User's Manual AXF Magnetic Flowmeter Integral ... - Yokogawa

5. MAINTENANCE
5.8.2 Unstable Zero
START
Investigate whether or not the flowtube
is filled with fluid and that it is free of
bubbles.
YES
*1
Is the flowtube
completely full of fluid?
NO
*1: When checking for bubbles, it is
convenient if there is a gas vent hole
on the flowtube’s downstream side.
Particular care must be taken in the case
of horizontal mounting. In order to ensure
complete filling of the tube, either adjust
the mounting position or switch to vertical
mounting.
Are there bubbles
in the fluid?
NO
YES
Install a defoaming device on the
flowtube’s upstream side.
Check for the presence of valve
leakage.
Are valves leaking?
YES
Replace the valve(s).
NO
• Confirm the flowmeter grounding.
• Confirm whether or not the
grounding wire is disconnected
from the earth flange.
Is the flowmeter properly
grounded?
YES
Recheck the fluid to be measured.
NO
Completely ground the converter and
flowtube (Refer to the section on
grounding in the relevant user's manual.)
• Does the fluid’s
conductivity vary?
• Is the fluid conductivity
within the limits?
NO
Is the fluid likely to
contain deposits?
NO
YES
YES
• Ensure that the fluid’s conductivity
changes as little as possible.
• Do not use the meter when fluid
conductivity is out of limits.
• Whenever possible, reduce the flow
velocity to being in the vicinity of the
lower conductivity limit.
• Remove dirt and scale of and near
electrodes.
• Use a soft brush or cloth to perform
scale removal, and make sure that
the lining is not damaged.
Is the flowmeter
located near motors, transformers,
or electric equipment?
NO
YES
Provide the meter with sufficient
shielding or move it away from the
electrical equipment
Contact a service center.
F0522.EPS
5-13
IM 01E20D01-01E