Technical Description: Inlet
Solenoid Inlet
C-34
Prima PRO & Sentinel PRO Mass Spectrometers User Guide
Thermo Fisher Scientific
pressure reading in air was 10
-5
mbar, the mass 32 peak height should
drop by a factor of 1000. If this is not achieved, it may be necessary
to leak check the analyser itself.
When complete reconnect the calibration manifold line to the
CALIBRATION INLET on the front panel of the solenoid assembly.
The following checks are to ascertain that each solenoid valve is
being driven correctly and that the correct gas is being sampled. It
should be noted that if any particular solenoid valve does not operate
correctly the system will sample the gas mixture in the common
exhaust. This condition may not be easy to detect if the composition
of the sample gases on the manifold are similar.
For the calibration inlets, select calibration gas inlet #1 from the
system software. A flow should be indicated on the flow sensor.
Verify that if the gas supply is switched off externally the indicated
flow drops to zero (allowing for the line to depressurise). Repeat for
all (used) calibration inlets.
For a sample inlet, connect a ‘distinctive’ gas (e.g. helium), set to a
typical flow rate, to the inlet and monitor the system in Histogram
Scan mode 0-50 amu. When the helium inlet is switched in the
spectrum of helium (mass 4 only, plus a few background peaks)
should be visible. As with the calibration inlets the flow sensor
should also register a reading. Purge with air or nitrogen and then
repeat the process for the remaining inlets.
If there appears to be a problem, check that there are no external
blockages. Remember that, for sample inlets, the selector valve must
be driven in addition to the individual inlet valve. Possible failure of
either the selector valve or inlet manifold valve must be considered.
If any given valve fails to operate, first check the 24 V drive signal to
that valve. If there is a problem trace this back, as far as the inlet
controller PCA if required. If the drive signal is present, check the
solenoid coil. The resistance should be approximately 115 Ω.
If there is still a problem, there may have been some contamination
causing a valve to ‘stick’. Follow the maintenance procedures in
Cross seat leakage can result from contamination on the valve seat
(as a result of inadequate gas filtering) or simply following
prolonged use resulting in minor deformation of the valve seat. As a
result a valve may not shut off fully, resulting in cross contamination
of samples or loss of valuable calibration gas if this occurs on a
calibration manifold valve.
Valve Function
Cross Seat Leakage
