Description; Model 6553 Purge Gas Monitor; Range Display - ABB 6553 Series Instruction Manual

2 DESCRIPTION

All the various system options consist of one or more of the
following units with the further option of fitting the monitor and
power supply units in a cubicle. Specific information relating to
a cubicle option will be supplied separately.

2.1 Model 6553 Purge Gas Monitor

The Purge Gas Monitor is a Unit suitable for panel mounting or
in a control cubicle in the safe area. The various monitor
options use one or two digital displays with protected access
for zero adjustments and may also have a range selector
switch or switches - see Fig. 2.1.
1 2
3
Range
Switches
1 2
3
Kent-Taylor
Purge Gas Monitor
Fig. 2.1 Model 6553 Gas monitor

2.1.1 Range Display

A selector switch for each display provides independent
parameter selection as follows:
Position (1) Percentage of Hydrogen in Air by volume.
This is the hydrogen purity measurement of the
coolant gas under normal operation of the
system. The display covers a range of 85 to
100% or 80 to 100% hydrogen in air depending
on the range selected. Alarm output and a value
retransmission signal (4 to 20 mA) are provided
for this switch position only.
Position (2) Percentage of Hydrogen in Carbon Dioxide by
volume.
This range is for use in hydrogen purging
operation. Alarm and retransmission signal are
inhibited in this switch position.
Position (3) Percentage of Air in Carbon Dioxide by volume.
This range is for use in carbon dioxide purging
operation. Alarm and retransmission signal are
inhibited in this switch position.
A further option of providing remote indication of range
selector switch may be available dependent on the number of
alarms specified.
95.0
Remote
%H2 IN AIR
Zero
Adjustment
95.0
%H2 IN AIR
The Model 4689 displays are dedicated variants of the
Company's Model 4600 Series Indicator/Controllers. With this
special variant (4689), the displays and alarm indicators on the
front panel remain the same but software control is specific to the
Katharometer systems. The relay action of the alarms is fixed as
'fail safe'. All user programmable data can be protected from
unauthorized alteration by a programmable 5-digit security
number.
The zero adjustments on the front panel of the monitor allow
remote zeroing of the katharometers in the hazardous area. The
adjustment access for a particular display is adjacent to the
display and at the same level.
The monitor unit has a protective case which can be removed for
access to the interior without removing the whole monitor unit
from the katharometer panel.
The monitor also contains encapsulated zener barrier units to
limit the electrical energy level that can be applied from the
instrument circuits into the hazardous area. These zener barrier
units are located below the display units, on a bus-bar which
MUST be earthed (grounded). A metal screening arrangement
segregates the connections made to equipment in the
hazardous area. A main fuse is fitted inside the monitor case for
the electricity supply line.
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