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10. APPENDIX I Piping Calculations

10.1 Suction Head Requirements

All reciprocating metering pumps require a net positive suction head (NPSH

). The NPSH

for PULSAR

Shadow

pumps is 5 psi (0.35 bar). The NPSH

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 NPSH

is required to assure metering accuracy.

The net positive suction head available (NPSH

) must be greater than the NPSH

. The NPSH

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.

Units Set

Variable

English Metric

NPSH psi bar

psia bar(a)

psi bar

psia bar(a)

feet meters

R strokes/min strokes/min

G no units no units

Q gallons/hr liters/hr

d inches millimeters

µ centipoise centipoise

feet Meters

psi bar

feet/sec meters/sec

24,600 640

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.)

1 2 ... 33 34 35 36 37 38 39 40 41 42 43 ... 47 48

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