Pulsafeeder PULSAR Shadow Series, Инструкция по установке, эксплуатации и обслуживанию

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10. APPENDIX I Piping Calculations
10.1 Suction Head Requirements
All reciprocating metering pumps require a net positive suction head (NPSHR). The
NPSHR for PULSAR Shadow® pumps is 5 psi (0.35 bar). 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. Satisfying the NPSHR is required to assure metering accuracy.
The net positive suction head available (NPSHA) must be greater than the NPSHR. The
NPSHA of any given system is calculated as follows:
Equation 1. For fluid viscosity below 50 centipoise.
Equation 2. For fluid viscosity at or above 50 centipoise.
The variables used in Equations 1 through 4 must be in the units shown in the table
below for the constants listed below to be used correctly.
Variable
Units Set
English Metric
NPSH psi bar
P
A
psia bar(a)
P
H
psi bar
P
V
psia bar(a)
L
S
feet meters
R strokes/min strokes/min
G no units no units
Q gallons/hr liters/hr
d inches millimeters
µ centipoise centipoise
L
D
feet Meters
P
T
psi bar
P
P
psi bar
V
P
feet/sec meters/sec
C
1
24,600 640
C
2
45,700 1.84
Note: If piping sizes vary
throughout the suction line,
different additive values may be
used for the pressure losses
attributed to the liquid’s
acceleration and deceleration.
Use the last term of Equation 1
or 2 as many times as needed in
the equation to adjust for
different lengths of different
pipe diameters in the suction
line. (Everything but the pipe
length and diameter will stay
the same in the equation.)