What Is a Dosing Pump?

Dosing pumps inject chemicals into water or fluid streams to cause a chemical or physical reaction. They can be used for a variety of purposes, including adding chlorine to water to kill bacteria.

They typically consist of a tank or chamber to hold the chemical, a pump, and an injection tube with a one-way foot valve. Today’s intelligent dosing pumps also include flow intelligence, pressure monitoring, and automatic flow adaptation.

Size

A Dosing Pump is a chemical injection pump that delivers accurate doses of liquid in a precise and consistent manner. It can be used to dispense various chemicals such as chlorine, phosphates and nutrients for aquarium water. Dosing pumps are available in different sizes and can be customized to meet specific application requirements. Typical specifications for dosing pumps include flow rate, pump head, pressure rating and horsepower.

Choosing the right chemical dosing pump for your application requires an analysis of manufacturer specifications. Besides flow rate and pump head, another important consideration is the turndown ratio – the range over which the pump operates within its accuracy rating. A higher turndown ratio means a pump can handle a wider range of flow rates.

SMART Digital S DDA, DDC and DDE pumps are based on tried-and-tested Dosing Pump Digital Dosing technology and open up a large range of dosing applications. These high-precision pumps offer a maximum turndown ratio of 1000:1, as well as a comprehensive range of features such as FlowControl, pressure monitoring and AutoFlowAdapt. Designed for easy operation and integration into a control system, these pumps are ideal for demanding industrial applications.

Flow Rate

Dosing Pumps are often utilized in water treatment applications. In these types of applications, it is important to understand how much the water flows through the process and how much chemical must be added during the processing of the water. This allows the chemistry of the water to be monitored, controlled, and balanced as necessary.

A typical Dosing Pump is a diaphragm metering pump that can be adjusted by the operator to control the flow rate of the chemicals being injected into the water. This is accomplished by adjusting the micrometer dial on the pump or through a variable speed drive which allows for the adjustment of the stroke lever.

There are many different types of Dosing Pumps available, depending on the specific needs of your application. Generally speaking, these pumps are used for adding a variety of chemicals to the water including disinfectants and flocculants in the water treatment industry but also for hygienic applications in the food industry and Cleaning-in-Place (CIP) applications. Some of these dosing pumps are directly programmable allowing the user to set and save their own dose rates without the need for external timers.

Dose Rate

Dosing pumps are small but deliver an extremely precise rate of chemicals or other substance into a water, steam or gas stream. They are an essential automation component in several industries including water treatment, agriculture, manufacturing and medical laboratories.

They work by drawing a certain amount of the chemical solution into a small chamber and then injecting that volume into the stream. They can be used to dispense acids and bases, corrosives and even slurries.

One of the big considerations when choosing a dosing pump is the volume it is capable of dispensing per minute. This is typically quoted in ml/min and can vary quite considerably. It’s important to understand what you need your pump to dose and how often so you can select the appropriate model for your needs.

A common way of controlling a piston diaphragm dosing pump is to use a 4-20 mA signal from a pH controller to control the motor speed – known as flow paced stroke control (Figure 13.1). This offers very accurate (+/-0.1 pH units) dosing. Alternatively, pulsed control can also be used.

Calibration

The pump must be calibrated regularly to ensure the accuracy of the chemical delivery. Typically, a calibration cylinder is filled with the same product that the pump feeds, and the starting level is recorded. The metering pump is then run for a specified time, usually 0.5 to 1 minute. The ending level of the calibration cylinder is compared to the maximum capacity of the pump at the same speed and stroke length.

Dosing pumps are used in various processes to inject a pre-set volume of chemicals into water Dosing Pump or steam streams. They are the central component of integrated dosing systems that enable automated dispensing of chemicals. Several different types of pumps are available for metering and dosing duties. These include piston, diaphragm and peristaltic pumps.

The HI84533-55 pump calibration solution is used to calibrate the dosing system of the HI84533 Formol Number Mini Titrator for Wine and Fruit Juice Analysis. This allows the titration to be performed with the highest degree of precision. The calibration solution contains a precise amount of reagent that is dosed into the water to calibrate the metering pump and achieve a correct titration result. Calibration columns are also available for determining the metering pump flow rate using an industry standard graduation scale, either in milliliters per minute (ml/min) or gallons per hour (GPH). They come in borosilicate glass and polyvinyl chloride, or PVC construction to provide a choice of materials depending on your process and environment.

Installation

Dosing pumps are used in a variety of water, liquid or food processing applications like disinfecting, mixing acid and caustic chemicals to raise or lower pH levels, sanitizing or cleaning-in-place (CIP). They are positive displacement chemical dosing pumps and vary in size, pressure and chemical handling capabilities.

A typical dosing pump has a chemical tank that holds the material to be dosed and a pump which is typically made from corrosion resistant PVC, PE or other plastics or rubbers with stainless steel being used for high-pressure applications. The pump has an inlet, suction line and dosing line with a foot valve that is placed into the product drum to keep it primed. Occasionally, the pump is fitted with a float switch to monitor the product level and activate an alarm when it runs out.

An injector is connected to the dosing line to overcome pipe pressure and mix the chemical into the product flow. Lastly, the dosing pumps are normally connected to a control system which ensures accuracy and turns them on and off at certain times. This can be as simple as a timer or a flow switch right up to a full SCADA central control system with sensors for pH, chlorine and similar as well as the ability to integrate into a larger operations system.