Dosing pumps convey liquids and provide precise quantity dispensing. The exact volume depends on the rotation, time, or (for reciprocating pumps) the stroke. Various pump technologies can be used as dosing pumps – each type has particular advantages, which can be used for the application in question. The dosing pump is therefore not an individual pump type, but instead refers to the functionality for precise dispensing of a fluid.
Delivery characteristics of the Dosing Pumps
from our alliance members
- Flow rate: 1 ml/h up to 2,500 m³/h
- Pressure: from vacuum up to 320 bar
- Temperature: -100 °C to +550 °C (-148 °F to +1020 °F)
- Viscosity: 0.1 to 40,000,000 mPa·s
- self-priming possible
- gas content: up to 95 %
- solid content: up to 70 % (max. 150 mm)
- API standard
- hygienic design available
How dosing pumps work
There is no uniform operating principle for dosing pumps, for various pump technologies are used to dose liquids. The most common technologies include reciprocating pumps, peristaltic pumps, diaphragm pumps, and gear pumps. However, other technologies can also be used for dosing, including rotary piston pumps, progressive cavity pumps, screw pumps, and a few more. All types offer very precise dosing technology, they will not run dry, and some are also self-priming.
All pumps that are used for dosing have one thing in common: they are displacement pumps. This means that they convey the medium in closed volumes. In contrast, flow machines (centrifugal pumps) convey the medium streams freely through the pump. That's why these pumps are not well-suited for dosing – their conveyance methods rely on a principle that is too imprecise.
The advantage of positive displacement pumps is that they can convey precise volumes, enabling them to dispense the defined dosing quantity of a liquid. Specifically, the pumps work like this:
- Reciprocating pumps handle liquids with a piston as displacing element; the piston performs a stroke movement in a cylinder with inlet and outlet. When the media is sucked in, it streams into the pump, and is subsequently pressed out of the pump during conveyance. With each stroke, the same quantity of liquid can be conveyed so that exact dosing is possible.
- Peristaltic pumps convey the medium by pressing it through a hose that is deformed by rollers. The rollers are moved by a rotor. Each rotation presses the same quantity of liquid through the pump – dosing is possible by determining the rotational speed.
- Diaphragm pumps move liquids through an elastic membrane that is connected to the conveying chamber. If negative pressure is exerted on the membrane, the diaphragm dosing pump sucks the medium into the pump chamber; with positive pressure, the liquid is conveyed. As with the piston pump, the dosing quantity is determined by the number of strokes.
- Gear pumps use two gears that rotate against each other to convey liquids: The medium is conveyed into the spaces between the gears and the pump housing. As with peristaltic pumps, the rotation determines the quantity of liquid that is conveyed.
- Progressive cavity pumps are based on a rotor that turns eccentrically in a stator. The medium is conveyed gently and exactly in the moving conveying chambers – with this technology, the rotational speed also determines the pump capacity.
- Rotary lobe pumps work like gear pumps: Two pistons with two or more blades rotate against one another in the pump. The fluid is transported in the conveying chambers. As with other technologies, the dosing is determined by the speed.
- Screw pumps are a diagonally interlocked variant of the gear pump: Liquid is conveyed into the conveying chambers between the two spindles. Here too, the pump capacity depends directly on the speed.
Areas of application for dosing pumps
The areas of application for dosing pumps are as varied as their technologies are flexible: These machines are required in all industries where exact mixing of fluids with other fluids, or a precise filling of the medium is required.
Dosing pumps are used in the chemical industry and for the production of pharmaceutical products, for the manufacturing of food and beverages, for water and wastewater applications, and to dose adhesives in automated packaging processes and fill fuels into tank systems.
In addition to the common dosing applications for fluids of all types, hermetically sealed dosing pumps do not leak, and they can be used for dosing media in an especially wide variety of applications:
- Abrasive (suspensions with SiO2, Al2O3, catalytic converters, grinding pastes)
- Explosive (hydrogen, silanes)
- Extreme purity (antibiotics and other pharmaceutical products)
- High vapor pressure (liquid gases)
- Corrosive (HCl, HF, HNO3)
- Radioactive (plutonium, uranium saline solutions)
- Reactive (soluble glass, sodium, aluminum alkyl)
- Poorly lubricating media (liquid gases)
- Sterile (lecithin, plant oils, dairy products)
- Toxic (chlorine, bromine)
- Valuable (spice extracts, liquid oils)
How large can dosing pumps be?
Given the wide range of applications, it is no wonder that dosing pumps also offer a broad range of outputs: The maximum flow rate depend on the technology they base. Small devices fill creme tubes exactly with a few grams of product. Large dosing systems in process industry applications are just as precise, even when they dose additives in production batches with volumes of several cubic meters.
Depending on their design, dosing pumps can come in many different sizes. Small dosing pumps are compact devices that can easily be operated and maintained by one employee. A large dosing system, by contrast, weighs several tons and requires a corresponding amount of space. Dosing technology of this size is usually incorporated into a process control system so that it can be operated and controlled safely and easily, even from afar.
Stepping motor pumps & microprocessor technology at dosing pumps
Dosing pumps have been available with state-of-the-art microprocessor technology already for some time. The operating principle of the diaphragm pump is applied in the stepping motor pump, but with a stepping motor as the drive. Stepping motors operate extremely precisely and therefore enable very exact dosing over a large power range.
The right dosing pump – from small all-rounders to large specialists
Regardless of whether you need to dose a few milliliters or many cubic meters per hour: There are dosing pumps for every application and nearly every medium. Finding the right dosing technology for the desired application is not always easy, however.
Are you seeking an efficient, exact dosing pump for your application? Make a non-binding inquiry for your application to the dosing pump manufacturers in our alliance!