Bronkhorst®
Instruction Manual MI Series Industrial mini CORI-FLOW™
9.17.120A
16
3
Operation
After correct installation and taking all necessary safety precautions, the mini CORI-FLOW™ can be used to measure and/or
control the required flow rates.
3.1
Powering up and powering down
·
It is recommended to turn on power before applying fluid pressure and to switch off power only after relieving fluid
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.
When applying pressure, avoid pressure shocks and bring the fluid system gradually up to the level of the specified
operating conditions; open and close the fluid supply gently.
3.2
First use
Adequate mass flow measurement is only possible if the fluid flows through the instrument in a single state (either gas or
liquid). To prevent so called 'slug flow' (two-phase flow) at start-up, take the following measures before starting
measurement and control:
·
for liquid applications, expel (dissolved) gas from the system, by flushing the instrument and all fluid lines with the
process fluid at a relatively high flow rate
·
for gas applications, expel condensation from the system, by purging the instrument and all fluid lines with a dry gas at
a relatively high flow rate
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.
The very first time the instrument is used, adjusting the zero point is recommended. See
background information and instructions.
3.3
Valve Safe State
When a controlling instrument is not powered, the control valve automatically returns to its default state (also called Safe
State), which is closed for a 'normally closed' valve (n/c) and fully open for a 'normally open' valve (n/o). To protect the
system, certain events (such as communication errors) may cause the instrument to switch to Valve Safe State (see also
).
Check the serial number label or the technical specifications to see which valve type is used on your instrument (if
applicable).
3.4
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.
3.5
Temperature considerations
Although the mini CORI-FLOW™ has excellent temperature stability, the best accuracy is achieved when temperature
gradients within and across the instrument are avoided. Take the following guidelines into account:
