Dosing pumps provide low volume, controllable discharge rates that are used to inject various chemicals, solutions of various viscosities.
Dosing pumps are also called metering pumps because they pump accurate volumetric rates of fluids.
Dosing pumps are usually made from plastic, thermoplastic, or stainless steel and provided with mounting holes or accessories such as suction, discharge tubes, and fittings.
Dosing pumps are generally attached with an electronic controller that enables the fluid flow to be monitored and adjusted easily.
Depending upon the design requirements, Dosing pumps can be operated based on the principle of dynamic pumps or positive displacement pumps.
Variable flow rates are produced by dynamic pumps, suitable for generating high flow rates with low viscosity fluids.
On the other hand, the positive displacement pumps produce a constant flow suited for producing high pressures (and low flow rates) with high viscosity fluids.
Most dosing pumps are positive displacement pumps, which provide steady, low flow for various types of viscous media.
Positive displacement pumps are of two types
Reciprocating pump work on repeated forward and reverse motion of Diaphragm, Piston, or plunger inside a chamber.
It makes the fluid move from suction to the discharge end.
It utilizes a flexible diaphragm membrane. By expanding the diaphragm, the volume in the chamber increases. The increased volume draws the fluid into the pump.
By compressing the diaphragm, the fluid is pushed out of the pump.
Non-return valves are installed at suction and discharge of the pump.
By moving the plunger or piston creates a vacuum in the chamber, which draws the fluid into the chamber.
Forward movement of the piston compresses the fluid and pumped out.
This kind of pump provides a continuous flow of solution, chemical dosing. They are Peristaltic, Vane, Lobe, Gear, and Screw pumps.
The PLC systems or independent controllers are used to provide proportional and integral action in dosing control.
The Vane pump consists of a cylindrical chamber in which the vane rotates and dosing of high viscosity fluids against the short head.
Used for dosing liquids having a higher viscosity than water. Pumping action is generated by rotating so-called lobes, which are of two, three, and four-lobe configurations.
The function of gear, screw, and lobe pumps are similar.
In this kind of dosing pump, two gears rotate in the counter-clockwise direction. Forwards the fluid that enters between the gear teeth, provides pulse-free dosing.
Gear positive displacement pumps are selected in applications where accurate dosing, or high pressure output is required. It helps in simple transfer of viscous liquids, with higher pressure. They pump constant amount of fluid for each rotation.
Peristaltic pumps consist of flexible rubber or plastic, friction-resistant tubes. They are often used for dosing pumps because the volumetric flow is proportional to the rotational speed and independent of discharge pressure.
Peristaltic pumps operate by rotating a roller across a hose thereby pushing liquid through the pump.
They are very accurate.
They can handle extremely small flows.
They are self-priming, requires no check valves.
Useful for low pressure applications.
Materials: The base materials of a dosing pump is essential to consider, as it affects the type of media that can be carried out effectively.
Dosing System fluids of different nature may be abrasive, acidic, caustic, very hot, very cold, or otherwise hazardous. Base materials such as plastic, cast iron, and stainless steel own different advantages for handling these various characteristics.
The basic parts of a chemical dosing system are as follows.
As dosing pumps deal with hazardous chemicals, with high temperature and pressure following precautions need to be taken.
Dosing pumps are
It is used for pH neutralization in various industries such as
Reference: Pumping Manual by Ronald Horace Warring.
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