9
7. MAINTENANCE
7.1 Fault finding during commissioning
If the BA304D fails to function during
commissioning the following procedure should be
followed:
Symptom Cause Solution
No display
Incorrect
There should be 1V
wiring
between terminals 1 &
3 with terminal 1
positive.
No display
Incorrect
Check that a current
and no volts
wiring or
is flowing in the loop.
between no
power
terminals 1
supply.
and 3.
Insufficient
Check supply voltage
loop voltage and voltage drops
to operate
caused by all
BA304D.
components in the
loop.
BA304D
Positive
The BA304D has been
displays 1
over-range
incorrectly calibrated &
is trying to display a
number greater than
1999.
BA304D
Negative
The BA304D has been
displays -1
over-range
incorrectly calibrated &
is trying to display a
number less than
-1999.
Unstable
4/20mA input Check loop supply
display
has a large
voltage.
ripple.
7.2 Fault finding after commissioning
ENSURE PLANT SAFETY BEFORE
STARTING MAINTENANCE
Live maintenance is permitted on
intrinsically safe equipment installed in a
hazardous area, but only certified test
equipment should be used unless a gas
clearance certificate is available.
If a BA304D fails after it has been functioning
correctly, the following table may help to identify
the cause of the failure.
Symptom Cause Solution
No display
No power
Check that a current
and no volts
supply
is flowing in the loop.
between
terminals 1
and 3
Unstable
4/20mA
Check loop supply
display
input has a
voltage.
large ripple
If this procedure does not reveal the cause of the
fault, it is recommended that the instrument is
replaced. Alternatively the electronic display
assembly may be exchanged as described in
section 7.3
7.3 Servicing
We recommend that faulty instruments
and instrument assemblies are returned
to BEKA associates or to your local
agent for repair.
Electronic components must not be
replaced or repaired on site.
To simplify servicing all BA304D indicators use a
common display assembly. Depending upon the
accessories fitted, one spare display assembly
may be used to replace any BA304D which fails.
The exchange may be made without disconnecting
the 4/20mA loop which will continue to function,
but the indicator voltage drop will increase from 1V
to 4V without the display assembly.
To exchange the indicator assembly remove the
terminal cover by unscrewing the two 'A' screws
which will reveal two concealed 'D' screws - see
Fig 4. Unscrew all four 'D' screws and carefully lift
off the instrument front. The instrument assembly
is secured by three Pozi headed screws which
should be removed. If the instrument is fitted with
a backlight the fly-lead connecting it to the
terminals must be unplugged. The replacement
display assembly may then be installed and the
enclosure reassembled.
If after replacement of the display assembly the
instrument still does not function, it is likely that the
fault is within the protection components on the
terminal assembly. Terminal assemblies may be
replaced on site providing instruments with a
backlight are fitted with a replacement board
including terminals 12 and 13.
