The other way: flow diagrams
The following two tables show all possibilities for the
positions Straight and Cut. Please note that the target is
always the left-hand (bright) path.
Position
Straight
Repeatedly inject test substance until only 1 peak appears optimally from column B
How many peaks ?
1 peak 2 peaks 3 peaks
From column B From the cut outlet From the cut outlet
and from column B
From the purge outlet
and from column B
From all three outlets
This is right!
But perhaps more is
flowing through the
coupling than is
necessary
We have cut operating
mode.
Possible faults:
-MV
Cut
is OFF instead
of ON
-Capillary is blocked
We have partial cut
operating mode. Cause:
P
A
is too high or
∆
p is too low
∆
p via the coupling
capillary is too large, i.e.
more comes out of the
coupling capillary than
passes into column B
This is a mixture of both
situations for "2 peaks".
Rotating NV
Straight
no
longer helps in this case!
Open NV
Straight
by e.g.
1/4 revolution until a
peak also appears at the
cut outlet. Then close
again until this peak just
disappears!
Normally only the
pressure at the right
auxiliary inlet is too high.
Therefore close
NV
Straight
by e.g. 1/2
revolution
Normally the pressure at
the right auxiliary inlet
is too high.
Therefore close
NV
Straight
by e.g. 1/2
revolution
Open NV
Straight
by e.g.
1/2 revolution
Reduce P
A
by 0.1 bar
If you are working with a temperature program repeat everything at the final temperature
Position
Cut
Repeatedly inject test substance until only 1 peak appears optimally from the cut outlet
How many peaks ?
1 peak 2 peaks
From the cut outlet From column B From the cut outlet
and from column B
This is right!
But perhaps more is flowing through the
coupling than is necessary
We have straight operating mode This is a mixture of both situations for "1
peak"
Open NV
Cut
by e.g. 1/4 revolution until a
peak also appears at the outlet of column
B. Then close again until this peak just
disappears.
The pressure at the left auxiliary inlet is
therefore too high.
Close NV
Cut
by e.g. 1/2 revolution
The pressure at the left auxiliary inlet is
therefore too high.
Close NV
Cut
by e.g. 1/2 revolution
If you are working with a temperature programrepeat everything at the final temperature
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
Live switching: troubleshooting
6 - 12
live.chp, Issue August 17, 1999
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