Page 122 - Know and Understand Centrifugal Pumps

The System Curve

flange on the suction pipe with the tank, and a 4 inch tramp with the
pump. There's a 3 inch tramp flange at the pump discharge and another
4 inch tramp at the discharge tank. The formula is:
Hf system tramp flanges = Hf suction tramps + Hf discharge
tramps
= K5' x HVS"Ct. + I<4* x Hvsuct. + I(4" x
HVdisch. + K3" HVdisch.
= (0) + (0.033 x 0.172) + (0.033 x
0.888) + (0.04 x 0.888)

= 0 + 0.005 + 0.029 + 0.035
Hf system tramp flanges = 0.007 feet
Admittedly, Hf of 0.007 foot is an insignificant number. Think of it this
way. With only one pump and less than 200 ft of pipe in our simple
system, there are four tramp unions. Imagine an oil refinery with
20,000 pumps and thousands of miles of pipe and equipment on site.
Imagine the number of tramp flanges in the fire water system in a
skyscraper building. In a real set of circumstances the Hf values through
tramp flnages unions could be significant, and they would have to be
calculated to specify the correct pumps.

Last, we need to calculate the Hf losses through other connections in
the piping
There is a sudden reduction in the suction between the tank and the
piping. There is an eccentric 6-to-4 reducer between the suction pipe
and the pump. There is a concentric 3-to-4 increaser from the pump
back into the piping, and a sudden enlargement going into the
discharge tank. The formula is:

Other Hf = Hf sudden reduction + Hf eccentric reducer + Hf concentric increaser
+ Hf sudden enlargement
= (0.05 x 0.172) + (0.28 x 0.172) + (0.192 x 0.888)
+ (1 x 0.888)
= 0.086 + 0.048 + 0.170 + 0.888
Other Hf = 1.192 feet
Now we have all the information to calculate the Hf in the system and
then the TDH of the system. Once again:
System Hf = Hf pipe + Hf elbows + Hf valves + Hf flanges + Hf
other

= 2.848 ft + 0.916 ft + 7.632 ft + 0.007 ft + 1.192 ft
= 12.595 ft

105 1