Metering Pumps
Metering pumps are a type of positive displacement pump, commonly known as chemical dosing pumps, engineered for precise and accurate fluid transfer and dosing applications.
Quick links to Metering Pumps Information
The History of Metering Pumps
Pumps have been utilized since Roman times to lift water, playing a vital role in both Roman water wheels and those used by ancient Egyptians, Persians, and Indians. The Archimedes screw, a water pump attributed to the Greek inventor Archimedes, is believed by many historians to have been used by the Assyrians to irrigate the Hanging Gardens of Babylon.
During the Middle Ages, increased interest in mining led to the development of the suction or piston pump, which helped remove water from mining sites. This pump worked by using atmospheric pressure to draw water into a cylinder and then expel it through an outlet valve. Comprehensive descriptions of these pump types are documented in the 1556 publication De Re Metallica by Georgius Agricola.
In the 1800s, the rise of industrialization spurred inventors and engineers to design various fluid pumps that regulated flow for municipal water supplies, steam engines, canal boats, and more. While these pumps improved flow control, they did not provide precise metering of liquids.
The first metering pump was developed in 1936 by Robert Sheen, who began building pumps in his father鈥檚 basement. Both he and his father, Milton Roy Sheen, worked for what is now GE Water. Their success led them to start Milton Roy Pumps. Early metering pump models used a plunger and crank-driven piston, offering adjustable flow rates, but they were prone to leaks due to direct liquid contact with the piston. This issue was later solved by manufacturers using a diaphragm to separate the piston from the fluid, as well as using non-corrosive materials like PTFE linings for improved durability and fluid purity.
In the 1970s, Gorman-Rupp of Ohio introduced the first bellows metering pump. That decade also saw the development of metering diaphragm pumps driven by solenoid coils, allowing the diaphragm to flex via magnetism. This advancement enabled electronic operation, fewer moving parts, and lower costs. However, early solenoid pumps couldn鈥檛 operate at slow speeds, limiting their applications and lifespan. This challenge was solved with new digital and CNC dosing controls. Today, ongoing innovations make fluid transfer pumps essential in metering systems for their high precision and reliability.
Advantages of Metering Pumps
The popularity of metering pumps is due to their many benefits, such as highly accurate dosing, the ability to handle high system pressures, reliable low flow rates measured in GPH or mL per hour, compatibility with hazardous or corrosive fluids, and the option for automated control via computer or microprocessor.
Metering Pump Design
- Pump Materials
- Manufacturers typically build metering pumps from corrosion-resistant and robust metals like stainless steel or durable plastics such as PTFE for enhanced longevity and chemical compatibility.
- Considerations and Customization
- To design a custom metering pump or select the right model, manufacturers evaluate specifications such as motor power, stroke length, discharge pressure, temperature limits, flow rates, pump configuration, motor type, fluid composition and viscosity, and how far the membrane, piston, or bellows can extend.
- The nature of the liquid being pumped is critical, as it directly affects pump performance. Most liquids are only slightly compressible, allowing for efficient displacement. However, the presence of gas bubbles complicates displacement, as air can compress significantly and may exceed the pump鈥檚 ability to expel the fluid effectively.
- Considering these factors, manufacturers can design or recommend the ideal metering pump for your needs. Metering pumps are highly adaptable to various industry requirements, with most models able to be adjusted for specific applications.
- Features
- Although drive mechanisms may differ, all metering pumps generally consist of a pump head, fluid reservoir, tubing or hoses, an intake check valve, an exhaust valve, a main body, a diaphragm, bellows or piston, and a motor or manual actuator.
- The pump head is a cylindrical chamber where fluids are held before displacement. The fluid reservoir connects to the pump head via hoses or tubes and passes through an intake check valve. The outlet valve on the opposite side connects to the main body, which directs the processed fluid flow. Each valve allows flow in only one direction. Inside the pump head, the diaphragm, bellows, or piston activates to draw in and discharge liquid. Depending on design, this motion is powered by a motor or manual pedal. While bellows and peristaltic pumps have unique structures, their operational principles are similar to other metering pumps.
