Bronkhorst EL-FLOW Prestige - Manual (Page 13)

Bronkhorst High-Tech B.V.
EL-FLOW Prestige 13 9.17.084
3 Basic operation
3.1 Mass flow measurement and control
After correct installation of the EL-FLOW Prestige Mass Flow Meter (MFM) or Mass Flow Controller (MFC) and when all safety
precautions have been taken into account (see chapter 2) the instrument can immediately be used for measuring/ controlling the
required flow rate in the system by means of the selected communication interface(s).
Here are some general guidelines for mass flow measurement/control:
EL-FLOW Prestige MFMs/MFCs are most accurate at the specified inlet/outlet pressure, temperature and process gas
conditions, however the instrument will function properly in a wide range of varying conditions. It is strongly advised to
use the FlowTune TM software available with the instrument to set the correct process conditions if the actual process
conditions differ from the conditions for which the instrument is set (see section 3.1.1).
Although EL-FLOW Prestige MFMs/MFCs have excellent temperature stability, the best accuracy is achieved when
temperature gradients across the instruments are avoided; so make sure that the gas temperature equals the ambient
temperature and mount the instruments on a rigid (heat conducting) surface.
EL-FLOW Prestige MFCs handle pressure shocks in the system well, but are not insensitive to pressure fluctuations. For
optimum control stability, provide a stable (pressure controlled) inlet pressure with sufficient buffer volume between
the pressure regulator and the MFC and avoid installing multiple MFCs or other control valves in close proximity to
another with small volume piping in between.
Mass Flow control
When an MFC (either with normally closed (n.c.) or normally
opened (n.o.) valve) is hooked-up, the control valve closes
when no setpoint is given. When the MFC receives a setpoint from
the active setpoint source, the internal PID controller will
immediately open the control valve until the required flow rate is
achieved and it will maintain that flow rate until another setpoint
is given.
3.1.1 Changing fluidset, range or operating conditions
When the EL-FLOW Prestige instrument is used for other processes/conditions than indicated on the instrument label, use the
FlowTune TM software for setting the instrument for the required conditions. With FlowTune the following settings can be changed:
Store up to eight different fluid sets
Select one of 25 pre-installed gases per fluidset or compose any
mixture consisting of these gases
Insert fluid properties for any other gas/mixture per fluidset
Change inlet- and/or outlet pressure according to actual process
conditions
Re-range the full scale (FS) flow rate within the instrument's
accepted flow range
Change the control speed per fluidset for faster or slower
(smoother) flow control