If it really were that simple ...
... then we would be finished. Why does live switching
therefore have to the adjusted?
The live T-piece has 6 connections, of which 3 can be
outputs. This means that a peak can be divided simulta-
neously amongst 3 outputs. And we can do without
that!
We can understand this better if we consider the flows
in the live T-piece.
Straight
Everything from column A must enter the coupling ca-
pillary, and everything from the coupling capillary must
enter column B. This functions reliably if the flow is
supplemented by the flows of the auxiliary inlets.
The flow in the coupling capillary is from left to right.
Cut
Everything from column A must pass on to the cut
outlet. This functions reliably if the flow is sup-
plemented by the flows of the auxiliary inlets.
The flow in the coupling capillary is from right to left.
Backflush
Backflushing functions exactly as described previously
under The solution: the back T-piece. The position in
which the live T-piece is currently being operated is
irrelevant.
NOTE:
The needle valve NV
Back bypass
is required so that the pressure
regulator is always loaded by a flow to prevent a sample from
diffusing into the carrier gas line during backflushing.
Straight
Coupling
capillary
Cut
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
Four pages ... - and you know how live switching functions!
live.chp, Issue August 17, 1999
6 - 7
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