Siemens PGC 302 Edition II - Page 206

Adjustment of flow
The required flow is specified in the application docu-
ments. The following rule applies:
The same quantity of gas must flow through
the detector, out of the backflush outlet, and
out of the cut outlet. This must always remain
the case, even when the valves are switched
over!
Exception: A greater amount may occasionally flow through
the backflush outlet as this does not influence the retention
times.
Adjustment of position Straight
Switch the backflush valve (Back) and the cut valve
(Cut) such that columns A, B and C are in series
Measure the flow of carrier gas at the detector out-
let, and adjust to the required value using the carrier
gas pressure regulator
Adjustment of position Cut
Switch over the cut valve
Adjust the flow through the detector using needle
valve NV 4. NV 4 now replaces columns A and B.
Adjust the flow at Cut outlet using needle valve
NV 3. NV 3 now replaces column C.
Adjustment of position Backflush
Switch back the cut valve
Switch over the backflush valve
Adjust the flow through the detector using needle
valve NV 1
Adjust the flow at the backflush outlet Back outlet
using needle valve NV 2
IMPORTANT with FID/FPD:
Turn off the combustion air and
combustion gas prior to the adjustment
Switch on the combustion air and
combustion gas again following the
adjustment.
Maintenance
Depending on the sample and the purity of the used
gases, the injection valve and the switching valves may
become contaminated. Clean and service the valves as
described under Sample injection: Diaphragm valves.
NV 1
NV 4
NV 3NV 2
Back Cut
A
BC
In
j
.
Back
outlet
Cut
outlet
Carrier
g
as
Det.
12
3
45
6
12
3
45
6
Straight
NV 1
NV 4
NV 3NV 2
Back Cut
A
BC
In
j
.
Back
outlet
Cut
outlet
Carrier
g
as
Det.
12
3
45
6
12
3
45
6
Cut
NV 1
NV 4
NV 3NV 2
Back Cut
A
BC
In
j
.
Back
outlet
Cut
outlet
Carrier
g
as
Det.
12
3
45
6
12
3
45
6
Backflush
Column switching with diaphragm valves
membran.chp, Issue August 17, 1999
6 - 15