Page 121 - Know and Understand Centrifugal Pumps

Know and Understand Centrifugal Pumps

Hf system piping = Hf suction piping+ Hf discharge piping.

= (K suction x L) +lo0 + (K discharge x L)
+ 100
= (4.89 x 40) +lo0 + (.637 x 140) +lo0

= 1.956 + 0.891
Hf system piping = 2.848 feet

Now we calculate the Hf in the elbows
The formula is:
Hf elbows = Hf suction elbows + Hf discharge elbows
= 2 x 0.280 x 0.172 + 3 x 0.310 x 0.888

= 0.096 + 0.82
Hf elbows = 0.916 feet

Next, we calculate the Hf for the valves
There are 5 valves in all. There are two 6 inch gate valves in the suction
pipe. There is a 4 inch gate valve, a 4 inch globe valve, and a 4 inch
check valve in the discharge pipe. The formula is:
Hf system valves = Hf suction valves + Hf discharge valves

= I(6' gate Hvsuction + I(4' gate HVdisch. +
I(4' check HVdisch. + I(4' globe HVdisch.
= (2 x .09 x 0.172) +(1 x 0.16 x 0.888) +
(1 x 2 x 0.888) + (1 x 6.4 x 0.888)
= 0.031 + 0.142 + 1.776 + 5.683
Hf system valves = 7.632 feet

Next we calculate the Hf in the tramp flanges in the system
A tramp flange is an unassociated flange or union. In the friction tables,
valves, elbows, and other fittings are categorized as to whether they are
flanged or screwed. This means they connect to the piping either by a
bolted flange, or screwed into the pipe with male and female threading.
For example, the friction losses through a 2 inch flanged elbow, or a 4
inch check valve, already takes into account the losses at the entrance
and exit port fittings. Then there are unassociated 'tramp' flanges and
unions. Examples would be unions between two lengths of pipe, or
between a pipe and a tank, or between a pipe and a pump. They must
be calculated because there is friction (and energy lost) as the fluid
passes through a union. In our simple system, there is a 6 inch tramp

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