We offer the widest product range of low-flow (mass) flow meters and controllers on the market. Numerous styles of both standard and bespoke instruments can be offered for applications in laboratory, machinery, industry and hazardous areas.
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Bronkhorst instruments are used for numerous applications in many different markets. In this section you will find an overview of the main markets for our equipment, illustrated with some typical examples of applications.
Are you looking for technical documentation, are you interested to learn more about the measuring principles of Bronkhorst products, or you do want to get in contact with a Bronkhorst Service Engineer? This section will guide you to the relevant service & support topics.
Bronkhorst High-Tech BV the leaders in Mass Flow Meter / Mass Flow Controller technology for gases and liquids, Pressure Controllers and Evaporation Systems.
As you might remember from reading the first part of this blog series, for (ultra) low liquid flows, tiny disturbances in the process or ambient conditions can have a large impact on flow stability. This second blog aims to help users of low-flow fluid systems optimise the stability and performance of their system, by giving tips and recommendations for dimensioning, choice of material and best practice procedures, based on years of experience, gathered by Bronkhorst High-Tech.
The core of the low-flow fluid system is obviously a liquid flow meter/controller. Deciding which instrument type is best for the low-flow application largely depends on accuracy and stability requirements. However, ambient or media conditions which are difficult to control can also play an important role in choosing the best solution.
Within the Bronkhorst range of products, some thermal and Coriolis flow devices are particularly suitable for (ultra) low liquid flow applications. The different working principles for thermal and Coriolis devices make them specifically suitable for different applications, requirements and conditions. In thermal-based mass flow devices, a constant temperature difference is created between two positions along a (capillary) tube. When liquid flows through this tube, the energy needed to maintain this temperature difference is proportional to the mass flow rate.
Read more about the thermal-based mass flow measurement working principle.
In the Coriolis setup, the liquid flow through a tube with a small diameter causes this tube to twist, and the change in deflection is a direct measure of the mass flow through the tube. Moreover, the resulting change in vibration frequency of the (filled) tube is proportional to the medium density.
Read more about the Coriolis mass flow measurement principle
Bearing in mind the above information, please read and observe the following tips with respect to low liquid flows:
The Bronkhorst website offers a product selector tool to help you choose the right low liquid flow meter or controller based on input parameters such as maximum (mass or volumetric) mass flow rate, operating pressure and operating temperature.
Thermal-based μ-FLOW and LIQUI-FLOW devices can handle liquids up to 2 g/h resp. 0.25 to 5 g/h in the lowest range. Coriolis-based mini CORI-FLOW ML120 mass flow meters have 200 g/h as their maximum full scale flow rate but can be easily scaled down to a minimum full scale flow rate of 5 g/h, with the same relative accuracy. They also have a minimum flow rate of 50 mg/h.
A highly stable inlet pressure of a flow controller is a prerequisite for a stable low liquid flow rate. Two methods are popular to achieve this: use a pressure vessel where gas is used to pressurise the liquid or use a pump. Please refer to parts 3 and 4 of this series of blogs for more background details.
Air or other gas bubbles dissolved in the liquid, or moving along the liquid flow, have a negative effect on the flow stability. To this end:
The quick response time, low internal volume and low heat generation of piezo valves are especially advantageous when using gas to pressurise the liquid. For an operating pressure higher than 5 bars, solenoid valves are an alternative. Preferably install the meter part of the flow controller between the valve and the process.
This is to help minimise filling times and to limit external disturbances. For this purpose:
This is especially important for skids. First connect all instruments and then de-aerate before starting to control or measure. To this end, the Bronkhorst skids contain a purge setting.
In the next parts of the blog series, we will focus on low liquid flow supply using a pressure vessel or a pump and give more background details on how to manage external conditions. After all, choosing a good flow device is important, but insight into how this influences the application process is equally essential.
As indicated in this blog, a highly stable inlet pressure in a flow controller is necessary to obtain a stable low liquid flow rate. In part 3, we will share tips on how to provide a stable inlet pressure to the liquid system. Read our blog about this in March!