4
INS/ANAINST/025-EN Rev. B
| Navigator ADS551 | Low level dissolved oxygen | Replacement / Upgrade procedures – wet section spares
6 Replacement procedures
6.1 Replacing the flowcell PCB housing gasket,
PCB housing cover and PCB
Part numbers:
— AW502 228 flowcell PCB housing gasket
— AW502 227 flowcell PCB housing cover
— AW502 225 PCB assembly
Referring to Fig. 6.1:
1.
Remove and retain 4 flowcell PCB cover fixing screws and
washers
A
and remove PCB cover
B
.
2.
Remove flowcell PCB housing gasket
C
. If replacing the
gasket, discard.
3.
If replacing PCB assembly
D
, disconnect all cables
from the terminal block on the PCB assembly, loosen all
cable glands then remove cables.
It is necessary to partially remove the glands, blanking
plugs and the LLDO connector to remove PCB assembly
D
.
4.
Remove and retain 2 PCB fixing screws and fibre washers
E
and remove PCB assembly
D
. Take care not to lose
2 spacers
F
fitted on the screw threads behind the PCB
assembly.
5.
Carefully offer PCB assembly
D
up into the flowcell PCB
housing and tighten 2 PCB fixing screws.
6.
Remake cable connections (disconnected at step 3) – refer
to Fig. 6.2 and Table 6.1 for terminal connections.
7.
Tighten the cable glands, plugs and LLDO connector into
the flowcell PCB housing to ensure a watertight seal.
8.
Refit, or for new items, fit flowcell PCB housing gasket
C
and cover
B
using 4 PCB cover fixing screws and
washers
A
. (Ensure flowcell PCB gasket
C
is located
correctly.)
IMPORTANT (NOTE)
To secure the new PCB into the flowcell PCB
housing, pass 2 PCB fixing screws and fibre
washers
E
through the PCB mounting holes, fit
the spacers
F
onto the screw threads.
Fig. 6.1 Replacing the flowcell PCB housing gasket, PCB housing and PCB
Fig. 6.2 Cable connections to transmitter – ADS551
Cable
Color
Terminal
block ID
Description
Serial
White
TB1
Data –ve
Green
Data +ve
Screen
Screen
Black 0
V
Red
24 V
Drain valve
Red
TB3
+ve
Black
–ve
Temp sensor
White
TB5
Pt1000
Screen
Pt1000
LLDO sensor
Red
TB4
+ve LLDO sensor
Blue
–ve LLDO sensor
Flowmeter
Red
TB2
+ve
Brown
GND
Black
–ve
Table 6.1 Cable connections to transmitter – ADS551
B
C
A
D
E
F
TB1
TB3
TB5
TB4
TB2
White
Serial (Tx)
cable
Drain valve
cable
Temp sensor
cable
LLDO
cable
Flow-
meter
cable
Green
Screen
Red
Black
Red
Black
White
Screen
Red
Blue Red Brown Black
