Pulsafeeder Pulsar Shadow - Manual (Page 13)

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4.3 Suction Pressure Requirements
Although PULSAR metering pumps have suction lift capability, all pump installations should have
minimum lift for optimum performance. 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. Piping should be sized to allow for best possible NPSH
conditions.
It is not recommended to install a PULSAlarm equipped pump in a suction lift system.
If suction lift is required, the net positive suction pressure required (NPSHr) is 0.21 bar (or 3 psia). If
this requirement is not met the process liquid may cavitate inside the pump, degrading metering
accuracy. To maintain prime on a suction installation, a foot valve is required. In addition, suction
pressure must be maintained at a minimum absolute value of 0.35 bar (or 5 psia) to ensure proper
hydraulic system and proper pump operation.
The maximum inlet pressure is limited to 30 psig with the standard composite diaphragm. Higher
suction pressures may be accommodated with optional diaphragm configurations.
It is critical that PULSAR pumps have free flowing and unobstructed suction conditions at all
times. Closed valves, clogged strainers, obstructed piping, etc, are to be avoided. Suction
restrictions can place stress on the diaphragm that may result in premature failure.
Refer to Appendix II for procedures for the calculation of suction pressure.
4.4 Discharge Pressure Requirements
All PULSAR 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 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 “flow-through”, 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.
Discharge systems should be protected from excessive pressures by utilizing a pressure relief or
pressure limiting valve in the piping system. Operation of the pump at pressure above its nameplate
rated maximum may result in damage to the pump components and/or unsafe system conditions.
Refer to Appendix II for procedures for the calculation of discharge pressure.
4.5 Automatic Control (DLC, DLCM or MPC)
Pumps equipped with the electronic controllers are provided with separate instructions. Refer to DLC
manual IOM-PS-DLC-1101, DLCM manual IOM-PS-DLCM-1101, or MPC manual IOM-MPC-0104.
Perform all DLC, DLCM or MPC installation procedures prior to pump startup.