Pulsafeeder Pulsar Shadow - Manual (Page 46)

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12. Appendix II Piping Calculations
Suction Head Requirements
All reciprocating metering pumps require a net positive suction head (NPSHR). Refer to Table 1 for the
(NPSHR) required for PULSAR pump models. The NPSHR is defined as the pressure required above
the absolute vapor pressure of the process fluid at the pumping temperature. This pressure is required at
the suction port of the pump throughout the entire pump stroking cycle in order to prevent cavitation of
the process fluid within the reagent head. The NPSHR is one of the requirements necessary to assure
metering accuracy.
Table 1. NPSH
R
values
NPSH
R
PULSAR
English (psi) 3
Metric (bar) 0.21
The net positive suction head available (NPSH
A
) must be greater than the NPSH
R
. The NPSH
A
of any
given system is calculated as follows for comparison to the NPSH
R
as shown in Table 1.
Equation 1. – For fluid viscosity below 50 centipoise.
Equation 2. – For fluid viscosity above 50 centipoise.
The variables used in the previous Equations must be in the units shown in Table 2 for the constants
listed to be used correctly.