How Metering Pumps Work
The operation of a metering pump involves two main actions. First is the suction or intake stroke, where the membrane or piston retracts or the bellows extends. This creates a vacuum effect, opening the inlet valve and drawing in the fluid鈥攚hether oil, water, syrup, or other liquids鈥攊nto the pump head.
The second stage occurs when suction ends and the inlet valve closes. The motor or manual operator then pushes the membrane or piston forward, or compresses the bellows, applying pressure to the fluid. This pressure opens the outlet valve, and the pressurized liquid is discharged from the pump head through displacement.
Types of Metering Pumps
The two primary categories of metering pumps for variable fluid dosing are variable displacement constant speed pumps and fixed displacement variable speed pumps.
- Variable Displacement Constant Speed Pumps
- These pumps control the volume of liquid delivered per minute by adjusting the displacement or stroke length. They maintain precise dosing and can provide a continuous flow of metered fluid to applications like dialysis machines or beverage dispensers.
- Fixed Displacement Variable Speed Pumps
- These pumps allow users to change the motor speed or cycle frequency to modify the flow rate. Adjusting the stroke requires a more sophisticated mechanism and a larger pump size to increase fluid throughput. As a result, fixed displacement variable speed pumps are widely used in industrial and commercial settings.
- Several specialized metering pump mechanisms are used to deliver accurate fluid volumes. Examples include micrometer adjustment screw pumps, pneumatic metering pumps, electronic metering pumps, bellows pumps, centrifugal pumps, chemical metering pumps, diaphragm metering pumps, dispensing pumps, drum pumps, electronic metering pumps, fluid transfer pumps, gear pumps, liquid pumps, peristaltic pumps, positive displacement pumps, piston metering pumps, and compact metering pumps.
- Micrometer Adjustment Screw Pumps
- These metering pumps use micrometer adjustment screws to regulate and fine-tune flow rates. They are commonly used for applications needing high-precision dosing.
- Pneumatic Metering Pumps
- These pumps use pneumatic actuator process signals to adjust flow rates, providing an alternative to mechanical or electronic adjustment methods.
- Bellows Pumps
- This type of metering pump uses pleated, accordion-like bellows to achieve positive displacement. Bellows pumps are chosen for applications requiring reliable performance and clean fluid transfer, often surpassing traditional piston pumps.
- Centrifugal Pumps
- These pumps utilize a spinning disk attached to a drive shaft to move fluid smoothly and without pulsation.
- Chemical Metering Pumps
- Designed for the accurate movement of chemicals, these pumps can handle acids, bases, corrosive liquids, viscous materials, and slurries with precision.
- Diaphragm Metering Pumps
- These pumps use flexible membranes to change the volume of a controlled chamber. The diaphragm鈥檚 motion displaces fluids, delivering accurate and precise dosing, while piston metering pumps achieve this with a plunger.
- Dispensing Pumps
- Engineered to dispense exact quantities of liquids or gases for various applications.
- Drum Pumps
- Specialized metering pumps designed to extract fluids from drums, barrels, tanks, or similar containers.
- Electronic Metering Pumps
- These fluid transfer pumps operate using electrical currents to power actuators for pumping. They allow for electronic adjustment of flow rates and enable automation through computer or programmable controls.
- Fluid Transfer Pumps
- A broad category of pumps created to move various fluids from one location to another, with less focus on power modulation or transfer efficiency.
- Gear Pumps
- Gear pumps transport fluid by trapping it between the rotating gears. They are especially well-suited for high-pressure systems and often feature magnetic drives.
- Liquid Pumps
- Pumps, including water pumps, that use positive displacement to move liquids from one area to another.
- Metering Systems
- These systems include all the devices and apparatus involved in the precise transfer of metered fluids using positive displacement, maintaining process streams of varying chemical compositions and monitoring flow rates.
- Metering Equipment
- Refers to any devices used for the precise metered transfer of fluids from high-pressure to low-pressure areas.
- Peristaltic Pumps
- These metering pumps use rollers to compress flexible rubber tubing, mimicking the rhythmic contractions of the gastrointestinal tract, to move fluids efficiently from one place to another.
