Pulsafeeder Pulsar Shadow - Manual (Page 15)

3. An inlet strainer, if the product is not a slurry. Pump check valves are susceptible to dirt and
other solid contaminants unless designed for that service, and any accumulation can cause
malfunction. The strainer should be located between the suction shutoff valve and the pump
suction valve. It must be sized to accommodate the flow rate and the anticipated level of
contamination. A 100-mesh screen size is recommended.
4. Vacuum/pressure gauges in the suction and discharge lines in order to check system
operation. Gauges should be fitted with protective shutoff valves for isolation while not in
use.
Piping weight must not be supported by valve housings or other portions of the reagent head, as
the resulting stresses can cause leaks. If appropriate, provide for thermal expansion and
contraction so that no excess force or moments are applied to the pump.
In piping assembly, use a sealing compound chemically compatible with the process material.
Users of sealing tape are cautioned to ensure that the entering pipe thread ends are not taped, and
that tape is removed from previously-used threads to the maximum practical extent prior to re-
use. Both new and existing piping should be cleaned, preferably by flushing with a clean liquid
(compatible with process material) and blown out with air, prior to connection to the pump.
4.3 Suction Pressure Requirements
Although PULSAR Shadow
® metering pumps have suction lift capability, a flooded suction (i.e.,
suction pressure higher than atmospheric pressure) is preferable whenever possible. The pump
should be located as close as possible to the suction side reservoir or other source.
For fluid with a vapor pressure of 5 psia or less (at operating temperature) the wet suction lift
capability is ten (10) feet. If this requirement is not met, the pump will not provide reliable,
accurate flow. The Net Positive Suction Head Required (NPSH
R
) is 0.35 bar (5 psi).
The maximum inlet pressure is limited to 0.35 bar (5 psi) below the operating discharge pressure.
Refer to Appendix I for procedures for the calculation of suction pressure.
4.4 Discharge Pressure Requirements
All PULSAR Shadow
® Metering Pumps are designed for continuous service at the rated
discharge pressure. If system suction pressure were to exceed system discharge pressure (a
condition sometimes described as “pumping downhill”), flow would be generated (siphoning) in
addition to that caused by the pump, resulting in a reduction in accuracy and loss of control over
the metering process. To prevent this condition, commonly referred to as “flowthrough”, the
discharge pressure must exceed suction pressure by at least 0.35 Bar (or 5 psi). This can be
achieved where necessary by the installation of a backpressure valve in the discharge line.
Damage to the pump will occur if operated at pressures beyond the maximum rating.
Refer to Appendix I for procedures for the calculation of discharge pressure.
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