Being able to measure the head at a point downstream or head loss between
points downstream becomes academic. For example:
Head available = 390 feet
Pipeline distance = 10 mile (52,800 feet)
H = 38.61 feet per mile (or 39)
Head available after one mile = 351
Head loss after three miles
= 117
390
351
312
273
234
195
156
117
78
39
1 2 3 4 5 6 7 8 9 10
MILES
In order to determine how much head is used and how much head is available,
draw a line from the lower left hand corner; as if the gradient was a
rectangle. Locate 4 miles on the X axis and move up the graph until you
intersect the sloping line. Move to the left and read 156 feet of head;
this gives you the head used and the head remaining which is 134 feet.
390
351
312
273
234
195
156
117
78
33
1 2 3 4 5 6 7 8 9 10
MILES
PART C FEET OF HEAD AVAILABLE
Feet of Head available. Given a storage tank containing DF1 at an elevation
of 225 feet above the feeder pump, the feeder line is 6 inch LWST, 9000 feet
long, with a flow rate of 400 BPH. Determine how many feet of head are
available at the suction side of the pump.
STEP 1: Determine the true gradient (400 BPH and 6.415 inch pipe) using
Figure 2-1. Hg = 24 ft/mi
DF1 at 40 F
Correction Factor = 1.20
True Gradient
24 ft/mi x 1.20 = 28.8 ft/mi
12-22
QM 5099