16-inch pipe, was carefully watched for the appearance and disappear- 

 ance of the colouring matter or bran. With the dye the exact instant of 

 appearance and disappearance, particularly the latter, could not be 

 determined with any very great accuracy, but the time of passing the 

 relief valve was apparently about one minute greater than the time 

 of admission. As the mean velocity was 582 feet per minute, this means 

 that the mixing had extended over a length equal to 58,200 -=- 12,750 = 

 4*6 per cent, of the distance traversed. The bran apparently took 

 eighteen minutes longer than the time of admission to pass the outlet 

 from the 16-inch pipe, indicating an admixture over about 8*5 per 

 cent, of the distance traversed. Experiments carried out with colouring 

 matter on a 4-inch and a 6-inch pipe line at Cornell 2 , conveying water at 

 velocities ranging between about *9 and 4'5 feet per second showed that 

 the admixture extended over a mean distance equal to about 13'3 per 

 cent, of the distance traversed in the 6-inch pipe, and 11 per cent, of this 

 distance in the 4-inch pipe. Both these pipes were spiral riveted, but the 

 4-inch pipe had an asphalted surface. On the whole it would appear 

 that the percentage distance for similar pipes diminishes with an 

 increase in diameter, and for pipes of the same diameter increases with 

 the roughness, apparently varying little with the mean velocity. 



Experiments by the Standard Oil Co. 2 on the admixture of oil of 

 different grades in a 6-inch pipe line, 24 miles long, showed that with 

 light amber oil, specific gravity *79, displacing heavy black oil, specific gravity 

 *85, with a mean velocity of flow of about 4 feet per second, the length 

 of admixture was between 8'5 and 12'1 per cent, of the distance travelled, 

 while, where the heavy displaced the light oil, the length was only '44 per 

 cent. Similar experiments on an oil-pipe line 210 miles long between 



1 J. L. Campbell, Engineering News, August 27, 1908, p. 227. 



3 Cornell Civil Engineer, Dec. 1911, p. 122, by Prof. E. W. Schoder. 



