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Series 500 Low Volume in 316 SS

Neptune Series 500 Low Volume Metering Pumps

Neptune Low Volume hydraulic diaphragm metering pumps are built to deliver very low flows, repeatable and accurate ranging down to quarts per day. Discharge pressures are higher than are possible with mechanical diaphragm pumps. Explosion-proof models are available for use in hazardous atmospheres.

These pumps are especially popular in oil/gas production, oil recovery and refineries. Typical applications include the injection of antifoam agents, corrosion inhibitors and other additives injected at very low volumes but high pressures. These pumps are also used for neat feeding of boiler chemicals.


  • High discharge pressures, to 3000 psi (210 kg/cm²). Exceeds limits of most small pumps, ideal for high pressure systems
  • EZE-CLEAN™ valves – Cartridges can be removed for cleaning without disturbing piping
  • Pneumatic and electric stroke-length control available. Automatic capacity control in response to standard 4-20 mA process signal*
  • Explosion-proof motors available, suitable for use in hazardous atmospheres
  • Low flow-rates – quarts per day. Accurate, reliable chemical feed

Specifications are given below, or you can download product information for the Series 500 Low Volume line (PDF format) here:

  • Data Sheet (specifications, performance charts & dimensions)
  Series 500 Low Volume Specifications
@ 100 PSI
Materials of
@ 1/3HP
@ 1/2HP
Per Minute
psi kg/cm² psi kg/cm²
481-S-N3 0.2 gph
4.8 gpd
17.8 lpd
316 SS 1500 105 n/a n/a 18
501-S-N1 0.5 gph
12 gpd
1.9 lph
44 lpd
Cast Iron 1500 105 n/a n/a 18
501-S-N3 316 SS 1500 105 3000 210
501-S-N4 C-20 1500 105 3000 210
501-S-N5 PVC 150 10.5 n/a n/a

Variable speed drives may not be used with models 481 or 501 due to low stroking speed.
501 models are available in simplex or duplex. 481 model is available as simplex only.
Use with flooded suction only.

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