Water Conveyance Loss and Designing Conveyance System - Practices of Irrigation and On-farm Water Management - page 30

D = inner diameter of the pipe (m)

specific wt. of the fluid (kg/m 3 ) w =

viscosity of the flowing fluid (kg/s/m 2 ) μ =

1.3.6.4 Calculation of Minor Loss

Minor loss can be expressed as

c V 2
2 g

h minor = (1.24)

where c is the minor loss coefficient. Thus, the total minor loss can be calculated
by summing the minor loss coefficients and multiplying the sum with the dynamic
pressure head. Minor loss coefficients of different components/fittings are given in
Table 1.3 .

Table 1.3 Minor loss coefficient for different fittings

Fittings Minor loss coefficient ( c )

Fully open ball valve 0.05

Threaded union 0.08

Fully open gate valve 0.15

1 / 2 closed gate valve

2.1

Fully open angle valve 2

Threaded long radius 90 ◦ elbows 0.2

Flanged 180 ◦ return bends 0.2

Flanged Tees, line flow 0.2

Threaded Tees, line flow 0.9

Threaded Tees, branch flow 2.0

Fully opened globe valve 10

1.3.6.5 Minimizing Head Loss in Pipe

One of the main aims of pipe design is to minimize the head losses associated with
pipe length (frictional loss), bends, diameter change, and transitions. Minimization
of head loss will keep the diameter of the pipeline to the minimum (necessary to
achieve the design flow capacity), and therefore its cost will be reduced.
Head losses in pipe can be minimized by

(1) Using large diameter pipe in the mainline
(2) Minimizing bends or turns
(3) Making/selecting internal surface of the pipe smoother