Bürkert’s new mass flow controller for low volume achieves high accuracy with any liquid

03 December, 2020

The Type 8756 is aimed at OEM integration and can control or measure an extremely wide variety of liquids, whether aggressive or neutral, for small quantity applications ranging from chemical injection to food & beverage flavourings.

A minimum measurable flow rate of 0.01 kg/h can be set up to a maximum of 25 kg/h with a high measuring range of 1:300, and the MFC/M also measures liquid density and temperature. Minimal calibration is required when controlling or measuring liquids with different viscosities, which saves time in set-up and the accuracy of readings is maintained. Liquids with viscosities up to 200 mPas can be measured, or higher on request.

Highest level of accuracy

Bürkert reports that the Type 8756’s Coriolis sensor provides the highest level of accuracy of flow measurement, achieving +/- 0.2% of the measured value at 0.0014 kg/h. This is combined with high repeatability with +/- 0.1% of the measured value at 0.007 kg/h and a fast measurement response time of

Bürkert comments that unlike various competing measuring principles, the Coriolis sensor does not require a set inlet or outlet section before or after the device to guarantee acuracy. The most significant advantage is claimed to be that the Coriolis measurement principle measures the true mass flow of a liquid and is not influenced by changing temperature or pressure conditions. In addition to the mass flow rate, the temperature & density of the medium are measured simultaneously. This system also means that the MFC/M is maintenance and wear free. 316L stainless steel construction of the MFC/M body and sensor also ensures resistance to corrosive substances.

The Coriolis principle is based on the continuous measurement of the phase shift of tube oscillation caused by the liquid which flows through it. The phase shift is proportional to the mass flow of the medium and is converted into a signal. The system comprises a thin S-shaped measuring tube, which is set in vibration by an external exciter coil. The high frequency measuring tube vibrates freely between two fixed points with the changing vibration, caused by the medium flowing through it, signifying the phase shift.

As a mass flow controller, the Type 8756 is designed for dosing of small quantities of typically expensive liquids conveyed from an unpressurised container. High precision dosing is achieved with a micro annular gear pump with a lowest flow rate of 50 µl, which provides extremely low pulsations across a very large control range. The pump is self-priming and is hermetically sealed.

For pharmaceutical applications, the Type 8756 MFC/M achieves FDA – Code of Federal Regulations Title 21 Paragraph 177 (CFR 21 177.2600) and accreditations also include USP Class VI chapter 87 in vitro and 88 in vivo, Implantation and Regulation (EG) No. 1935/2004 about materials and articles intended to come into contact with foodstuffs. Additional accreditations can be provided on request.

Communication with the process control infrastructure takes place via CANopen or CANopen-based büS as well as an analogue option. Configuration and diagnostics are easily implemented by the Bürkert Communicator software tool, which is available as a free download.

Image caption -  According to Bürkert , the Type 8756 provides high precision and repeatability for small quantities of virtually any liquid.

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