What Is a Dosing Pump?

Dosing pumps are used to inject a precise amount of chemicals into the water supply. This is often done for pH adjustment of water and for mixing disinfectants, flocculants and scale inhibitors.

There are several different types of dosing pumps available including diaphragm type constant injection and peristaltic (roller) pumps. It is important to choose a pump that will fit your needs and budget.

Pump Types

Dosing pumps are a type of positive displacement pump that is used to add a variety of chemicals to a liquid stream at an accurate and controlled flow rate. They are frequently found in water treatment, agriculture, industrial, manufacturing, medical, and food processing applications.

Dosing Pumps are used for a wide range of products, from adding a caustic chemical to a storage tank to changing the pH level in a solution. They are also often used to add chlorine or other oxidizers to kill bacteria.

There are several different types of dosing pumps, including diaphragm-type constant injection pump, piston/plunger metering pump, peristaltic rotary pumps and gear positive displacement pumps. Each type has its own unique uses and specifications.

Diaphragm-Type Constant Injection Pump – This pump uses a chamber filled with a diaphragm and a valve that allows the diaphragm to be withdrawn during suction strokes and refilled during discharge strokes. This method is the most accurate compared to other dosing/metering pumps, but the design makes it not suitable for many applications.

Peristaltic Pump – These pumps are flexible rubber or plastic tubes that rotate across a hose, pushing liquid through the pump. They are able to handle extremely small flows and can be self-priming, requiring no check valves.

They are also very easy to clean and maintain, so they are popular in a number of industries.

Gear Positive Displacement Pump – This type of dosing pump is often selected when precision dosing or high pressure output are needed. This type of pump is capable of handling a variety of different fluids, varying temperatures and can operate at high pressures up to 1,000 bar.

Base Materials – The type of base material the pump is made from affects the type of media it can handle effectively. The base material may be cast iron, stainless steel or plastic. The base material is important because it will determine Dosing Pump how the pump can withstand abrasion, acidic, caustic, cold, hot, and other conditions that might be present in a system.

Dosing pumps are also typically backed by a number of accessories that are designed to improve the accuracy and reliability of the overall system. Some of the most common include:

Flow Rates

Flow rates, or the amount of chemical pumped per unit of time, are an important feature of a dosing pump. They are used in many applications including water treatment and the blending of liquids for food processing, as well as wastewater, oil, gas, and other industrial processes.

The flow rate a metering pump is designed to produce is dependent on several factors. Among them are the pump’s head, pressure, horsepower, and operating temperature.

A metering pump’s accuracy is another important factor to consider when selecting one. In general, a pump with a higher accuracy will pump the measured volumes of fluid more accurately and with less variability than a pump with a lower accuracy.

If a metering pump is being used for chemical metering, then it’s crucial that the accuracy meets specifications. Accuracy is often given in +/- percent, but it can also be expressed in terms of gallons of injected chemical per hour or liters of pumped liquid per minute.

For example, if a metering pump is delivering 5 gallons of a chemical per hour, the accuracy will be +/- 1.0% or better. However, if the application is being operated at a low pressure, such as 50 psi, then accuracy will drop a bit.

When it comes to measuring the accuracy of a dosing pump, it’s a good idea to perform a few calibration tests. The first one will be to measure the volume of water drawn down from a tank and then calculate the number of strokes it takes for that same volume to be drawn back up again.

Once you’ve determined the pump’s accuracy, you can set it to the desired dose rate. This is typically done by adjusting the pump’s stroke length or effective stroke length, but can also be done using an electronic or pneumatic actuator that changes the flow rate in response to a process signal.

The most common methods of controlling the injection flow rate and the amount of injected chemical at each dosing are through valves, sensors or timers. Each type has its advantages and disadvantages depending on the application.

Flow Control

The flow control on a dosing pump is an important part of the system. This allows a user to accurately dose the correct amount of product into a pipe or fluid stream. Dosing pumps are often used in water treatment plants, agriculture and industrial facilities to add chemicals to a fluid stream, such as chlorine or acid.

Flow control on dosing pumps is typically done through a timer or flow switch that is set up to turn the pump on at a certain time and then off after the specified time. This is an easy way to ensure the product is being injected at the correct rate and is not overflowing in a pipe or affecting other parts of the system.

Another common method of flow control on dosing pumps is through a valve in the discharge line that opens when a certain amount of air is trapped inside the head. This is to prevent a buildup of air in the pump which can cause premature wear and tear and potentially leakage.

There are various types of dosing pumps that use different mechanisms to achieve this. They can range from a simple plunger or piston type positive displacement to a more complex reciprocating mechanism which uses a piston, diaphragm or bellows to move the fluid through the chamber.

Diaphragm (constant injection) pumps use a piston to draw in a liquid and inject it into the chamber at a specific speed, typically Dosing Pump a percentage of the maximum flow rate. They are generally more accurate than pulse injection pumps, but are less accurate than gear pumps.

Reciprocating (pulse injection) pumps use a solenoid to take in the liquid and inject it into a chamber in short pulses, again at a preset rate. These are less accurate than constant injection pumps but they can be cheaper and simpler to design.

Peristaltic (lobe) pumps are also a very specialised type of dosing pump that works by having a tube which is bent in a semi-circle and then a small roller moves over the outside to catch a portion of the liquid which then pushes it along into the main pipe stream. This is an accurate and very hygienic pump, which is used widely in the medical industry.

Pressure Control

The pressure control system on a dosing pump is designed to control the dosing rate and ensure that it stays accurate. This is often as simple as a timer and flow switch or can be more sophisticated such as a full centralised operations system with sensors for pH, chlorine and similar.

A dosing pump is a type of metering pump used to add chemicals into liquid streams or other vessels. They are usually able to deliver liquid with an accuracy of greater than 3% across a wide range of discharge pressures and fluid viscosity.

These pumps are typically a reciprocating design with a plunger, piston or diaphragm. The main advantage of these designs is that they can maintain a steady flow rate over a large range of pressures.

The metering pump can also be equipped with air chambers to dampen pulsations that can occur as the pump is moving in a fluid pipe system. This is done by allowing the liquid to accumulate in the air chamber over time to reduce pulsations and contribute to a stable and smooth liquid flow.

Dosing pumps are widely used in a variety of industries. These include water treatment, agriculture, industrial, manufacturing, medical, food processing and mining.

To ensure that a dosing pump is working as intended, it is important to calibrate it regularly. This is where a calibrating cylinder can help. A calibration cylinder is placed on the suction side of the metering pump and provides an accurate reading when there is a change in fluid characteristics or any time the flow rate is changed.

When a metering pump is used in an environment where there is high temperatures, it should be fitted with a thermal protection device. This will prevent the temperature of the liquid in the metering pump from rising to excessive levels and damage the components.

Another way to protect the equipment is by installing an anti-syphon check valve. This prevents fluids from being sucked out of the discharge line after the pump has stopped working. This can lead to problems such as overfeeding and backflow in the main line.