User`s guide

Routine Maintenance
249
Changing the O-Rings in the Fixed and
Mobile Seals
The sample tube is sealed into the carrier gas circuit by compressing
it between two o-rings. These seals are located within the carrier
block at the inlet end and within the nozzle at the outlet end of the
tube.
After several months of operation, leak test failures may begin to
occur. When operating near the maximum valve and tube desorption
temperatures, o-ring life expectancy could be approximately 100
analyses. If the leak test repeatedly fails with successive tubes, it is
likely that the o-rings in the seals have deteriorated.
The TD and ATD have o-rings in both the fixed seal and in the
mobile seal.
To maintain a high level of performance, replace the o-rings in the
fixed and mobile seals and the filter disks at the same time.
Replacing the O-Rings and the Filter Disk in
the Fixed Seal Assembly
The fixed seal contains two o-rings: the grip-seal o-ring (nearest the
tube) and the chamfer-seal o-ring. In addition to the o-rings, the
fixed seal also contains a porous PTFE filter. This filter disk
prevents particles of adsorbent, glass wool fibers and other waste
from the sample tube, from entering and damaging the heated valve.
Replace the filter disk (P/N L100-3029) when it has been damaged,
when it appears discolored, or when the o-ring is replaced.
A consideration for high temperature operation is the o-rings
contained in the fixed seal of the tube handling system. Your
instrument is shipped with Viton o-rings (P/N L1003006 and
L1003008). These o-rings are intended to be used at temperatures up
to 225 °C. Beyond this temperature they will degrade rapidly and
leak. You may also want to install high temperature o-rings into the
fixed seal assembly. The high temperature o-rings (P/N 0920-0092
CAUTION
The filter disk is essential! If the filter disk is removed, it must
be replaced with a new one.