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> Introduction
Bronkhorst High-Tech B.V. manufactures the largest variety of
thermal Mass Flow Meters and Controllers for gases and liquids.
The L10/L20/L30 Series Mass Flow Meters of the LIQUI-FLOW
Series are compact, modular instruments for capacities from
0,1...5 g/h up to 0,4...20 kg/h. The CORI-FLOW product range
offers a range from 200 g/h up to 600 kg/h. Both LIQUI-FLOW
and CORI-FLOW instruments can be combined with integrated
or separate control valves. This leaflet describes an alternative
way of liquid flow control, i.e. by using a close-coupled pump.
> Control valve or controlled pump ?
The concept of using a straight forward Mass Flow Controller is
simple and economical. It requires a certain head pressure, which
can be achieved by pressurising a vessel filled with liquid, for
instance by using an inert gas blanket. In some applications this
method is not possible or not recommended. The alternative of using
a pump for fluid transfer seems logical, but was not always advisable
because of the pulsating flow pattern of most low-flow pumps.
> Liquid Dosing Systems
Bronkhorst offers Liquid Dosing Systems to cover their liquid flow
range of 20 mg/h up to 600 kg/h. Each Liquid Dosing System
consists of a flow sensor of the LIQUI-FLOW or CORI-FLOW
series with controlling function, a gear pump, a filter, a check
valve and all interconnecting material. Furthermore, Bronkhorst
will take care of electrical and mechanical connection, testing
and optimization including the PID-integrated controller.
In addition to the Bronkhorst LIQUI-FLOW Pump for small flow
ranges, a complete series of pumps is available for those
applications which require higher flow rates, higher pressures,
wide control ranges or aggressive fluids. Further to operation in
analog mode, the system can also be used digitally with RS232
or with an on-board interface to Profibus-DP, DeviceNet,
Modbus-RTU or FLOW-BUS.
> Low Flow Liquid Pump
The new Bronkhorst LIQUI-FLOW Pump unit has a rotary
positive-displacement pump, which is virtually pulsation-free.
It can easily be applied for low-viscosity fluids in a control loop with
a LIQUI-FLOW Mass Flow Meter, using the standard controller
function on its pc-board. Currently the LIQUI-FLOW pumps can be
offered in the ranges of 10500 g/h, 201000 g/h and 804000 g/h.
> Features
Simple and compact assembly; easy to use
No need to pressurise liquid source
Pump controlled by mass flow instrument with adjustable
PID-controller via voltage output signal
Direct mass flow measurement/control (not volumetric)
High accuracy and stability (nearly pulse free)
Desired flow to be set via: analog 05(10) V / 0(4)...20 mA
or digital communication by RS232 or fieldbus
> Applications
Liquid Dosing Systems offer precise, automated mass
flow control of reactants, additives or catalysts in:
Analytical laboratories and systems
Chemical industry
Petrochemical and Offshore industry
Food and Pharmaceutical industry
Energy (fuel cells)
Liquid Dosing Systems
Using flow meter controlled pumps
