Metering Pumps

What is a metering pump?

A pump that is designed to move fluids at precise flow rates. Most have the ability to set and adjust the flow rate with a hand dial or digital touch pad. Flow rates for metering pumps are usually quite low due to the nature of the application, with most flow rates being rated in gallons per hour (gph) rather than the traditional gallons per minute (gpm) used for most pumps.

The most common types are diaphragm pumps, with the diaphragm mechanically or hydraulically actuated, or moved via a solenoid. However, other types of positive displacement pumps such as piston pumps, peristaltic pumps, plunger pumps, or several other rotary pump types may also serve as metering pumps.

Metering pumps generally work within the following ranges:

  • Flow rate ranges between .001 gph and 20 gpm
  • Total head (pressure) ranges between 10 and 30,000 psi
  • Horsepower ranges between 0.125 and 5 hp

How do they work?

There are two main types, both of which may adjust the flow rate by any number of different pumping mechanisms:

1. Variable displacement pumps adjust the flow by changing the amount of fluid that enters the pump, while the motor always runs at a constant speed. They often do this by adjusting the stroke length, or in some cases the amount of hydraulic fluid that is bypassed.

2. Fixed displacement pumps adjust the flow by changing the speed of the motor, while the same amount of fluid is displaced with each revolution.

Where are they used?

Metering pumps are used wherever the flow rate of a liquid needs to be regularly measured and adjusted to precise levels. They’re most commonly used to pump treatment chemicals in water treatment applications, such as treatment of water for drinking, swimming pools, boilers, cooling towers, or in treatment of wastewater. The treatment chemicals are pumped into the water to adjust the pH, alkalinity, and to disinfect the water.

They are also used in food processing plants for blending of liquid ingredients, in process metering applications where one chemical needs to be added to another in precise amounts, in pipelines to decrease the frictional losses as the oil moves through the line, and in various laboratory and medical applications.

Here are a few metering pump manufacturers to consider.

Metering Pump Manufacturers
LMI Pumps (Pump Manufacturer)

LMI Milton Roy produces and manufactures electronic and motor-driven metering pumps for water treatment, fertilizer injection, cooling water, swimming pool, boiler water, paper chemical feed and other related applications. The company’s trademark yellow and black products are the standard for water treatment application.

Milton Roy Company (Pump Manufacturer)

Milton Roy is a leading manufacturer of metering pumps for water & wastewater treatment, oil & gas in power generation, and hydrocarbon processing applications. The company manufactures hydraulic diaphragm pumps and mechanical diaphragm pumps. Milton Roy Company offers several popular models including its mRoy, Milroyal, MacRoy, Centrac, and Primeroyal Series pumps. The pumps have a flow capacity up to 4,200 gph and pressures to 30,000 psig.

Zenith Pumps (Pump Manufacturer)

For more than 85 years, Zenith Pumps, a Colfax Business Unit, has provided the process industries with precise, pulseless and reliable precision gear metering pumps. Zenith pumps are used in numerous markets, including fiber, extrusion, polymer processing, pharmaceutical, adhesives, paints, coatings and food. Zenith Pumps offers a complete line of precision gear pumps and metering systems to handle the many critical applications in the process industries.

Neptune Chemical Pump Co. (Pump Manufacturer)

Neptune manufacturers a variety of diaphragm metering pumps for the petro-chem, power gen, oil & gas, and irrigation markets. Neptune’s diaphragm metering pump line includes its Hydraulic 500 and 600 series, its mechanical 7000 series, and its PZ series. The hydraulic 500 series provides leak free metering in several applications including flammable, corrosive, and hazardous fluids. The pump can handle flow rates to 97 gph at 3,000 psi. In addition, the 7000 series mechanical diaphragm metering pump allows for self-priming and is designed to handle chemicals that off-gas.

Expert Advice

Outrageous claims are often made about the turndown capabilities of various pumping technologies, and their ability to act as metering pumps. This paper presents data to clarify turndown, its unbreakable bond to accuracy, and the real benefit of turndown to a process.

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