- Positive Displacement Pumps
- Move liquids and gases by displacing them from a high-pressure area to a low-pressure area with each stroke or rotation.
- Piston Metering Pumps
- Employ a reciprocating plunger to move liquid through the pump, achieving maximum pressure and metering accuracy with a rigid piston assembly.
- Small Metering Pumps
- Compact positive displacement pumps designed for highly precise dosing of small fluid volumes. The term 'small' can refer to the pump鈥檚 physical size, weight (as little as 39 grams), or its low flow rate capability.
Metering Pump Applications
Often called proportioning, controlled-volume, or dispensing pumps, metering pumps are valued for their ability to deliver exact fluid volumes with high accuracy and repeatability within a specific time frame.
Industries rely on metering pumps to cyclically introduce consistent fluid doses into continuous-flow streams, promoting uniformity in processing.
Metering pumps are used across diverse markets, including pharmaceuticals, food and beverage manufacturing, water treatment, medical devices, commercial vending, irrigation, petroleum, chemical processing, milling, sewage handling, plastic fabrication, metalworking, and laboratory applications.
Standards and Specifications for Metering Pumps
The required standards for metering pumps vary by region, industry, and application. Additionally, some voluntary standards indicate high product quality. Common examples include certifications and standards from ANSI, NEMA, ATEX (used in the EU), the FDA, and military specifications (Mil-Specs). Consult industry leaders to determine which metering pump certifications are most relevant for your needs.
Things to Consider When Purchasing Metering Pumps
If you arrived here through a web search, you have likely seen that there are many metering pump manufacturers to choose from. While options are good, too much information can make decision-making difficult. To help, we have compiled a list of the most reliable, experienced, and reputable metering pump companies, which you can review by scrolling up on this page.
Before browsing manufacturers, make a list of your requirements, questions, and concerns. Consider standards, budget, lead time, delivery preferences, and any post-delivery services such as installation or maintenance. Once your list is ready, compare it to the offerings from our recommended suppliers. Select a few companies to contact and discuss your needs. After speaking with each, review and compare their solutions and services to choose the best fit for your application and budget.
Metering Pump Accessories
Metering pump accessories provide effective ways to enhance the accuracy and efficiency of metering pumps during dosing operations. Common accessories include injection valves, calibration cylinders, strainers, pressure control valves, inline pressure relief valves, pulsation dampeners, and foot valves.
Metering Pump Terms
- Air Bound
- The condition where a centrifugal pump is filled with air, preventing vacuum formation and stopping water flow through the piping system.
- Back Pressure
- The pressure a pump must overcome to inject fluid at the dosing point, measured in bar.
- Capacity
- The volume of water a pump can handle or move.
- Cavitation
- The formation of vacuum pockets in a pipe, which can eventually cause the pipe to collapse inward.
- Dead Head
- The situation where a pump operates against a closed valve or any blockage that prevents discharge flow.
- Discharge Hose
- A hose used to transport discharged water away from the pump outlet.
- Drain Plugs
- Removable plugs in the piping used to drain water when the pump is not in use.
- Electronic Controller
- A control system that provides feedback to the pump to maintain accurate chemical dosing and improve efficiency.
- Flooded Suction
- A setup in which the pump is located below the level of the liquid being pumped.
- Flow Switch
- A device that confirms fluid is flowing and the pump is operating as intended.
- Metering Pump Accessories
- Products designed to enhance the performance or accuracy of a metering pump.
- Pressure
- The force applied per unit area.
- Prime
- Establishing a vacuum within a pump to initiate fluid movement.
- Pump Housing
- The exterior casing of the pump, which can be made from materials such as plastic, stainless steel, aluminum, or iron.
- Pumping Level
- The lowest water level reached during the pumping process.
- Shock Mounts
- Rubber mounts used to minimize vibration produced by the pump.
- Strainer
- A filter located at the end of the suction hose to prevent large debris from entering the pump.
- Thermal Overload Sensor
- A sensor that shuts down the pump if the operating temperature exceeds safe limits.
- Viscosity
- The measure of a fluid's resistance to flow when subjected to pressure.