During previous instruction you were given an understanding of the flow of

fluids in pipelines. We discussed equations that can be used to determine

how fast the fluids flow and what effects the flow has on pressure. The

purpose of this instruction is to teach you how to obtain information from

other methods that are much easier. Although the information obtained may

not be as accurate, it is suitable for Army pipelines.

obtaining friction loss per mile of pipe in military pipelines. Although the

results are not exact, it is close enough and is a much faster way than

using the Darcy Weisbach equation. The basic graph (Figure 2-1) contains

the following information. Barrels per hour top horizontal line. Gallons

per minute bottom horizontal line. Friction loss per mile of pipe left

vertical line. The other lines on the graph represent pipe diameter in

inches and velocity of the fuel in feet per second. The graph has been

constructed using MOGAS at 60, F as the design fuel, Kinematic viscosity of

8 x 10 minus 6 ft per sec and absolute roughness of 0.00015. For this

reason you must use a correction factor for fuels other than MOGAS and at

temperatures other than 60, F.

Using Figure 2-1, given a flow rate of 700 gallons per minute and a pipe

diameter of 8.415 inches: enter the graph at the lower right hand corner

and move to the left to 700 gallons per minute. Move up the graph until you

locate the pipe diameter (8.415). Read to the left and read 33 feet. This

means that for every mile of pipe you will lose 33 feet of head. If the

pipeline was 10 miles long you would lose 330 feet of head.

MOGAS at 60, F, it becomes necessary to correct the value obtained from

Figure 2-1. Table 2-1 contains correction factors for all military fuels at

temperatures ranging from -20 F to 80, F.

At temperatures other than these, interpolation must be used. These

factors can be used for any flow rate and for API pipe or light weight steel

tubing having the same nominal diameter as that shown in the tables.

If we use the same flow rate and the same pipe diameter (700 GPM and

8.415), we know that our head loss is 33 feet per mile. If we were pumping

DF2 at a temperature of 80, F, we must use the correction factor.

Using Table 2-1, locate DF2 at 80, F and read the correction factor 1.17.

Multiply 33 feet by 1.17 which equals 38.61 feet or 39 feet. You now have

the friction loss per mile of pipe for DF2 flowing at 700 GPM through an

8.415 diameter pipeline.

Once computed, the head loss due to friction for one mile of pipe has a

special name; hydraulic gradient (hg). Since hg is a constant ratio of two

linear dimensions: head loss in feet over pipe distance in miles; it can be

expressed graphically as the slope of a straight line.

12-19

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