A dosing pump is a positive displacement pump that is used to inject chemicals or other materials into a flow of water, gas, or steam. Small dosing pumps provide an exceedingly accurate flow rate for the best possible control. They serve as the focal point of an integrated dosing system created for the chemical industry’s automatic chemical dispersion. This definition of dosing applies to a wide range of applications and industries, including wastewater treatment and food processing.
Dosing pumps are also known as chemical metering pumps, are utilised in industrial plants, agricultural, manufacturing facilities, medical labs, and mining activities. To adjust the pH of a water storage tank, a chemical feed pump may be used to deliver an acid or caustic chemical. In order to destroy microorganisms, it can also be utilised as a chlorine pump. A chemical dosing pump is made to work in difficult conditions, like high-temperature and high-pressure settings.
Types of Dosing Pumps Used in Industries
Similar to other industrial pumps, these dosing pumps are classified according to their intended use and normal operations. They are made to dose various compounds under various pressures. According to their function and mode of operation, the following are the types of dosing pump.
1. Reciprocating Pump
Reciprocating pumps operate by repeatedly moving a piston, plunger, or diaphragm forward and backward inside a chamber. The fluid is forced to migrate from the suction end to the discharge end.
2. Diaphragm Pump
The pumps are known as diaphragm pumps because they operate using a diaphragm mechanism. Diaphragm pumps come in two varieties: pumps with steady injection and pumps with pulse injection. These two pumps both rely on a diaphragm mechanism. Valves and pistons are found on the outlet and inlet of diaphragm constant injection pumps. By drawing in or out, the piston can both empty and fill the chamber. When the piston is brought in, the chamber is filled. A precise dose of a chemical is delivered at a set rate. Additionally, diaphragm pulse injection pumps are fixed with a solenoid coil, which helps to inject chemicals in pulses. These pumps cost little money and have straightforward designs.
3. Piston or Plunger Pump
The fluid is drawn into the chamber by creating a vacuum inside it by moving the plunger or piston. The fluid is compressed by the piston’s forward motion and pumped out.
- They are used to deliver high pressure.
- They emit pulsing flows that can be muted and call for a check valve.
- The volume discharged is essentially independent of pressure.
- They function on their own.
4. Rotary Pump
Chemical dosing is provided continuously by this type of pump. They are screw, vane, lobe, gear, and peristaltic pumps. Proportional and integral action in dosage control are provided by PLC systems or standalone controllers.
5. Vane Pump
The vane pump has a cylindrical chamber in which the vane rotates and a short head against which high viscosity fluids are dosed.
6. Lobe Pump
These pumps have impellers with meshing gears. They run these impellers with a set amount of chemicals. High viscosity fluids work well with lobe pumps. Low flow rates are not intended for these pumps.
7. Gear Pump
Two gears in this type of dosage pump revolve in the opposite direction of one another. Moving forward, pulse-free dosing is provided by the fluid that enters between the gear teeth. When precise dosage or high pressure output are necessary, gear positive displacement pumps are chosen. It facilitates the straightforward transport of viscous liquids under greater pressure. For each spin, a fixed amount of fluid is pumped.
8. Peristaltic Pump
These are the dosing pumps that are now in use that are the most precise of all those mentioned on this list. The fluids can pass through the tubes because they are flexible and curved. The pump has a roller that aids in regulating the fluid flow.
How Does Dosing Pumps Work?A dosing pump draws a certain volume of fluid into its chamber, injects the chemical into a tank or pipe containing the fluid to be dosed, and then repeats the process. It is powered by an electric motor or an air actuator, and it features a controller that controls the flow rate and turns the pump on and off. More advanced control mechanisms are featured in some versions.
Applications Of Dosing Pumps
The best dosing pumps are utilised in a wide variety of applications. Pumps are mostly used to change the pH Level of water and also used as protection against corrosion and precipitation. The pumps are frequently used to combine flocculants, scale inhibitors, and disinfectants. Of course, there are additional uses for the pumps. The following section includes a number of application examples.
