Yokogawa AXFA14G/C - Manual (Page 101)

IM 01E20C02-01E 10-5
10. MAINTENANCE
10.3.2 Unstable Zero
START
Check for the presence of valve
leakage.
• Confirm the flowmeter grounding.
• Confirm whether or not the
grounding wire is disconnected
from the earth flange.
Recheck the fluid to be measured.
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.
Install a defoaming device on the
flowtube’s upstream side.
Replace the valve(s).
Completely ground the converter and
flowtube (Refer to the section on
grounding in the relevant user’s manual.)
• 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.
Provide the meter with sufficient
shielding or move it away from the
electrical equipment.
NO
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
YES
YES
YES
Are there bubbles
in the fluid?
Are valves leaking?
Is the fluid likely to
contain deposits?
• Does the fluid’s
conductivity vary?
• Is the fluid conductivity
within the limits?
Is the flowtube
completely full of fluid?
Is the flowmeter properly
grounded?
Contact a service center.
*1: When checking for bubbles, it is
convenient if there is a gas vent hole
on the flowtube’s downstream side.
*1
Investigate whether or not the flowtube
is filled with fluid and that it is free of
bubbles.
Is the flowmeter
located near motors, transformers,
or electric equipment?
F1009.EPS