Burkert 8626 Instructions De Service page 46

Problem
Process value varies No porper FE connection
Controller tends to
oscillate
Setpoint value w = 0,
flow still present after
a few seconds
Setpoint value w = 0,
valve closed, no flow;
but process value
output shows a small
flow
Controller shows
strong overswing
starting after a step
in the setpoint of 0%.
In the case of flame
control, the flame
extinguishes after a
step in the setpoint.
46 - MFC/MFM
Possible cause
Controller must
continuously correct
disturbances in an unstable
pressure supply.
Residual ripple of supply
voltage too high.
Operating pressure lies far
above that at which the last
Autotune was executed.
Control parameters do not
correspond to the section
behaviour.
A medium is being used
other than that intended on
calibration.
Residual ripple of supply
voltage too high.
Operating pressure above
the leak-tight pressure of
the proportional valve.
Operating pressure
significantly higher than
that used for calibration
(→ increased intrinsic con-
vection, only with 8716 and
8626)
Incorrect installation
position
(→ increased intrinsic con-
vection, only with 8716 and
8626)
A medium is being used
other than that intended on
calibration.
On using an aditional
isolation valve, the drive
sequence was not adhered
to.
Flame is starved of oxygen
because medium
concentration too high.
Remedy
Connect the FE to the earthing
point (as short as possible,
wires min. 2.5 mm²).
Install a suitable pressure
regulator upstream.
Select a suitable voltage
source.
Execute an Autotune to adapt
to the operating conditions.
Adapt the control dynamics
with the PC software
MassFlowCommunicator.
Return the device to the
manufacturer for recalibration
for the operating medium.
Select a suitable voltage
source.
Lower the operating pressure.
Execute an Autotune to adapt
to the operating conditions.
Install the MFC in the position
calibrated or execute an
Autotune to adapt to the
operating conditions.
Return the device to the
manufacturer for recalibration
for the operating medium.
See Section Operation with an
Additional Isolation Valve.
Activate the ramp function with
the PC software
MassFlowCommunicator.