The experience acquired in the construction and management of pipe-lines in the oil region has shown the comparative economic value of this method of transportation. The adoption of this method is based upon the quantity of the fluid to be carried being ample and correspondingly cheap. To arrive at an estimate of the relative values of railroad and pipe-line transportation, it is necessary, in tho computation of the working capacity and required force of a pipe-line, to note that 75-80 per cent. of the pumping force required by a pipe-line is necessary to overcome the friction dependent on the velocity of flow. Also, that in building a line, if the pipe were made very heavy, one pump would force it a long distance, and save the cost of labour and fuel attendant on intermediate stations; but that, if there were a great many intermediate stations, the pipe could be made very light, and the expense of construction be greatly reduced, the cost of fuel and labour being proportionately increased. The mean length of line which can be operated to advantage by one pump, with the lines at present in use, is about 15 miles ; with care in the construction of the line, it could bo extended to 20 miles.
In the construction of ordinary lines, which are of equal thickness for their entire length, there is just twice the amount of iron used that is actually required. The area of internal section of a 3-in. pipe ie eq. in.; contents of line (20 miles), 105,600 ft., 38,776 gal., or 901 barrels; to deliver 3600 barrels a day would require a velocity of flow of 5 ft. a second. Weisbach's formula to ascertain the head required to overcome friction, is as follows : 01746) 1 (.0144 + x x , v d h' = head required in feet.
v = velocity in feet per second. 1 = length of the line in feet.
d = diameter of the pipe in inches.
This formula applied would be 01746) x 10600 5 25 ( 0144 + 4/ 5 3 x 4 = 2473.9 In practioe, this is found to be, for these long pipes, about 25 per cent. in excess, where the route is carefully selected, and the line is properly laid. As these lines follow vertically the contour of the ground in a hilly country, this is somewhat remarkable, especially when it is considered that no account is taken of any increased friction for the rise of the line in many places above the hydraulic mean gradient, from the highest point to be overcome to the point of delivery.
If the line be enlarged at every five miles, 5 miles of 3-in. pipe will require a friction-head of .. ft.
5,, 3s /2 22 22 5,, 31 530.0 5 4 23 .. Total ' 2183.4 ft.
Being a saving in head of nearly 300 ft.
An equivalent to this gain may he obtained by a reduction of the diameter of the pipe at the pump, or by an increased velocity, thus : Being still less than the friction-head required for a continuous 3-in. pipe.
It will also be found that the reduced line contains barrels instead of 901 ; and since the element of friction represents the greatest resistance to be overcome, the enlargement will cause a constant reduction of velocity, and therefore of friction.
In 20 miles of straight pipe there will probably be elevations to overcome. Assuming 400 ft. as an extreme, and adding it to the head required, the total head will be : The head of 400 ft. is carried through all the sections, in the absence of given levels of any actual line ; otherwise the heads and pressures for the last two or three sections would be very much reduced.
Weisbach's formula was based upon the results obtained with water ; by multiplying the pressures given by the difference in sp. gr. of water and the oil of commerce, we get: The first section will contain 177,117 lb. of iron ; 2nd, 146,176 lb. ; 3rd, 100,320 lb. ; 4th, 76,824 lb. ; total, 500,437 lb.
The weight of the line, if made of the ordinary 2-in. tubing in the usual manner, would be 387,235 lb. ; and its capacity for delivery would be but 1000 barrels a day, against 3600 in the line described. The work of the line would equal 366,291,200 gal. raised 1 ft. high in 24 hours, requiring for its exertion a horse-power of 77 for water, and 62 for oil.
To move this 3600 barrels of oil a day would require the direct services of four men ; two engineers relieve each other at the pump every 12 hours, one man receives the oil from the wells and keeps the gauges, and one man receives and ships the oil at the railway-station.
The cost of an engine and train of 36 tank-cars, which would be required to carry 3600 barrels of oil, would exceed the cost of the entire pipe-line, exclusive of any estimate of the cost of the roadway, which is about ten times the cost per mile.
With an ample supply of the fluid, and the required number of 20-mile sections, the estimate made would cover any distance required.
Storing.The storage of petroleum in bulk is generally effected in huge tanks made of boiler plate, varying in capacity from 8000 to 25,000 barrels (of 42 gal.). The top is more usually of wood than of iron. Wooden tops are often recessed so as to hold a body of water, or are covered with earth. Tops are always provided with man-holes, giving entrance to the tank for cleaning and repairs. The supply-pipe, which may conduct the oil from wells many miles distant, feeds at the top of the tank, near the man-hole ; and draw-off taps are fixed at about 1 in. above the bottom. A distance of at least 200 ft. should separate tanks, in case of fire.