Siemens PGC 302 Edition II Manual page 172

FPD - flame photometric detector
DETECTOR GAS SUPPLY
The FPD requires the following gases:
Type of gas
Combustion gas
Hydrogen (D1)
Combustion air (D2)
Make-up gas
Synthetic air (D3)
IMPORTANT
The FPD is a very sensitive detector. The
gases and their supply lines must be
extremely clean if you wish to achieve a high
signal/noise ratio.
Selection of carrier gas
Nitrogen, helium, argon or air can be used as the carrier
gas. Larger quantities of hydrogen change the flame
shape and may make the nozzle glow. Hydrogen can
therefore only be used with capillary columns and with
carrier gas with flows < 10 ml/min.
Increasing the sensitivity
The sensitivity of the FPD can be increased by reducing
the flow of combustion air. The highest sensitivity is
achieved when the air flow is approximately the same
as the hydrogen flow. The FPD cannot be ignited with
this air/hydrogen ratio, however. Therefore initially
open the solenoid valve Z for the higher air flow when
igniting, and then close again.
Make-up gas
The addition of synthetic air supplements the small car-
rier gas volume of capillary columns to the value of
packed columns.
Column connection
An extension piece is required in the PGC 302 for the
non-Ex version.
4 - 24
Gas quantity
75 - 85 ml/min
110 - 130 ml/min
Approx. 10 ml/min
Combustion gas
Ex-FPD
D1
Tempe-
rature
limiter
+24 V
Temperature limiter
The surface temperature of the Ex-FPD could rise
above the permissible value if the combustion air con-
troller is faulty or if the combustion air flow has been
set too high by mistake. This permissible value is
defined by the temperature class.
To prevent unacceptable heating-up, the temperature
limiter reduces the flow of combustion air early enough
by means of a solenoid valve.
WARNING: Ex-FPD
The restrictors D1 and D2 are screw-in parts
with soldered capillaries. They are provided
for explosion protection and must not be
changed.
NOTE: piping diagram for non-Ex version
Deviating from the above diagram, the restrictors D1 and D2
are positioned in the gas inlet lines. The temperature limiter
with solenoid valve is omitted.
Gas supply
synthetic air
Exhaust
Digital
output
G N D G N D
Comb. air
D2
D3
Make-up
EXFPD.CHP Stand September 14, 1999
Z