Environmental Engineering FOURTH EDITION

Water Supply 127

Table 6-4. Minor Losses of Head

Nature of

resistance

Nature of

Loss (K) resistance Loss (K)

45" elbow

Angle valve wide open

Butterfly valve

e = 10"

8 =40"

8 = 70"

Check valves

Horizontal lifts

Ball

swing

Gate valves

Wide open

0.25 closed

0.5 closed

0.75 closed

Globe valves wide open

90" elbow

Regular flanged

Long-radius flanged

Short-radius screwed

Medium-radius

Long-radius screwed

screwed

Use 3/4 loss for

90" bend of

same radius

2-5

1

10

320

8-12

65-70

0.6-2.5

1.2

5.6

24.0

10

0.21-0.30

0.14-0.23

0.9

0.75

0.60

22.5" elbow

Entrance losses

Pipe projects into

tank

Pipe end flush

with tank

Slightly rounded

Bell-mouthed

Outlet losses from

pipe into still

water or

atmosphere

Sudden contraction

d/D = 0.25

d/D = 0.5

d/D = 0.75

Sudden enlargement

d/ D = 0.25

d/D = 0.5

d/D = 0.75

Use 1/2 loss for

90" bend of

same radius

0.8-1.0

0.5

0.23

0.04

1 .o

0.42

0.33

0.19

0.92

0.56

0.91

EXAMPLE 6.9. For the pipes in series as shown in Fig. 6-12b, find the diameter of
equivalent pipe (length is assumed to be 1000 ft).

1. Quantity of water flowing through pipes 3 and 4 is the same.


2. Assume any arbitraty flow through pipes 3 and 4, say 500 gpm.