86
9.6
Troubleshooting
Operational errors may be caused by:
–
The
process
medium
–
The installation
–
The measuring system
Most frequently, errors occur in the measuring system when it is installed and switched on for
the first time. They are normally due to incorrect installation of the primary head.
When the measuring system is switched on and the converter's self-test has been carried out
(Display message 'TEST') the message 'STARTUP' is displayed. During this time, the
converter tries to activate the primary head. Usually, the desired value for the oscillation
amplitude is reached after a few seconds and the converter starts displaying mass flow.
However, if the display is flashing, the system cannot enter the measuring mode. The problem
is signalled by the arrow to 'Status' on the front plate.
First of all, it is advisable to inspect the installation to determine if it was installed in
compliance with the installation instructions. If this is the case, then the following steps should
be taken for localising the fault :
If the primary head is not installed in a vertical position, increase the flush period and flow rate
in order to remove air bubbles and solid materials from the primary head.
If the primary head starts to oscillate, but the measured values are erratic or the primary head
keeps returning to STARTUP, then the possible cause of the trouble could be:
1.
Poor installation causing an excessively high installation factor.
2.
Bad zero calibration.
Monitor the primary head's INSTAL.FACT using Fct. 2.7.4. If the reading is high, (see Section
2) then this indicates either poor meter clamping or excessive gas in the process fluid. For
horizontally installed systems, flush the meter at a high flow rate to remove any air bubbles
that may have collected. Shut off the flow and recheck the drive level. If the drive reading is
still high, check that the meter has been installed and clamped correctly. In a poor installation,
drive power is wasted in transmitting vibrations to the attached pipe work, and this greatly
degrades meter performance. As a general guide, the clamping should be adjusted as
described in the installation manual.
Sympathetic vibrations, which are transmitted to the primary head via the floor or the pipe
system, can lead to an unstable zero point. This can cause the mass totalizer to “creep” with
time, even when the flow is shut off.
Another reason for an increase in the display of the flow rate is due to calibrating the zero
point with a non-zero flow rate. In this case, make sure that the shutoff valves are completely
closed and then re-calibrate the zero point.
Problems occurring during the measuring process
During operation the system is continually checking itself and its measured values against
various conditions. If one or more of these conditions are broken, then the system indicates
that a problem has occurred and various messages are stored in an internal message list.
Whenever a new problem is found the display starts to flash and the status arrow is lit,
drawing the operator's attention to the problem. The display will continue to flash indefinitely
until the operator acknowledges the warnings.