- Disinfection of process water
- Chemical industrial applications
- Food and beverages
- Disinfection and pH adjustment
- Dairy farms
- Power generation
- Oil and gas
Components Of A Dosing Pump
A dosing pump is made up of a number of parts that actively support how it works. These components are described below
- Chemical Tank: The tank is intended to hold the dosed material.
- Dosing Pump: A pump has three features: a suction line, a dosing line, and an inlet. The size and composition of a pump vary depending on the use. Various materials, including rubber, plastic, and stainless steel, are used to create dosing pumps.
- Injector: This is a non-return valve used to inject the chemical into the flow. The injector makes it simple to mix a chemical into a liquid or product in equal doses while overcoming pipe pressure. Once the pump has stopped, the injector features a self-actuated mechanism that helps prevent the liquid in the delivery line from flowing upward. This injector also directs the chemical delivery to the centre of the flow, assisting in reducing product waste brought on by improper chemical dosing on the side walls. When chemicals are used incorrectly, especially when they contain acids or peroxides, the walls can occasionally also be harmed.
- Foot Valve: This is a one-way or non-return valve that is connected to the suction line, as the name would imply. Most of the time, it is placed at the product drum. It has a float switch attached to it so you can see if the product is still available. As soon as the product runs out, this switch sounds an alarm.
- Dosing Line: A dosing line is a reinforced, rigid tube that can be made of stainless steel, PVC, or PE for usage under high pressure.
- Control System: The majority of plant owners today use software and control systems to make sure the pumps are running properly. Additionally, these control systems automate the pumps for optimum performance. SCADA technologies and sensor-driven central control systems are employed for this. Systems for sensor control are made to measure pH, chlorine, and other chemicals.
Advantages Of Dosing Pumps
- Reliable metering
- easily maintained
- capable of supporting dry running
- They can operate with corrosive, abrasive, and viscous fluids, making them useful in a variety of applications.
- They can be used to inject chemicals in high-temperature, high-pressure situations.
How large Can Dosing Pumps Be?
Dosing pumps provide a wide range of outputs, which should come as no surprise given the variety of applications: The highest flow rate depends on the technology on which it is built. Small machines precisely measure out a few grams of substance to fill cream tubes. Even when dosing chemicals in manufacturing batches with sizes of several cubic metres, large dosing systems in the process sector are just as accurate.
Dosing pumps can be any size, depending on how they are made. Small dosing pumps are convenient, easy-to-use machines that only require one employee for maintenance. On the other hand, a substantial dosing system weighs several tonnes and occupies a sizable space. Large-scale dosing technology is typically integrated into a process control system to provide safe and simple operation and control, even from a distance.
Dos and Don’ts Of Using Dosing PumpsPrecautions must be made since dosing pumps work with dangerous substances under conditions of high temperature and pressure.
- When working close to chemical dosing pumps, wear on PPE such as protective gear, gloves, and safety glasses.
- Make sure that all tubes are firmly connected to the fitting before pumping any chemicals.
- Tubing should be properly protected or shielded to avoid potential injury in the case of a rupture or accidental damage.
- Plastic connectors and pieces shouldn’t be handled with hand tools like pliers or pipe wrenches. An open-end wrench was tightened to perfection.
- Do not overtighten the plastic components as this could harm the threads.
- If a hose is utilised, it must be firmly fixed to supports such as walls, columns, and bracing. Check to see if the hose connection will stay secure and leak-free.
- The suction and discharge connections are made in accordance with the direction of chemical flow, which is indicated by an arrow on the pump.
How To Choose A Dosing Pump?It is necessary to consider the following information while choosing a dosing pump:
- The required dosage expressed in L/h.
- Calculate the back pressure (this must be higher than the pressure of the line or equipment to which you want to dose).
- Find the point where the two numbers connect on a pressure versus flow graph representing the performance of the pump.