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NOTE: THE FACTORY SUPPLIED CHECK VALVES ARE FITTED WITH VITON O-RINGS. CHECK CHEMICAL
COMPATIBILITY, IF NOT COMPATIBLE REPLACE WITH SUPPLIED TEFLON O-RINGS.
All piping systems should include:
1.1.1
A separate system relief valve to protect piping and process equipment, including the pump, from excess
process pressures.
*
An external relief valve is required to safeguard pump and the piping system.
1.1.2
Isolation valves and unions (or flanges) on suction and discharge piping. This permits check valve
inspection without draining long runs of piping. Isolation valves should be of the same size as
connecting pipe. Full flow ball valves are preferred since they offer minimum flow restriction.
1.1.3
An inlet strainer, if the product is not 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 isolation valve and the pump suction check valve. It must be sized
to accommodate the flow rate and the anticipated level of contamination. A 100-mesh screen size is
recommended.
1.1.4
Check valve housings or other portions of the liquid head must not support piping weight, as the resulting
stresses can cause leaks. In piping assembly, use a sealing compound chemically compatible with the
process material.
SUCTION PRESSURE REQUIREMENTS
Although Mechanical Diaphragm metering pumps have suction lift capability, a flooded suction is
preferable whenever possible. The pump should be located as close as possible to the suction side
reservoir or other source keeping suction piping as short as possible.
The pump will self-prime with 10 ft. (3 meters) of water suction lift (wetted valves, zero back pressure, full
stroke and speed, water like solutions). A foot valve is required to maintain prime. Once primed, the
pump is capable of up to 20 feet (6 meters) of water suction lift.
Neptune Mechanically Actuated Diaphragm metering pumps are designed for continuous service at the
rated discharge pressure. The discharge pressure must exceed suction pressure by at least
1.75 Bar). This can be achieved where necessary by the installation of a backpressure valve in the
discharge line.
2.0
SUCTION PIPING
2.0.1 The suction piping to the pump must be absolutely airtight for optimum operation. Any leakage in the
suction line will reduce or even eliminate pumping capacity. Suction pipe should be at least one size
larger than suction port size of the pump's Liquid Head. It is suggested that the suction piping be tested
with low air pressure and a soap solution to assure that no leaks exist. Limit the total length of the suction
line to 5-8 feet for suction lift or 8-10 feet for flooded suction. Minimize bends, elbows, or other restrictions
for better pumping efficiency.
2.0.2 NEPTUNE RECOMMENDS THAT THE MECHANICALLY ACTUATED DIAPHRAGM METERING
PUMPS BE OPERATED WITH A FLOODED SUCTION, AS THIS WILL FACILITATE START-UP AND
INCREASE THE SERVICE LIFE OF THE PUMP.
2.0.3 It is recommended that all solution tanks be furnished with a low level cut off switch or low-level alarm
and cut off switch to prevent the pump from running dry. Although the pump can run dry for a few
minutes, OPERATION AGAINST A DRY SYSTEM UNDER PRESSURE FOR A PROLONGED PERIOD
MAY CAUSE DAMAGE TO THE PUMP DIAPHRAGM AND REDUCE THE OPERATING LIFE OF THE
PUMP.
9
25 psiA (or
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