Pulsafeeder PULSAR 25HJ, Installation, Operation & Maintenance Manual

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Table 2. Unit sets and constant values for use in NPSH Equations .
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
C
3
46.8 0.91
If piping sizes vary throughout the suction line, different additive values may be used for
the pressure losses attribu
ted 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.)
All reciprocating metering pumps also require that a minimum absolute pressure and minimum
suction head (MSH), be maintained at the pump inlet throughout the pumping cycle to ensure a
stable hydraulic system and proper pump operation. The sum of the NPSH
A
and the vapor
pressure (P
V
) must be greater than the values shown in Table 3.
Table 3. Minimum values for the sum of NPSH
A
and vapor pressure. (MSH)
MSH PULSAR PULSAR*
English,
(psia) 5 7.5
Metric,
(bar(a)) 0.35 0.53
* PULSAR Pump with PULSAlarm leak detection diaphragm.