Revision 5
41
August 2021
and the analyzer concentration measurements to return to stable process values prior to
returning to the Run state.
If there are any faults currently present (i.e. Status relay is in fault state) the Mode
indicator CANNOT switch to Calibrate – Calibration is ONLY possible when all fault
conditions are cleared, and the Status relay is in the Normal condition. The only
condition under which the Status relay can be in Fault while the Mode relay is in
Calibrate is if the analyzer power is off.
3.3.2.4
Control
The
Control
output indicates whether the analog output signals are valid. Table 6
describes the Control relay.
Table 6: Control Relay States
Condition
Display Indicator Colour
Explanation
Auto
Green
ALL the following conditions are true:
•
Status indicator is Normal (i.e. no
fault conditions present)
•
Mode indicator is in Run state
(i.e. analyzer is not performing a
zero calibration)
•
Online / Offline switch is in the
Online position (i.e. analyzer is
not under maintenance)
•
Analyzer power is on
Manual
Yellow
At least one of the conditions for the relay
to be in the Auto state is NOT true.
When the relay is in the
Auto
state, the analyzer is indicating that it believes that the data
being output on the analog outputs are valid current measurements of the tail gas process
steam. If the Control relay is in the
Manual
state, this indicates that the analyzer believes
that the data being output may not be valid. The purpose of this indicator is to signify
when the analyzer outputs are suitable for use as closed loop control inputs. When this
indicator is in the Manual state, no control action should be taken based on the analyzer
output signals. This indicator is generated on the basis of the other analyzer indicators,
as well as the condition of the
Online / Offline
mode toggle on the display (refer to
Section 4.3.1). The Control relay state is automatically returned to Auto once all the
conditions required for the Auto state have been met. While the Control relay is in the
Manual state, any analog output that is configured as Hold
will be held.
3.3.2.4
Loss of Purge
The
Loss of Purge
signal relay, which is an integral component of the Purge Control box
on the top of the analyzer control cabinet, indicates the status of the analyzer’s control
cabinet safety purge. When a safe positive pressure as described in Section 3.2.1 is
present inside the analyzer’s control cabinet, the Purge indicator on the outside of the
purge control box will be green and the purge fail relay will be in the normal state. When
the safe positive pressure is lost, such as when purge air flow is lost or the control cabinet
Содержание 943-TGXeNA
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Страница 131: ...Revision 5 131 August 2021 Figure 83 Control Cabinet Door Removed ...
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Страница 134: ...Revision 5 134 August 2021 Figure 86 DC Signals and Wiring Diagram ...
Страница 135: ...Revision 5 135 August 2021 Figure 87 Flow Diagram ...