PUMP-FLO Method Of Solution

PUMP-FLO is a pump selection and analysis program. It can select centrifugal, regenerative turbine, and
air operated double diaphragm (AODD) pumps. Centrifugal is a broad classification of pumps that use
kinetic energy to move the fluid. They use the centrifugal force of a rotating impeller to impart kinetic
energy to the fluid (as opposed to jet pumps and eductors). Regenerative turbines share many of the
same operating principles as centrifugal pumps, but have different performance characteristics due to
their unique impeller design. Regenerative turbines are capable of producing high pressures at low
capacities. AODD pumps are positive displacement pumps that use compressed air to move a diaphragm
back and forth, pumping the fluid on the other side of the diaphragm.
For centrifugal pumps, the Hydraulic Institute Standards (Reference 1) is the basis for the PUMP-FLO
program. The Hydraulic Institute is composed of organizations and individuals who manufacture and sell
pumps in the open market. When there is a discrepancy between the PUMP-FLO program and the
current revision of the Hydraulic Institute Standards, the Standards take precedence.
PUMP-FLO selects pumps from a pump catalog and evaluates their operation in an application. Within
the range of the manufacturer’s recommendations, the program allows you to adjust the pump
parameters and see the effect it has on the pump operation.
In general, the majority of this method of solution document applies to centrifugal pump selection. Please
see the Air Operated Double Diaphragm Pumps section at the end of this document for a specific
discussion of these pumps.
Definitions
The definitions that follow are found in Reference 1 and are used in this section for the discussion of
PUMP-FLO’s solution method.
Head The quantity used to express a form (or combination of forms) of the energy content of the liquid,
per unit weight of the liquid, referred to any arbitrary datum. All head quantities are in terms of footpounds
of energy per pound of liquid, or feet of liquid.
Flow The unit of flow rate in the United States is expressed in units of gallons per minute (gpm). The
standard fluid for all pump curves is water at 60 °F.
NPSH The net positive suction head is the total suction head in feet of liquid (absolute) determined at the
suction nozzle and the referred datum less the vapor pressure of the liquid in feet (absolute). NPSHa is
the net positive suction head available in the pumping system. NPSHr is the net positive suction head
required by the pump.
Pump Input The horsepower delivered to the pump shaft (designated as brake horsepower).
Pump Efficiency The ratio of the energy delivered by the pump to the energy supplied to the pump shaft
(the ratio of the liquid horsepower to the brake horsepower).

Pump Sizing
Each pump in the catalog can have up to ten impeller diameters or speed curves. Each curve can have
up to twenty data points describing the pump operation. The data points for the curve consist of the flow
rate and head, and optionally the pump’s efficiency (or power) and NPSHr.
Regenerative turbine head curves can be generated at a particular NPSHa rather than an impeller
diameter. Each pump in the catalog can have up to ten head curves based on the NPSHa. A regenerative
turbine is listed in the search results if it can produce the design point head at a flow rate that is equal to
or greater than the design point flow rate, for a particular NPSHa. Regenerative turbines with flow rates
greater than the design point are only selected if the flow rate falls within a certain percentage of the
design point flow rate. This percentage is specified by the manufacturer.
When the design point of the pump falls between a set of known curves, the program interpolates
between them to arrive at a calculated curve. Often manufacturers allow impeller diameters to be
adjusted only in fixed increments of their choosing. For example, a manufacturer can force the program to
limit the impeller diameter increments to 0.125 inch. Alternatively, they may not allow any trimming of the
impellers

 

http://www.cadfamily.com/HTML/Tutorial/PUMP-FLO%20Method%20Of%20Solution_305954.htm