Page 123 - Water and wastewater engineering

3-20 WATER AND WASTEWATER ENGINEERING

2
v /2g
d
h h
fd fvd
EGL
2
v /2g HGL
d

H = TDH H
t
stat
H g
h
gd
h
d
h
h h fvs ent
fs
2
v s /2g
h
s
h
Pump gs
Gauge Gauge
Datum
NPSH
H A
barometric
Key
Butterfly valve
H vapor
Check valve
Absolute zero pressure
FIGURE 3-13
Terminology for a pump with a positive suction head.

Sanks (2006) offers several warnings in the use of this equation for estimating friction losses.
Errors of up to 40 percent may be encountered for pipes less than 200 mm in diameter and more
than 1,500 mm in diameter, for very cold or hot water, and for unusually high or low veloci-
ties. Growths of slime layers and corrosion add to the inherent potential for errors in using the
Hazen-Williams equation or, for that matter, any equation for estimating friction losses. The
prudent engineer will use a range of coefficients to define a probable region of losses that may
be encountered.
The fitting and valve losses are estimated using Equation 3-6:

v 2
h fvs or h fvd K (3-6)
2 g

where K energy loss coefficient. Energy loss coefficients are given in Appendix C.