M&C TechGroup SP3200 Operator's manual - Manual (Page 9)

2-1.3.9-ME Gas sampling and gas conditioning technology 9
General safety instructions for back flushing and feeding of calibration gas
A backflushing gas suitable for the sampling point must be selected for backflushing.
The backflushing pressure / calibration gas pressure must always be higher than the process
pressure. This minimum pressure must be monitored with a press switch at the inlet side of the
accumulator or the check valve. If the flush gas pressure drops below the process pressure, the
backflushing solenoid valve must not be operated.
The maximum permissible pressures of 6 bar abs. must not be exceeded (see technical data).
Do not choose back flush intervals longer than 3 seconds because in case of strong pollution of
the pre-filter pressure inside the probe would be rising and than discharging to the analyser via
the patented pressure control valve in the outlet of the probe due to a defined leak rate of this
valve.
At sampling points with inerting, backflushing must be performed with corresponding inert gas.
It must be ensured that the inert gas does not introduce oxygen or combustible gases into the
system.
8.1
BACKFLUSH UNIT TYPE /RS
The backflush unit type /RS consists of a pressure relief valve, solenoid valve, accumulator and patented
pressure control valve in the probe outlet.
The cyclical operation of the solenoid valve and monitoring of the backflushing pressure must be effected
externally. The electrical connection of the solenoid valve must be made in an EEx e connection box. An ad-
ditional solenoid valve in the sample gas outlet of the probe is not necessary because the patented pressure
control valve shuts the probe outlet during back purging in order to protect the downstream analysis against
the pressure push of the back purge.
8.2 OPTION /R, /BB AND /BBF FOR TEST GAS FEEDING OR BACKFLUSHING VIA CHECK VALVE R 1/4“,
BB 3/8“ OR BBF 3/8“
For back purging of the probe tube or the preliminary filter, flush gas is fed via the check valve. Hereby, it is
recommended to separate the downstream analysing system from the probe in order to avoid pressure
pushes to the system (Option /I). The opening pressure of the check valve is 0,7 bar. The flush gas or calibra-
tion gas pressure should be higher than 0,7 bar.
Options /R and /BB are for backflush of the inside space of the probe and the preliminary filter, the option
BBF is for backflush of the probe filter and the preliminary filter.
N O T E !
In order to avoid the cooling down of the inside probe, it is recommended to effect the
backflush in short intervals of <1s.
During the feeding of test gas, the analyse system remains connected. The quantity of test gas should be at
least 25% higher than the quantity of sample gas which is taken in by the analysing system, thus avoiding a
mixture with the test gas. For processes with overpressure, this kind of feeding the test gas is not recom-
mended. In this case, you should use an integrated ball valve in the inlet of the probe as stop valve.