A metering pump installation must be planned from the day tank or liquid source up to the injection point. Remember that hydraulic metering pumps will "push" against great pressures but they will not "pull" for great distances. Because it is easier to prime - and more forgiving - a flooded suction is always preferred. A flooded prime must be used for fluids where vapor pressure might be less than the suction lift.

Be careful to limit the suction to 4' in a suction-lift application, and a foot valve must be used in a top-mount application. Limit the length of a flooded suction to 6 or 7' and use an adequately sized line with minimized bends, elbows or other restrictions.

When considering the piping, the safest rule-of-thumb for selecting suction pipe size is to use one size larger than the pump suction connection. For discharge piping, specify piping that is suitable for the discharge pressure.

Other accessories to be considered when planning a metering-pump installation include:
  • Suction strainer.
  • Flanges, unions or compression fittings
  • Isolation valves.
  • Calibration column.
  • Relief valve.
  • Back-pressure valve.
  • Pressure gauge.
  • Pulsation dampener.
  • Injection quill and check valve.
Finally, remember that when replacing equipment or changing chemical programs, it is best to ask questions.
  • Will the new program operate at the same feed rates as the previous one?
  • Is the equipment properly sized for the new products?
  • How well has the equipment been operating?
  • Are there any problems with reliability, accuracy or unusually high maintenance requirements?
There is no better start to a new chemical-feed program than to ensure that the chemical is delivered accurately with trouble-free equipment.

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