PRECISE AND EXTREMELY COMPACT PUMP CONTROL

Mini Coriolis Mass Flowmeter as a compact mass flow controller. In process engineering, whilst measurement and control often belong together these two tasks are usually realised separately. A new compact flow meter/controller for gases or liquids capable of flow rates down to as little as 0.1 grams per hour offers both the specifier and the end-user a saving in engineering time, the number of components and commissioning time therefore ultimately saving cost.

Whether investigating the requirements for batch dosing, pump monitoring or valve control technology, clients often find that the engineering costs for small-scale measurement are relatively high when compared with the instrumentation required for larger systems. Bronkhorst have been focusing their attention on this for a number of years and can provide mass flow meters / controllers for such applications, either based on Thermal sensors or Coriolis principle devices, which are configured as Mass flow control systems. These compact units consist of a flow meter together with either an integrated or external valve or together with a standard pump, utilizing gear, diaphragm, peristaltic, etc designs which, together, form a tailor-made compact and guaranteed solution to a given application.

For Bronkhorst, the direct measurement of the mass flow rather than the more commonly used volumetric flow rate, is primarily about accuracy. Other measurement principles determine mass per unit of real-time indirectly by such methods as converting flow velocity, by retrospective gravimetric analysis, by calculating from differential pressure and by converting from a measured volumetric flow rate. Each of these can be influenced by process variables, such as pressure and temperature fluctuation, and hence can result in significant errors. However with direct, real-time, mass measurement – either latest generation Thermal or Coriolis principle – the measurement signal is more accurately based on only the actual mass flow rate.

For over 30 years, and with constant technological update, Bronkhorst has been supplying LIQUI-FLOW™ and EL-FLOW® mass flow meters/controllers based on thermal principles. Whilst these designs are tried and tested over these many years, and over a broad spectrum of gas and liquid applications, there is still in truth one challenge that remains: the measurement principle is dependent on the medium to be measured. For example, as the thermal capacity of a fluid changes in proximity to vapour pressure, supercritical media cannot be recorded using thermal sensors. An alternative solution is offered in the form of the Coriolis principle whereby the measurement signal only depends on the mass flow and not on the properties of the fluid to be measured. There are numerous possible applications, a few typical examples of which are given below:

*    Mass flow control applications in Pharmaceuticals, Medical, Chemical, Food additives or odorants.
*    Microreactor technology.
*    The measurement and control of Supercritical fluids.
*    The control and measurement for batch processes.
*    The dosing of highly reactive fluids.
*    The measurement or control of unknown fluids or mixtures.
*    Master / Slave proportional dosing applications.

Over the past decade, Bronkhorst CORI-FLOW™ has provided a mass flow meter for fluids and gases that can be used to measure flow rates ranging from 200 g to many thousands of kg/h. The new mini CORI-FLOW™ has significantly reduced this lower limit even further, while the physical size of the device has also been reduced considerably. Available in three models, the devices can measure flow rates from 0.1 g/h to 30 kg/h with a measuring accuracy of 0.2 %(Rd) for fluids, 0.5 % (Rd) for gases. In addition to the Mass flow rate, the mini CORI-FLOW™ also measures the process temperature and density. “The aim of the design process was to develop a compact cost-effective device for measuring and controlling very low flow rates with a high level of precision”, explains David Bowers, Coriolis Product Manager for Bronkhorst UK Limited.

Key benefits to your application
*    Direct measurement of mass flow using the Coriolis principle, characterised by a high level of accuracy independent of the fluid properties.
*    Mass Flow, Temperature and Density measurements all available from one device.
*    Many of the errors that can occur during the configuration and design of control systems are avoided due to the use of pre-configured compact and guaranteed Bronkhorst Mass Flow Controllers.
*    Bronkhorst software comprising of configurable PID control, counter and batch functions, Proportional Master / Slave control with configurable ratio, Alarm output functions, Real time data acquisition writable to excel spreadsheet.
*    Low cost of ownership and compact sized.
*    “First time right” batch (no overrun correction required)
*    Peak to peak measurement of peristaltic flow
*    Fast and Precise PID control of pump or valve (configurable to end-users required control response).
*    Continuous process for dosing thereby saving time when compared against weight scale measurement.

New sensor technology ensures zero-point stability

The Bronkhorst mini CORI-FLOW™ has a single-tube assembly designed as a rectangular sensor with a small internal volume. The flow tube is excited by being magnetically activated and the flow tube distortion caused by the Coriolis Effect is optically scanned. As a result the zero-point stability, which is so crucial for accuracy, is much enhanced with the M12 model (0.1 to 200 g/h) achieving a performance of less than 0.02 g/h. In addition, the enhanced design of the sensor ensures less sensitivity to external vibrations, thereby enabling pumps and valves to be installed in extremely compact spaces along with the sensor. In applications for which a Thermal mass flow meter has been used previously, mini CORI-FLOW™ devices can now be used as an alternative because their process connections, electrical hook-up and dimensions in respect of the Thermal meters/controllers are so similar.

Using the integrated optional CORI-FILL™ technology, the Coriolis meter’s totalizer is capable of highly accurate batch dosage. It also ensures the actuator will react immediately once the batch limit has been reached. Commonly several components would be required to achieve this, however, CORI-FILL™ offers all this functionality in one component, one assembly and from one supplier, without the need of complex programming. CORI-FILL™ has been successfully applied for dosage of additives, fragrances, flavours, colorants and sterilization fluid (H2O2).

Temperature ºC
Zero stability and reproducibility of mini CORI-FLOW™ model M13

Engineering costs reduced

Bronkhorst Coriolis Mass flow controllers are available pre-configured and complete with either a pump or a valve, thereby reducing end-user / specifier engineering time (and money) and providing a “single point responsibility” during commissioning. “This has provided us with a huge market and has also brought a significant benefit for the end-user compared with conventional solutions”, says David Bowers as he explains the increasing demand for such solutions. “Our ethos is to work as a close partner to our customer and our software tools add real value to the smaller, but important, details such as pressure losses and variations in the physical state of the fluid which must be taken into account when selecting valves and pumps” he adds. Additionally, our experience in the use of gear, peristaltic and diaphragm pumps as integrated units means that a compact system can be installed in areas where space is at a premium. For valve control systems, the mass flow meter can be supplied either with an integrated valve with flush connection suitable for aggressive fluids or with a separate external valve. The design process is made easier by the CoriCalc™ software tool which can be used to calculate pressure losses, select sensors and configure valves, as well as to calculate in mass or volumetric flow units, to show detailed information about the accuracy and whether the fluid is in the gaseous or the liquid phase.

Mini-CORIOLIS DEVICE

Measurement and control in compact spaces even with the most sensitive measurement range

*    The mini CORI-FLOW™ is a compact flow meter / controller for mass flows ranging from 0.1 g/h to 30 kg/h.
*    The principle of measurement offers independence from fluid properties.
*    The device has the same design “footprint” as the widely used “Thermal principle” mass flow meters and controllers.
*    The end-user can adjust the Full Scale measurement range (measurement range span of up to 1:2000) using Bronkhorst software or plug-in BRIGHT™ colour display.
*    The combination of controller with either a valve or pump enables the precise control of dosing processes.
*    Density and Temperature is provided as an additional measurement both digital and (optional) analogue output.
*    Optional fieldbus such as; Profibus-DP®, DeviceNet™, Modbus-RTU, FLOW-BUS.