M&C TechGroup CSS-VC2 Operator's manual - Manual (Page 30)

30 Gas sampling and gas conditioning technology 14.1a-ME
15.3.4 THE BACKFLUSH MODULE
With the backflush module, on the TCU a backflush programme can be set for gas sampling probes
(duration of a backflush pulse, number of backflush pulses, time between backflush pulses, timing of
backflush). The programme switches with time delay two solid-state relays with which in turn solenoid
valves can be switched, which accordingly release purging air to the gas sampling probe.
At start and end of a backflush programme, another solid-state relay is switched one second before
start and after the end of the programme, with which a solenoid valve can be controlled, which
releases control air to shut off and open the sample gas output of the gas sampling probe with
pneumatic valve.
In addition, at the start and end of a backflush programme, a changeover relay for status monitoring
(measuring/backflush) is switched. Here at the TCU dead time can be specified to ensure that, on the
"Measure" message, sample gas is currently flowing in the analyser. In addition, a connection is
present for pressure monitoring of the backflush gas. For this purpose, a pressure switch is connected
in the backflush line which closes the contact at upcoming pressure.
Figure 14 Electrical connections backflush module