Pulsafeeder OMNI Series DC7 - Manual (Page 7)

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5.2 Piping System
1. All systems should include a pressure relief valve on the discharge side, to protect piping and
process equipment, including the pump, from excess process pressures. An external relief
valve is required! There should be no devices capable of restricting flow (such as a valve)
located between the pump and the relief device.
2. Shutoff valves and unions (or flanges) on suction and discharge piping are recommended.
This permits check valve inspection without draining long runs of piping, making periodic
maintenance and inspection easier.
Shutoff valves should be of the same size as connecting pipe. Ball valves are preferred since
they offer minimum flow restriction.
3. Suction systems should include an inlet strainer, if appropriate for the product being pumped.
Pump check valves are susceptible to dirt and other solid contaminants, 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 generally recommended.
4. Vacuum/pressure gauges in the suction and discharge lines are helpful in order to check
system operation. Gauges should be fitted with protective shutoff valves for isolation while
not in use.
5. 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.
6. 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. Debris from the piping system that prevents proper check valve operation is a
common startup issue.
5.3 Suction Pressure Requirements
Although OMNI ® metering pumps have some 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 fluid supply source.
For fluid with a vapor pressure of 5 psia or less (at operating temperature) the wet suction lift
capability is approximately ten (10) feet. If this requirement is not met, the pump will not
provide reliable, accurate flow. In suction lift conditions, the use of a foot valve is
recommended at the lowest point of the pickup tube or pipe. Pumps under suction lift
conditions may require some liquid priming before they will operate reliably.
For long suction lines, and also for pumps that have a high stroking rate, the largest possible
suction line diameter should be used to provide best suction conditions. In some cases, the
proper line size may exceed the suction connection size on the pump. Consult your local
Pulsafeeder Representative for assistance and further information on proper suction system
design.