When it comes to precise pumping applications, the terms metering pump and dosing pump are often used interchangeably. However, there are some key distinctions between these pump types that process engineers should understand.
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What is a Metering Pump?
A metering pump, also called a volumetric pump, dispenses precise volumes of liquid based on the number of strokes of the pumping head or piston. Each full forward and back stroke of the plunger discharges a known fixed volume. By controlling the stroke speed in strokes per minute (SPM), the flow rate in gallons/liters per hour can be accurately adjusted.
Typical metering pumps use diaphragm, piston, or peristaltic pumping actions. Applications include chemical injection for water treatment, mixing adhesives or paints, transferring acids/caustics, and dispensing liquid reagents in laboratories. Metering pumps are ideal when flow rates from milliliters to liters per hour are required.
What is a Dosing Pump?
While both terms refer to low-flow pumps, a dosing pump has a more specific function - to discharge an exact preset volume, or dose, of liquid with each cycle or pulse. The key distinction is dosing pumps are designed to add precise amounts of one liquid into another stream on demand.
For example, food-grade dosing pumps are commonly used to inject flavours, vitamins or preservatives into beverage or food processing lines. Each time the pump is triggered, it will discharge a set dose value regardless of flow conditions in the main pipe. This ensures accurate and consistent ingredient addition levels.
Features of Food Grade Dosing Pumps
For applications where the pumped liquid will contact food, beverages, or pharmaceuticals, it's important dosing pumps are selected that conform to rigorous hygienic design standards. Look for pumps with components like:
Wetted parts constructed of FDA compliant materials like 316 stainless steel, PFA or FKM.
Hermetically sealed pump heads impervious to moisture and easy to disassemble for cleaning-in-place (CIP).
Precision gears, valves and seals for minimum shear and bubble/foam formation.
Electronic controls allowing remote operation, monitoring and adjustment of dose settings.
With sanitary certifications like 3A or EHEDG, food grade dosing pumps keep ingredients and processes extremely pure for consumer safety.
Summary
In review, while metering pumps focus on continual adjustable flow rates, dosing pumps excel at injecting set volumes into external systems on command. For applications involving precise addition of one liquid into another, progressive cavity pump food grade is an ideal choice to maintain stringent hygienic standards.
With proper selection and maintenance, both metering and dosing pump technologies can effectively meet the process control demands of various flow chemistry and mixing operations.