|
|
Determining Pump Requirements
To select the most suitable pump(s)
for your application, follow the steps below:
- Establish the following factors:
- Fluid type
- Flow rate required
- Hose (or pipe) lengths required
- Static suction lift
- Static discharge head
- Seepage
|
|
- Calculate the dynamic suction head, which equals
the sum of the static suction lift and the friction loss added
by suction pipe, valves, and fittings needed for the installation.
To begin, select a pipe or hose diameter based on the flow rate
required, referring to a reference chart that plots flow, velocity,
and friction loss per 100' of length for various diameters of
hose or pipe. Friction loss for valves and fittings is expressed
in equivalent feet of straight pipe of the same diameter, which
is obtained using reference conversion charts. The sum of the
friction losses for suction pipe, valves, and fittings is divided
by 100 to calculate the friction loss in feet, which is added
to the static suction lift to determine the dynamic suction head.
To utilize centrifugal pumps, the dynamic suction head must be
less than 25'. Submersible pumps must be used if the dynamic suction
head is greater than 25'.
Tip: Using
larger diameter suction pipe may reduce friction loss enough to
lower the dynamic suction head to a workable range in applications
with a high static suction lift (15' or larger).
- Calculate the dynamic discharge head, which
equals the sum of the static discharge head and the friction loss
for discharge pipe, valves, and fittings needed for the installation.
The friction loss for the discharge line is calculated in the
same manner as the suction side. Add this number to the static
discharge head to determine the dynamic discharge head.
Tip: Long discharge
lines add significant friction losses to a pump system. To reduce
friction loss, use larger diameter pipe for all (or part) of the
discharge line.
The total dynamic head is the sum of the dynamic
suction head and the dynamic discharge head. To match a pump to
the application, refer to the performance curve
for a given pump, which plots total head and flow rates at various
static suction lifts. Performance curves for diesel-driven pumps
also plot pump performance at various engine RPM's.
Note: Large pump
installations, such as sewer bypass jobs, may require multiple pumps,
along with custom manifolds and extensive pipeline fabrication.
[ top ]
|
