Adjusting the live switching
IMPORTANT
For safety reasons the function
Backflush
was previously switched on if the solenoid
valve MV
Back
was OFF! The same applies to
MV
Cut
. In other words: MV
Cut
ON = straight,
MV
Back
OFF = straight!
We have retained this so that you need not
be concerned with different versions.
However this can be changed in two
manners using the configuration software:
- The valves can be configured as inverted
- The names of the valves can be changed,
e.g. into
No backflush
.
In this description we consider the non-
modified version!
Adjusting the live switching
There are three outlets!
During the adjustment, peaks cab be output from the
live T-piece via three outlets:
Cut outlet
Flushing outlet
Column B outlet.
Therefore all three outlets must be observed! This is
easiest using monitor detectors (version 1).
If you do not have a monitor detector, the outlet Purge
outlet must be routed to the main detector in straight
operating mode (version 2), or the outlet Cut outlet in
cut operating mode (version 3). To do this, connect the
respective capillary from the outlet of needle valve
NV
Cut outlet
or NV
Purge outlet
to the detector.
The following applies in all cases: the peak via column
B always arrives later than the peaks via the cut or
purge outlet. Therefore: detailed consideration is
necessary, especially with versions such as Distribu-
tion!
The suitable test substance
The test substance for the adjustment should generate
only one peak without a short retention time. An alkane
with approximately the same boiling point as the
measured component is appropriate. Example: methane
for gas injection or hexane for liquid injection.
NOTE:
The solenoid valve MV
Back
_____
is usually replaced by a needle
valve in the case of capillary switching!
Off we go!
Install columns. See Installation of columns on live T-
piece. Check everything for leaks.
1. Adjustment of flow through column B
Measure flow at outlet of column B
Set P
M
– according to the application data
– or look up the optimum flow in the tables pro-
vided by the column manufacturer, measure and
set P
M
accordingly
Set P
A
according to the equation
P
A
=
P
M
+
Length
Column
_
A
Length
Column
_
B
×
P
M
Set initial temperatures
2. Adjustment of needle valves
Set split. See Injectors.
Completely open NV
Cut
and NV
Straight
Set NV
Cut outlet
and NV
Purge outlet
– according to the application data
– or to 10 ... 70 ml/min at the outlet Cut outlet
(optimum, approx. 5 * flow
A-column
)
and 10 ... 30 ml/min at the outlet Purge outlet
NOTE:
If you use a monitor detector, it is connected to the outlet
Cut outlet
using a capillary. The needle valve NV
Cut outlet
is
not present in this case. The flow is adjusted by shortening
the capillary.
A
B
A
A
21
3
P
M
NV
P
A
NV
NV
PURGE
OUTLET
CUT
OUTLET
MV
BACK
MV
BACK
NV
STRAIGHT
NV
CUT
MV
CUT
BACK
BYPASS
Column A Column B
Live T-piece
Adjusting the live switching
6 - 8
live.chp, Issue August 17, 1999
To Next Page
Loading...
