A dosing pump, also known as a metering pump or chemical injection pump, is a type of positive displacement pump used to precisely meter and deliver small, accurate doses of liquid chemicals or additives into water or other liquids. Dosing pumps play an essential role in many industrial and commercial processes where consistent and controlled dosing is required. 

Why Are Dosing Pumps Needed?

Many applications require very accurate and repeatable dosing of additives and chemicals. Without a dosing pump, it would be extremely difficult to precisely meter small quantities with any level of consistency. Some example scenarios where dosing pumps are commonly used include:

• Water treatment facilities - Accurately dosing chemicals like chlorine, fluoride, and phosphates into municipal water supplies.
• Swimming pools and spas - Precisely dosing chlorine, pH adjusters, and other pool chemicals to maintain ideal water quality.
• Agricultural and horticultural applications - Dosing fertilizers, nutrients, pH adjusters, and other chemicals into irrigation systems.
• Food and beverage production - Adding precise amounts of preservatives, acids, bases, flavorings, and other ingredients during manufacturing.
• Laboratory applications - Safely and accurately metering reagents, solvents, acids, and other materials during experiments and procedures.

In all of these scenarios, consistent and controlled dosing is crucial. Without it, the process is difficult to regulate and quality control suffers. This is where dosing pumps excel by precisely metering small, repeatable doses of additives time after time.

How Do Dosing Pumps Work?

At their core, dosing pumps use positive displacement principles to pump exact amounts of liquid with each stroke or cycle. There are a few main types of dosing pumps commonly used:

Peristaltic pumps - These use a mechanism with rollers that compress a flexible tube, propelling the liquid through the tube with each revolution. They are self-priming, easy to use, and ideal for shear-sensitive or particulate-heavy liquids.

Diaphragm pumps - A flexible diaphragm is used to draw in and expel liquid through check valves with each cycle. They are durable, chemically resistant, and suitable for a wide range of liquids and flow rates.

Piston pumps - A precisely fitted piston or plunger draws in and pushes out liquid with each stroke through check valves. They offer high precision and are well-suited to food contact applications.

Regardless of the specific displacement principle, dosing pumps meter out an exact volume—often calibrated down to milliliters or even microliters—with each cycle or stroke. Flow rates can be precisely controlled through variables like pump speed, stroke length, and cycle frequency.

Programmability and Controls

Modern dosing pumps feature programmable microprocessor-based controls that allow for sophisticated dosing regimes and recipes. Parameters like flow rates, dosing amounts, cycle intervals, and even multi-step sequencing can all be programmed in. Operators have full control over the dosing parameters from a simple touchscreen interface.

Controls also allow pumps to be networked together for centralized control of large multi-pump systems. Pumps may be triggered or dosed based on feedback from other sensors and instruments via built-in I/O capabilities. Accurately logging run times, volumes dosed, and running totalized amounts is also common.

Key Components

In addition to the pumping mechanism and electronics/controls, food grade dosing pump consists of these core wetted components that come into direct contact with the dosed liquid:

• Pump head - Houses the pumping mechanism and interfaces with inlet/outlet plumbing.
• Check valves - Prevent backflow by allowing flow in only one direction through the pump head.
• Suction and discharge tubing/plumbing - Transports the liquid to and from the pump head.
• Wetted materials - Construction materials like food grade stainless steel that are corrosion-resistant and suitable for direct contact with chemicals.

Selecting the Right Dosing Pump

When choosing a dosing pump, key specifications to consider include the flow rate range needed, maximum viscosity of liquids to be dosed, chemical compatibility of wetted materials, tubing/plumbing requirements, programming/control needs, and certifications required for the application such as NSF/ANSI Standard 61 certification for food contact.

Brands to evaluate include prominent pump OEMs like Doseuro, Seepex, LMI Milton Roy, LEWA, Tacmina, and others offering precision positive displacement pumps across various technology platforms to suit nearly any application. Consultation with application engineers can help specify the optimal pump design.

Dosing Pump Maintenance

To maintain accuracy and reliability, dosing pumps should receive regular preventative maintenance including:

• Inspecting and cleaning wetted components like check valves, tubing, and the pump head.
• Replacing worn check valves, seals, and o-rings as needed.
• Calibration checks against a calibrated instrument.
• Lubricating mechanical parts per OEM guidelines.
• Regular inspections for leaks, unusual noises, or other faults.

Proper maintenance is key to protecting your process and maximizing pump lifespan through prevention of premature wear issues. Follow maintenance schedules responsibly.