Liquid Dosing with Flow Meters

• Liquid dosing is used in a wide range of applications from hydrogen storage for renewable fuels, to the oil and energy industry, to mRNA vaccine production, etc.
• When adding a flow meter into a new or existing dosing process, you can create savings in raw materials, increase consistency across batches, provide traceable flow values, and more
• Coriolis, thermal, and ultrasonic flow meters can be used for liquid dosing with ultra low flow rates, as low as 0.05 grams per hour

Almost every day you come across products that use a liquid dosing system in the production process. And this even includes when you eat sweets or chocolate, when you do laundry, or put on some nice perfume.

Applications that Use Liquid Dosing Systems

We see many applications in the field using liquid dosing systems. For example, in the:

• food industry to add fragrances and flavorings
• household chemical industry to add dyes to detergent
• perfume industry to add fragrances
• petrochemical industry to dose additives like catalysts and odorants

There are several options for how you can dose additives. And some dosing systems will use a flow meter in combination with a dosing pump. Meanwhile, other dosing systems may simply just use a pump.

Dosing Additives with a Flow Meter and/or Dosing Pump

1. What’s the difference between liquid dosing with just a flow meter, and using a flow meter combined with a dosing pump? 

Bronkhorst flow meters precisely measure and verify the quantity of liquid being dosed. By doing this, the process can have extremely accurate dosing, which has several benefits: 

• Savings in raw materials and additives
• Better process quality
• Traceable flow values

Dosing pumps move a known volume per unit of time, without measuring the flow that goes into the process. For instance, if you dose additives using a dosing pump – without a flow meter – the value can deviate up to 50% from the desired quantity of liquid that you want to dose. And this can be caused by wear and tear, air pockets, or fluctuations in pressure and temperature.

By reading our customer story, you can learn more about the flow solution for dosing low-flow liquefied gases.

2. What is important to know when dosing liquids at a low flow rate?

It’s important that you purge your process well. For example, a small air or gas bubble can distort the dosing process and flow measurement values. But we have a great deal of experience with these kinds of processes, and can give you advice on how to tackle this issue. Simply ask us for help if you’re facing these types of issues.

Liquid Dosing in an Existing Process

3. We have an application that requires liquid dosing in the process. Can you help with that?

We sure can, our low flow meters from Bronkhorst are great for liquid dosing, including thermal, Coriolis, and ultrasonic flow meters. After all, Bronkhorst flow instrumentation specializes in low flow rates, anywhere from 0.05 g/h to 600 kg/h. And all of our Bronkhorst liquid flow meters can both control and dose liquids. Since these flow meters measure mass with a high degree of accuracy, many customers choose a Coriolis instrument for dosing applications, such as the mini CORI-FLOW series.

If volume dosing is the only requirement in your process, the best option is the ES-FLOW ultrasonic liquid flow meter. Meanwhile, thermal flow instruments, such as the u-FLOW series, are ideal for applications with an extremely low flow rate, <100 mg/h.

4. Can I connect a Bronkhorst flow meter to my dosing pump in an existing process?

Yes, absolutely – when connecting a flow meter to a dosing pump, you can measure exactly what the pump is doing. Thus, flow instruments can control the pump for greater precision. And this is a significant added value offered by our flow instruments. Also, we can help with advice and on-site system installation.

Liquid Dosing System

5. In my process, can I switch between continuous dosing and batch dosing?

Yes, you can realize different types of dosing using the integrated PID controller and the batch controller in our Coriolis and ultrasonic flow instruments. And this allows for continuous dosing, where the flow controller maintains the flow rate in the process at a set value. So, if the setpoint is changed, the system immediately adjusts. Also, you can track the output signal from another flow meter, allowing you to adjust, mix, or blend other additives (in ppm). This is called ratio control – when a ratio of the main flow is mixed or blended into the main flow.

In addition to continuous dosing, you can also do batch dosing. And with batch dosing, the PID controller regulates the fill times. So for extremely short fill times, less than a couple of seconds, open/close valves are used.

6. Can you also fill jars?

Yes, filling jars is quick and easy using the batch controller function on our Coriolis and ultrasonic flow meters. You only have to enter the batch value on the flow meter once. Then for each batch, you can simply re-start the counter. When desired, the batch controller can automatically adjust to the changing conditions.

7. What kinds of speeds can be achieved for my filling process?

For dosing applications, speeds of up to 50 msec can be achieved using special on/off valves. So you often see these in production lines where jars or soft drink bottles on a conveyor belt have to be filled quickly with flavorings or other additives.

8. What kinds of quantities can I dose?

For a process with continuous dosing, anywhere from a couple of mg/h (with the u-FLOW series) up to around 1000 kg/h (with the CORI-FLOW series) can be achieved. And with batch dosing, the batch size depends on the dosing time and maximum flow rate. So it varies from 50 μg to 278 g in around one second, up to many times that amount if the dosing times are longer.

Bronkhorst Flow Instrumentation with Dosing Pump Combinations

9. Can Bronkhorst provide complete dosing solutions?

Of course, there are a number of options available: 

• Compact Dosing Solutions – These sets comprise a flow meter with a dosing pump or valve on a mass block or plate.
• Skids 
• Liquid Dosing Modules – This includes a custom casing, complete with PLC/HMI for operation.

10. What are the benefits of dosing liquids with Bronkhorst flow meters?

When using Coriolis and ultrasonic flow meters, you can dose independently of the medium properties or the environmental conditions. Thus, the flow meters will ensure that temperature and pressure variations barely impact the result. And our flow meters offer several other benefits:

• PID Controller On-board: Bronkhorst Coriolis and ultrasonic flow meters have an integrated PID controller. So this allows you to adjust the control valve or pump based on the actual flow measurement. And this is ideal for highly accurate dosing and minimal additive waste.
• Improved Quality Control: with this, you know exactly what you’re dosing. And this is important in certain industries where you have to keep accurate records. Also, it can help reduce product rejections.
• No PLC/PC Necessary: peak flows and back flows are included in the measurement, without the need for a PLC/PC. And this results in an extremely compact solution.