Bronkhorst®
Instruction Manual EL-FLOW® Select
9.17.099J
20
3
Operation
After correct installation of the
EL-FLOW® Select
and when all safety precautions have been taken into account, the
instrument can be used for measuring and/or controlling mass flow in the system.
3.1
Powering up and powering down
To maintain control of the fluid system and ensure a safe situation, it is recommended to turn on power before applying
fluid pressure and to switch off power only after the fluid system is depressurized.
When pressurizing, prevent pressure shocks by gradually bringing the fluid system to the required operating pressure.
For best performance, allow the device to warm up and stabilize for at least 30 minutes before starting measurement
and/or control. This may be done with or without media flow.
3.2
First use
In systems for use with corrosive or reactive media, purging for at least 30 minutes with a dry, inert gas (like Nitrogen or
Argon) is absolutely necessary before use. After use with corrosive, reactive or hazardous media (e.g. toxic or flammable),
purging is also necessary before the fluid system is exposed to air.
If the instrument is mounted in a position with upward or downward flow, adjusting the zero point is advised before using
the instrument for the first time. See
for background information and instructions.
3.3
Mass flow measurement and control
When powering up, the instrument needs a couple of seconds
to start up the electronics. As soon as the start-up sequence
has finished (green LED glows continuously), the instrument is
ready to measure mass flows, however, optimal accuracy is
only reached after warming up (see
).
After powering up, the control valve closes (normally open) or
stays closed (normally closed). The valve stays closed until the
instrument receives a setpoint from the active setpoint source.
The internal PID controller then immediately opens the control
valve, until the measured flow rate matches the setpoint. It
maintains the resulting flow rate until another setpoint is
given.
EL-FLOW® Select
instruments 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™ 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
).
Although
EL-FLOW® Select
instruments have excellent temperature stability, the best accuracy is achieved when
temperature gradients across the instruments are avoided. Make sure that the gas temperature matches the ambient
temperature as good as possible and mount the instruments on a rigid (heat conducting) surface.
EL-FLOW® Select
instruments 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 instrument and avoid installing multiple instruments or control valves in close proximity to
another with small volume piping in between.
