User`s guide

Theory of Thermal Desorption
308
Figure 90 Pressurize Sample Tube
Primary and Secondary Leak Test of the
Sample Tube
If no large leaks are detected, SV1 is closed, sealing the tube part of
the system. The instrument remains in this state for 30 seconds for
the primary leak test.
If, after this period, a pressure decrease is sensed that exceeds a
fraction (1/32) of the set column pressure or 1.4 kPa (0.2 psi),
whichever is greater, then the test is repeated on the same tube. It is
re-pressurized for 5 seconds and the pressure drop is monitored for a
further 30 seconds. This is the secondary leak test.
If the tube fails the primary and secondary leak tests, a “tube leaked”
deviation is recorded, the Fail signal contacts close for 1 second, and
the tube is rejected and returned to the carousel.
Transfer Line t
o GC
Sample
Tube
SV2
Carrier Supply
Carrier
Pressure
SV1
Desorb Supply
SV4
Outlet Split
SV5
Inlet Split
SV3
Desorb Vent
Leak
Pressure
Inlet Split/
Tube Condition Vent
A
Trap
Outlet Split
Vent
Desorb Flow
Vent
Pressure
Regulator
Supply
PR
Valve A
Position B
2
3
4
1