Metering Pumps

About Metering Pumps and Metering Pump Manufacturers Including: Chemical Metering Pumps, Dispensing Pumps & Liquid Pumps.

Metering pumps, also referred to as dispensing, liquid, chemical feed, proportioning and fluid metering pumps, are positive displacement pumps that move exact amounts of liquid in any given time frame, resulting in accurate flow rates. These pumps move a consistent volume of liquid with each cycle or revolution. The distinguishing characteristic of these pumps is their accuracy. Metering pumps have an average accuracy rate of plus or minus one percent. Another feature of metering pumps is their ability to vary the flow rate. This is either manual or automatic, depending on the system and process requirements.

Metering pump manufacturers equip the majority of their products with a micrometer screw adjustment, but a pneumatic or electronic actuator can also be used if the pump flow rate requires alteration due to a process signal. These pumps move fluid in two stages. First is the intake stroke in which liquid is carried into the pump cavity beyond the inlet check valve. In the next stage, after the inlet valve closes, the outlet valve opens and the fluid is forced out. Altering the stroke length or stroking speed adjusts the flow rate of the metering pump.

Metering pumps can be dispensing devices of chemicals and other fluids. Typically, these pumps are used to meet any or all of the following requirements: high accuracy dispensing, high system pressure, low flow rates in GPH or mL/hr, the ability to move hazardous or corrosive fluids or controlled dispensing via a microprocessor, computer or PLC. Water treatment systems, chemical processing and laboratory applications utilize metering pump manufacturers. Plastic extrusion machines use metering pumps to maintain a constant flow of melted plastic through the die. These pumps are also great for spray paint applications, as they enable quick changeover of colors. Additionally, manufacturers of processed food use metering pumps to ensure a constant rate of food additives during their processes.

Different factors determine which metering pump is appropriate for a specific application. Since each fluid that needs to be pumped is unique, it is important to select a pump based on the specific characteristics of the fluid, such as whether or not it is abrasive or corrosive. Some other important factors include fluid viscosity, temperature, flow and pressure rates. Since metering refers to the accurate delivery of a measured amount of liquid, metering pump manufacturers cater to numerous applications throughout the world.   

Calibration Cylinders for Metering Pump Accuracy

Pressure Relief Valves for Accurate, Safe Metering Pumps

Metering Pumps and Metering Pump Manufacturers Images Provided by Primary Fluid Systems Inc.

Types of Metering Pumps

• Bellows pumps transport fluid via a reciprocating bellows cavity that joins to a driving rod.
  
• Centrifugal pumps use a revolving disk attached to a drive shaft that transports fluid without pulsation as it spins.  
  
• Chemical metering pumps are precise instruments used to move chemicals.
• Dispensing pumps are designed to dispense a precise amount of liquid or gas.
  
• Gear pumps use gears to trap fluid between the teeth of two or three rotating gears. Gear pumps are ideal for high system pressure applications and are typically magnetically powered.
  
• Liquid pumps use displacement to move fluids from one place to another.
• Peristaltic pumps use tubing in their operation and rollers that squeeze or occlude the tubing in the direction of the flow. First, the rotor rollers apply pressure to the tubing, which pushes the fluid in, and then the tubing returns to its shape following the occlusion, which creates a vacuum that pulls more fluid in.
  
• Positive displacement pumps transfer liquids and gases from an area of high pressure to an area of low pressure.
  
• Piston pumps use a reciprocating plunger to displace liquid through the machine. A rigid piston assembly gives them the maximum pressure and accuracy of metering pumps.

Metering Pump Terms

Air Bound - The situation in which a centrifugal pump is filled with air, which prevents a vacuum from forming. In this case, water will not flow through the pipe.
 
Back Pressure - The amount of pressure a pump is required to overcome to dose at the point of injection, measured in bar.
 
Capacity - The water handling ability of a water pump.
 
Cavitation - A situation in which vacuum pockets form in a pipe, eventually causing the pipe to implode.
 
Dead Head - A situation in which a pump attempts to run against a closed valve or against any other condition preventing discharge.  
 
Discharge Hose - A hose that moves the discharged water from the pipe.
 
Drain Plugs - Plugs that are removable from the pipe, used to drain water during inactivity.
 
Electronic Controller - An entire control system that supplies feedback to the pump to sustain the accurate chemical dosage, which can increase efficiency.
 
Flooded Suction - A condition wherein a pump is located below the liquid being pumped.
 
Flow Switch - A device that supplies a positive indication that the fluid is flowing and the pump is running.
 
Pressure - Force applied per unit area.
 
Prime - Creation of a vacuum in a pump.
 
Pump Housing - The casing of the pump, made of plastic, stainless steel, aluminum or iron.
 
Pumping Level - The lowest level of water during the pumping process.
 
Shock Mounts - Rubber mounts that are used to help control a pump's vibration.
 
Strainer - A filter at the end of the suction hose that prevents large objects from entering.
 
Thermal Overload Sensor - A sensor in a pump that shuts down the system when the operating temperature exceeds the limit of safety.
 
Viscosity - The degree to which a fluid resists flow when pressure is applied.