Table of Contents
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1 INTRODUCTION
1.1 Description
The Model 8237 Carbon Dioxide Monitor is a microprocessor
based analyser using a gas sensing membrane probe to monitor
the level of CO
in cooling water samples in AGR Nuclear Power
2
Stations.
1.2 Training
Due to the specialised nature of the above instrument, it is
recommended that, where the end users personnel have had no
previous experience of maintaining this equipment, training be
provided by this Company.
Such training is available via the local Company in the UK, or
Overseas Agent elsewhere and may be carried out either on the
users premises or at the factory.
1.3 Location and Function of Main Components –
Fig. 1.1
Monitoring of carbon dioxide involves the addition of an acid
reagent to liberate bicarbonate ions in the sample as carbon
dioxide gas. The gas sensing probe responds to the partial
pressure and hence the concentration of carbon dioxide gas.
The 8237 carbon dioxide monitor has a liquid handling section in
the lower half of a moulded plastic enclosure, and the electronics
section in the upper portion.
Microprocessor
Unit
Solenoid Valves
(behind case)
Guard Tubes
(behind case)
Push-to-Release
Latch
Hinged Door
2
Hinged Case
Standard
Constant Head Unit
Solution
Containers
with Sample Inlet and
Drain Connections
Fig. 1.1 Location of Instrument Components
Sample inlet and drain connections are at the base of the
instrument. A peristaltic pump, mounted centrally, proportions
sample and reagent through a mixing and reaction coil to a flow-
through cap at the end of a gas sensing probe where the
measurement takes place.
To maintain optimum measurement accuracy, it is necessary to
carry out two point calibration by introducing 'low' and 'high'
standard solutions of known concentration. The 8237 monitor
uses solenoid valves to introduce these solutions automatically at
programmable intervals under the control of the microprocessor.
Access to the probe, pump and calibration solution containers is
by means of a hinged acrylic door, which is held open or closed by
use of a push/push latch. The instrument case is also hinged to
allow access to the electronics section, guard tubes and solenoid
valves etc. for maintenance.
The electronics section consists of a microprocessor unit situated
at the top left which controls the instrument functions, and a user
junction box for all external electrical connections, at the top right
behind the hinged case.
Peristaltic
(behind case)
Pump
Case Lock
Cable Entry Glands
User Junction Box
(behind case)
Probe and Temperature
Sensors
(cover removed)
Case Lock
Temperature
Controlled Block
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